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1. Fewer supermassive binary black holes in pulsar timing array observations

Author: Goncharov, Boris, Sardana, Shubhit, Sesana, A., Antoniadis, J., Chalumeau, A., Champion, D., Chen, S., Keane, E. F., Shaifullah, G., and Speri, L.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, General Relativity and Quantum Cosmology
Abstract: We reanalyse the second data release of the European Pulsar Timing Array (EPTA) using an observationally-driven model for ensemble properties of pulsar noise. We show that the revised gravitational wave background properties are in better agreement with theoretical expectations for the strain spectrum. Our improved model for ensemble pulsar noise properties reduces a systematic error at $1\sigma$ level and increases Bayesian odds of Hellings-Downs correlations by $\sim 10\%$., Comment: 6 pages, 2 figures
Published: 2024

2. Comparing recent PTA results on the nanohertz stochastic gravitational wave background

Author: The International Pulsar Timing Array Collaboration, Agazie, G., Antoniadis, J., Anumarlapudi, A., Archibald, A. M., Arumugam, P., Arumugam, S., Arzoumanian, Z., Askew, J., Babak, S., Bagchi, M., Bailes, M., Nielsen, A. -S. Bak, Baker, P. T., Bassa, C. G., Bathula, A., Bécsy, B., Berthereau, A., Bhat, N. D. R., Blecha, L., Bonetti, M., Bortolas, E., Brazier, A., Brook, P. R., Burgay, M., Burke-Spolaor, S., Burnette, R., Caballero, R. N., Cameron, A., Case, R., Chalumeau, A., Champion, D. J., Chanlaridis, S., Charisi, M., Chatterjee, S., Chatziioannou, K., Cheeseboro, B. D., Chen, S., Chen, Z. -C., Cognard, I., Cohen, T., Coles, W. A., Cordes, J. M., Cornish, N. J., Crawford, F., Cromartie, H. T., Crowter, K., Curyło, M., Cutler, C. J., Dai, S., Dandapat, S., Deb, D., DeCesar, M. E., DeGan, D., Demorest, P. B., Deng, H., Desai, S., Desvignes, G., Dey, L., Dhanda-Batra, N., Di Marco, V., Dolch, T., Drachler, B., Dwivedi, C., Ellis, J. A., Falxa, M., Feng, Y., Ferdman, R. D., Ferrara, E. C., Fiore, W., Fonseca, E., Franchini, A., Freedman, G. E., Gair, J. R., Garver-Daniels, N., Gentile, P. A., Gersbach, K. A., Glaser, J., Good, D. C., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Gültekin, K., Guo, Y. J., Gupta, Y., Grunthal, K., Hazboun, J. S., Hisano, S., Hobbs, G. B., Hourihane, S., Hu, H., Iraci, F., Islo, K., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jennings, R. J., Jessner, A., Johnson, A. D., Jones, M. L., Joshi, B. C., Kaiser, A. R., Kaplan, D. L., Kapur, A., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kelley, L. Z., Kerr, M., Key, J. S., Kharbanda, D., Kikunaga, T., Klein, T. C., Kolhe, N., Kramer, M., Krishnakumar, M. A., Kulkarni, A., Laal, N., Lackeos, K., Lam, M. T., Lamb, W. G., Larsen, B. B., Lazio, T. J. W., Lee, K. J., Levin, Y., Lewandowska, N., Littenberg, T. B., Liu, K., Liu, T., Liu, Y., Lommen, A., Lorimer, D. R., Lower, M. E., Luo, J., Luo, R., Lynch, R. S., Lyne, A. G., Ma, C. -P., Maan, Y., Madison, D. R., Main, R. A., Manchester, R. N., Mandow, R., Mattson, M. A., McEwen, A., McKee, J. W., McLaughlin, M. A., McMann, N., Meyers, B. W., Meyers, P. M., Mickaliger, M. B., Miles, M., Mingarelli, C. M. F., Mitridate, A., Natarajan, P., Nathan, R. S., Ng, C., Nice, D. J., Niţu, I. C., Nobleson, K., Ocker, S. K., Olum, K. D., Osłowski, S., Paladi, A. K., Parthasarathy, A., Pennucci, T. T., Perera, B. B. P., Perrodin, D., Petiteau, A., Petrov, P., Pol, N. S., Porayko, N. K., Possenti, A., Prabu, T., Leclere, H. Quelquejay, Radovan, H. A., Rana, P., Ransom, S. M., Ray, P. S., Reardon, D. J., Rogers, A. F., Romano, J. D., Russell, C. J., Samajdar, A., Sanidas, S. A., Sardesai, S. C., Schmiedekamp, A., Schmiedekamp, C., Schmitz, K., Schult, L., Sesana, A., Shaifullah, G., Shannon, R. M., Shapiro-Albert, B. J., Siemens, X., Simon, J., Singha, J., Siwek, M. S., Speri, L., Spiewak, R., Srivastava, A., Stairs, I. H., Stappers, B. W., Stinebring, D. R., Stovall, K., Sun, J. P., Surnis, M., Susarla, S. C., Susobhanan, A., Swiggum, J. K., Takahashi, K., Tarafdar, P., Taylor, J., Taylor, S. R., Theureau, G., Thrane, E., Thyagarajan, N., Tiburzi, C., Toomey, L., Turner, J. E., Unal, C., Vallisneri, M., van der Wateren, E., van Haasteren, R., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Vigeland, S. J., Wahl, H. M., Wang, S., Wang, Q., Witt, C. A., Wang, J., Wang, L., Wayt, K. E., Wu, Z., Young, O., Zhang, L., Zhang, S., Zhu, X. -J., and Zic, A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract: The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within $1\sigma$. The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we "extended" each PTA's data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the Hellings and Downs correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA's Data Release 3, which will involve not just adding in additional pulsars, but also including data from all three PTAs where any given pulsar is timed by more than as single PTA., Comment: 21 pages, 9 figures, submitted to ApJ
Published: 2023

3. The second data release from the European Pulsar Timing Array: VI. Challenging the ultralight dark matter paradigm

Author: Smarra, Clemente, Goncharov, Boris, Barausse, Enrico, Antoniadis, J., Babak, S., Nielsen, A. -S. Bak, Bassa, C. G., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Desvignes, G., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Graikou, E., Grie, J. -M., Guillemot, L., Guo, Y. J., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Karuppusamy, R., Keane, E. F., Keith, M. J., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Main, R. A., Mickaliger, M. B., Niţu, I. C., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Leclere, H. Quelquejay, Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Speri, L., Spiewak, R., Stappers, B. W., Susarla, S. C., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Wang, J., Wang, L., and Wu, Z.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, General Relativity and Quantum Cosmology, High Energy Physics - Phenomenology
Abstract: Pulsar Timing Array experiments probe the presence of possible scalar or pseudoscalar ultralight dark matter particles through decade-long timing of an ensemble of galactic millisecond radio pulsars. With the second data release of the European Pulsar Timing Array, we focus on the most robust scenario, in which dark matter interacts only gravitationally with ordinary baryonic matter. Our results show that ultralight particles with masses $10^{-24.0}~\text{eV} \lesssim m \lesssim 10^{-23.3}~\text{eV}$ cannot constitute $100\%$ of the measured local dark matter density, but can have at most local density $\rho\lesssim 0.3$ GeV/cm$^3$., Comment: 5 pages + acknowledgements + refs, 2 figures. Text and figures match the version published in PRL
Published: 2023
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4. The second data release from the European Pulsar Timing Array: IV. Implications for massive black holes, dark matter and the early Universe

Author: Antoniadis, J., Arumugam, P., Arumugam, S., Auclair, P., Babak, S., Bagchi, M., Nielsen, A. -S. Bak, Barausse, E., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Caprini, C., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Crisostomi, M., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Fastidio, F., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Gualandris, A., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Khizriev, T., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Middleton, H., Neronov, A., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Postnov, K., Leclere, H. Quelquejay, Rana, P., Pol, A. Roper, Samajdar, A., Sanidas, S. A., Semikoz, D., Sesana, A., Shaifullah, G., Singha, J., Smarra, C., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Steer, D. A., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., Truant, R. J., van der Wateren, E., Valtolina, S., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, General Relativity and Quantum Cosmology
Abstract: The European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases respectively, with the correlation properties of a gravitational wave background (GWB). Such signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, cosmic strings and tensor mode generation by non-linear evolution of scalar perturbations in the early Universe; oscillations of the Galactic potential in the presence of ultra-light dark matter (ULDM). At the current stage of emerging evidence, it is impossible to discriminate among the different origins. Therefore, in this paper, we consider each process separately, and investigate the implications of the signal under the hypothesis that it is generated by that specific process. We find that the signal is consistent with a cosmic population of inspiralling SMBHBs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the SMBH-host galaxy scaling relations. If this origin is confirmed, this is the first direct evidence that SMBHBs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. As for early Universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. Other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. Finally, a ULDM origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of ULDM in our Galaxy., Comment: 30 pages, 23 figures, replaced to match the version published in Astronomy & Astrophysics, note the change in the numbering order in the series (now paper IV)
Published: 2023

5. The second data release from the European Pulsar Timing Array V. Search for continuous gravitational wave signals

Author: Antoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Nielsen, A. S. Bak, Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferranti, I., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Manzini, S., Mickaliger, M. B., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Leclere, H. Quelquejay, Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, General Relativity and Quantum Cosmology
Abstract: We present the results of a search for continuous gravitational wave signals (CGWs) in the second data release (DR2) of the European Pulsar Timing Array (EPTA) collaboration. The most significant candidate event from this search has a gravitational wave frequency of 4-5 nHz. Such a signal could be generated by a supermassive black hole binary (SMBHB) in the local Universe. We present the results of a follow-up analysis of this candidate using both Bayesian and frequentist methods. The Bayesian analysis gives a Bayes factor of 4 in favor of the presence of the CGW over a common uncorrelated noise process, while the frequentist analysis estimates the p-value of the candidate to be 1%, also assuming the presence of common uncorrelated red noise. However, comparing a model that includes both a CGW and a gravitational wave background (GWB) to a GWB only, the Bayes factor in favour of the CGW model is only 0.7. Therefore, we cannot conclusively determine the origin of the observed feature, but we cannot rule it out as a CGW source. We present results of simulations that demonstrate that data containing a weak gravitational wave background can be misinterpreted as data including a CGW and vice versa, providing two plausible explanations of the EPTA DR2 data. Further investigations combining data from all PTA collaborations will be needed to reveal the true origin of this feature., Comment: 13 figures, 15 pages, accepted
Published: 2023
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6. The second data release from the European Pulsar Timing Array II. Customised pulsar noise models for spatially correlated gravitational waves

Author: Antoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Nielsen, A. S. Bak, Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Niţu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Leclere, H. Quelquejay, Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The nanohertz gravitational wave background (GWB) is expected to be an aggregate signal of an ensemble of gravitational waves emitted predominantly by a large population of coalescing supermassive black hole binaries in the centres of merging galaxies. Pulsar timing arrays, ensembles of extremely stable pulsars, are the most precise experiments capable of detecting this background. However, the subtle imprints that the GWB induces on pulsar timing data are obscured by many sources of noise. These must be carefully characterized to increase the sensitivity to the GWB. In this paper, we present a novel technique to estimate the optimal number of frequency coefficients for modelling achromatic and chromatic noise and perform model selection. We also incorporate a new model to fit for scattering variations in the pulsar timing package temponest and created realistic simulations of the European Pulsar Timing Array (EPTA) datasets that allowed us to test the efficacy of our noise modelling algorithms. We present an in-depth analysis of the noise properties of 25 millisecond pulsars (MSPs) that form the second data release (DR2) of the EPTA and investigate the effect of incorporating low-frequency data from the Indian PTA collaboration. We use enterprise and temponest packages to compare noise models with those reported with the EPTA DR1. We find that, while in some pulsars we can successfully disentangle chromatic from achromatic noise owing to the wider frequency coverage in DR2, in others the noise models evolve in a more complicated way. We also find evidence of long-term scattering variations in PSR J1600$-$3053. Through our simulations, we identify intrinsic biases in our current noise analysis techniques and discuss their effect on GWB searches. The results presented here directly help improve sensitivity to the GWB and are already being used as part of global PTA efforts., Comment: 20 pages, 6 figures, 9 tables
Published: 2023
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7. The second data release from the European Pulsar Timing Array I. The dataset and timing analysis

Author: Antoniadis, J., Babak, S., Nielsen, A. -S. Bak, Bassa, C. G., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Desvignes, G., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Karuppusamy, R., Keane, E. F., Keith, M. J., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Main, R. A., Mickaliger, M. B., Nitu, I. C., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Samajdar, H. Quelquejay Leclere A., Sanidas, S. A., Sesana, A., Shaifullah, G., Speri, L., Spiewak, R., Stappers, B. W., Susarla, S. C., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics, General Relativity and Quantum Cosmology
Abstract: Pulsar timing arrays offer a probe of the low-frequency gravitational wave spectrum (1 - 100 nanohertz), which is intimately connected to a number of markers that can uniquely trace the formation and evolution of the Universe. We present the dataset and the results of the timing analysis from the second data release of the European Pulsar Timing Array (EPTA). The dataset contains high-precision pulsar timing data from 25 millisecond pulsars collected with the five largest radio telescopes in Europe, as well as the Large European Array for Pulsars. The dataset forms the foundation for the search for gravitational waves by the EPTA, presented in associated papers. We describe the dataset and present the results of the frequentist and Bayesian pulsar timing analysis for individual millisecond pulsars that have been observed over the last ~25 years. We discuss the improvements to the individual pulsar parameter estimates, as well as new measurements of the physical properties of these pulsars and their companions. This data release extends the dataset from EPTA Data Release 1 up to the beginning of 2021, with individual pulsar datasets with timespans ranging from 14 to 25 years. These lead to improved constraints on annual parallaxes, secular variation of the orbital period, and Shapiro delay for a number of sources. Based on these results, we derived astrophysical parameters that include distances, transverse velocities, binary pulsar masses, and annual orbital parallaxes., Comment: 29 pages, 9 figures, 13 tables, Astronomy & Astrophysics in press
Published: 2023
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8. The second data release from the European Pulsar Timing Array III. Search for gravitational wave signals

Author: Antoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Nielsen, A. -S. Bak, Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Leclere, H. Quelquejay, Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract: We present the results of the search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using the second data release of the European Pulsar Timing Array (EPTA) for 25 millisecond pulsars and a combination with the first data release of the Indian Pulsar Timing Array (InPTA). We analysed (i) the full 24.7-year EPTA data set, (ii) its 10.3-year subset based on modern observing systems, (iii) the combination of the full data set with the first data release of the InPTA for ten commonly timed millisecond pulsars, and (iv) the combination of the 10.3-year subset with the InPTA data. These combinations allowed us to probe the contributions of instrumental noise and interstellar propagation effects. With the full data set, we find marginal evidence for a GWB, with a Bayes factor of four and a false alarm probability of $4\%$. With the 10.3-year subset, we report evidence for a GWB, with a Bayes factor of $60$ and a false alarm probability of about $0.1\%$ ($\gtrsim 3\sigma$ significance). The addition of the InPTA data yields results that are broadly consistent with the EPTA-only data sets, with the benefit of better noise modelling. Analyses were performed with different data processing pipelines to test the consistency of the results from independent software packages. The inferred spectrum from the latest EPTA data from new generation observing systems is rather uncertain and in mild tension with the common signal measured in the full data set. However, if the spectral index is fixed at 13/3, the two data sets give a similar amplitude of ($2.5\pm0.7)\times10^{-15}$ at a reference frequency of $1\,{\rm yr}^{-1}$. By continuing our detection efforts as part of the International Pulsar Timing Array (IPTA), we expect to be able to improve the measurement of spatial correlations and better characterise this signal in the coming years., Comment: 21 pages, 14 figures, 4 appendix figures, accepted for publication in A&A
Published: 2023
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9. Practical approaches to analyzing PTA data: Cosmic strings with six pulsars

Author: Leclere, Hippolyte Quelquejay, Auclair, Pierre, Babak, Stanislav, Chalumeau, Aurélien, Steer, Danièle A., Antoniadis, J., Nielsen, A. -S. Bak, Bassa, C. G., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Desvignes, G., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Karuppusamy, R., Keane, E. F., Keith, M. J., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Main, R. A., Mickaliger, M. B., Niţu, I. C., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Speri, L., Spiewak, R., Stappers, B. W., Susarla, S. C., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Subjects: General Relativity and Quantum Cosmology, Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Theory
Abstract: We search for a stochastic gravitational wave background (SGWB) generated by a network of cosmic strings using six millisecond pulsars from Data Release 2 (DR2) of the European Pulsar Timing Array (EPTA). We perform a Bayesian analysis considering two models for the network of cosmic string loops, and compare it to a simple power-law model which is expected from the population of supermassive black hole binaries. Our main strong assumption is that the previously reported common red noise process is a SGWB. We find that the one-parameter cosmic string model is slightly favored over a power-law model thanks to its simplicity. If we assume a two-component stochastic signal in the data (supermassive black hole binary population and the signal from cosmic strings), we get a $95\%$ upper limit on the string tension of $\log_{10}(G\mu) < -9.9$ ($-10.5$) for the two cosmic string models we consider. In extended two-parameter string models, we were unable to constrain the number of kinks. We test two approximate and fast Bayesian data analysis methods against the most rigorous analysis and find consistent results. These two fast and efficient methods are applicable to all SGWBs, independent of their source, and will be crucial for analysis of extended data sets., Comment: 14 pages, 6 figures; typo corrected in (5)
Published: 2023
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10. Searching for continuous Gravitational Waves in the second data release of the International Pulsar Timing Array

Author: Falxa, M., Babak, S., Baker, P. T., Bécsy, B., Chalumeau, A., Chen, S., Chen, Z., Cornish, N. J., Guillemot, L., Hazboun, J. S., Mingarelli, C. M. F., Parthasarathy, A., Petiteau, A., Pol, N. S., Sesana, A., Spolaor, S. B., Taylor, S. R., Theureau, G., Vallisneri, M., Vigeland, S. J., Witt, C. A., Zhu, X., Antoniadis, J., Arzoumanian, Z., Bailes, M., Bhat, N. D. R., Blecha, L., Brazier, A., Brook, P. R., Caballero, N., Cameron, A. D., Casey-Clyde, J. A., Champion, D., Charisi, M., Chatterjee, S., Cognard, I., Cordes, J. M., Crawford, F., Cromartie, H. T., Crowter, K., Dai, S., DeCesar, M. E., Demorest, P. B., Desvignes, G., Dolch, T., Drachler, B., Feng, Y., Ferrara, E. C., Fiore, W., Fonseca, E., Garver-Daniels, N., Glaser, J., Goncharov, B., Good, D. C., Griessmeier, J., Guo, Y. J., Gültekin, K., Hobbs, G., Hu, H., Islo, K., Jang, J., Jennings, R. J., Johnson, A. D., Jones, M. L., Kaczmarek, J., Kaiser, A. R., Kaplan, D. L., Keith, M., Kelley, L. Z., Kerr, M., Key, J. S., Laal, N., Lam, M. T., Lamb, W. G., Lazio, T. J. W., Liu, K., Liu, T., Luo, J., Lynch, R. S., Madison, D. R., Main, R., Manchester, R., McEwen, A., McKee, J., McLaughlin, M. A., Ng, C., Nice, D. J., Ocker, S., Olum, K. D., Osłowski, S., Pennucci, T. T., Perera, B. B. P., Perrodin, D., Porayko, N., Possenti, A., Quelquejay-Leclere, H., Ransom, S. M., Ray, P. S., Reardon, D. J., Russell, C. J., Samajdar, A., Sarkissian, J., Schult, L., Shaifullah, G., Shannon, R. M., Shapiro-Albert, B. J., Siemens, X., Simon, J. J., Siwek, M., Smith, T. L., Speri, L., Spiewak, R., Stairs, I. H., Stappers, B., Stinebring, D. R., Swiggum, J. K., Tiburzi, C., Turner, J., Vecchio, A., Verbiest, J. P. W., Wahl, H., Wang, S. Q., Wang, J., Wu, Z., Zhang, L., and Zhang, S.
Subjects: General Relativity and Quantum Cosmology, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The International Pulsar Timing Array 2nd data release is the combination of datasets from worldwide collaborations. In this study, we search for continuous waves: gravitational wave signals produced by individual supermassive black hole binaries in the local universe. We consider binaries on circular orbits and neglect the evolution of orbital frequency over the observational span. We find no evidence for such signals and set sky averaged 95% upper limits on their amplitude h 95 . The most sensitive frequency is 10nHz with h 95 = 9.1 10-15 . We achieved the best upper limit to date at low and high frequencies of the PTA band thanks to improved effective cadence of observations. In our analysis, we have taken into account the recently discovered common red noise process, which has an impact at low frequencies. We also find that the peculiar noise features present in some pulsars data must be taken into account to reduce the false alarm. We show that using custom noise models is essential in searching for continuous gravitational wave signals and setting the upper limit.
Published: 2023
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11. Constraining the evolution of Newton's constant with slow inspirals observed from spaceborne gravitational-wave detectors

Author: Barbieri, R., Savastano, S., Speri, L., Antonelli, A., Sberna, L., Burke, O., Gair, J. R., and Tamanini, N.
Subjects: General Relativity and Quantum Cosmology
Abstract: Spaceborne gravitational-wave (GW) detectors observing at milli-Hz and deci-Hz frequencies are expected to detect large numbers of quasi-monochromatic signals. The first and second time-derivative of the GW frequency ($\dot f_0$ and $\ddot f_0$) can be measured for the most favourable sources and used to look for negative post-Newtonian corrections, which can be induced by the source's environment or modifications of general relativity. We present an analytical, Fisher-matrix-based approach to estimate how precisely such corrections can be constrained. We use this method to estimate the bounds attainable on the time evolution of the gravitational constant $G(t)$ with different classes of quasi-monochromatic sources observable with LISA and DECIGO, two representative spaceborne detectors for milli-Hz and deci-Hz GW frequencies. We find that the most constraining source among a simulated population of LISA galactic binaries could yield $\dot G/G_0 \lesssim 10^{-6}\text{yr}^{-1}$, while the best currently known verification binary will reach $\dot G/G_0 \lesssim 10^{-4}\text{yr}^{-1}$. We also perform Monte-Carlo simulations using quasi-monochromatic waveforms to check the validity of our Fisher-matrix approach, as well as inspiralling waveforms to analyse binaries that do not satisfy the quasi-monochromatic assumption. We find that our analytical Fisher matrix produces good order-of-magnitude constraints even for sources well beyond its regime of validity. Monte-Carlo investigations also show that chirping stellar-mass compact binaries detected by DECIGO-like detectors at cosmological distances of tens of Mpc can yield constraints as tight as $\dot G/G_0 \lesssim 10^{-11}\text{yr}^{-1}$., Comment: 10 pages, 3 figures
Published: 2022
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12. The International Pulsar Timing Array second data release: Search for an isotropic Gravitational Wave Background

Author: Antoniadis, J., Arzoumanian, Z., Babak, S., Bailes, M., Nielsen, A. -S. Bak, Baker, P. T., Bassa, C. G., Becsy, B., Berthereau, A., Bonetti, M., Brazier, A., Brook, P. R., Burgay, M., Burke-Spolaor, S., Caballero, R. N., Casey-Clyde, J. A., Chalumeau, A., Champion, D. J., Charisi, M., Chatterjee, S., Chen, S., Cognard, I., Cordes, J. M., Cornish, N. J., Crawford, F., Cromartie, H. T., Crowter, K., Dai, S., DeCesar, M. E., Demorest, P. B., Desvignes, G., Dolch, T., Drachler, B., Falxa, M., Ferrara, E. C., Fiore, W., Fonseca, E., Gair, J. R., Garver-Daniels, N., Goncharov, B., Good, D. C., Graikou, E., Guillemot, L., Guo, Y. J., Hazboun, J. S., Hobbs, G., Hu, H., Islo, K., Janssen, G. H., Jennings, R. J., Johnson, A. D., Jones, M. L., Kaiser, A. R., Kaplan, D. L., Karuppusamy, R., Keith, M. J., Kelley, L. Z., Kerr, M., Key, J. S., Kramer, M., Lam, M. T., Lamb, W. G., Lazio, T. J. W., Lee, K. J., Lentati, L., Liu, K., Luo, J., Lynch, R. S., Lyne, A. G., Madison, D. R., Main, R. A., Manchester, R. N., McEwen, A., McKee, J. W., McLaughlin, M. A., Mickaliger, M. B., Mingarelli, C. M. F., Ng, C., Nice, D. J., lowski, S. Os, Parthasarathy, A., Pennucci, T. T., Perera, B. B. P., Perrodin, D., Petiteau, A., Pol, N. S., Porayko, N. K., Possenti, A., Ransom, S. M., Ray, P. S., Reardon, D. J., Russell, C. J., Samajdar, A., Sampson, L. M., Sanidas, S., Sarkissian, J. M., Schmitz, K., Schult, L., Sesana, A., Shaifullah, G., Shannon, R. M., Shapiro-Albert, B. J., Siemens, X., Simon, J., Smith, T. L., Speri, L., Spiewak, R., Stairs, I. H., Stappers, B. W., Stinebring, D. R., Swiggum, J. K., Taylor, S. R., Theureau, G., Tiburzi, C., Vallisneri, M., van der Wateren, E., Vecchio, A., Verbiest, J. P. W., Vigeland, S. J., Wahl, H., Wang, J. B., Wang, J., Wang, L., Witt, C. A., Zhang, S., and Zhu, X. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We searched for an isotropic stochastic gravitational wave background in the second data release of the International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns in North America, Europe, and Australia. In our reference search for a power law strain spectrum of the form $h_c = A(f/1\,\mathrm{yr}^{-1})^{\alpha}$, we found strong evidence for a spectrally-similar low-frequency stochastic process of amplitude $A = 3.8^{+6.3}_{-2.5}\times10^{-15}$ and spectral index $\alpha = -0.5 \pm 0.5$, where the uncertainties represent 95\% credible regions, using information from the auto- and cross-correlation terms between the pulsars in the array. For a spectral index of $\alpha = -2/3$, as expected from a population of inspiralling supermassive black hole binaries, the recovered amplitude is $A = 2.8^{+1.2}_{-0.8}\times10^{-15}$. Nonetheless, no significant evidence of the Hellings-Downs correlations that would indicate a gravitational-wave origin was found. We also analyzed the constituent data from the individual pulsar timing arrays in a consistent way, and clearly demonstrate that the combined international data set is more sensitive. Furthermore, we demonstrate that this combined data set produces comparable constraints to recent single-array data sets which have more data than the constituent parts of the combination. Future international data releases will deliver increased sensitivity to gravitational wave radiation, and significantly increase the detection probability., Comment: 17 pages, 12 figures, accepted in MNRAS
Published: 2022
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13. Noise analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search

Author: Chalumeau, A., Babak, S., Petiteau, A., Chen, S., Samajdar, A., Caballero, R. N., Theureau, G., Guillemot, L., Desvignes, G., Parthasarathy, A., Liu, K., Shaifullah, G., Hu, H., van der Wateren, E., Antoniadis, J., Nielsen, A. -S. Bak, Bassa, C. G., Berthereau, A., Burgay, M., Champion, D. J., Cognard, I., Falxa, M., Ferdman, R. D., Freire, P. C. C., Gair, J. R., Graikou, E., Guo, Y. J., Jang, J., Janssen, G. H., Karuppusamy, R., Keith, M. J., Kramer, M., Lee, K. J., Liu, X. J., Lyne, A. G., Main, R. A., McKee, J. W., Mickaliger, M. B., Perera, B. B. P., Perrodin, D., Porayko, N. K., Possenti, A., Sanidas, S. A., Sesana, A., Speri, L., Stappers, B. W., Tiburzi, C., Vecchio, A., Verbiest, J. P. W., Wang, J., Wang, L., and Xu, H.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The European Pulsar Timing Array (EPTA) collaboration has recently released an extended data set for six pulsars (DR2) and reported evidence for a common red noise signal. Here we present a noise analysis for each of the six pulsars. We consider several types of noise: (i) radio frequency independent, "achromatic", and time-correlated red noise; (ii) variations of dispersion measure and scattering; (iii) system and band noise; and (iv) deterministic signals (other than gravitational waves) that could be present in the PTA data. We perform Bayesian model selection to find the optimal combination of noise components for each pulsar. Using these custom models we revisit the presence of the common uncorrelated red noise signal previously reported in the EPTA DR2 and show that the data still supports it with a high statistical significance. Next, we confirm that there is no preference for or against the Hellings-Downs spatial correlations expected for the stochastic gravitational-wave background. The main conclusion of the EPTA DR2 paper remains unchanged despite a very significant change in the noise model of each pulsar. However, modelling the noise is essential for the robust detection of gravitational waves and its impact could be significant when analysing the next EPTA data release, which will include a larger number of pulsars and more precise measurements., Comment: 21 pages, 11 figures, 7 tables, 1 appendix figure and 1 appendix table, accepted for publication to MNRAS
Published: 2021
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14. Common-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: Inferences in the stochastic gravitational-wave background search

Author: Chen, S., Caballero, R. N., Guo, Y. J., Chalumeau, A., Liu, K., Shaifullah, G., Lee, K. J., Babak, S., Desvignes, G., Parthasarathy, A., Hu, H., van der Wateren, E., Antoniadis, J., Nielsen, A. -S. Bak, Bassa, C. G., Berthereau, A., Burgay, M., Champion, D. J., Cognard, I., Falxa, M., Ferdman, R. D., Freire, P. C. C., Gair, J. R., Graikou, E., Guillemot, L., Jang, J., Janssen, G. H., Karuppusamy, R., Keith, M. J., Kramer, M., Liu, X. J., Lyne, A. G., Main, R. A., McKee, J. W., Mickaliger, M. B., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Samajdar, A., Sanidas, S. A., Sesana, A., Speri, L., Stappers, B. W., Theureau, G., Tiburzi, C., Vecchio, A., Verbiest, J. P. W., Wang, J., Wang, L., and Xu, H.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present results from the search for a stochastic gravitational-wave background (GWB) as predicted by the theory of General Relativity using six radio millisecond pulsars from the Data Release 2 (DR2) of the European Pulsar Timing Array (EPTA) covering a timespan up to 24 years. A GWB manifests itself as a long-term low-frequency stochastic signal common to all pulsars, a common red signal (CRS), with the characteristic Hellings-Downs (HD) spatial correlation. Our analysis is performed with two independent pipelines, \eprise{} and \tn{}+\ftwo{}, which produce consistent results. A search for a CRS with simultaneous estimation of its spatial correlations yields spectral properties compatible with theoretical GWB predictions, but does not result in the required measurement of the HD correlation, as required for GWB detection. Further Bayesian model comparison between different types of CRSs, including a GWB, finds the most favoured model to be the common uncorrelated red noise described by a power-law with $A = 5.13_{-2.73}^{+4.20} \times 10^{-15}$ and $\gamma = 3.78_{-0.59}^{+0.69}$ (95\% credible regions). Fixing the spectral index to $\gamma=13/3$ as expected from the GWB by circular, inspiralling supermassive black-hole binaries results in an amplitude of $A =2.95_{-0.72}^{+0.89} \times 10^{-15}$. We implement three different models, BAYESEPHEM, LINIMOSS and EPHEMGP, to address possible Solar-system ephemeris (SSE) systematics and conclude that our results may only marginally depend on these effects. This work builds on the methods and models from the studies on the EPTA DR1. We show that under the same analysis framework the results remain consistent after the data set extension., Comment: 25 pages, 10 figures, 7 tables, 2 appendix tables and 1 appendix figure
Published: 2021
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15. The second data release from the European Pulsar Timing Array: IV. Implications for massive black holes, dark matter, and the early Universe

Author: Antoniadis, J, Arumugam, P, Arumugam, S, Babak, S, Bagchi, M, Bak Nielsen, A, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Gualandris, A, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Mickaliger, M, Niţu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Quelquejay Leclere, H, Rana, P, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Singha, J, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, Van Der Wateren, E, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, Auclair, P, Antoniadis J., Arumugam P., Arumugam S., Babak S., Bagchi M., Bak Nielsen A. S., Bassa C. G., Bathula A., Berthereau A., Bonetti M., Bortolas E., Brook P. R., Burgay M., Caballero R. N., Chalumeau A., Champion D. J., Chanlaridis S., Chen S., Cognard I., Dandapat S., Deb D., Desai S., Desvignes G., Dhanda-Batra N., Dwivedi C., Falxa M., Ferdman R. D., Franchini A., Gair J. R., Goncharov B., Gopakumar A., Graikou E., Grießmeier J. M., Gualandris A., Guillemot L., Guo Y. J., Gupta Y., Hisano S., Hu H., Iraci F., Izquierdo Villalba D., Jang J., Jawor J., Janssen G. H., Jessner A., Joshi B. C., Kareem F., Karuppusamy R., Keane E. F., Keith M. J., Kharbanda D., Kikunaga T., Kolhe N., Kramer M., Krishnakumar M. A., Lackeos K., Lee K. J., Liu K., Liu Y., Lyne A. G., McKee J. W., Maan Y., Main R. A., Mickaliger M. B., Niţu I. C., Nobleson K., Paladi A. K., Parthasarathy A., Perera B. B. P., Perrodin D., Petiteau A., Porayko N. K., Possenti A., Prabu T., Quelquejay Leclere H., Rana P., Samajdar A., Sanidas S. A., Sesana A., Shaifullah G., Singha J., Speri L., Spiewak R., Srivastava A., Stappers B. W., Surnis M., Susarla S. C., Susobhanan A., Takahashi K., Tarafdar P., Theureau G., Tiburzi C., Van Der Wateren E., Vecchio A., Venkatraman Krishnan V., Verbiest J. P. W., Wang J., Wang L., Wu Z., Auclair P., Antoniadis, J, Arumugam, P, Arumugam, S, Babak, S, Bagchi, M, Bak Nielsen, A, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Gualandris, A, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Mickaliger, M, Niţu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Quelquejay Leclere, H, Rana, P, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Singha, J, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, Van Der Wateren, E, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, Auclair, P, Antoniadis J., Arumugam P., Arumugam S., Babak S., Bagchi M., Bak Nielsen A. S., Bassa C. G., Bathula A., Berthereau A., Bonetti M., Bortolas E., Brook P. R., Burgay M., Caballero R. N., Chalumeau A., Champion D. J., Chanlaridis S., Chen S., Cognard I., Dandapat S., Deb D., Desai S., Desvignes G., Dhanda-Batra N., Dwivedi C., Falxa M., Ferdman R. D., Franchini A., Gair J. R., Goncharov B., Gopakumar A., Graikou E., Grießmeier J. M., Gualandris A., Guillemot L., Guo Y. J., Gupta Y., Hisano S., Hu H., Iraci F., Izquierdo Villalba D., Jang J., Jawor J., Janssen G. H., Jessner A., Joshi B. C., Kareem F., Karuppusamy R., Keane E. F., Keith M. J., Kharbanda D., Kikunaga T., Kolhe N., Kramer M., Krishnakumar M. A., Lackeos K., Lee K. J., Liu K., Liu Y., Lyne A. G., McKee J. W., Maan Y., Main R. A., Mickaliger M. B., Niţu I. C., Nobleson K., Paladi A. K., Parthasarathy A., Perera B. B. P., Perrodin D., Petiteau A., Porayko N. K., Possenti A., Prabu T., Quelquejay Leclere H., Rana P., Samajdar A., Sanidas S. A., Sesana A., Shaifullah G., Singha J., Speri L., Spiewak R., Srivastava A., Stappers B. W., Surnis M., Susarla S. C., Susobhanan A., Takahashi K., Tarafdar P., Theureau G., Tiburzi C., Van Der Wateren E., Vecchio A., Venkatraman Krishnan V., Verbiest J. P. W., Wang J., Wang L., Wu Z., and Auclair P.
Abstract: The European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases, respectively, with the correlation properties of a gravitational wave background (GWB). Such a signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, cosmic strings, and tensor mode generation by the non-linear evolution of scalar perturbations in the early Universe; and oscillations of the Galactic potential in the presence of ultra-light dark matter (ULDM). At the current stage of emerging evidence, it is impossible to discriminate among the different origins. Therefore, for this paper, we consider each process separately, and investigated the implications of the signal under the hypothesis that it is generated by that specific process. We find that the signal is consistent with a cosmic population of inspiralling SMBHBs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the SMBH-host galaxy scaling relations. If this origin is confirmed, this would be the first direct evidence that SMBHBs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. As for early Universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. Other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. Finally, a ULDM origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of ULDM in our Galaxy.
Published: 2024

16. Cosmology with the Laser Interferometer Space Antenna

Author: Auclair, P, Bacon, D, Baker, T, Barreiro, T, Bartolo, N, Belgacem, E, Bellomo, N, Ben-Dayan, I, Bertacca, D, Besancon, M, Blanco-Pillado, J, Blas, D, Boileau, G, Calcagni, G, Caldwell, R, Caprini, C, Carbone, C, Chang, C, Chen, H, Christensen, N, Clesse, S, Comelli, D, Congedo, G, Contaldi, C, Crisostomi, M, Croon, D, Cui, Y, Cusin, G, Cutting, D, Dalang, C, De Luca, V, Pozzo, W, Desjacques, V, Dimastrogiovanni, E, Dorsch, G, Ezquiaga, J, Fasiello, M, Figueroa, D, Flauger, R, Franciolini, G, Frusciante, N, Fumagalli, J, Garcia-Bellido, J, Gould, O, Holz, D, Iacconi, L, Jain, R, Jenkins, A, Jinno, R, Joana, C, Karnesis, N, Konstandin, T, Koyama, K, Kozaczuk, J, Kuroyanagi, S, Laghi, D, Lewicki, M, Lombriser, L, Madge, E, Maggiore, M, Malhotra, A, Mancarella, M, Mandic, V, Mangiagli, A, Matarrese, S, Mazumdar, A, Mukherjee, S, Musco, I, Nardini, G, No, J, Papanikolaou, T, Peloso, M, Pieroni, M, Pilo, L, Raccanelli, A, Renaux-Petel, S, Renzini, A, Ricciardone, A, Riotto, A, Romano, J, Rollo, R, Pol, A, Morales, E, Sakellariadou, M, Saltas, I, Scalisi, M, Schmitz, K, Schwaller, P, Sergijenko, O, Servant, G, Simakachorn, P, Sorbo, L, Sousa, L, Speri, L, Steer, D, Tamanini, N, Tasinato, G, Torrado, J, Unal, C, Vennin, V, Vernieri, D, Vernizzi, F, Volonteri, M, Wachter, J, Wands, D, Witkowski, L, Zumalacarregui, M, Annis, J, Ares, F, Avelino, P, Avgoustidis, A, Barausse, E, Bonilla, A, Bonvin, C, Bosso, P, Calabrese, M, Caliskan, M, Cembranos, J, Chala, M, Chernoff, D, Clough, K, Criswell, A, Das, S, Silva, A, Dayal, P, Domcke, V, Durrer, R, Easther, R, Escoffier, S, Ferrans, S, Fryer, C, Gair, J, Gordon, C, Hendry, M, Hindmarsh, M, Hooper, D, Kajfasz, E, Kopp, J, Koushiappas, S, Kumar, U, Kunz, M, Lagos, M, Lilley, M, Lizarraga, J, Lobo, F, Maleknejad, A, Martins, C, Meerburg, P, Meyer, R, Mimoso, J, Nesseris, S, Nunes, N, Oikonomou, V, Orlando, G, Ozsoy, O, Pacucci, F, Palmese, A, Petiteau, A, Pinol, L, Zwart, S, Pratten, G, Prokopec, T, Quenby, J, Rastgoo, S, Roest, D, Rummukainen, K, Schimd, C, Secroun, A, Sesana, A, Sopuerta, C, Tereno, I, Tolley, A, Urrestilla, J, Vagenas, E, van de Vis, J, van de Weygaert, R, Wardell, B, Weir, D, White, G, Swiezewska, B, Zhdanov, V, Auclair P., Bacon D., Baker T., Barreiro T., Bartolo N., Belgacem E., Bellomo N., Ben-Dayan I., Bertacca D., Besancon M., Blanco-Pillado J. J., Blas D., Boileau G., Calcagni G., Caldwell R., Caprini C., Carbone C., Chang C. -F., Chen H. -Y., Christensen N., Clesse S., Comelli D., Congedo G., Contaldi C., Crisostomi M., Croon D., Cui Y., Cusin G., Cutting D., Dalang C., De Luca V., Pozzo W. D., Desjacques V., Dimastrogiovanni E., Dorsch G. C., Ezquiaga J. M., Fasiello M., Figueroa D. G., Flauger R., Franciolini G., Frusciante N., Fumagalli J., Garcia-Bellido J., Gould O., Holz D., Iacconi L., Jain R. K., Jenkins A. C., Jinno R., Joana C., Karnesis N., Konstandin T., Koyama K., Kozaczuk J., Kuroyanagi S., Laghi D., Lewicki M., Lombriser L., Madge E., Maggiore M., Malhotra A., Mancarella M., Mandic V., Mangiagli A., Matarrese S., Mazumdar A., Mukherjee S., Musco I., Nardini G., No J. M., Papanikolaou T., Peloso M., Pieroni M., Pilo L., Raccanelli A., Renaux-Petel S., Renzini A. I., Ricciardone A., Riotto A., Romano J. D., Rollo R., Pol A. R., Morales E. R., Sakellariadou M., Saltas I. D., Scalisi M., Schmitz K., Schwaller P., Sergijenko O., Servant G., Simakachorn P., Sorbo L., Sousa L., Speri L., Steer D. A., Tamanini N., Tasinato G., Torrado J., Unal C., Vennin V., Vernieri D., Vernizzi F., Volonteri M., Wachter J. M., Wands D., Witkowski L. T., Zumalacarregui M., Annis J., Ares F. R., Avelino P. P., Avgoustidis A., Barausse E., Bonilla A., Bonvin C., Bosso P., Calabrese M., Caliskan M., Cembranos J. A. R., Chala M., Chernoff D., Clough K., Criswell A., Das S., Silva A., Dayal P., Domcke V., Durrer R., Easther R., Escoffier S., Ferrans S., Fryer C., Gair J., Gordon C., Hendry M., Hindmarsh M., Hooper D. C., Kajfasz E., Kopp J., Koushiappas S. M., Kumar U., Kunz M., Lagos M., Lilley M., Lizarraga J., Lobo F. S. N., Maleknejad A., Martins C. J. A. P., Meerburg P. D., Meyer R., Mimoso J. P., Nesseris S., Nunes N., Oikonomou V., Orlando G., Ozsoy O., Pacucci F., Palmese A., Petiteau A., Pinol L., Zwart S. P., Pratten G., Prokopec T., Quenby J., Rastgoo S., Roest D., Rummukainen K., Schimd C., Secroun A., Sesana A., Sopuerta C. F., Tereno I., Tolley A., Urrestilla J., Vagenas E. C., van de Vis J., van de Weygaert R., Wardell B., Weir D. J., White G., Swiezewska B., Zhdanov V. I., Auclair, P, Bacon, D, Baker, T, Barreiro, T, Bartolo, N, Belgacem, E, Bellomo, N, Ben-Dayan, I, Bertacca, D, Besancon, M, Blanco-Pillado, J, Blas, D, Boileau, G, Calcagni, G, Caldwell, R, Caprini, C, Carbone, C, Chang, C, Chen, H, Christensen, N, Clesse, S, Comelli, D, Congedo, G, Contaldi, C, Crisostomi, M, Croon, D, Cui, Y, Cusin, G, Cutting, D, Dalang, C, De Luca, V, Pozzo, W, Desjacques, V, Dimastrogiovanni, E, Dorsch, G, Ezquiaga, J, Fasiello, M, Figueroa, D, Flauger, R, Franciolini, G, Frusciante, N, Fumagalli, J, Garcia-Bellido, J, Gould, O, Holz, D, Iacconi, L, Jain, R, Jenkins, A, Jinno, R, Joana, C, Karnesis, N, Konstandin, T, Koyama, K, Kozaczuk, J, Kuroyanagi, S, Laghi, D, Lewicki, M, Lombriser, L, Madge, E, Maggiore, M, Malhotra, A, Mancarella, M, Mandic, V, Mangiagli, A, Matarrese, S, Mazumdar, A, Mukherjee, S, Musco, I, Nardini, G, No, J, Papanikolaou, T, Peloso, M, Pieroni, M, Pilo, L, Raccanelli, A, Renaux-Petel, S, Renzini, A, Ricciardone, A, Riotto, A, Romano, J, Rollo, R, Pol, A, Morales, E, Sakellariadou, M, Saltas, I, Scalisi, M, Schmitz, K, Schwaller, P, Sergijenko, O, Servant, G, Simakachorn, P, Sorbo, L, Sousa, L, Speri, L, Steer, D, Tamanini, N, Tasinato, G, Torrado, J, Unal, C, Vennin, V, Vernieri, D, Vernizzi, F, Volonteri, M, Wachter, J, Wands, D, Witkowski, L, Zumalacarregui, M, Annis, J, Ares, F, Avelino, P, Avgoustidis, A, Barausse, E, Bonilla, A, Bonvin, C, Bosso, P, Calabrese, M, Caliskan, M, Cembranos, J, Chala, M, Chernoff, D, Clough, K, Criswell, A, Das, S, Silva, A, Dayal, P, Domcke, V, Durrer, R, Easther, R, Escoffier, S, Ferrans, S, Fryer, C, Gair, J, Gordon, C, Hendry, M, Hindmarsh, M, Hooper, D, Kajfasz, E, Kopp, J, Koushiappas, S, Kumar, U, Kunz, M, Lagos, M, Lilley, M, Lizarraga, J, Lobo, F, Maleknejad, A, Martins, C, Meerburg, P, Meyer, R, Mimoso, J, Nesseris, S, Nunes, N, Oikonomou, V, Orlando, G, Ozsoy, O, Pacucci, F, Palmese, A, Petiteau, A, Pinol, L, Zwart, S, Pratten, G, Prokopec, T, Quenby, J, Rastgoo, S, Roest, D, Rummukainen, K, Schimd, C, Secroun, A, Sesana, A, Sopuerta, C, Tereno, I, Tolley, A, Urrestilla, J, Vagenas, E, van de Vis, J, van de Weygaert, R, Wardell, B, Weir, D, White, G, Swiezewska, B, Zhdanov, V, Auclair P., Bacon D., Baker T., Barreiro T., Bartolo N., Belgacem E., Bellomo N., Ben-Dayan I., Bertacca D., Besancon M., Blanco-Pillado J. J., Blas D., Boileau G., Calcagni G., Caldwell R., Caprini C., Carbone C., Chang C. -F., Chen H. -Y., Christensen N., Clesse S., Comelli D., Congedo G., Contaldi C., Crisostomi M., Croon D., Cui Y., Cusin G., Cutting D., Dalang C., De Luca V., Pozzo W. D., Desjacques V., Dimastrogiovanni E., Dorsch G. C., Ezquiaga J. M., Fasiello M., Figueroa D. G., Flauger R., Franciolini G., Frusciante N., Fumagalli J., Garcia-Bellido J., Gould O., Holz D., Iacconi L., Jain R. K., Jenkins A. C., Jinno R., Joana C., Karnesis N., Konstandin T., Koyama K., Kozaczuk J., Kuroyanagi S., Laghi D., Lewicki M., Lombriser L., Madge E., Maggiore M., Malhotra A., Mancarella M., Mandic V., Mangiagli A., Matarrese S., Mazumdar A., Mukherjee S., Musco I., Nardini G., No J. M., Papanikolaou T., Peloso M., Pieroni M., Pilo L., Raccanelli A., Renaux-Petel S., Renzini A. I., Ricciardone A., Riotto A., Romano J. D., Rollo R., Pol A. R., Morales E. R., Sakellariadou M., Saltas I. D., Scalisi M., Schmitz K., Schwaller P., Sergijenko O., Servant G., Simakachorn P., Sorbo L., Sousa L., Speri L., Steer D. A., Tamanini N., Tasinato G., Torrado J., Unal C., Vennin V., Vernieri D., Vernizzi F., Volonteri M., Wachter J. M., Wands D., Witkowski L. T., Zumalacarregui M., Annis J., Ares F. R., Avelino P. P., Avgoustidis A., Barausse E., Bonilla A., Bonvin C., Bosso P., Calabrese M., Caliskan M., Cembranos J. A. R., Chala M., Chernoff D., Clough K., Criswell A., Das S., Silva A., Dayal P., Domcke V., Durrer R., Easther R., Escoffier S., Ferrans S., Fryer C., Gair J., Gordon C., Hendry M., Hindmarsh M., Hooper D. C., Kajfasz E., Kopp J., Koushiappas S. M., Kumar U., Kunz M., Lagos M., Lilley M., Lizarraga J., Lobo F. S. N., Maleknejad A., Martins C. J. A. P., Meerburg P. D., Meyer R., Mimoso J. P., Nesseris S., Nunes N., Oikonomou V., Orlando G., Ozsoy O., Pacucci F., Palmese A., Petiteau A., Pinol L., Zwart S. P., Pratten G., Prokopec T., Quenby J., Rastgoo S., Roest D., Rummukainen K., Schimd C., Secroun A., Sesana A., Sopuerta C. F., Tereno I., Tolley A., Urrestilla J., Vagenas E. C., van de Vis J., van de Weygaert R., Wardell B., Weir D. J., White G., Swiezewska B., and Zhdanov V. I.
Abstract: The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universe.
Published: 2023

17. The second data release from the European Pulsar Timing Array. III. Search for gravitational wave signals

Author: Antoniadis, J, Arumugam, P, Arumugam, S, Babak, S, Bagchi, M, Bak Nielsen, A, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Mickaliger, M, Niţu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Quelquejay Leclere, H, Rana, P, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Singha, J, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, van der Wateren, E, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, Antoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Bak Nielsen, A. -S., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Niţu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Quelquejay Leclere, H., Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Venkatraman Krishnan, V., Verbiest, J. P. W., Wang, J., Wang, L., Wu, Z., Antoniadis, J, Arumugam, P, Arumugam, S, Babak, S, Bagchi, M, Bak Nielsen, A, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Mickaliger, M, Niţu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Quelquejay Leclere, H, Rana, P, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Singha, J, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, van der Wateren, E, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, Antoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Bak Nielsen, A. -S., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Niţu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Quelquejay Leclere, H., Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Venkatraman Krishnan, V., Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Abstract: We present the results of the search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using the second data release of the European Pulsar Timing Array (EPTA) for 25 millisecond pulsars and a combination with the first data release of the Indian Pulsar Timing Array (InPTA). A robust GWB detection is conditioned upon resolving the Hellings-Downs angular pattern in the pairwise cross-correlation of the pulsar timing residuals. Additionally, the GWB is expected to yield the same (common) spectrum of temporal correlations across pulsars, which is used as a null hypothesis in the GWB search. Such a common-spectrum process has already been observed in pulsar timing data. We analysed (i) the full 24.7-year EPTA data set, (ii) its 10.3-year subset based on modern observing systems, (iii) the combination of the full data set with the first data release of the InPTA for ten commonly timed millisecond pulsars, and (iv) the combination of the 10.3-year subset with the InPTA data. These combinations allowed us to probe the contributions of instrumental noise and interstellar propagation effects. With the full data set, we find marginal evidence for a GWB, with a Bayes factor of four and a false alarm probability of 4%. With the 10.3-year subset, we report evidence for a GWB, with a Bayes factor of 60 and a false alarm probability of about 0.1% (3significance). The addition of the InPTA data yields results that are broadly consistent with the EPTA-only data sets, with the benefit of better noise modelling. Analyses were performed with different data processing pipelines to test the consistency of the results from independent software packages. The latest EPTA data from new generation observing systems show non-negligible evidence for the GWB. At the same time, the inferred spectrum is rather uncertain and in mild tension with the common signal measured in the full data set. However, if the spectral index is fixed at 13/3, the two data sets
Published: 2023

18. The second data release from the European Pulsar Timing Array: I. The dataset and timing analysis

Author: Antoniadis, J, Babak, S, Bak Nielsen, A, Bassa, C, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Desvignes, G, Falxa, M, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Graikou, E, Grieaßmeier, J, Guillemot, L, Guo, Y, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Karuppusamy, R, Keane, E, Keith, M, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Main, R, Mickaliger, M, Niţu, I, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Quelquejay Leclere, H, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Speri, L, Spiewak, R, Stappers, B, Susarla, S, Theureau, G, Tiburzi, C, Van Der Wateren, E, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, Antoniadis J., Babak S., Bak Nielsen A. S., Bassa C. G., Berthereau A., Bonetti M., Bortolas E., Brook P. R., Burgay M., Caballero R. N., Chalumeau A., Champion D. J., Chanlaridis S., Chen S., Cognard I., Desvignes G., Falxa M., Ferdman R. D., Franchini A., Gair J. R., Goncharov B., Graikou E., Grieaßmeier J. M., Guillemot L., Guo Y. J., Hu H., Iraci F., Izquierdo-Villalba D., Jang J., Jawor J., Janssen G. H., Jessner A., Karuppusamy R., Keane E. F., Keith M. J., Kramer M., Krishnakumar M. A., Lackeos K., Lee K. J., Liu K., Liu Y., Lyne A. G., McKee J. W., Main R. A., Mickaliger M. B., Niţu I. C., Parthasarathy A., Perera B. B. P., Perrodin D., Petiteau A., Porayko N. K., Possenti A., Quelquejay Leclere H., Samajdar A., Sanidas S. A., Sesana A., Shaifullah G., Speri L., Spiewak R., Stappers B. W., Susarla S. C., Theureau G., Tiburzi C., Van Der Wateren E., Vecchio A., Venkatraman Krishnan V., Verbiest J. P. W., Wang J., Wang L., Wu Z., Antoniadis, J, Babak, S, Bak Nielsen, A, Bassa, C, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Desvignes, G, Falxa, M, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Graikou, E, Grieaßmeier, J, Guillemot, L, Guo, Y, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Karuppusamy, R, Keane, E, Keith, M, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Main, R, Mickaliger, M, Niţu, I, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Quelquejay Leclere, H, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Speri, L, Spiewak, R, Stappers, B, Susarla, S, Theureau, G, Tiburzi, C, Van Der Wateren, E, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, Antoniadis J., Babak S., Bak Nielsen A. S., Bassa C. G., Berthereau A., Bonetti M., Bortolas E., Brook P. R., Burgay M., Caballero R. N., Chalumeau A., Champion D. J., Chanlaridis S., Chen S., Cognard I., Desvignes G., Falxa M., Ferdman R. D., Franchini A., Gair J. R., Goncharov B., Graikou E., Grieaßmeier J. M., Guillemot L., Guo Y. J., Hu H., Iraci F., Izquierdo-Villalba D., Jang J., Jawor J., Janssen G. H., Jessner A., Karuppusamy R., Keane E. F., Keith M. J., Kramer M., Krishnakumar M. A., Lackeos K., Lee K. J., Liu K., Liu Y., Lyne A. G., McKee J. W., Main R. A., Mickaliger M. B., Niţu I. C., Parthasarathy A., Perera B. B. P., Perrodin D., Petiteau A., Porayko N. K., Possenti A., Quelquejay Leclere H., Samajdar A., Sanidas S. A., Sesana A., Shaifullah G., Speri L., Spiewak R., Stappers B. W., Susarla S. C., Theureau G., Tiburzi C., Van Der Wateren E., Vecchio A., Venkatraman Krishnan V., Verbiest J. P. W., Wang J., Wang L., and Wu Z.
Abstract: Pulsar timing arrays offer a probe of the low-frequency gravitational wave spectrum (1"100 nHz), which is intimately connected to a number of markers that can uniquely trace the formation and evolution of the Universe. We present the dataset and the results of the timing analysis from the second data release of the European Pulsar Timing Array (EPTA). The dataset contains high-precision pulsar timing data from 25 millisecond pulsars collected with the five largest radio telescopes in Europe, as well as the Large European Array for Pulsars. The dataset forms the foundation for the search for gravitational waves by the EPTA, presented in associated papers. We describe the dataset and present the results of the frequentist and Bayesian pulsar timing analysis for individual millisecond pulsars that have been observed over the last ~25 yr. We discuss the improvements to the individual pulsar parameter estimates, as well as new measurements of the physical properties of these pulsars and their companions. This data release extends the dataset from EPTA Data Release 1 up to the beginning of 2021, with individual pulsar datasets with timespans ranging from 14 to 25 yr. These lead to improved constraints on annual parallaxes, secular variation of the orbital period, and Shapiro delay for a number of sources. Based on these results, we derived astrophysical parameters that include distances, transverse velocities, binary pulsar masses, and annual orbital parallaxes.
Published: 2023

19. The second data release from the European Pulsar Timing Array. II. Customised pulsar noise models for spatially correlated gravitational waves

Author: Antoniadis, J, Arumugam, P, Arumugam, S, Babak, S, Bagchi, M, Nielsen, A, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Mickaliger, M, Niţu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Leclere, H, Rana, P, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Singha, J, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, van der Wateren, E, Vecchio, A, Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, Antoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Nielsen, A. -S. Bak, Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Niţu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Leclere, H. Quelquejay, Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., Wu, Z., Antoniadis, J, Arumugam, P, Arumugam, S, Babak, S, Bagchi, M, Nielsen, A, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Mickaliger, M, Niţu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Leclere, H, Rana, P, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Singha, J, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, van der Wateren, E, Vecchio, A, Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, Antoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Nielsen, A. -S. Bak, Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Niţu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Leclere, H. Quelquejay, Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Abstract: Aims. The nanohertz gravitational wave background (GWB) is expected to be an aggregate signal of an ensemble of gravitational waves emitted predominantly by a large population of coalescing supermassive black hole binaries in the centres of merging galaxies. Pulsar timing arrays (PTAs), which are ensembles of extremely stable pulsars at approximately kiloparsec distances precisely monitored for decades, are the most precise experiments capable of detecting this background. However, the subtle imprints that the GWB induces on pulsar timing data are obscured by many sources of noise that occur on various timescales. These must be carefully modelled and mitigated to increase the sensitivity to the background signal. Methods. In this paper, we present a novel technique to estimate the optimal number of frequency coefficients for modelling achromatic and chromatic noise, while selecting the preferred set of noise models to use for each pulsar. We also incorporated a new model to fit for scattering variations in the Bayesian pulsar timing package temponest. These customised noise models enable a more robust characterisation of single-pulsar noise. We developed a software package based on tempo2 to create realistic simulations of European Pulsar Timing Array (EPTA) datasets that allowed us to test the efficacy of our noise modelling algorithms. Results. Using these techniques, we present an in-depth analysis of the noise properties of 25 millisecond pulsars (MSPs) that form the second data release (DR2) of the EPTA and investigate the effect of incorporating low-frequency data from the Indian Pulsar Timing Array collaboration for a common sample of ten MSPs. We used two packages, enterprise and temponest, to estimate our noise models and compare them with those reported using EPTA DR1. We find that, while in some pulsars we can successfully disentangle chromatic from achromatic noise owing to the wider frequency coverage in DR2, in others the noise models evolve in a much
Published: 2023

20. Quality over quantity: Optimizing pulsar timing array analysis for stochastic and continuous gravitational wave signals

Author: Speri, L, Porayko, N, Falxa, M, Chen, S, Gair, J, Sesana, A, Taylor, S, Speri L., Porayko N. K., Falxa M., Chen S., Gair J. R., Sesana A., Taylor S. R., Speri, L, Porayko, N, Falxa, M, Chen, S, Gair, J, Sesana, A, Taylor, S, Speri L., Porayko N. K., Falxa M., Chen S., Gair J. R., Sesana A., and Taylor S. R.
Abstract: The search for gravitational waves using Pulsar Timing Arrays (PTAs) is a computationally expensive complex analysis that involves source-specific noise studies. As more pulsars are added to the arrays, this stage of PTA analysis will become increasingly challenging. Therefore, optimizing the number of included pulsars is crucial to reduce the computational burden of data analysis. Here, we present a suite of methods to rank pulsars for use within the scope of PTA analysis. First, we use the maximization of the signal-to-noise ratio as a proxy to select pulsars. With this method, we target the detection of stochastic and continuous gravitational wave signals. Next, we present a ranking that minimizes the coupling between spatial correlation signatures, namely monopolar, dipolar, and Hellings & Downs correlations. Finally, we also explore how to combine these two methods. We test these approaches against mock data using frequentist and Bayesian hypothesis testing. For equal-noise pulsars, we find that an optimal selection leads to an increase in the log-Bayes factor two times steeper than a random selection for the hypothesis test of a gravitational wave background versus a common uncorrelated red noise process. For the same test but for a realistic European PTA (EPTA) data set, a subset of 25 pulsars selected out of 40 can provide a log-likelihood ratio that is 89 % of the total, implying that an optimally selected subset of pulsars can yield results comparable to those obtained from the whole array. We expect these selection methods to play a crucial role in future PTA data combinations.
Published: 2023

21. The second data release from the European Pulsar Timing Array IV. Search for continuous gravitational wave signals

Author: Antoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Nielsen, A. S. Bak, Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferranti, I., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Manzini, S., Mickaliger, M. B., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Leclere, H. Quelquejay, Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, Joris, Wang, J., Wang, L., Wu, Z., AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and Laboratoire Univers et Théories (LUTH (UMR_8102))
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics of Galaxies (astro-ph.GA), [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, General Relativity and Quantum Cosmology, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present the results of a search for continuous gravitational wave signals (CGWs) in the second data release (DR2) of the European Pulsar Timing Array (EPTA) collaboration. The most significant candidate event from this search has a gravitational wave frequency of 4-5 nHz. Such a signal could be generated by a supermassive black hole binary (SMBHB) in the local Universe. We present the results of a follow-up analysis of this candidate using both Bayesian and frequentist methods. The Bayesian analysis gives a Bayes factor of 4 in favor of the presence of the CGW over a common uncorrelated noise process, while the frequentist analysis estimates the p-value of the candidate to be 1%, also assuming the presence of common uncorrelated red noise. However, comparing a model that includes both a CGW and a gravitational wave background (GWB) to a GWB only, the Bayes factor in favour of the CGW model is only 0.7. Therefore, we cannot conclusively determine the origin of the observed feature, but we cannot rule it out as a CGW source. We present results of simulations that demonstrate that data containing a weak gravitational wave background can be misinterpreted as data including a CGW and vice versa, providing two plausible explanations of the EPTA DR2 data. Further investigations combining data from all PTA collaborations will be needed to reveal the true origin of this feature., 12 figures, 15 pages, to be submitted
Published: 2023

22. Searching for continuous Gravitational Waves in the second data release of the International Pulsar Timing Array

Author: Falxa, M, Babak, S, Baker, P T, Bécsy, B, Chalumeau, A, Chen, S, Chen, Z, Cornish, N J, Guillemot, L, Hazboun, J S, Mingarelli, C M F, Parthasarathy, A, Petiteau, A, Pol, N S, Sesana, A, Spolaor, S B, Taylor, S R, Theureau, G, Vallisneri, M, Vigeland, S J, Witt, C A, Zhu, X, Antoniadis, J, Arzoumanian, Z, Bailes, M, Bhat, N D R, Blecha, L, Brazier, A, Brook, P R, Caballero, N, Cameron, A D, Casey-Clyde, J A, Champion, D, Charisi, M, Chatterjee, S, Cognard, I, Cordes, J M, Crawford, F, Cromartie, H T, Crowter, K, Dai, S, DeCesar, M E, Demorest, P B, Desvignes, G, Dolch, T, Drachler, B, Feng, Y, Ferrara, E C, Fiore, W, Fonseca, E, Garver-Daniels, N, Glaser, J, Goncharov, B, Good, D C, Griessmeier, J, Guo, Y J, Gültekin, K, Hobbs, G, Hu, H, Islo, K, Jang, J, Jennings, R J, Johnson, A D, Jones, M L, Kaczmarek, J, Kaiser, A R, Kaplan, D L, Keith, M, Kelley, L Z, Kerr, M, Key, J S, Laal, N, Lam, M T, Lamb, W G, Lazio, T J W, Liu, K, Liu, T, Luo, J, Lynch, R S, Madison, D R, Main, R, Manchester, R, McEwen, A, McKee, J, McLaughlin, M A, Ng, C, Nice, D J, Ocker, S, Olum, K D, Osłowski, S, Pennucci, T T, Perera, B B P, Perrodin, D, Porayko, N, Possenti, A, Quelquejay-Leclere, H, Ransom, S M, Ray, P S, Reardon, D J, Russell, C J, Samajdar, A, Sarkissian, J, Schult, L, Shaifullah, G, Shannon, R M, Shapiro-Albert, B J, Siemens, X, Simon, J J, Siwek, M, Smith, T L, Speri, L, Spiewak, R, Stairs, I H, Stappers, B, Stinebring, D R, Swiggum, J K, Tiburzi, C, Turner, J, Vecchio, A, Verbiest, Joris, Wahl, H, Wang, S Q, Wang, J, Wang, Jun, Wu, Ziwei, Zhang, L, Zhang, S, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire Univers et Théories (LUTH (UMR_8102)), and IPTA
Subjects: noise, data analysis method, gravitational radiation, orbit: circle, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), sensitivity, frequency: high, General Relativity and Quantum Cosmology, confidence limit, frequency: low, black hole: binary, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), pulsar
Abstract: The International Pulsar Timing Array 2nd data release is the combination ofdatasets from worldwide collaborations. In this study, we search for continuouswaves: gravitational wave signals produced by individual supermassive blackhole binaries in the local universe. We consider binaries on circular orbitsand neglect the evolution of orbital frequency over the observational span. Wefind no evidence for such signals and set sky averaged 95% upper limits ontheir amplitude h 95 . The most sensitive frequency is 10nHz with h 95 = 9.110-15 . We achieved the best upper limit to date at low and high frequencies ofthe PTA band thanks to improved effective cadence of observations. In ouranalysis, we have taken into account the recently discovered common red noiseprocess, which has an impact at low frequencies. We also find that the peculiarnoise features present in some pulsars data must be taken into account toreduce the false alarm. We show that using custom noise models is essential insearching for continuous gravitational wave signals and setting the upperlimit.
Published: 2023

23. A roadmap of gravitational wave data analysis

Author: Speri, L, Karnesis, N, Renzini, A, Gair, J, Speri L., Karnesis N., Renzini A. I., Gair J. R., Speri, L, Karnesis, N, Renzini, A, Gair, J, Speri L., Karnesis N., Renzini A. I., and Gair J. R.
Abstract: As gravitational wave detectors improve, the rate at which sources are observed is steadily increasing. Scientific exploitation of these sources relies on careful analysis of the data, and so gravitational wave data analysis is also a rapidly growing and evolving field. In this Perspective, we provide an introduction to the basic concepts of gravitational wave data analysis with reference to current pipelines. We describe some of the computational advancements and machine learning techniques that have recently been introduced to reduce the computational burden of the analysis. We conclude by discussing some of the challenges that will be encountered in the analysis of data from future detectors.
Published: 2022

24. Searching for continuous Gravitational Waves in the second data release of the International Pulsar Timing Array

Author: Falxa, M, primary, Babak, S, additional, Baker, P T, additional, Bécsy, B, additional, Chalumeau, A, additional, Chen, S, additional, Chen, Z, additional, Cornish, N J, additional, Guillemot, L, additional, Hazboun, J S, additional, Mingarelli, C M F, additional, Parthasarathy, A, additional, Petiteau, A, additional, Pol, N S, additional, Sesana, A, additional, Spolaor, S B, additional, Taylor, S R, additional, Theureau, G, additional, Vallisneri, M, additional, Vigeland, S J, additional, Witt, C A, additional, Zhu, X, additional, Antoniadis, J, additional, Arzoumanian, Z, additional, Bailes, M, additional, Bhat, N D R, additional, Blecha, L, additional, Brazier, A, additional, Brook, P R, additional, Caballero, N, additional, Cameron, A D, additional, Casey-Clyde, J A, additional, Champion, D, additional, Charisi, M, additional, Chatterjee, S, additional, Cognard, I, additional, Cordes, J M, additional, Crawford, F, additional, Cromartie, H T, additional, Crowter, K, additional, Dai, S, additional, DeCesar, M E, additional, Demorest, P B, additional, Desvignes, G, additional, Dolch, T, additional, Drachler, B, additional, Feng, Y, additional, Ferrara, E C, additional, Fiore, W, additional, Fonseca, E, additional, Garver-Daniels, N, additional, Glaser, J, additional, Goncharov, B, additional, Good, D C, additional, Griessmeier, J, additional, Guo, Y J, additional, Gültekin, K, additional, Hobbs, G, additional, Hu, H, additional, Islo, K, additional, Jang, J, additional, Jennings, R J, additional, Johnson, A D, additional, Jones, M L, additional, Kaczmarek, J, additional, Kaiser, A R, additional, Kaplan, D L, additional, Keith, M, additional, Kelley, L Z, additional, Kerr, M, additional, Key, J S, additional, Laal, N, additional, Lam, M T, additional, Lamb, W G, additional, Lazio, T J W, additional, Liu, K, additional, Liu, T, additional, Luo, J, additional, Lynch, R S, additional, Madison, D R, additional, Main, R, additional, Manchester, R, additional, McEwen, A, additional, McKee, J, additional, McLaughlin, M A, additional, Ng, C, additional, Nice, D J, additional, Ocker, S, additional, Olum, K D, additional, Osłowski, S, additional, Pennucci, T T, additional, Perera, B B P, additional, Perrodin, D, additional, Porayko, N, additional, Possenti, A, additional, Quelquejay-Leclere, H, additional, Ransom, S M, additional, Ray, P S, additional, Reardon, D J, additional, Russell, C J, additional, Samajdar, A, additional, Sarkissian, J, additional, Schult, L, additional, Shaifullah, G, additional, Shannon, R M, additional, Shapiro-Albert, B J, additional, Siemens, X, additional, Simon, J J, additional, Siwek, M, additional, Smith, T L, additional, Speri, L, additional, Spiewak, R, additional, Stairs, I H, additional, Stappers, B, additional, Stinebring, D R, additional, Swiggum, J K, additional, Tiburzi, C, additional, Turner, J, additional, Vecchio, A, additional, Verbiest, J P W, additional, Wahl, H, additional, Wang, S Q, additional, Wang, J, additional, Wu, Z, additional, Zhang, L, additional, and Zhang, S, additional
Published: 2023
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25. The second data release from the European Pulsar Timing Array: V. Implications for massive black holes, dark matter and the early Universe

Author: Antoniadis, J., Arumugam, P., Arumugam, S., Auclair, P., Babak, S., Bagchi, M., Nielsen, A. -S. Bak, Barausse, E., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Caprini, C., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Crisostomi, M., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Fastidio, F., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Gualandris, A., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Khizriev, T., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Middleton, H., Neronov, A., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Postnov, K., Leclere, H. Quelquejay, Rana, P., Pol, A. Roper, Samajdar, A., Sanidas, S. A., Semikoz, D., Sesana, A., Shaifullah, G., Singha, J., Smarra, C., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Steer, D. A., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., Truant, R. J., van der Wateren, E., Valtolina, S., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., Wu, Z., Antoniadis, J., Arumugam, P., Arumugam, S., Auclair, P., Babak, S., Bagchi, M., Nielsen, A. -S. Bak, Barausse, E., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Caprini, C., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Crisostomi, M., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Fastidio, F., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Gualandris, A., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Khizriev, T., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Middleton, H., Neronov, A., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Postnov, K., Leclere, H. Quelquejay, Rana, P., Pol, A. Roper, Samajdar, A., Sanidas, S. A., Semikoz, D., Sesana, A., Shaifullah, G., Singha, J., Smarra, C., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Steer, D. A., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., Truant, R. J., van der Wateren, E., Valtolina, S., Vecchio, A., Krishnan, V. Venkatraman, Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.
Abstract: The European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases respectively, with the correlation properties of a gravitational wave background (GWB). Such signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, cosmic strings and tensor mode generation by non-linear evolution of scalar perturbations in the early Universe; oscillations of the Galactic potential in the presence of ultra-light dark matter (ULDM). At the current stage of emerging evidence, it is impossible to discriminate among the different origins. Therefore, in this paper, we consider each process separately, and investigate the implications of the signal under the hypothesis that it is generated by that specific process. We find that the signal is consistent with a cosmic population of inspiralling SMBHBs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the SMBH-host galaxy scaling relations. If this origin is confirmed, this is the first direct evidence that SMBHBs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. As for early Universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. Other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. Finally, a ULDM origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of ULDM in our Galaxy., Comment: 31 pages, 23 figures, to be submitted to Astronomy & Astrophysics
Published: 2023

26. Noise analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search

Author: Chalumeau, A., Babak, S., Petiteau, A., Chen, S., Samajdar, A., Caballero, R.N., Theureau, G., Guillemot, L., Desvignes, G., Parthasarathy, A., Shaifullah, G., Hu, H., Wateren, M.A. van der, Antoniadis, J., Bak Nielsen, A.-S., Bassa, C.G., Berthereau, A., Burgay, M., Champion, D.J., Cognard, I., Falxa, M., Ferdman, R.D., Freire, P.C.C., Gair, J.R., Graikou, E., Guo, Y.J., Jang, J., Janssen, G.H., Karuppusamy, R., Keith, M.J., Kramer, M, Lee, K.J., Liu, X.J., Lyne, A.G., Main, R.A., McKee, J.W., Mickaliger, M.B., Perera, B.B.P., Perrodin, D., Porayko, N.K., Possenti, A., Sanidas, S.A., Sesana, A., Speri, L., Stappers, B.W., Tiburzi, C., Vecchio, A., Verbiest, J.P.W., Xu, H., Chalumeau, A., Babak, S., Petiteau, A., Chen, S., Samajdar, A., Caballero, R.N., Theureau, G., Guillemot, L., Desvignes, G., Parthasarathy, A., Shaifullah, G., Hu, H., Wateren, M.A. van der, Antoniadis, J., Bak Nielsen, A.-S., Bassa, C.G., Berthereau, A., Burgay, M., Champion, D.J., Cognard, I., Falxa, M., Ferdman, R.D., Freire, P.C.C., Gair, J.R., Graikou, E., Guo, Y.J., Jang, J., Janssen, G.H., Karuppusamy, R., Keith, M.J., Kramer, M, Lee, K.J., Liu, X.J., Lyne, A.G., Main, R.A., McKee, J.W., Mickaliger, M.B., Perera, B.B.P., Perrodin, D., Porayko, N.K., Possenti, A., Sanidas, S.A., Sesana, A., Speri, L., Stappers, B.W., Tiburzi, C., Vecchio, A., Verbiest, J.P.W., and Xu, H.
Abstract: Contains fulltext : 247353.pdf (Publisher’s version ) (Open Access)
Published: 2022

27. Workshop on Gravitational-Wave Astrophysics for Early Career Scientists

Author: Bayle, J.B., Bonga, B.P., Doneva, D., Hinderer, T., Ghosh, A., Karnesis, N., Korobko, M., Korol, V., Maggio, E., Muratore, M., Renzini, A.I., Ricciardone, A., Shah, S., Shaifullah, G., Shao, L.J., Speri, L., Tamanini, N., Weir, D., Bayle, J.B., Bonga, B.P., Doneva, D., Hinderer, T., Ghosh, A., Karnesis, N., Korobko, M., Korol, V., Maggio, E., Muratore, M., Renzini, A.I., Ricciardone, A., Shah, S., Shaifullah, G., Shao, L.J., Speri, L., Tamanini, N., and Weir, D.
Abstract: Contains fulltext : 249246.pdf (Publisher’s version ) (Closed access)
Published: 2022

28. Modeling transient resonances in extreme-mass-ratio inspirals

Author: Gupta, P., Speri, L., Bonga, B.P., Chua, A.J.K., Tanaka, T., Gupta, P., Speri, L., Bonga, B.P., Chua, A.J.K., and Tanaka, T.
Abstract: Contains fulltext : 285174.pdf (Publisher’s version ) (Open Access)
Published: 2022

29. Noise analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search

Author: Chalumeau, A, Babak, S, Petiteau, A, Chen, S, Samajdar, A, Caballero, R, Theureau, G, Guillemot, L, Desvignes, G, Parthasarathy, A, Liu, K, Shaifullah, G, Hu, H, van der Wateren, E, Antoniadis, J, Bak Nielsen, A, Bassa, C, Berthereau, A, Burgay, M, Champion, D, Cognard, I, Falxa, M, Ferdman, R, Freire, P, Gair, J, Graikou, E, Guo, Y, Jang, J, Janssen, G, Karuppusamy, R, Keith, M, Kramer, M, Lee, K, Liu, X, Lyne, A, Main, R, Mckee, J, Mickaliger, M, Perera, B, Perrodin, D, Porayko, N, Possenti, A, Sanidas, S, Sesana, A, Speri, L, Stappers, B, Tiburzi, C, Vecchio, A, Verbiest, J, Wang, J, Wang, L, Xu, H, Caballero, RN, Bak Nielsen, A-S, Bassa, CG, Champion, DJ, Ferdman, RD, Freire, PCC, Gair, JR, Guo, YJ, Janssen, GH, Keith, MJ, Lee, KJ, Liu, XJ, Lyne, AG, Main, RA, McKee, JW, Mickaliger, MB, Perera, BBP, Porayko, NK, Sanidas, SA, Stappers, BW, Verbiest, JPW, Chalumeau, A, Babak, S, Petiteau, A, Chen, S, Samajdar, A, Caballero, R, Theureau, G, Guillemot, L, Desvignes, G, Parthasarathy, A, Liu, K, Shaifullah, G, Hu, H, van der Wateren, E, Antoniadis, J, Bak Nielsen, A, Bassa, C, Berthereau, A, Burgay, M, Champion, D, Cognard, I, Falxa, M, Ferdman, R, Freire, P, Gair, J, Graikou, E, Guo, Y, Jang, J, Janssen, G, Karuppusamy, R, Keith, M, Kramer, M, Lee, K, Liu, X, Lyne, A, Main, R, Mckee, J, Mickaliger, M, Perera, B, Perrodin, D, Porayko, N, Possenti, A, Sanidas, S, Sesana, A, Speri, L, Stappers, B, Tiburzi, C, Vecchio, A, Verbiest, J, Wang, J, Wang, L, Xu, H, Caballero, RN, Bak Nielsen, A-S, Bassa, CG, Champion, DJ, Ferdman, RD, Freire, PCC, Gair, JR, Guo, YJ, Janssen, GH, Keith, MJ, Lee, KJ, Liu, XJ, Lyne, AG, Main, RA, McKee, JW, Mickaliger, MB, Perera, BBP, Porayko, NK, Sanidas, SA, Stappers, BW, and Verbiest, JPW
Abstract: The European Pulsar Timing Array (EPTA) collaboration has recently released an extended data set for six pulsars (DR2) and reported evidence for a common red noise signal. Here we present a noise analysis for each of the six pulsars. We consider several types of noise: (i) radio frequency independent, 'achromatic', and time-correlated red noise; (ii) variations of dispersion measure and scattering; (iii) system and band noise; and (iv) deterministic signals (other than gravitational waves) that could be present in the PTA data. We perform Bayesian model selection to find the optimal combination of noise components for each pulsar. Using these custom models we revisit the presence of the common uncorrelated red noise signal previously reported in the EPTA DR2 and show that the data still supports it with a high statistical significance. Next, we confirm that there is no preference for or against the Hellings-Downs spatial correlations expected for the stochastic gravitational-wave background. The main conclusion of the EPTA DR2 paper remains unchanged despite a very significant change in the noise model of each pulsar. However, modelling the noise is essential for the robust detection of gravitational waves and its impact could be significant when analysing the next EPTA data release, which will include a larger number of pulsars and more precise measurements.
Published: 2022

30. Workshop on Gravitational-Wave Astrophysics for Early Career Scientists

Author: Bayle, J, Bonga, B, Doneva, D, Hinderer, T, Ghosh, A, Karnesis, N, Korobko, M, Korol, V, Maggio, E, Muratore, M, Renzini, A, Ricciardone, A, Shah, S, Shaifullah, G, Shao, L, Speri, L, Tamanini, N, Weir, D, Bayle, J-B, Renzini, AI, Bayle, J, Bonga, B, Doneva, D, Hinderer, T, Ghosh, A, Karnesis, N, Korobko, M, Korol, V, Maggio, E, Muratore, M, Renzini, A, Ricciardone, A, Shah, S, Shaifullah, G, Shao, L, Speri, L, Tamanini, N, Weir, D, Bayle, J-B, and Renzini, AI
Abstract: Gravitational-wave science is rapidly growing in maturity as a research area; in May 2021 the next generation of gravitational-wave scientists gathered together to create a vision of the future of the field.
Published: 2022

31. The International Pulsar Timing Array second data release: Search for an isotropic gravitational wave background

Author: Antoniadis, J, primary, Arzoumanian, Z, additional, Babak, S, additional, Bailes, M, additional, Bak Nielsen, A-S, additional, Baker, P T, additional, Bassa, C G, additional, Bécsy, B, additional, Berthereau, A, additional, Bonetti, M, additional, Brazier, A, additional, Brook, P R, additional, Burgay, M, additional, Burke-Spolaor, S, additional, Caballero, R N, additional, Casey-Clyde, J A, additional, Chalumeau, A, additional, Champion, D J, additional, Charisi, M, additional, Chatterjee, S, additional, Chen, S, additional, Cognard, I, additional, Cordes, J M, additional, Cornish, N J, additional, Crawford, F, additional, Cromartie, H T, additional, Crowter, K, additional, Dai, S, additional, DeCesar, M E, additional, Demorest, P B, additional, Desvignes, G, additional, Dolch, T, additional, Drachler, B, additional, Falxa, M, additional, Ferrara, E C, additional, Fiore, W, additional, Fonseca, E, additional, Gair, J R, additional, Garver-Daniels, N, additional, Goncharov, B, additional, Good, D C, additional, Graikou, E, additional, Guillemot, L, additional, Guo, Y J, additional, Hazboun, J S, additional, Hobbs, G, additional, Hu, H, additional, Islo, K, additional, Janssen, G H, additional, Jennings, R J, additional, Johnson, A D, additional, Jones, M L, additional, Kaiser, A R, additional, Kaplan, D L, additional, Karuppusamy, R, additional, Keith, M J, additional, Kelley, L Z, additional, Kerr, M, additional, Key, J S, additional, Kramer, M, additional, Lam, M T, additional, Lamb, W G, additional, Lazio, T J W, additional, Lee, K J, additional, Lentati, L, additional, Liu, K, additional, Luo, J, additional, Lynch, R S, additional, Lyne, A G, additional, Madison, D R, additional, Main, R A, additional, Manchester, R N, additional, McEwen, A, additional, McKee, J W, additional, McLaughlin, M A, additional, Mickaliger, M B, additional, Mingarelli, C M F, additional, Ng, C, additional, Nice, D J, additional, Osłowski, S, additional, Parthasarathy, A, additional, Pennucci, T T, additional, Perera, B B P, additional, Perrodin, D, additional, Petiteau, A, additional, Pol, N S, additional, Porayko, N K, additional, Possenti, A, additional, Ransom, S M, additional, Ray, P S, additional, Reardon, D J, additional, Russell, C J, additional, Samajdar, A, additional, Sampson, L M, additional, Sanidas, S, additional, Sarkissian, J M, additional, Schmitz, K, additional, Schult, L, additional, Sesana, A, additional, Shaifullah, G, additional, Shannon, R M, additional, Shapiro-Albert, B J, additional, Siemens, X, additional, Simon, J, additional, Smith, T L, additional, Speri, L, additional, Spiewak, R, additional, Stairs, I H, additional, Stappers, B W, additional, Stinebring, D R, additional, Swiggum, J K, additional, Taylor, S R, additional, Theureau, G, additional, Tiburzi, C, additional, Vallisneri, M, additional, van der Wateren, E, additional, Vecchio, A, additional, Verbiest, J P W, additional, Vigeland, S J, additional, Wahl, H, additional, Wang, J B, additional, Wang, J, additional, Wang, L, additional, Witt, C A, additional, Zhang, S, additional, and Zhu, X J, additional
Published: 2022
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32. Noise analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search

Author: Chalumeau, A, primary, Babak, S, additional, Petiteau, A, additional, Chen, S, additional, Samajdar, A, additional, Caballero, R N, additional, Theureau, G, additional, Guillemot, L, additional, Desvignes, G, additional, Parthasarathy, A, additional, Liu, K, additional, Shaifullah, G, additional, Hu, H, additional, van der Wateren, E, additional, Antoniadis, J, additional, Bak Nielsen, A-S, additional, Bassa, C G, additional, Berthereau, A, additional, Burgay, M, additional, Champion, D J, additional, Cognard, I, additional, Falxa, M, additional, Ferdman, R D, additional, Freire, P C C, additional, Gair, J R, additional, Graikou, E, additional, Guo, Y J, additional, Jang, J, additional, Janssen, G H, additional, Karuppusamy, R, additional, Keith, M J, additional, Kramer, M, additional, Lee, K J, additional, Liu, X J, additional, Lyne, A G, additional, Main, R A, additional, McKee, J W, additional, Mickaliger, M B, additional, Perera, B B P, additional, Perrodin, D, additional, Porayko, N K, additional, Possenti, A, additional, Sanidas, S A, additional, Sesana, A, additional, Speri, L, additional, Stappers, B W, additional, Tiburzi, C, additional, Vecchio, A, additional, Verbiest, J P W, additional, Wang, J, additional, Wang, L, additional, and Xu, H, additional
Published: 2021
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33. Common-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: inferences in the stochastic gravitational-wave background search

Author: Chen, S, primary, Caballero, R N, additional, Guo, Y J, additional, Chalumeau, A, additional, Liu, K, additional, Shaifullah, G, additional, Lee, K J, additional, Babak, S, additional, Desvignes, G, additional, Parthasarathy, A, additional, Hu, H, additional, van der Wateren, E, additional, Antoniadis, J, additional, Bak Nielsen, A-S, additional, Bassa, C G, additional, Berthereau, A, additional, Burgay, M, additional, Champion, D J, additional, Cognard, I, additional, Falxa, M, additional, Ferdman, R D, additional, Freire, P C C, additional, Gair, J R, additional, Graikou, E, additional, Guillemot, L, additional, Jang, J, additional, Janssen, G H, additional, Karuppusamy, R, additional, Keith, M J, additional, Kramer, M, additional, Liu, X J, additional, Lyne, A G, additional, Main, R A, additional, McKee, J W, additional, Mickaliger, M B, additional, Perera, B B P, additional, Perrodin, D, additional, Petiteau, A, additional, Porayko, N K, additional, Possenti, A, additional, Samajdar, A, additional, Sanidas, S A, additional, Sesana, A, additional, Speri, L, additional, Stappers, B W, additional, Theureau, G, additional, Tiburzi, C, additional, Vecchio, A, additional, Verbiest, J P W, additional, Wang, J, additional, Wang, L, additional, and Xu, H, additional
Published: 2021
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34. Behaviour of brick-NHL render systems in presence of NaCl solution

Author: Speri, L., LAURA FALCHI, Balliana, E., Zuena, M., and Zendri, E.
Subjects: brick, lcsh:Fine Arts, salt transport, lcsh:NX1-820, double-layer systems, rising damp, lcsh:N, lcsh:Arts in general, render, Render, double-layer systems, salt transport, brick, rising damp, Settore CHIM/12 - Chimica dell'Ambiente e dei Beni Culturali
Abstract: Double-layer renders were formulated for ensuring salt migration, ancient masonries conservation and environmental sustainability. Thus, natural hydraulic lime as binder and recycled aggregates from render wastes were selected. The properties were adjusted by adding an air-entraining agent in the inner layer and different percentages of water-repellent admixtures in the outer layer. The systems were applied on bricks and subjected to rising damp-evaporation cycles, for investigating their behaviour and properties in respect to NaCl migration. Mono-material prismatic render specimens were also studied. Water vapour permeability, capillary absorption, drying behaviour, compressive strength, mechanical resistance, conductivity and porosity of each formulation were evaluated. Good durability was observed whenever the render layers had different microstructure, either there was salts deposition within the lower layer,or if there was tefflorescences formation. If the layers had similar structure, deposition of salt at the brick-render interface occurred causing damages to the substrate.
Published: 2017

35. DEVELOPMENT OF COMPATIBLE AND SUSTAINABLE RENDER SYSTEMS FOR SALT-CONTAMINATED BRICK MASONRIES

Author: Speri, L., Falchi, Laura, Balliana, Eleonora, Zuena, Martina, and Zendri, Elisabetta
Subjects: Settore CHIM/12 - Chimica dell'Ambiente e dei Beni Culturali
Published: 2016

36. 'Latte Materno: il più naturale che c'è'. Un progetto Nazionale di promozione dell'allattamento al seno in Ospedale

Author: Farchi, S, Asole, S, Privitera, M, Chapin, E, Speri, L, Bettinelli, M, Benedetti, E, Murè, R, Di Lallo, D, Guasticchi, G., FIRENZE, Alberto, Farchi, S, Asole, S, Privitera, M, Chapin, E, Speri, L, Bettinelli, M, Benedetti, E, Murè, R, Firenze, A, Di Lallo, D, and Guasticchi, G.
Subjects: Seno, Allattamento, Ospedale
Published: 2012

37. Prevalence, exclusivity, and duration of breast-feeding in Lombardia

Author: Macchi, L., Pirola, M. E., Monaco, G., Pavan, A., Bettinelli, M. E., Zapparoli, B., Agosti, M., Bonati, M., Banderali, G., Colombo, A., Giovannini, M., Mosca, F., Narducci, M., Nino, M. L., Rondini, G., Speri, L., Riva, E., and Fortinguerra, F.
Published: 2008

38. Prevalenza, esclusività e durata dell'allattamento al seno in Lombardia

Author: Macchi, L., Pirola, M. E., Monaco, G., Pavan, A., Bettinelli, M. E., Zapparoli, B., Agosti, M., Bonati, M., Banderali, G., Colombo, A., Giovannini, M., Mosca, F., Narducci, M., Nino, M. L., Rondini, G., Speri, L., Riva, E., and Fortinguerra, Filomena
Subjects: Medicine (all)
Published: 2008

39. Prevalence, exclusivity, and duration of breast-feeding in Lombardia,Prevalenza, esclusività e durata dell'allattamento al seno in Lombardia

Author: Macchi, L., Pirola, M. E., Monaco, G., Pavan, A., Bettinelli, M. E., Zapparoli, B., Agosti, M., Bonati, M., Banderali, G., Colombo, A., Giovannini, M., FABIO MOSCA, Narducci, M., Nino, M. L., Rondini, G., Speri, L., Riva, E., and Fortinguerra, F.

40. The second data release from the European Pulsar Timing Array: V. Implications for massive black holes, dark matter and the early Universe

Author: Antoniadis, J, Arumugam, P, Arumugam, S, Auclair, P, Babak, S, Bagchi, M, Bak Nielsen, A, Barausse, E, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Caprini, C, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Crisostomi, M, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Fastidio, F, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Gualandris, A, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Khizriev, T, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Mickaliger, M, Middleton, H, Neronov, A, Nitu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Postnov, K, Quelquejay Leclere, H, Rana, P, Roper Pol, A, Samajdar, A, Sanidas, S, Semikoz, D, Sesana, A, Shaifullah, G, Singha, J, Smarra, C, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Steer, D, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, Truant, R, van der Wateren, E, Valtolina, S, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, J. Antoniadis, P. Arumugam, S. Arumugam, P. Auclair, S. Babak, M. Bagchi, A. -S. Bak Nielsen, E. Barausse, C. G. Bassa, A. Bathula, A. Berthereau, M. Bonetti, E. Bortolas, P. R. Brook, M. Burgay, R. N. Caballero, C. Caprini, A. Chalumeau, D. J. Champion, S. Chanlaridis, S. Chen, I. Cognard, M. Crisostomi, S. Dandapat, D. Deb, S. Desai, G. Desvignes, N. Dhanda-Batra, C. Dwivedi, M. Falxa, F. Fastidio, R. D. Ferdman, A. Franchini, J. R. Gair, B. Goncharov, A. Gopakumar, E. Graikou, J. -M. Grießmeier, A. Gualandris, L. Guillemot, Y. J. Guo, Y. Gupta, S. Hisano, H. Hu, F. Iraci, D. Izquierdo-Villalba, J. Jang, J. Jawor, G. H. Janssen, A. Jessner, B. C. Joshi, F. Kareem, R. Karuppusamy, E. F. Keane, M. J. Keith, D. Kharbanda, T. Khizriev, T. Kikunaga, N. Kolhe, M. Kramer, M. A. Krishnakumar, K. Lackeos, K. J. Lee, K. Liu, Y. Liu, A. G. Lyne, J. W. McKee, Y. Maan, R. A. Main, M. B. Mickaliger, H. Middleton, A. Neronov, I. C. Nitu, K. Nobleson, A. K. Paladi, A. Parthasarathy, B. B. P. Perera, D. Perrodin, A. Petiteau, N. K. Porayko, A. Possenti, T. Prabu, K. Postnov, H. Quelquejay Leclere, P. Rana, A. Roper Pol, A. Samajdar, S. A. Sanidas, D. Semikoz, A. Sesana, G. Shaifullah, J. Singha, C. Smarra, L. Speri, R. Spiewak, A. Srivastava, B. W. Stappers, D. A. Steer, M. Surnis, S. C. Susarla, A. Susobhanan, K. Takahashi, P. Tarafdar, G. Theureau, C. Tiburzi, R. J. Truant, E. van der Wateren, S. Valtolina, A. Vecchio, V. Venkatraman Krishnan, J. P. W. Verbiest, J. Wang, L. Wang, Z. Wu, Antoniadis, J, Arumugam, P, Arumugam, S, Auclair, P, Babak, S, Bagchi, M, Bak Nielsen, A, Barausse, E, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Caprini, C, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Crisostomi, M, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Fastidio, F, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Gualandris, A, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Khizriev, T, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Mickaliger, M, Middleton, H, Neronov, A, Nitu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Postnov, K, Quelquejay Leclere, H, Rana, P, Roper Pol, A, Samajdar, A, Sanidas, S, Semikoz, D, Sesana, A, Shaifullah, G, Singha, J, Smarra, C, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Steer, D, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, Truant, R, van der Wateren, E, Valtolina, S, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, J. Antoniadis, P. Arumugam, S. Arumugam, P. Auclair, S. Babak, M. Bagchi, A. -S. Bak Nielsen, E. Barausse, C. G. Bassa, A. Bathula, A. Berthereau, M. Bonetti, E. Bortolas, P. R. Brook, M. Burgay, R. N. Caballero, C. Caprini, A. Chalumeau, D. J. Champion, S. Chanlaridis, S. Chen, I. Cognard, M. Crisostomi, S. Dandapat, D. Deb, S. Desai, G. Desvignes, N. Dhanda-Batra, C. Dwivedi, M. Falxa, F. Fastidio, R. D. Ferdman, A. Franchini, J. R. Gair, B. Goncharov, A. Gopakumar, E. Graikou, J. -M. Grießmeier, A. Gualandris, L. Guillemot, Y. J. Guo, Y. Gupta, S. Hisano, H. Hu, F. Iraci, D. Izquierdo-Villalba, J. Jang, J. Jawor, G. H. Janssen, A. Jessner, B. C. Joshi, F. Kareem, R. Karuppusamy, E. F. Keane, M. J. Keith, D. Kharbanda, T. Khizriev, T. Kikunaga, N. Kolhe, M. Kramer, M. A. Krishnakumar, K. Lackeos, K. J. Lee, K. Liu, Y. Liu, A. G. Lyne, J. W. McKee, Y. Maan, R. A. Main, M. B. Mickaliger, H. Middleton, A. Neronov, I. C. Nitu, K. Nobleson, A. K. Paladi, A. Parthasarathy, B. B. P. Perera, D. Perrodin, A. Petiteau, N. K. Porayko, A. Possenti, T. Prabu, K. Postnov, H. Quelquejay Leclere, P. Rana, A. Roper Pol, A. Samajdar, S. A. Sanidas, D. Semikoz, A. Sesana, G. Shaifullah, J. Singha, C. Smarra, L. Speri, R. Spiewak, A. Srivastava, B. W. Stappers, D. A. Steer, M. Surnis, S. C. Susarla, A. Susobhanan, K. Takahashi, P. Tarafdar, G. Theureau, C. Tiburzi, R. J. Truant, E. van der Wateren, S. Valtolina, A. Vecchio, V. Venkatraman Krishnan, J. P. W. Verbiest, J. Wang, L. Wang, and Z. Wu
Abstract: The European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases respectively, with the correlation properties of a gravitational wave background (GWB). Such signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, cosmic strings and tensor mode generation by non-linear evolution of scalar perturbations in the early Universe; oscillations of the Galactic potential in the presence of ultra-light dark matter (ULDM). At the current stage of emerging evidence, it is impossible to discriminate among the different origins. Therefore, in this paper, we consider each process separately, and investigate the implications of the signal under the hypothesis that it is generated by that specific process. We find that the signal is consistent with a cosmic population of inspiralling SMBHBs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the SMBH-host galaxy scaling relations. If this origin is confirmed, this is the first direct evidence that SMBHBs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. As for early Universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. Other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. Finally, a ULDM origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of ULDM in our Galaxy.

41. The second data release from the European Pulsar Timing Array IV. Search for continuous gravitational wave signals

Author: Antoniadis, J, Arumugam, P, Arumugam, S, Babak, S, Bagchi, M, Bak Nielsen, A, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Ferranti, I, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Manzini, S, Mickaliger, M, Nitu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Quelquejay Leclere, H, Rana, P, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Singha, J, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, van der Wateren, E, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, J. Antoniadis, P. Arumugam, S. Arumugam, S. Babak, M. Bagchi, A. S. Bak Nielsen, C. G. Bassa, A. Bathula, A. Berthereau, M. Bonetti, E. Bortolas, P. R. Brook, M. Burgay, R. N. Caballero, A. Chalumeau, D. J. Champion, S. Chanlaridis, S. Chen, I. Cognard, S. Dandapat, D. Deb, S. Desai, G. Desvignes, N. Dhanda-Batra, C. Dwivedi, M. Falxa, I. Ferranti, R. D. Ferdman, A. Franchini, J. R. Gair, B. Goncharov, A. Gopakumar, E. Graikou, J. M. Grießmeier, L. Guillemot, Y. J. Guo, Y. Gupta, S. Hisano, H. Hu, F. Iraci, D. Izquierdo-Villalba, J. Jang, J. Jawor, G. H. Janssen, A. Jessner, B. C. Joshi, F. Kareem, R. Karuppusamy, E. F. Keane, M. J. Keith, D. Kharbanda, T. Kikunaga, N. Kolhe, M. Kramer, M. A. Krishnakumar, K. Lackeos, K. J. Lee, K. Liu, Y. Liu, A. G. Lyne, J. W. McKee, Y. Maan, R. A. Main, S. Manzini, M. B. Mickaliger, I. C. Nitu, K. Nobleson, A. K. Paladi, A. Parthasarathy, B. B. P. Perera, D. Perrodin, A. Petiteau, N. K. Porayko, A. Possenti, T. Prabu, H. Quelquejay Leclere, P. Rana, A. Samajdar, S. A. Sanidas, A. Sesana, G. Shaifullah, J. Singha, L. Speri, R. Spiewak, A. Srivastava, B. W. Stappers, M. Surnis, S. C. Susarla, A. Susobhanan, K. Takahashi, P. Tarafdar, G. Theureau, C. Tiburzi, E. van der Wateren, A. Vecchio, V. Venkatraman Krishnan, J. P. W. Verbiest, J. Wang, L. Wang, Z. Wu, Antoniadis, J, Arumugam, P, Arumugam, S, Babak, S, Bagchi, M, Bak Nielsen, A, Bassa, C, Bathula, A, Berthereau, A, Bonetti, M, Bortolas, E, Brook, P, Burgay, M, Caballero, R, Chalumeau, A, Champion, D, Chanlaridis, S, Chen, S, Cognard, I, Dandapat, S, Deb, D, Desai, S, Desvignes, G, Dhanda-Batra, N, Dwivedi, C, Falxa, M, Ferranti, I, Ferdman, R, Franchini, A, Gair, J, Goncharov, B, Gopakumar, A, Graikou, E, Grießmeier, J, Guillemot, L, Guo, Y, Gupta, Y, Hisano, S, Hu, H, Iraci, F, Izquierdo-Villalba, D, Jang, J, Jawor, J, Janssen, G, Jessner, A, Joshi, B, Kareem, F, Karuppusamy, R, Keane, E, Keith, M, Kharbanda, D, Kikunaga, T, Kolhe, N, Kramer, M, Krishnakumar, M, Lackeos, K, Lee, K, Liu, K, Liu, Y, Lyne, A, Mckee, J, Maan, Y, Main, R, Manzini, S, Mickaliger, M, Nitu, I, Nobleson, K, Paladi, A, Parthasarathy, A, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Prabu, T, Quelquejay Leclere, H, Rana, P, Samajdar, A, Sanidas, S, Sesana, A, Shaifullah, G, Singha, J, Speri, L, Spiewak, R, Srivastava, A, Stappers, B, Surnis, M, Susarla, S, Susobhanan, A, Takahashi, K, Tarafdar, P, Theureau, G, Tiburzi, C, van der Wateren, E, Vecchio, A, Venkatraman Krishnan, V, Verbiest, J, Wang, J, Wang, L, Wu, Z, J. Antoniadis, P. Arumugam, S. Arumugam, S. Babak, M. Bagchi, A. S. Bak Nielsen, C. G. Bassa, A. Bathula, A. Berthereau, M. Bonetti, E. Bortolas, P. R. Brook, M. Burgay, R. N. Caballero, A. Chalumeau, D. J. Champion, S. Chanlaridis, S. Chen, I. Cognard, S. Dandapat, D. Deb, S. Desai, G. Desvignes, N. Dhanda-Batra, C. Dwivedi, M. Falxa, I. Ferranti, R. D. Ferdman, A. Franchini, J. R. Gair, B. Goncharov, A. Gopakumar, E. Graikou, J. M. Grießmeier, L. Guillemot, Y. J. Guo, Y. Gupta, S. Hisano, H. Hu, F. Iraci, D. Izquierdo-Villalba, J. Jang, J. Jawor, G. H. Janssen, A. Jessner, B. C. Joshi, F. Kareem, R. Karuppusamy, E. F. Keane, M. J. Keith, D. Kharbanda, T. Kikunaga, N. Kolhe, M. Kramer, M. A. Krishnakumar, K. Lackeos, K. J. Lee, K. Liu, Y. Liu, A. G. Lyne, J. W. McKee, Y. Maan, R. A. Main, S. Manzini, M. B. Mickaliger, I. C. Nitu, K. Nobleson, A. K. Paladi, A. Parthasarathy, B. B. P. Perera, D. Perrodin, A. Petiteau, N. K. Porayko, A. Possenti, T. Prabu, H. Quelquejay Leclere, P. Rana, A. Samajdar, S. A. Sanidas, A. Sesana, G. Shaifullah, J. Singha, L. Speri, R. Spiewak, A. Srivastava, B. W. Stappers, M. Surnis, S. C. Susarla, A. Susobhanan, K. Takahashi, P. Tarafdar, G. Theureau, C. Tiburzi, E. van der Wateren, A. Vecchio, V. Venkatraman Krishnan, J. P. W. Verbiest, J. Wang, L. Wang, and Z. Wu
Abstract: We present the results of a search for continuous gravitational wave signals (CGWs) in the second data release (DR2) of the European Pulsar Timing Array (EPTA) collaboration. The most significant candidate event from this search has a gravitational wave frequency of 4-5 nHz. Such a signal could be generated by a supermassive black hole binary (SMBHB) in the local Universe. We present the results of a follow-up analysis of this candidate using both Bayesian and frequentist methods. The Bayesian analysis gives a Bayes factor of 4 in favor of the presence of the CGW over a common uncorrelated noise process, while the frequentist analysis estimates the p-value of the candidate to be 1%, also assuming the presence of common uncorrelated red noise. However, comparing a model that includes both a CGW and a gravitational wave background (GWB) to a GWB only, the Bayes factor in favour of the CGW model is only 0.7. Therefore, we cannot conclusively determine the origin of the observed feature, but we cannot rule it out as a CGW source. We present results of simulations that demonstrate that data containing a weak gravitational wave background can be misinterpreted as data including a CGW and vice versa, providing two plausible explanations of the EPTA DR2 data. Further investigations combining data from all PTA collaborations will be needed to reveal the true origin of this feature.

42. The International Pulsar Timing Array second data release: Search for an isotropic gravitational wave background

Author: J Antoniadis, Z Arzoumanian, S Babak, M Bailes, A-S Bak Nielsen, P T Baker, C G Bassa, B Bécsy, A Berthereau, M Bonetti, A Brazier, P R Brook, M Burgay, S Burke-Spolaor, R N Caballero, J A Casey-Clyde, A Chalumeau, D J Champion, M Charisi, S Chatterjee, S Chen, I Cognard, J M Cordes, N J Cornish, F Crawford, H T Cromartie, K Crowter, S Dai, M E DeCesar, P B Demorest, G Desvignes, T Dolch, B Drachler, M Falxa, E C Ferrara, W Fiore, E Fonseca, J R Gair, N Garver-Daniels, B Goncharov, D C Good, E Graikou, L Guillemot, Y J Guo, J S Hazboun, G Hobbs, H Hu, K Islo, G H Janssen, R J Jennings, A D Johnson, M L Jones, A R Kaiser, D L Kaplan, R Karuppusamy, M J Keith, L Z Kelley, M Kerr, J S Key, M Kramer, M T Lam, W G Lamb, T J W Lazio, K J Lee, L Lentati, K Liu, J Luo, R S Lynch, A G Lyne, D R Madison, R A Main, R N Manchester, A McEwen, J W McKee, M A McLaughlin, M B Mickaliger, C M F Mingarelli, C Ng, D J Nice, S Osłowski, A Parthasarathy, T T Pennucci, B B P Perera, D Perrodin, A Petiteau, N S Pol, N K Porayko, A Possenti, S M Ransom, P S Ray, D J Reardon, C J Russell, A Samajdar, L M Sampson, S Sanidas, J M Sarkissian, K Schmitz, L Schult, A Sesana, G Shaifullah, R M Shannon, B J Shapiro-Albert, X Siemens, J Simon, T L Smith, L Speri, R Spiewak, I H Stairs, B W Stappers, D R Stinebring, J K Swiggum, S R Taylor, G Theureau, C Tiburzi, M Vallisneri, E van der Wateren, A Vecchio, J P W Verbiest, S J Vigeland, H Wahl, J B Wang, J Wang, L Wang, C A Witt, S Zhang, X J Zhu, Antoniadis, J, Arzoumanian, Z, Babak, S, Bailes, M, Bak Nielsen, A, Baker, P, Bassa, C, Becsy, B, Berthereau, A, Bonetti, M, Brazier, A, Brook, P, Burgay, M, Burke-Spolaor, S, Caballero, R, Casey-Clyde, J, Chalumeau, A, Champion, D, Charisi, M, Chatterjee, S, Chen, S, Cognard, I, Cordes, J, Cornish, N, Crawford, F, Cromartie, H, Crowter, K, Dai, S, Decesar, M, Demorest, P, Desvignes, G, Dolch, T, Drachler, B, Falxa, M, Ferrara, E, Fiore, W, Fonseca, E, Gair, J, Garver-Daniels, N, Goncharov, B, Good, D, Graikou, E, Guillemot, L, Guo, Y, Hazboun, J, Hobbs, G, Hu, H, Islo, K, Janssen, G, Jennings, R, Johnson, A, Jones, M, Kaiser, A, Kaplan, D, Karuppusamy, R, Keith, M, Kelley, L, Kerr, M, Key, J, Kramer, M, Lam, M, Lamb, W, Lazio, T, Lee, K, Lentati, L, Liu, K, Luo, J, Lynch, R, Lyne, A, Madison, D, Main, R, Manchester, R, Mcewen, A, Mckee, J, Mclaughlin, M, Mickaliger, M, Mingarelli, C, Ng, C, Nice, D, Oslowski, S, Parthasarathy, A, Pennucci, T, Perera, B, Perrodin, D, Petiteau, A, Pol, N, Porayko, N, Possenti, A, Ransom, S, Ray, P, Reardon, D, Russell, C, Samajdar, A, Sampson, L, Sanidas, S, Sarkissian, J, Schmitz, K, Schult, L, Sesana, A, Shaifullah, G, Shannon, R, Shapiro-Albert, B, Siemens, X, Simon, J, Smith, T, Speri, L, Spiewak, R, Stairs, I, Stappers, B, Stinebring, D, Swiggum, J, Taylor, S, Theureau, G, Tiburzi, C, Vallisneri, M, Van Der Wateren, E, Vecchio, A, Verbiest, J, Vigeland, S, Wahl, H, Wang, J, Wang, L, Witt, C, Zhang, S, Zhu, X, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire Univers et Théories (LUTH (UMR_8102)), ANR-18-CE31-0015,PTA-France,Recherche d'ondes gravitationnelles avec un réseau de pulsars en France(2018), ITA, USA, GBR, FRA, DEU, AUS, CAN, GRC, NLD, CHN, RUS, CHE, and HUN
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, [PHYS]Physics [physics], Astrophysics and Astronomy, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, methods: Data analysi, pulsars: General, methods: data analysis, gravitational waves, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), gravitational wave, astro-ph.IM
Abstract: We searched for an isotropic stochastic gravitational wave background in the second data release of the International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns in North America, Europe, and Australia. In our reference search for a power law strain spectrum of the form $h_c = A(f/1\,\mathrm{yr}^{-1})^{\alpha}$, we found strong evidence for a spectrally-similar low-frequency stochastic process of amplitude $A = 3.8^{+6.3}_{-2.5}\times10^{-15}$ and spectral index $\alpha = -0.5 \pm 0.5$, where the uncertainties represent 95\% credible regions, using information from the auto- and cross-correlation terms between the pulsars in the array. For a spectral index of $\alpha = -2/3$, as expected from a population of inspiralling supermassive black hole binaries, the recovered amplitude is $A = 2.8^{+1.2}_{-0.8}\times10^{-15}$. Nonetheless, no significant evidence of the Hellings-Downs correlations that would indicate a gravitational-wave origin was found. We also analyzed the constituent data from the individual pulsar timing arrays in a consistent way, and clearly demonstrate that the combined international data set is more sensitive. Furthermore, we demonstrate that this combined data set produces comparable constraints to recent single-array data sets which have more data than the constituent parts of the combination. Future international data releases will deliver increased sensitivity to gravitational wave radiation, and significantly increase the detection probability., 17 pages, 12 figures, accepted in MNRAS
Published: 2022

43. Workshop on Gravitational-Wave Astrophysics for Early Career Scientists

Author: Jean-Baptiste Bayle, Béatrice Bonga, Daniela Doneva, Tanja Hinderer, Archisman Ghosh, Nikolaos Karnesis, Mikhail Korobko, Valeriya Korol, Elisa Maggio, Martina Muratore, Arianna I. Renzini, Angelo Ricciardone, Sweta Shah, Golam Shaifullah, Lijing Shao, Lorenzo Speri, Nicola Tamanini, David Weir, Bayle, J, Bonga, B, Doneva, D, Hinderer, T, Ghosh, A, Karnesis, N, Korobko, M, Korol, V, Maggio, E, Muratore, M, Renzini, A, Ricciardone, A, Shah, S, Shaifullah, G, Shao, L, Speri, L, Tamanini, N, and Weir, D
Subjects: Astrophysic, Cosmology and Nongalactic Astrophysic, Instrumentation and Methods for Astrophysic, Astronomy and Astrophysics, High Energy Physics, General Relativity and Quantum Cosmology
Abstract: Gravitational wave science is a dynamical, fast-expanding research field founded on results, tools and methodologies drawn from different research areas and communities. Early career scientists entering this field must learn and combine knowledge and techniques from a range of disciplines. The Workshop on Gravitational-Wave Astrophysics for Early Career Scientists (GWAECS), held virtually in May 2021, planted the seeds of an interdisciplinary, well-connected and all-inclusive community of early career scientists working on gravitational waves, able to exchange relevant information and ideas, build a healthy professional and international environment, share and learn valuable skills, and ensure that ongoing research efforts are perpetuated and expanded in order to attain the main scientific goals envisioned by the whole community. GWAECS was the first event unifying early career scientists belonging to different communities, historically associated with different large-scale gravitational wave experiments. It provided a broad perspective on the future of gravitational waves, offered training on soft and transferable skills and allowed ample time for informal discussions between early career scientists and well-known research experts. The essence of those activities is summarised and collected in the present document, which presents a recap of each session of the workshop and aims to provide all early career scientists with a long-lasting, useful reference which constitutes the legacy of all the ideas that circulated at GWAECS.
Published: 2022

44. The Role of Emotional Competences in Parents’ Vaccine Hesitancy

Author: Anna Sannino, Alessandra Tasso, A Ferro, Lorella Lotto, Teresa Gavaruzzi, Enrico Rubaltelli, Irene Leo, Marta Caserotti, Elena Fretti, Leonardo Speri, Gavaruzzi T., Caserotti M., Leo I., Tasso A., Speri L., Ferro A., Fretti E., Sannino A., Rubaltelli E., and Lotto L.
Subjects: Vaccine safety, Mediational analysis, Immunology, lcsh:Medicine, emotions, Article, decision making, Developmental psychology, Emotional competence, 03 medical and health sciences, 0302 clinical medicine, 030225 pediatrics, Intervention (counseling), Drug Discovery, Pharmacology (medical), 030212 general & internal medicine, Valence (psychology), Emotion, Pharmacology, lcsh:R, parents, vaccines, Infectious Diseases, Parent, attitude, Vaccine refusal, Psychology, Attitude, Decision making, Emotions, Parents, Vaccines, Mental image, Intrapersonal communication
Abstract: The role of parents’ emotional competencies on vaccine hesitancy and decision making has been seldom examined. Two studies investigated the relationship between parents’ attitudes towards childhood vaccines and self-reported behavior (Study 1) and between parents’ emotional competence and attitudes towards vaccines (Study 2). In Study 1, predictors of temporal, partial, or complete vaccine refusal (having voluntarily postponed/forgone some/all vaccines) were examined in 2778 parents. In Study 2, psychological predictors of the attitude towards vaccines were examined in 593 parents, using the Profile of Emotional Competence and the valence of mental images spontaneously associated with the term “vaccine”. In Study 1, attitudes were aggregated in three independent factors (concerns about vaccine safety, diseases prevented by vaccines, and naturalistic views) that independently predicted vaccine refusal. In Study 2, a significant mediational analysis showed a positive indirect effect of intrapersonal emotional competences on attitudes towards vaccines, through mental images associated with the word “vaccine”. Parents’ intrapersonal emotional competences affected all dimensions of attitudes towards vaccines, suggesting that being able to manage, identify, and recognize one’s own emotions is central to vaccine acceptance. These findings suggest that intervention strategies, rather than stressing the pro-social benefits of vaccinating, should focus on aspects related to one’s own emotions.
Published: 2021

45. Common-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: inferences in the stochastic gravitational-wave background search

Author: Cees Bassa, J. W. McKee, A.-S. Bak Nielsen, E. van der Wateren, J. Wang, Antoine Petiteau, Andrea Possenti, Mitchell B. Mickaliger, Alberto Sesana, Kejia Lee, Delphine Perrodin, E. Graikou, Lan Wang, A. Chalumeau, R. N. Caballero, Kang Liu, Caterina Tiburzi, N. K. Porayko, Siyuan Chen, H. Xu, Alberto Vecchio, H. Hu, M. Falxa, Gemma H. Janssen, X. J. Liu, Ramesh Karuppusamy, John Antoniadis, David Champion, Ismaël Cognard, Michael Kramer, Benetge Perera, Gregory Desvignes, Stanislav Babak, Aditya Parthasarathy, Gilles Theureau, Y J Guo, L. Speri, Lucas Guillemot, Robert D. Ferdman, S. A. Sanidas, Paulo C. C. Freire, Michael Keith, Ben Stappers, J. Jang, Jonathan R. Gair, A. Berthereau, Andrew Lyne, G. Shaifullah, A. Samajdar, R. A. Main, M. Burgay, Joris P. W. Verbiest, RUS, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), ANR-18-CE31-0015,PTA-France,Recherche d'ondes gravitationnelles avec un réseau de pulsars en France(2018), Chen, S, Caballero, R, Guo, Y, Chalumeau, A, Liu, K, Shaifullah, G, Lee, K, Babak, S, Desvignes, G, Parthasarathy, A, Hu, H, Van Der Wateren, E, Antoniadis, J, Bak Nielsen, A, Bassa, C, Berthereau, A, Burgay, M, Champion, D, Cognard, I, Falxa, M, Ferdman, R, Freire, P, Gair, J, Graikou, E, Guillemot, L, Jang, J, Janssen, G, Karuppusamy, R, Keith, M, Kramer, M, Liu, X, Lyne, A, Main, R, Mckee, J, Mickaliger, M, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Samajdar, A, Sanidas, S, Sesana, A, Speri, L, Stappers, B, Theureau, G, Tiburzi, C, Vecchio, A, Verbiest, J, Wang, J, Wang, L, and Xu, H
Subjects: Spatial correlation, General relativity, Astronomy, Astrophysics, 01 natural sciences, Gravitational wave background, Pulsar, Millisecond pulsar, pulsars: general, 0103 physical sciences, gravitational wave, 010303 astronomy & astrophysics, Physics, Spectral index, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astronomy and Astrophysics, methods: data analysis, European Pulsar Timing Array, Amplitude, gravitational waves, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics - High Energy Astrophysical Phenomena, methods: data analysi, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present results from the search for a stochastic gravitational-wave background (GWB) as predicted by the theory of General Relativity using six radio millisecond pulsars from the Data Release 2 (DR2) of the European Pulsar Timing Array (EPTA) covering a timespan up to 24 years. A GWB manifests itself as a long-term low-frequency stochastic signal common to all pulsars, a common red signal (CRS), with the characteristic Hellings-Downs (HD) spatial correlation. Our analysis is performed with two independent pipelines, \eprise{} and \tn{}+\ftwo{}, which produce consistent results. A search for a CRS with simultaneous estimation of its spatial correlations yields spectral properties compatible with theoretical GWB predictions, but does not result in the required measurement of the HD correlation, as required for GWB detection. Further Bayesian model comparison between different types of CRSs, including a GWB, finds the most favoured model to be the common uncorrelated red noise described by a power-law with $A = 5.13_{-2.73}^{+4.20} \times 10^{-15}$ and $\gamma = 3.78_{-0.59}^{+0.69}$ (95\% credible regions). Fixing the spectral index to $\gamma=13/3$ as expected from the GWB by circular, inspiralling supermassive black-hole binaries results in an amplitude of $A =2.95_{-0.72}^{+0.89} \times 10^{-15}$. We implement three different models, BAYESEPHEM, LINIMOSS and EPHEMGP, to address possible Solar-system ephemeris (SSE) systematics and conclude that our results may only marginally depend on these effects. This work builds on the methods and models from the studies on the EPTA DR1. We show that under the same analysis framework the results remain consistent after the data set extension., Comment: 25 pages, 10 figures, 7 tables, 2 appendix tables and 1 appendix figure
Published: 2021

46. Noise analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search

Author: A Chalumeau, S Babak, A Petiteau, S Chen, A Samajdar, R N Caballero, G Theureau, L Guillemot, G Desvignes, A Parthasarathy, K Liu, G Shaifullah, H Hu, E van der Wateren, J Antoniadis, A-S Bak Nielsen, C G Bassa, A Berthereau, M Burgay, D J Champion, I Cognard, M Falxa, R D Ferdman, P C C Freire, J R Gair, E Graikou, Y J Guo, J Jang, G H Janssen, R Karuppusamy, M J Keith, M Kramer, K J Lee, X J Liu, A G Lyne, R A Main, J W McKee, M B Mickaliger, B B P Perera, D Perrodin, N K Porayko, A Possenti, S A Sanidas, A Sesana, L Speri, B W Stappers, C Tiburzi, A Vecchio, J P W Verbiest, J Wang, L Wang, H Xu, Chalumeau, A, Babak, S, Petiteau, A, Chen, S, Samajdar, A, Caballero, R, Theureau, G, Guillemot, L, Desvignes, G, Parthasarathy, A, Liu, K, Shaifullah, G, Hu, H, van der Wateren, E, Antoniadis, J, Bak Nielsen, A, Bassa, C, Berthereau, A, Burgay, M, Champion, D, Cognard, I, Falxa, M, Ferdman, R, Freire, P, Gair, J, Graikou, E, Guo, Y, Jang, J, Janssen, G, Karuppusamy, R, Keith, M, Kramer, M, Lee, K, Liu, X, Lyne, A, Main, R, Mckee, J, Mickaliger, M, Perera, B, Perrodin, D, Porayko, N, Possenti, A, Sanidas, S, Sesana, A, Speri, L, Stappers, B, Tiburzi, C, Vecchio, A, Verbiest, J, Wang, J, Wang, L, Xu, H, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ITA, USA, GBR, FRA, DEU, CAN, GRC, NLD, CHN, RUS, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and ANR-18-CE31-0015,PTA-France,Recherche d'ondes gravitationnelles avec un réseau de pulsars en France(2018)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, methods: data analysis, 01 natural sciences, gravitational waves, Space and Planetary Science, pulsars: general, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), gravitational wave, methods: data analysi
Abstract: The European Pulsar Timing Array (EPTA) collaboration has recently released an extended data set for six pulsars (DR2) and reported evidence for a common red noise signal. Here we present a noise analysis for each of the six pulsars. We consider several types of noise: (i) radio frequency independent, "achromatic", and time-correlated red noise; (ii) variations of dispersion measure and scattering; (iii) system and band noise; and (iv) deterministic signals (other than gravitational waves) that could be present in the PTA data. We perform Bayesian model selection to find the optimal combination of noise components for each pulsar. Using these custom models we revisit the presence of the common uncorrelated red noise signal previously reported in the EPTA DR2 and show that the data still supports it with a high statistical significance. Next, we confirm that there is no preference for or against the Hellings-Downs spatial correlations expected for the stochastic gravitational-wave background. The main conclusion of the EPTA DR2 paper remains unchanged despite a very significant change in the noise model of each pulsar. However, modelling the noise is essential for the robust detection of gravitational waves and its impact could be significant when analysing the next EPTA data release, which will include a larger number of pulsars and more precise measurements., 21 pages, 11 figures, 7 tables, 1 appendix figure and 1 appendix table, accepted for publication to MNRAS
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47. Second Data Release from the European Pulsar Timing Array: Challenging the Ultralight Dark Matter Paradigm.

Author: Smarra C, Goncharov B, Barausse E, Antoniadis J, Babak S, Nielsen AB, Bassa CG, Berthereau A, Bonetti M, Bortolas E, Brook PR, Burgay M, Caballero RN, Chalumeau A, Champion DJ, Chanlaridis S, Chen S, Cognard I, Desvignes G, Falxa M, Ferdman RD, Franchini A, Gair JR, Graikou E, Grießmeier JM, Guillemot L, Guo YJ, Hu H, Iraci F, Izquierdo-Villalba D, Jang J, Jawor J, Janssen GH, Jessner A, Karuppusamy R, Keane EF, Keith MJ, Kramer M, Krishnakumar MA, Lackeos K, Lee KJ, Liu K, Liu Y, Lyne AG, McKee JW, Main RA, Mickaliger MB, Niţu IC, Parthasarathy A, Perera BBP, Perrodin D, Petiteau A, Porayko NK, Possenti A, Leclere HQ, Samajdar A, Sanidas SA, Sesana A, Shaifullah G, Speri L, Spiewak R, Stappers BW, Susarla SC, Theureau G, Tiburzi C, van der Wateren E, Vecchio A, Krishnan VV, Wang J, Wang L, and Wu Z
Abstract: Pulsar Timing Array experiments probe the presence of possible scalar or pseudoscalar ultralight dark matter particles through decade-long timing of an ensemble of galactic millisecond radio pulsars. With the second data release of the European Pulsar Timing Array, we focus on the most robust scenario, in which dark matter interacts only gravitationally with ordinary baryonic matter. Our results show that ultralight particles with masses 10^{-24.0} eV≲m≲10^{-23.3} eV cannot constitute 100% of the measured local dark matter density, but can have at most local density ρ≲0.3 GeV/cm^{3}.
Published: 2023
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48. A New "Denervation" Technique for Painful Arthritic Wrist.

Author: Rigoni M, Raggi M, and Speri L
Abstract: Wrist denervation is, by the way, one of the most performed and long-lasting surgical technique for wrist arthritis. Despite many progresses in upper extremity joint arthroplasty, wrist arthritis remains difficult to treat specially in young patients and heavy manual workers. The aim of this technical article is to describe a new outpatient's procedure in which applying pulsed radio frequency on nerve structure of the wrist could achieve similar clinical results of a wrist denervation without surgical incision., Competing Interests: Conflict of Interest None declared., (Thieme. All rights reserved.)
Published: 2021
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49. The Role of Emotional Competences in Parents' Vaccine Hesitancy.

Author: Gavaruzzi T, Caserotti M, Leo I, Tasso A, Speri L, Ferro A, Fretti E, Sannino A, Rubaltelli E, and Lotto L
Abstract: The role of parents' emotional competencies on vaccine hesitancy and decision making has been seldom examined. Two studies investigated the relationship between parents' attitudes towards childhood vaccines and self-reported behavior (Study 1) and between parents' emotional competence and attitudes towards vaccines (Study 2). In Study 1, predictors of temporal, partial, or complete vaccine refusal (having voluntarily postponed/forgone some/all vaccines) were examined in 2778 parents. In Study 2, psychological predictors of the attitude towards vaccines were examined in 593 parents, using the Profile of Emotional Competence and the valence of mental images spontaneously associated with the term "vaccine". In Study 1, attitudes were aggregated in three independent factors (concerns about vaccine safety; diseases prevented by vaccines; and naturalistic views) that independently predicted vaccine refusal. In Study 2, a significant mediational analysis showed a positive indirect effect of intrapersonal emotional competences on attitudes towards vaccines, through mental images associated with the word "vaccine". Parents' intrapersonal emotional competences affected all dimensions of attitudes towards vaccines, suggesting that being able to manage, identify, and recognize one's own emotions is central to vaccine acceptance. These findings suggest that intervention strategies, rather than stressing the pro-social benefits of vaccinating, should focus on aspects related to one's own emotions.
Published: 2021
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50. [The health determinants in young children: testing a new surveillance system in Italy].

Author: Pizzi E, Spinelli A, Battilomo S, Azzarito C, Balducci MT, Bettinelli ME, Campostrini S, Germinario C, Mazzarella G, Mignuoli AD, Morbidoni M, Porchia S, Simeoni L, and Speri L
Subjects: Child, Preschool, Humans, Infant, Italy, Child Health, Population Surveillance
Abstract: In recent years, the scientific community has stressed the need to invest in the first 1,000 days of life - the time spanning between conception and the 2nd birthday - because it is during this period that the foundations of health are laid and whose effects will be present throughout the life and may influence the next generation. Taking this into account, in 2013 the National Centre for Disease Prevention and Control (CCM) of the Italian Ministry of Health promoted and financed a project to test a surveillance system of the main determinants of health concerning the child between the conception period and the 2nd years of life which are included in the National Programme "GenitoriPiù": folic acid before and during pregnancy, abstention from tobacco and alcohol during pregnancy and lactation, breastfeeding, infant sleep position, vaccination attitude, and early reading. The Project, started in January 2014 and ended in August 2016, has piloted the design, testing, and evaluation of the surveillance system with the view to national extension and the repeatability over time. The surveillance system has been designed to collect data through a questionnaire compiled by mothers in vaccination centres, in order to produce indicators which will enable territorial and intertemporal comparisons to be made. The project has shown the feasibility of this system, identifying favourable conditions and possible difficulties, and its ability to collect important information on children's health.
Published: 2019
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