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1. 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., 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., and Dandapat, S.

Subjects
BINARY black holes, SUPERMASSIVE black holes, BAYESIAN analysis, DATA release, PULSARS
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 favour of the presence of the CGW over a common uncorrelated noise process. In contrast, 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, nor can we 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 for the EPTA DR2 data. Further investigations combining data from all PTA collaborations will be needed to reveal the true origin of this feature. [ABSTRACT FROM AUTHOR]

Published
2024
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2. 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

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

Author

EPTA Collaboration and InPTA Collaboration, 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., and Cognard, I.

Subjects
BLACK holes, DARK matter, INFLATIONARY universe, DATA release, BINARY black holes, UNIVERSE
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. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Validation of global ionospheric models using long-term observations of pulsar Faraday rotation with the LOFAR radio telescope

Author

Porayko, N, Mevius, M, Hernandez-Pajares, M, Tiburzi, C, Olivares Pulido, G, Liu, Q, Verbiest, J, Kunsemoller, J, Krishnakumar, M, Bak Nielsen, A, Bruggen, M, Graffigna, V, Dettmar, R, Kramer, M, Oslowski, S, Schwarz, D, Shaifullah, G, Wucknitz, O, Porayko N. K., Mevius M., Hernandez-Pajares M., Tiburzi C., Olivares Pulido G., Liu Q., Verbiest J. P. W., Kunsemoller J., Krishnakumar M. A., Bak Nielsen A. -S., Bruggen M., Graffigna V., Dettmar R. -J., Kramer M., Oslowski S., Schwarz D. J., Shaifullah G. M., Wucknitz O., Porayko, N, Mevius, M, Hernandez-Pajares, M, Tiburzi, C, Olivares Pulido, G, Liu, Q, Verbiest, J, Kunsemoller, J, Krishnakumar, M, Bak Nielsen, A, Bruggen, M, Graffigna, V, Dettmar, R, Kramer, M, Oslowski, S, Schwarz, D, Shaifullah, G, Wucknitz, O, Porayko N. K., Mevius M., Hernandez-Pajares M., Tiburzi C., Olivares Pulido G., Liu Q., Verbiest J. P. W., Kunsemoller J., Krishnakumar M. A., Bak Nielsen A. -S., Bruggen M., Graffigna V., Dettmar R. -J., Kramer M., Oslowski S., Schwarz D. J., Shaifullah G. M., and Wucknitz O.

Abstract

Broad band pulsar radiation can be effectively used to monitor the properties of the magneto-ionic media through which it propagates. Faraday rotation calculated from polarised pulsar observations provides an integrated product of electron densities and the line-of-sight component of the magnetic field in the intervening plasma. In particular, a time-variable effect mainly associated with the rapidly changing column density of the Earth’s ionosphere and plasmasphere heavily dominates the observed Faraday rotation of pulsar radiation. In this work, we aim to carry out a performance test of three GNSS-based models of the ionosphere using observations of PSR J0332+5434 taken with the LOw Frequency ARray (LOFAR). As it was shown in Porayko et al. (Month Not Roy Astron Soc 483(3):4100–4113, 2019. https://doi.org/10.1093/mnras/sty3324 . arXiv:1812.01463), the conventional single layer model (SLM), which assumes that the ionosphere is a thin slab at a fixed effective height, is not capable of fully accounting for the ionospheric Faraday rotation in pulsar data. The simplified physics of the SLM is upgraded within IRI-Plas (International Reference Ionosphere and Plasmasphere) extended SLM and the dual-layer voxel TOmographic Model of the Ionosphere (TOMION), both of which partially account for the thickness and vertical dynamics of the terrestrial plasma. Although the last two improve the reconstruction of the ionospheric Faraday rotation, none of the considered models completely purge the observed residual variations. With this study, we show that the long term LOFAR observations of Faraday rotation of pulsars provide an excellent tool to test and improve models of the magneto-ionic content of the Earth’s atmosphere.

Published
2023

5. 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

6. 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

7. The LOFAR Tied-Array All-Sky Survey: Timing of 35 radio pulsars and an overview of the properties of the LOFAR pulsar discoveries

Author

van der Wateren, E., primary, Bassa, C. G., additional, Cooper, S., additional, Grießmeier, J.-M., additional, Stappers, B. W., additional, Hessels, J. W. T., additional, Kondratiev, V. I., additional, Michilli, D., additional, Tan, C. M., additional, Tiburzi, C., additional, Weltevrede, P., additional, Bak Nielsen, A.-S., additional, Carozzi, T. D., additional, Ciardi, B., additional, Cognard, I., additional, Dettmar, R.-J., additional, Karastergiou, A., additional, Kramer, M., additional, Künsemöller, J., additional, Osłowski, S., additional, Serylak, M., additional, Vocks, C., additional, and Wucknitz, O., additional

Published
2023
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8. 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

9. 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

10. 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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11. 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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12. 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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13. 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., Shaifullah, G., Lee, K.J., Babak, S., Desvignes, G., Parthasarathy, A., 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., 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., Xu, H., Chen, S., Caballero, R.N., Guo, Y.J., Chalumeau, A., Shaifullah, G., Lee, K.J., Babak, S., Desvignes, G., Parthasarathy, A., 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., 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., and Xu, H.

Abstract

Contains fulltext : 239732.pdf (Publisher’s version ) (Open Access)

Published
2021

14. The impact of solar wind variability on pulsar timing

Author

Tiburzi, C, Shaifullah, G, Bassa, C, Zucca, P, Verbiest, J, Porayko, N, Van Der Wateren, E, Fallows, R, Main, R, Janssen, G, Anderson, J, Bak Nielsen, A, Donner, J, Keane, E, Kunsemoller, J, Oslowski, S, Griessmeier, J, Serylak, M, Bruggen, M, Ciardi, B, Dettmar, R, Hoeft, M, Kramer, M, Mann, G, Vocks, C, Tiburzi C., Shaifullah G. M., Bassa C. G., Zucca P., Verbiest J. P. W., Porayko N. K., Van Der Wateren E., Fallows R. A., Main R. A., Janssen G. H., Anderson J. M., Bak Nielsen A. -S., Donner J. Y., Keane E. F., Kunsemoller J., Oslowski S., Griessmeier J. -M., Serylak M., Bruggen M., Ciardi B., Dettmar R. -J., Hoeft M., Kramer M., Mann G., Vocks C., Tiburzi, C, Shaifullah, G, Bassa, C, Zucca, P, Verbiest, J, Porayko, N, Van Der Wateren, E, Fallows, R, Main, R, Janssen, G, Anderson, J, Bak Nielsen, A, Donner, J, Keane, E, Kunsemoller, J, Oslowski, S, Griessmeier, J, Serylak, M, Bruggen, M, Ciardi, B, Dettmar, R, Hoeft, M, Kramer, M, Mann, G, Vocks, C, Tiburzi C., Shaifullah G. M., Bassa C. G., Zucca P., Verbiest J. P. W., Porayko N. K., Van Der Wateren E., Fallows R. A., Main R. A., Janssen G. H., Anderson J. M., Bak Nielsen A. -S., Donner J. Y., Keane E. F., Kunsemoller J., Oslowski S., Griessmeier J. -M., Serylak M., Bruggen M., Ciardi B., Dettmar R. -J., Hoeft M., Kramer M., Mann G., and Vocks C.

Abstract

Context. High-precision pulsar timing requires accurate corrections for dispersive delays of radio waves, parametrized by the dispersion measure (DM), particularly if these delays are variable in time. In a previous paper, we studied the solar wind (SW) models used in pulsar timing to mitigate the excess of DM that is annually induced by the SW and found these to be insufficient for high-precision pulsar timing. Here we analyze additional pulsar datasets to further investigate which aspects of the SW models currently used in pulsar timing can be readily improved, and at what levels of timing precision SW mitigation is possible. Aims. Our goals are to verify: (a) whether the data are better described by a spherical model of the SW with a time-variable amplitude, rather than a time-invariant one as suggested in literature, and (b) whether a temporal trend of such a model's amplitudes can be detected. Methods. We use the pulsar timing technique on low-frequency pulsar observations to estimate the DM and quantify how this value changes as the Earth moves around the Sun. Specifically, we monitor the DM in weekly to monthly observations of 14 pulsars taken with parts of the LOw-Frequency ARray (LOFAR) across time spans of up to 6 years. We develop an informed algorithm to separate the interstellar variations in the DM from those caused by the SW and demonstrate the functionality of this algorithm with extensive simulations. Assuming a spherically symmetric model for the SW density, we derive the amplitude of this model for each year of observations. Results. We show that a spherical model with a time-variable amplitude models the observations better than a spherical model with a constant amplitude, but that both approaches leave significant SW-induced delays uncorrected in a number of pulsars in the sample. The amplitude of the spherical model is found to be variable in time, as opposed to what has been previously suggested.

Published
2021

15. The impact of solar wind variability on pulsar timing

Author

Tiburzi, C., primary, Shaifullah, G. M., additional, Bassa, C. G., additional, Zucca, P., additional, Verbiest, J. P. W., additional, Porayko, N. K., additional, van der Wateren, E., additional, Fallows, R. A., additional, Main, R. A., additional, Janssen, G. H., additional, Anderson, J. M., additional, Bak Nielsen, A.-S., additional, Donner, J. Y., additional, Keane, E. F., additional, Künsemöller, J., additional, Osłowski, S., additional, Grießmeier, J.-M., additional, Serylak, M., additional, Brüggen, M., additional, Ciardi, B., additional, Dettmar, R.-J., additional, Hoeft, M., additional, Kramer, M., additional, Mann, G., additional, and Vocks, C., additional

Published
2021
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16. Dispersion measure variability for 36 millisecond pulsars at 150 MHz with LOFAR

Author

Donner, J. Y., primary, Verbiest, J. P. W., additional, Tiburzi, C., additional, Osłowski, S., additional, Künsemöller, J., additional, Bak Nielsen, A.-S., additional, Grießmeier, J.-M., additional, Serylak, M., additional, Kramer, M., additional, Anderson, J. M., additional, Wucknitz, O., additional, Keane, E., additional, Kondratiev, V., additional, Sobey, C., additional, McKee, J. W., additional, Bilous, A. V., additional, Breton, R. P., additional, Brüggen, M., additional, Ciardi, B., additional, Hoeft, M., additional, van Leeuwen, J., additional, and Vocks, C., additional

Published
2020
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17. International Pulsar Timing Array second data release: Search for an isotropic gravitational wave background.

Author

Antoniadis, J, Arzoumanian, Z, Babak, S, Bailes, M, Bak Nielsen, A-S, Baker, P T, Bassa, C G, Bécsy, 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, and Chatterjee, S

Subjects
DATA release, PULSARS, BINARY black holes, SUPERMASSIVE black holes, GRAVITATIONAL waves, STOCHASTIC processes
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 |$A = 3.8^{+6.3}_{-2.5}\times 10^{-15}$| and spectral index α = −0.5 ± 0.5, where the uncertainties represent 95 per cent credible regions, using information from the auto- and cross-correlation terms between the pulsars in the array. For a spectral index of α = −2/3, as expected from a population of inspiralling supermassive black hole binaries, the recovered amplitude is |$A = 2.8^{+1.2}_{-0.8}\times 10^{-15}$|⁠. None the less, no significant evidence of the Hellings–Downs correlations that would indicate a gravitational-wave origin was found. We also analysed 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. [ABSTRACT FROM AUTHOR]

Published
2022
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18. Timing stability of three black widow pulsars

Author

Bak Nielsen, A.-S., Janssen, G.H., Shaifullah, G., Verbiest, J.P.W., Champion, D.J., Desvignes, G., Guillemot, L., Karuppusamy, R., Kramer, M, Lyne, A.G., Possenti, A., Stappers, B.W., Bassa, C., Cognard, I., Theureau, G., Bak Nielsen, A.-S., Janssen, G.H., Shaifullah, G., Verbiest, J.P.W., Champion, D.J., Desvignes, G., Guillemot, L., Karuppusamy, R., Kramer, M, Lyne, A.G., Possenti, A., Stappers, B.W., Bassa, C., Cognard, I., and Theureau, G.

Abstract

Contains fulltext : 219305.pdf (publisher's version ) (Open Access)

Published
2020

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