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1. Pulsar timing methods for evaluating dispersion measure time series

Author: Iraci, F., Chalumeau, A., Tiburzi, C., Verbiest, J. P. W., Possenti, A., Shaifullah, G. M., Susarla, S. C., Krishnakumar, M. A., Lam, M. T., Cromartie, H. T., Kerr, M., and Grießmeier, Jean-Mathias
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Radio pulsars allow the study of the ionised interstellar medium and its dispersive effects, a major noise source in gravitational wave searches using pulsars. In this paper, we compare the functionality and reliability of three commonly used schemes to measure temporal variations in interstellar propagation effects in pulsar-timing data. We carry out extensive simulations at low observing frequencies (100-200 MHz) by injecting long-term correlated noise processes with power-law spectra and white noise, to evaluate the robustness, accuracy and precision of the following three mitigation methods: epoch-wise (EW) measurements of interstellar dispersion; the DMX method of simultaneous, piece-wise fits to interstellar dispersion; and DMGP, which models dispersion variations through Gaussian processes using a Bayesian analysis method. We then evaluate how reliably the input signals are reconstructed and how the various methods react to the presence of achromatic long-period noise. All the methods perform well, provided the achromatic long-period noise is modeled for DMX and DMGP. The most precise method is DMGP, followed by DMX and EW, while the most accurate is EW, followed by DMX and DMGP. We also test different scenarios including simulations of L-band ToAs and realistic DM injection, with no significant variation in the obtained results. Given the nature of our simulations and our scope, we deem that EW is the most reliable method to study the Galactic ionized media. Future works should be conducted to confirm this result via more realistic simulations. We note that DM GP and DMX seem to be the most performing techniques in removing long-term correlated noise, and hence for gravitational wave studies. However, full simulations of pulsar timing array experiments are needed to support this interpretation.
Published: 2024

2. Exploring the time variability of the Solar Wind using LOFAR pulsar data

Author: Susarla, S. C., Chalumeau, A., Tiburzi, C., Keane, E. F., Verbiest, J. P. W., Hazboun, J. S., Krishnakumar, M. A., Iraci, F., Shaifullah, G. M., Golden, A., Nielsen, A. S. Bak, Donner, J., Grießmeier, J. M., Keith, M. J., Osłowski, S., Porayko, N. K., Serylak, M., Anderson, J. M., Brüggen, M., Ciardi, B., Dettmar, R. J., Hoeft, M., Künsemöller, J., Schwarz, D., and Vocks, C.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: High-precision pulsar timing is highly dependent on precise and accurate modeling of any effects that impact the data. It was shown that commonly used Solar Wind models do not accurately account for variability in the amplitude of the Solar wind on both short and long time scales. In this study, we test and validate a new, cutting-edge Solar wind modeling method included in the \texttt{enterprise} software suite through extended simulations, and we apply it to investigate temporal variability in LOFAR data. Our model testing scheme in itself provides an invaluable asset for pulsar timing array (PTA) experiments. As improperly accounting for the solar wind signature in pulsar data can induce false-positive signals, it is of fundamental importance to include in any such investigations. We employ a Bayesian approach utilizing a continuously varying Gaussian process to model the solar wind referred to as Solar Wind Gaussian Process (SWGP). We conduct noise analysis on eight pulsars from the LOFAR dataset with most pulsars having a timespan of $\sim 11$ years encompassing one full solar activity cycle. Our analysis reveals a strong correlation between the electron density at 1 AU and the ecliptic latitude (ELAT) of the pulsar. Pulsars with $|ELAT|< 3^{\circ}$ exhibit significantly higher average electron densities. We observe distinct temporal patterns in electron densities in different pulsars. In particular, pulsars within $|ELAT|< 3^{\circ}$ exhibit similar temporal variations, while the electron densities of those outside this range correlate with the solar activity cycle. The continuous variability in electron density offered in this model represents a substantial improvement over previous models, which assume a single value for piece-wise bins of time. This advancement holds promise for solar wind modeling in future International Pulsar Timing Array data combinations., Comment: Accepted in Section 9. Sun and the Heliosphere, Astronomy and Astrophysics
Published: 2024
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3. 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

4. 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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5. 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

6. 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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7. 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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8. 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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9. 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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10. 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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11. Enabling ultra-low-voltage switching in BaTiO3

Author: Jiang, Y, Parsonnet, E, Qualls, A, Zhao, W, Susarla, S, Pesquera, D, Dasgupta, A, Acharya, M, Zhang, H, Gosavi, T, Lin, C-C, Nikonov, DE, Li, H, Young, IA, Ramesh, R, and Martin, LW
Subjects: Nanoscience & Nanotechnology
Abstract: Single crystals of BaTiO3 exhibit small switching fields and energies, but thin-film performance is considerably worse, thus precluding their use in next-generation devices. Here, we demonstrate high-quality BaTiO3 thin films with nearly bulk-like properties. Thickness scaling provides access to the coercive voltages (
Published: 2022

12. 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

13. Differences in the Mechanical Properties of Monolayer and Multilayer WSe2/MoSe2

Author: Jaques, Y. M., Manimunda, P., Nakanishi, Y., Susarla, S., Woellner, C. F., Bhowmick, S., Asif, S. A. S., Galvão, D. S., Tiwary, C. S., and Ajayan, P. M.
Subjects: Condensed Matter - Mesoscale and Nanoscale Physics
Abstract: Transition metal dichalcogenides are 2D structures with remarkable electronic, chemical, optical and mechanical properties. Monolayer and crystal properties of these structures have been extensively investigated, but a detailed understanding of the properties of their few-layer structures are still missing. In this work we investigated the mechanical differences between monolayer and multilayer WSe2 and MoSe2, through fully atomistic molecular dynamics simulations (MD). It was observed that single layer WSe2/MoSe2 deposited on silicon substrates have larger friction coefficients than 2, 3 and 4 layered structures. For all considered cases it is always easier to peel off and/or to fracture MoSe2 structures. These results suggest that the interactions between first layer and substrate are stronger than interlayer interactions themselves. Similar findings have been reported for other nanomaterials and it has been speculated whether this is a universal-like behavior for 2D layered materials. We have also analyzed fracture patterns. Our results show that fracture is chirality dependent with crack propagation preferentially perpendicular to W(Mo)-Se bonds and faster for zig-zag-like defects.
Published: 2018

14. Interfacility Transfer Guidelines for Isolated Facial Trauma: A Multi-disciplinary Expert Consensus.

Author: Pontell, ME, Steinberg, JP, Mackay, DR, Rodriguez, ED, Strong, EB, Olsson, AB, Kriet, JD, Kelly, KJ, Ochs, MW, Taub, PJ, Desai, SC, MacLeod, S, Susarla, S, Tollefson, TT, Schubert, W, Drolet, BC, and Golinko, MS
Published: 2022
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15. 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

16. 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

17. 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

18. Relation Of Quantitative Plaque With Total Coronary Lumen Volume To Left Ventricular Myocardial Mass Ratio: Evaluation By Computer Tomographic Coronary Angiography

Author: Niazi, A., primary, Manubolu, V., additional, Kinninger, A., additional, Roy, S., additional, Budoff, M., additional, Pourafkari, L., additional, Fazlalizadeh, H., additional, Tong, C., additional, Susarla, S., additional, Seok, H., additional, and Popoola, T., additional
Published: 2023
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19. Comparison Of Left Sided Cardiac Chamber Volumes Measured On Transthoracic Echocardiography And Cardiac Computed Tomography Angiography

Author: Jaalouk, E., primary, Manubolu, V., additional, Barforoshi, S., additional, Schwarzman, L., additional, Tong, C., additional, Seok, H., additional, Susarla, S., additional, Popoola, T., additional, Bikhazi, O., additional, Parikh, S., additional, Kinninger, A., additional, and Budoff, M., additional
Published: 2023
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20. Relationship Between Coronary Artery Calcium Burden And Coronary Volume To Left Ventricular Myocardial Mass Ratio: Evaluation By Cardiac Computed Tomography

Author: Niazi, A., primary, Manubolu, V., additional, Kinninger, A., additional, Pourafkari, L., additional, Fazlalizadeh, H., additional, Tong, C., additional, Susarla, S., additional, Seok, H., additional, Popoola, T., additional, Roy, S., additional, and Budoff, M., additional
Published: 2023
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21. Distribution Of Coronary Artery Calcium Score By Age And Sex In Asymptomatic Adults: Results From A Large Cohort Of 60,000 Patients-single Center Core Lab

Author: Fazlalizadeh, H., primary, Kinninger, A., additional, Manubolu, V., additional, Ichikawa, K., additional, Jairo, A., additional, Pourafkari, L., additional, Tong, C., additional, Susarla, S., additional, Seok, H., additional, Parikh, S., additional, Popoola, T., additional, Bikhazi, O., additional, Baskett, M., additional, Roy, S, additional, and Budoff, M., additional
Published: 2023
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22. 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

23. 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

24. Detection and Conversion of Co2 Into Moist

Author: Suryasri, Susarla S S V, primary, Reddy, M. Satya Sai, additional, Reddy, E. Lohika, additional, and Kumar, M.Naresh, additional
Published: 2023
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25. Detection and Conversion of Co2 Into Moist

Author: Susarla S S V Suryasri, M. Satya Sai Reddy, E. Lohika Reddy, and M.Naresh Kumar
Published: 2023

26. A room temperature polar magnetic metal

Author: Zhang, H, Zhang, H, Shao, YT, Chen, R, Chen, X, Susarla, S, Raftrey, D, Reichanadter, JT, Caretta, L, Huang, X, Settineri, NS, Chen, Z, Zhou, J, Bourret-Courchesne, E, Ercius, P, Yao, J, Fischer, P, Neaton, JB, Muller, DA, Birgeneau, RJ, Ramesh, R, Zhang, H, Zhang, H, Shao, YT, Chen, R, Chen, X, Susarla, S, Raftrey, D, Reichanadter, JT, Caretta, L, Huang, X, Settineri, NS, Chen, Z, Zhou, J, Bourret-Courchesne, E, Ercius, P, Yao, J, Fischer, P, Neaton, JB, Muller, DA, Birgeneau, RJ, and Ramesh, R
Abstract: The emergence of long-range magnetic order in noncentrosymmetric compounds has stimulated interest in the possibility of exotic spin transport phenomena and topologically protected spin textures for applications in next-generation spintronics. Polar magnets, with broken symmetries of spatial inversion and time reversal, usually host chiral spin textures. This work reports on a wurtzite-structure polar magnetic metal, identified as AA′-stacked (Fe0.5Co0.5)5GeTe2, which exhibits a Néel-type skyrmion lattice as well as a Rashba-Edelstein effect at room temperature. Atomic resolution imaging of the structure reveals a structural transition as a function of Co-substitution, leading to the emergence of the polar phase at 50% Co. This discovery reveals an unprecedented layered polar magnetic system for investigating intriguing spin topologies, and it ushers in a promising new framework for spintronics.
Published: 2022

27. Supplementary Information Enabling ultralow voltage switching in BaTiO3

Author: Martin, Lane W. [lwmartin@berkeley.edu], Jiang, Yizhe, Parsonnet, Eric, Qualls, Alexander, Zhao, Wenbo, Susarla, S., Pesquera, David, Dasgupta, A., Acharya, Megha, Zhang, H., Gosavi, Tanay, Lin, Chia-Ching, Nikonov, Dmitri E., Li, Hai, Young, Ian A., Ramesh, Ramamoorthy, Martin, Lane W., Martin, Lane W. [lwmartin@berkeley.edu], Jiang, Yizhe, Parsonnet, Eric, Qualls, Alexander, Zhao, Wenbo, Susarla, S., Pesquera, David, Dasgupta, A., Acharya, Megha, Zhang, H., Gosavi, Tanay, Lin, Chia-Ching, Nikonov, Dmitri E., Li, Hai, Young, Ian A., Ramesh, Ramamoorthy, and Martin, Lane W.
Published: 2022

28. Enabling ultra-low-voltage switching in BaTiO3

Author: Department of Energy (US), National Science Foundation (US), European Commission, US Army Research Office, Jiang, Yizhe, Parsonnet, Eric, Qualls, Alexander, Zhao, Wenbo, Susarla, S., Pesquera, David, Dasgupta, A., Acharya, Megha, Zhang, H., Gosavi, Tanay, Lin, Chia-Ching, Nikonov, Dmitri E., Li, Hai, Young, Ian A., Ramesh, Ramamoorthy, Martin, Lane W., Department of Energy (US), National Science Foundation (US), European Commission, US Army Research Office, Jiang, Yizhe, Parsonnet, Eric, Qualls, Alexander, Zhao, Wenbo, Susarla, S., Pesquera, David, Dasgupta, A., Acharya, Megha, Zhang, H., Gosavi, Tanay, Lin, Chia-Ching, Nikonov, Dmitri E., Li, Hai, Young, Ian A., Ramesh, Ramamoorthy, and Martin, Lane W.
Abstract: Single crystals of BaTiO3 exhibit small switching fields and energies, but thin-film performance is considerably worse, thus precluding their use in next-generation devices. Here, we demonstrate high-quality BaTiO3 thin films with nearly bulk-like properties. Thickness scaling provides access to the coercive voltages (<100 mV) and fields (<10 kV cm−1) required for future applications and results in a switching energy of <2 J cm−3 (corresponding to <2 aJ per bit in a 10 × 10 × 10 nm3 device). While reduction in film thickness reduces coercive voltage, it does so at the expense of remanent polarization. Depolarization fields impact polar state stability in thicker films but fortunately suppress the coercive field, thus driving a deviation from Janovec–Kay–Dunn scaling and enabling a constant coercive field for films <150 nm in thickness. Switching studies reveal fast speeds (switching times of ~2 ns for 25-nm-thick films with 5-µm-diameter capacitors) and a pathway to subnanosecond switching. Finally, integration of BaTiO3 thin films onto silicon substrates is shown. We also discuss what remains to be demonstrated to enable the use of these materials for next-generation devices.
Published: 2022

29. Association Between Aortic Arch Calcification And Education Level At Varying Levels Of Coronary Artery Calcium: Multi-Ethnic Study Of Atherosclerosis (MESA).

Author: Susarla, S., Trujillo, R., McClelland, R., Hansen, S., Ghanem, A., Kinninger, A., and Budoff, M.
Published: 2024
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30. Adsorption and Desorption of Herbicide Chemicals in Fixed Soil Beds

Author: IPENZ (1994: Nelson, N.Z.), Susarla, S, Bhaskar, GV, and Rao Bhamidimarri, SM
Published: 1994

31. High precision measurements of interstellar dispersion measure with the upgraded GMRT

Author: Krishnakumar, M. A., primary, Manoharan, P. K., additional, Joshi, B. C., additional, Girgaonkar, R., additional, Desai, S., additional, Bagchi, M., additional, Nobleson, K., additional, Dey, L., additional, Susobhanan, A., additional, Susarla, S. C., additional, Surnis, M. P., additional, Maan, Y., additional, Gopakumar, A., additional, Basu, A., additional, Batra, N. D., additional, Choudhary, A., additional, De, K., additional, Gupta, Y., additional, Naidu, A. K., additional, Pathak, D., additional, Singha, J., additional, and Prabu, T., additional
Published: 2021
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32. The Impact Of Severity Of Nonobstructive Lesion On Developing Obstructive Disease.

Author: Ichikawa, K., Kinninger, A., Krishnan, S., Benzing, T., Kianoush, S., Aldana-Bitar, J., Ghanem, A., Javier, D., Hamal, S., Susarla, S., Lee, D., Erbay, M., Sandhu, H., Yusufu, I., Konka, V., Siddhant, W., and Budoff, M.
Published: 2024
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33. Distribution Of Coronary Plaque Subtypes Among Races Quantified By Automated Coronary Plaque Analysis.

Author: Erbay, M., Susarla, S., Lee, D., Manubolu, V., Kinninger, A., Sandhu, H., Behjatnia, D., Bikhazi, O., Ngo, K., Jung, A., Yusufu, I., Ahmad, T., and M, Budoff
Published: 2024
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34. Predicting dental school performance based on prior dental experience and exposure

Author: Park, S. E., Da Silva, J. D., Barnes, J. L., Susarla, S. M., and Howell, T. H.
Published: 2010
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35. Differences in clinical grading associated with instructor status

Author: Park, R. D., Susarla, S. M., Howell, T. H., and Karimbux, N. Y.
Published: 2009

36. Redox Potential as a Parameter To Predict the Reductive Dechlorination Pathway of Chloroanilines in Anaerobic Environments

Author: Susarla, S., Masunaga, S., and Yonezawa, Y.
Published: 1997
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37. Kinetics of the Sequential Dechlorination of Chloroorganics in an Anaerobic Sediment

Author: Susarla, S., Masunaga, S., and Yonezawa, Y.
Published: 1997
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38. S3-10 SESSION 3

Author: Kapadia, H., primary, Susarla, S., additional, Mercan, E., additional, Kurnik, N., additional, Calis, M., additional, and Hopper, R., additional
Published: 2019
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39. S4B-15 SESSION 4B

Author: Susarla, S., primary, Kapadia, H., additional, Ettinger, R., additional, Preston, K., additional, and Egbert, M., additional
Published: 2019
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40. Differences in the Mechanical Properties of Monolayer and Multilayer WSe2/MoSe2

Author: Jaques, Y. M., primary, Manimunda, P., additional, Nakanishi, Y., additional, Susarla, S., additional, Woellner, C. F., additional, Bhowmick, S., additional, Asif, S. A. S., additional, Galvão, D. S., additional, Tiwary, C. S., additional, and Ajayan, P. M., additional
Published: 2018
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41. Nanoscale deformation and friction characteristics of atomically thin WSe 2 and heterostructure using nanoscratch and Raman spectroscopy

Author: Manimunda, P, primary, Nakanishi, Y, additional, Jaques, Y M, additional, Susarla, S, additional, Woellner, C F, additional, Bhowmick, S, additional, Asif, S A S, additional, Galvão, D S, additional, Tiwary, C S, additional, and Ajayan, P M, additional
Published: 2017
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42. Health‐related quality of life in 794 patients with a peripheral facial palsy using the FaCE Scale: a retrospective cohort study

Author: Kleiss, I. J., primary, Hohman, M. H., additional, Susarla, S. M., additional, Marres, H. A. M., additional, and Hadlock, T. A., additional
Published: 2015
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43. LOP34

Author: Swanson, E. W., primary, Cheng, H.- T., additional, Susarla, S. M., additional, Yalanis, G. C., additional, Lough, D. M., additional, Johnson, O., additional, Tufaro, A. P., additional, Manson, P. N., additional, and Sacks, J. M., additional
Published: 2015
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44. Investigation of Steven Impact Test Using a Transportation Hook Projectile with Gauged Experiments and 3D Modeling

Author: Daniel W. Greenwood, Jerry W. Forbes, Susarla S. Murty, Frank Garcia, Kevin S. Vandersall, Steven K. Chidester, and Craig M. Tarver
Subjects: Impact testing, Physics, Hook, Projectile, business.industry, Impact test, Gauge (firearms), 3D modeling, Term (time), law.invention, Ignition system, law, business, Simulation, Marine engineering
Abstract: The Steven Impact Test and associated modeling offer valuable practical predictions for evaluating numerous safety scenarios involving low velocity impact of energetic materials by different projectile geometries. One such scenario is the impact of energetic material by a transportation hook during shipping, which offers complexity because of the irregular hook projectile shape. Experiments were performed using gauged Steven Test targets with PBX9404 impacted by a transportation hook projectile to compliment previous non‐gauged experiments that established an impact threshold of approximately 69 m/s. Modeling of these experiments was performed with LS‐DYNA code using an Ignition and Growth reaction criteria with a friction term. Comparison of the experiment to the model shows reasonable agreement with some details requiring more attention. The experimental results (including carbon resistor gauge records), model calculations, and a discussion of the dominant reaction mechanisms in light of comparisons between experiment and model will be presented.
Published: 2004

45. Abstract 51

Author: Ganske, Ingrid, primary, Susarla, S, additional, Helliwell, L, additional, Morris, D, additional, Eriksson, E, additional, and Chun, Y, additional
Published: 2013
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46. Three-Dimensional Airway Changes in Children With Congenital Micrognathia and Obstructive Sleep Apnea Following Mandibular Distraction Osteogenesis

Author: Abramson, Z., primary, Lawler, M., additional, Susarla, S., additional, Troulis, M., additional, and Kaban, L., additional
Published: 2011
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47. Upper Airway Length Decreases Following Maxillomandibular Advancement in Patients With Obstructive Sleep Apnea

Author: Susarla, S., primary, Abramson, Z., additional, Dodson, T., additional, and Kaban, L., additional
Published: 2011
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48. Cephalometric Measurement of Upper Airway Length Correlates With the Presence and Severity of Obstructive Sleep Apnea

Author: Susarla, S., primary
Published: 2010
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49. Does Computed Tomographic Evidence of Inferior Alveolar Canal Cortical Integrity Predict Nerve Exposure During Third Molar Surgery?

Author: Susarla, S., primary
Published: 2010
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50. Link between allergic asthma and airway mucosal infection suggested by proteinase-secreting household fungi

Author: Porter, P, primary, Susarla, S C, additional, Polikepahad, S, additional, Qian, Y, additional, Hampton, J, additional, Kiss, A, additional, Vaidya, S, additional, Sur, S, additional, Ongeri, V, additional, Yang, T, additional, Delclos, G L, additional, Abramson, S, additional, Kheradmand, F, additional, and Corry, D B, additional
Published: 2009
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