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1. The impact on astrometry by solar-wind effect in pulsar timing.

Author

Liu, K, Parthasarathy, A, Keith, M, Tiburzi, C, Susarla, S C, Antoniadis, J, Chalumeau, A, Chen, S, Cognard, I, Golden, A, Grießmeier, J -M, Guillemot, L, Janssen, G H, Keane, E F, Kramer, M, McKee, J W, Mickaliger, M B, Theureau, G, and Wang, J

Subjects
STELLAR parallax, ASTROMETRY, WIND measurement, PULSARS, DATA release, SOLAR wind
Abstract

Astrometry of pulsars, particularly their distances, serves as a critical input for various astrophysical experiments using pulsars. Pulsar timing is a primary approach for determining a pulsar's position, parallax, and distance. In this paper, we explore the influence of the solar wind on astrometric measurements obtained through pulsar timing, focusing on its potential to affect the accuracy of these parameters. Using both theoretical calculation and mock-data simulations, we demonstrate a significant correlation between the pulsar position, annual parallax, and the solar-wind density parameters. This correlation strongly depends on the pulsar's ecliptic latitude. We show that fixing solar-wind density to an arbitrary value in the timing analysis can introduce significant bias in the estimated pulsar position and parallax, and its significance is highly dependent on the ecliptic latitude of the pulsar and the timing precision of the data. For pulsars with favourable ecliptic latitude and timing precision, the astrometric and solar-wind parameters can be measured jointly with other timing parameters using single-frequency data. The parameter correlation can be mitigated by using multifrequency data, which also significantly improves the measurement precision of these parameters; this is particularly important for pulsars at a medium or high ecliptic latitude. Additionally, for a selection of pulsars we reprocess their European Pulsar Timing Array Data Release 2 data to include modelling of solar-wind effect in the timing analysis. This delivers significant measurements of both parallax and solar-wind density, the latter of which are consistent with those obtained at low-frequency band. In the future, combining pulsar timing data at gigahertz and lower frequencies will probably deliver the most robust and precise measurements of astrometry and solar wind properties in pulsar timing. [ABSTRACT FROM AUTHOR]

Published
2025
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2. 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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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. The RoboPol sample of optical polarimetric standards

Author

Blinov, D., Maharana, S., Bouzelou, F., Casadio, C., Gjerløw, E., Jormanainen, J., Kiehlmann, S., Kypriotakis, J. A., Liodakis, I., Mandarakas, N., Markopoulioti, L., Panopoulou, G. V., Pelgrims, V., Pouliasi, A., Romanopoulos, S., Skalidis, R., Anche, R. M., Angelakis, E., Antoniadis, J., Medhi, B. J., Hovatta, T., Kus, A., Kylafis, N., Mahabal, A., Myserlis, I., Paleologou, E., Papadakis, I., Pavlidou, V., Papamastorakis, I., Pearson, T. J., Potter, S. B., Ramaprakash, A. N., Readhead, A. C. S., Reig, P., Słowikowska, A., Tassis, K., and Zensus, J. A.

Subjects
FOS: Physical sciences, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

Optical polarimeters are typically calibrated using measurements of stars with known and stable polarization parameters. However, there is a lack of such stars available across the sky. Many of the currently available standards are not suitable for medium and large telescopes due to their high brightness. Moreover, as we find, some of the used polarimetric standards are in fact variable or have polarization parameters that differ from their cataloged values. Our goal is to establish a sample of stable standards suitable for calibrating linear optical polarimeters with an accuracy down to $10^{-3}$ in fractional polarization. For five years, we have been running a monitoring campaign of a sample of standard candidates comprised of 107 stars distributed across the northern sky. We analyzed the variability of the linear polarization of these stars, taking into account the non-Gaussian nature of fractional polarization measurements. For a subsample of nine stars, we also performed multiband polarization measurements. We created a new catalog of 65 stars (see Table 2) that are stable, have small uncertainties of measured polarimetric parameters, and can be used as calibrators of polarimeters at medium- and large-size telescopes.

Published
2023

5. 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., 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, Laboratoire Univers et Théories (LUTH (UMR_8102)), and EPTA

Subjects
High Energy Physics - Theory, kink, binary: mass, noise, data analysis method, Cosmology and Nongalactic Astrophysics (astro-ph.CO), gravitational radiation: stochastic, string tension, gravitational radiation: background, FOS: Physical sciences, statistical analysis: Bayesian, General Relativity and Quantum Cosmology (gr-qc), parametric, General Relativity and Quantum Cosmology, High Energy Physics - Theory (hep-th), black hole: binary, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], string: closed, string model, simplex, Astrophysics - Cosmology and Nongalactic Astrophysics, cosmic string: network, pulsar
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 $\log_{10}(Gμ) < -9.9$ ($-10.5$) 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., 13 pages, 5 figures

Published
2023

6. 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

7. 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., 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, Laboratoire Univers et Théories (LUTH (UMR_8102)), and European Pulsar Timing Array

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Cosmology and Nongalactic Astrophysics (astro-ph.CO), dark matter, interaction, density, local, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), GeV, Astrophysics - Astrophysics of Galaxies, General Relativity and Quantum Cosmology, High Energy Physics - Phenomenology, High Energy Physics - Phenomenology (hep-ph), gravitation, Astrophysics of Galaxies (astro-ph.GA), [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph], [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], galaxy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, pseudoscalar, dark matter, density, pulsar, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Pulsar Timing Array experiments probe the presence of possible scalar/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 $10^{-24.0}~\text{eV} \lesssim m \lesssim 10^{-23.2}~\text{eV}$ cannot constitute $100\%$ of the measured local dark matter density, but can have at most local density $\rho\lesssim 0.15$ GeV/cm$^3$., Comment: 5 pages + acknowledgements + refs, 2 figures

Published
2023

8. Variable Scintillation Arcs of Millisecond Pulsars observed with the Large European Array for Pulsars

Author

Main, R. A., Antoniadis, J., Chen, S., Cognard, I., Hu, H., Jang, J., Karuppusamy, R., Kramer, M., Liu, K., Liu, Y., Mall, G., McKee, J. W., Mickaliger, M. B., Perrodin, D., Sanidas, S. A., Stappers, B. W., Sprenger, T., Wucknitz, O., Bassa, C. G., Burgay, M., Concu, R., Gaikwad, M., Janssen, G. H., Lee, K. J., Melis, A., Pilia, M., Possenti, A., Wang, L., and Zhu, W. W.

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics - Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

We present the first large sample of scintillation arcs in millisecond pulsars, analysing 12 sources observed with the Large European Array for Pulsars (LEAP), and the Effelsberg 100\,m telescope. We estimate the delays from multipath propagation, measuring significant correlated changes in scattering timescales over a 10-year timespan. Many sources show compact concentrations of power in the secondary spectrum, which in PSRs J0613$-$0200 and J1600$-$3053 can be tracked between observations, and are consistent with compact scattering at fixed angular positions. Other sources such as PSRs J1643$-$1224 and J0621+1002 show diffuse, asymmetric arcs which are likely related to phase-gradients across the scattering screen. PSR B1937+21 shows at least three distinct screens which dominate at different times and evidence of varying screen axes or multi-screen interactions. We model annual and orbital arc curvature variations in PSR J0613$-$0200, providing a measurement of the longitude of ascending node, resolving the sense of the orbital inclination, where our best fit model is of a screen with variable axis of anisotropy over time, corresponding to changes in the scattering of the source. Unmodeled variations of the screen's axis of anisotropy are likely to be a limiting factor in determining orbital parameters with scintillation, requiring careful consideration of variable screen properties, or independent VLBI measurements. Long-term scintillation studies such as this serve as a complementary tool to pulsar timing, to measure a source of correlated noise for pulsar timing arrays, solve pulsar orbits, and to understand the astrophysical origin of scattering screens., Submitted to MNRAS, first revision. 18 pages, 16 figures

Published
2023

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

Author

Falxa, M, Babak, S, Baker, P T, Bécsy, B, Chalumeau, A, Chen, S, Chen, Z, Cornish, N J, Guillemot, L, Hazboun, J S, Mingarelli, C M F, Parthasarathy, A, Petiteau, A, Pol, N S, Sesana, A, Spolaor, S B, Taylor, S R, Theureau, G, Vallisneri, M, Vigeland, S J, Witt, C A, Zhu, X, Antoniadis, J, Arzoumanian, Z, Bailes, M, Bhat, N D R, Blecha, L, Brazier, A, Brook, P R, Caballero, N, Cameron, A D, Casey-Clyde, J A, Champion, D, Charisi, M, Chatterjee, S, Cognard, I, Cordes, J M, Crawford, F, Cromartie, H T, Crowter, K, Dai, S, DeCesar, M E, Demorest, P B, Desvignes, G, Dolch, T, Drachler, B, Feng, Y, Ferrara, E C, Fiore, W, Fonseca, E, Garver-Daniels, N, Glaser, J, Goncharov, B, Good, D C, Griessmeier, J, Guo, Y J, Gültekin, K, Hobbs, G, Hu, H, Islo, K, Jang, J, Jennings, R J, Johnson, A D, Jones, M L, Kaczmarek, J, Kaiser, A R, Kaplan, D L, Keith, M, Kelley, L Z, Kerr, M, Key, J S, Laal, N, Lam, M T, Lamb, W G, Lazio, T J W, Liu, K, Liu, T, Luo, J, Lynch, R S, Madison, D R, Main, R, Manchester, R, McEwen, A, McKee, J, McLaughlin, M A, Ng, C, Nice, D J, Ocker, S, Olum, K D, Osłowski, S, Pennucci, T T, Perera, B B P, Perrodin, D, Porayko, N, Possenti, A, Quelquejay-Leclere, H, Ransom, S M, Ray, P S, Reardon, D J, Russell, C J, Samajdar, A, Sarkissian, J, Schult, L, Shaifullah, G, Shannon, R M, Shapiro-Albert, B J, Siemens, X, Simon, J J, Siwek, M, Smith, T L, Speri, L, Spiewak, R, Stairs, I H, Stappers, B, Stinebring, D R, Swiggum, J K, Tiburzi, C, Turner, J, Vecchio, A, Verbiest, Joris, Wahl, H, Wang, S Q, Wang, J, Wang, Jun, Wu, Ziwei, Zhang, L, Zhang, S, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire Univers et Théories (LUTH (UMR_8102)), and IPTA

Subjects
noise, data analysis method, gravitational radiation, orbit: circle, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), sensitivity, frequency: high, General Relativity and Quantum Cosmology, confidence limit, frequency: low, black hole: binary, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), pulsar
Abstract

The International Pulsar Timing Array 2nd data release is the combination ofdatasets from worldwide collaborations. In this study, we search for continuouswaves: gravitational wave signals produced by individual supermassive blackhole binaries in the local universe. We consider binaries on circular orbitsand neglect the evolution of orbital frequency over the observational span. Wefind no evidence for such signals and set sky averaged 95% upper limits ontheir amplitude h 95 . The most sensitive frequency is 10nHz with h 95 = 9.110-15 . We achieved the best upper limit to date at low and high frequencies ofthe PTA band thanks to improved effective cadence of observations. In ouranalysis, we have taken into account the recently discovered common red noiseprocess, which has an impact at low frequencies. We also find that the peculiarnoise features present in some pulsars data must be taken into account toreduce the false alarm. We show that using custom noise models is essential insearching for continuous gravitational wave signals and setting the upperlimit.

Published
2023
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10. 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, 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), FOS: Physical sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics
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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11. Mass measurements and 3D orbital geometry of PSR J1933$-$6211

Author

Geyer, M., Krishnan, V. Venkatraman, Freire, P. C. C., Kramer, M., Antoniadis, J., Bailes, M., Bernadich, M. C. i, Buchner, S., Cameron, A. D., Champion, D. J., Karastergiou, A., Keith, M. J., Lower, M. E., Osłowski, S., Possenti, A., Parthasarathy, A., Reardon, D. J., Serylak, M., Shannon, R. M., Spiewak, R., van Straten, W., and Verbiest, Joris

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics - Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

PSR J1933$-$6211 is a 3.5-ms pulsar in a 12.8-d orbit with a white dwarf (WD). Its high proper motion and low dispersion measure result in such significant interstellar scintillation that high signal-to-noise detections require long observing durations or fortuitous timing. We turn to the sensitive MeerKAT telescope and, combined with historic Parkes data, leverage PSR J1933$-$6211's kinematic and relativistic effects to constrain its 3D orbital geometry and the component masses. We obtain precise proper motion and parallax estimates, and measure their effects as secular changes in the Keplerian orbital parameters: a variation in orbital period of $7(1) \times 10^{-13}$ s s$^{-1}$ and a change in projected semi-major axis of $1.60(5) \times 10^{-14}$ s s$^{-1}$. A self-consistent analysis of all kinematic and relativistic effects yields a distance of $1.6^{+0.2}_{-0.3}$ kpc, an orbital inclination, $i = 55(1)$ deg and a longitude of the ascending node, $\Omega = 255^{+8}_{-14}$ deg. The probability densities for $\Omega$ and $i$ and their symmetric counterparts, ($180-i$, $360-\Omega$), are seen to depend on the fiducial orbit used to measure the time of periastron passage. We investigate this unexpected dependence and rule out software-related causes using simulations. Nevertheless, we constrain the pulsar and WD masses to $1.4^{+0.3}_{-0.2}$ M$_\odot$ and $0.43(5)$ M$_\odot$ respectively. These strongly disfavour a helium-dominated WD. The orbital similarities between PSRs J1933$-$6211 and J1614$-$2230 suggest they underwent Case A Roche lobe overflow, an extended evolution while the companion star is still on the Main Sequence. However, with a mass of $\sim 1.4$ M$_\odot$, PSR J1933$-$6211 has not accreted significant matter. This highlights the low accretion efficiency of the spin-up process and suggests that observed neutron star masses are mostly a result of supernova physics., Comment: 16 pages, 7 figures. Abstract shortened to adhere to ArXiv limit

Published
2023

12. Variable scintillation arcs of millisecond pulsars observed with the Large European Array for Pulsars.

Author

Main, R A, Antoniadis, J, Chen, S, Cognard, I, Hu, H, Jang, J, Karuppusamy, R, Kramer, M, Liu, K, Liu, Y, Mall, G, McKee, J W, Mickaliger, M B, Perrodin, D, Sanidas, S A, Stappers, B W, Sprenger, T, Wucknitz, O, Bassa, C G, and Burgay, M

Subjects
*SCINTILLATION counters, *VERY long baseline interferometry
Abstract

We present the first large sample of scintillation arcs in millisecond pulsars (MSPs), analysing 12 sources observed with the Large European Array for Pulsars (LEAP), and the Effelsberg 100-m telescope. We estimate the delays from multipath propagation, measuring significant correlated changes in scattering time-scales over a 10 yr time span. Many sources show compact concentrations of power in the secondary spectrum, which in PSRs J0613−0200 and J1600−3053 can be tracked between observations, and are consistent with compact scattering at fixed angular positions. Other sources such as PSRs J1643−1224 and J0621+1002 show diffuse, asymmetric arcs which are likely related to phase-gradients across the scattering screen. PSR B1937+21 shows at least three distinct screens which dominate at different times and evidence of varying screen axes or multiscreen interactions. We model annual and orbital arc curvature variations in PSR J0613−0200, providing a measurement of the longitude of ascending node, resolving the sense of the orbital inclination, where our best-fit model is of a screen with variable axis of anisotropy over time, corresponding to changes in the scattering of the source. Unmodelled variations of the screen's axis of anisotropy are likely to be a limiting factor in determining orbital parameters with scintillation, requiring careful consideration of variable screen properties, or independent very long baseline interferometry (VLBI) measurements. Long-term scintillation studies such as this serve as a complementary tool to pulsar timing, to measure a source of correlated noise for pulsar timing arrays, solve pulsar orbits, and to understand the astrophysical origin of scattering screens. [ABSTRACT FROM AUTHOR]

Published
2023
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13. Robust parameter estimation from pulsar timing data.

Author

Samajdar, A, Shaifullah, G M, Sesana, A, Antoniadis, J, Burgay, M, Chen, S, Cognard, I, Guillemot, L, Kramer, M, McKee, J W, Mickaliger, M B, Theureau, G, and Van der Wateren, E

Subjects
MARKOV chain Monte Carlo, PARAMETER estimation, PULSARS
Abstract

Recently, global pulsar timing arrays have released results from searching for a nano-Hertz gravitational wave background signal. Although there has not been any definite evidence of the presence of such a signal in residuals of pulsar timing data yet, with more and improved data in future, a statistically significant detection is expected to be made. Stochastic algorithms are used to sample a very large parameter space to infer results from data. In this paper, we attempt to rule out effects arising from the stochasticity of the sampler in the inference process. We compare different configurations of nested samplers and the more commonly used markov chain monte carlo method to sample the pulsar timing array parameter space and account for times taken by the different samplers on same data. Although we obtain consistent results on parameters from different sampling algorithms, we propose two different samplers for robustness checks on data in the future to account for cross-checks between sampling methods as well as realistic run-times. [ABSTRACT FROM AUTHOR]

Published
2022
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14. Detection of quasi-periodic micro-structure in three millisecond pulsars with the Large European Array for Pulsars.

Author

Liu, K, Antoniadis, J, Bassa, C G, Chen, S, Cognard, I, Gaikwad, M, Hu, H, Jang, J, Janssen, G H, Karuppusamy, R, Kramer, M, Lee, K J, Main, R A, Mall, G, McKee, J W, Mickaliger, M B, Perrodin, D, Sanidas, S A, Stappers, B W, and Wang, L

Subjects
*PULSARS, *MICROSTRUCTURE, *LINEAR polarization, *RADIO frequency, *BREWSTER'S angle
Abstract

We report on the detection of quasi-periodic micro-structure in three millisecond pulsars (MSPs), PSRs J1022+1001, J2145−0750, and J1744−1134, using high time resolution data acquired with the Large European Array for Pulsars at a radio frequency of 1.4 GHz. The occurrence rate of quasi-periodic micro-structure is consistent among pulses with different peak flux densities. Using an auto-correlation analysis, we measure the periodicity and width of the micro-structure in these three pulsars. The detected micro-structure from PSRs J1022+1001 and J1744−1134 is often highly linearly polarized. In PSR J1022+1001, the linear polarization position angles of micro-structure pulses are in general flat with a small degree of variation. Using these results, we further examine the frequency and rotational period dependency of micro-structure properties established in previous work, along with the angular beaming and temporal modulation models that explain the appearance of micro-structure. We also discuss a possible link of micro-structure to the properties of some of the recently discovered fast radio bursts which exhibit a very similar emission morphology. [ABSTRACT FROM AUTHOR]

Published
2022
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15. Modelling annual scintillation arc variations in PSR J1643−1224 using the Large European Array for Pulsars.

Author

Mall, G, Main, R A, Antoniadis, J, Bassa, C G, Burgay, M, Chen, S, Cognard, I, Concu, R, Corongiu, A, Gaikwad, M, Hu, H, Janssen, G H, Karuppusamy, R, Kramer, M, Lee, K J, Liu, K, McKee, J W, Melis, A, Mickaliger, M B, and Perrodin, D

Subjects
PULSARS, BINARY pulsars, INTERSTELLAR medium, RELATIVE velocity, POWER spectra
Abstract

In this work, we study variations in the parabolic scintillation arcs of the binary millisecond pulsar PSR J1643−1224 over five years using the Large European Array for Pulsars (LEAP). The two-dimensional (2D) power spectrum of scintillation, called the secondary spectrum, often shows a parabolic distribution of power, where the arc curvature encodes the relative velocities and distances of the pulsar, ionized interstellar medium, and Earth. We observe a clear parabolic scintillation arc, which varies in curvature throughout the year. The distribution of power in the secondary spectra is inconsistent with a single scattering screen, which is fully 1D or entirely isotropic. We fit the observed arc curvature variations with two models: an isotropic scattering screen and a model with two independent 1D screens. We measure the distance to the scattering screen to be in the range 114–223 pc, depending on the model, consistent with the known distance of the foreground large-diameter H  ii region Sh 2-27 (112 ± 17 pc), suggesting that it is the dominant source of scattering. We obtain only weak constraints on the pulsar's orbital inclination and longitude of ascending node, since the scintillation pattern is not very sensitive to the pulsar's motion and the screen is much closer to the Earth than the pulsar. More measurements of this kind – where scattering screens can be associated with foreground objects – will help to inform the origins and distribution of scattering screens within our galaxy. [ABSTRACT FROM AUTHOR]

Published
2022
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16. 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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17. A revisit of PSR J1909−3744 with 15-yr high-precision timing.

Author

Liu, K, Guillemot, L, Istrate, A G, Shao, L, Tauris, T M, Wex, N, Antoniadis, J, Chalumeau, A, Cognard, I, Desvignes, G, Freire, P C C, Kehl, M S, and Theureau, G

Subjects
RELATIVE motion, GRAVITATIONAL waves, SOLAR system, OPTICAL measurements, RADIO telescopes, BINARY pulsars, PULSARS
Abstract

We report on a high-precision timing analysis and an astrophysical study of the binary millisecond pulsar, PSR J1909−3744, motivated by the accumulation of data with well improved quality over the past decade. Using 15 yr of observations with the Nançay Radio Telescope, we achieve a timing precision of approximately 100 ns. We verify our timing results by using both broad-band and sub-band template matching methods to create the pulse time-of-arrivals. Compared with previous studies, we improve the measurement precision of secular changes in orbital period and projected semimajor axis. We show that these variations are both dominated by the relative motion between the pulsar system and the Solar system barycentre. Additionally, we identified four possible solutions to the ascending node of the pulsar orbit, and measured a precise kinetic distance of the system. Using our timing measurements and published optical observations, we investigate the binary history of this system using the stellar evolution code mesa , and discuss solutions based on detailed WD cooling at the edge of the WD age dichotomy paradigm. We determine the 3D velocity of the system and show that it has been undergoing a highly eccentric orbit around the centre of our Galaxy. Furthermore, we set up a constraint over dipolar gravitational radiation with the system, which is complementary to previous studies given the mass of the pulsar. We also obtain a new limit on the parametrized post-Newtonian parameter, |$\left| \hat\alpha_1 \right|$| < 2.1 × 10−5 at 95 per cent confidence level, which is fractionally better than previous best published value and achieved with a more concrete method. [ABSTRACT FROM AUTHOR]

Published
2020
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18. Measuring interstellar delays of PSR J0613−0200 over 7 yr, using the Large European Array for Pulsars.

Author

Main, R A, Sanidas, S A, Antoniadis, J, Bassa, C, Chen, S, Cognard, I, Gaikwad, M, Hu, H, Janssen, G H, Karuppusamy, R, Kramer, M, Lee, K J, Liu, K, Mall, G, McKee, J W, Mickaliger, M B, Perrodin, D, Stappers, B W, Tiburzi, C, and Wucknitz, O

Subjects
RELATIVE velocity, WAVE analysis, GRAVITATIONAL waves, POWER spectra, BINARY pulsars, PULSARS
Abstract

Using data from the Large European Array for Pulsars, and the Effelsberg telescope, we study the scintillation parameters of the millisecond pulsar PSR J0613−0200 over a 7 yr timespan. The 'secondary spectrum' – the 2D power spectrum of scintillation – presents the scattered power as a function of time delay, and contains the relative velocities of the pulsar, observer, and scattering material. We detect a persistent parabolic scintillation arc, suggesting scattering is dominated by a thin, anisotropic region. The scattering is poorly described by a simple exponential tail, with excess power at high delays; we measure significant, detectable scattered power at times out to |${\sim}5 \, \mu {\rm s}$|⁠ , and measure the bulk scattering delay to be between 50 to 200 ns with particularly strong scattering throughout 2013. These delays are too small to detect a change of the pulse profile shape, yet they would change the times of arrival as measured through pulsar timing. The arc curvature varies annually, and is well fitted by a one-dimensional scattering screen |${\sim}40{{\ \rm per\ cent}}$| of the way towards the pulsar, with a changing orientation during the increased scattering in 2013. Effects of uncorrected scattering will introduce time delays correlated over time in individual pulsars, and may need to be considered in gravitational wave analyses. Pulsar timing programmes would benefit from simultaneously recording in a way that scintillation can be resolved, in order to monitor the variable time delays caused by multipath propagation. [ABSTRACT FROM AUTHOR]

Published
2020
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19. Radio afterglows of very high-energy gamma-ray bursts 190829A and 180720B.

Author

Rhodes, L, van der Horst, A J, Fender, R, Monageng, I M, Anderson, G E, Antoniadis, J, Bietenholz, M F, Böttcher, M, Bright, J S, Green, D A, Kouveliotou, C, Kramer, M, Motta, S E, Wijers, R A M J, Williams, D R A, and Woudt, P A

Subjects
GAMMA ray bursts, X-ray telescopes, RADIOS, LIGHT curves, MEERKAT
Abstract

We present high-cadence multifrequency radio observations of the long gamma-ray burst (GRB) 190829A, which was detected at photon energies above 100 GeV by the High Energy Stereoscopic System (H.E.S.S.). Observations with the Meer Karoo Array Telescope (MeerKAT, 1.3 GHz) and Arcminute Microkelvin Imager – Large Array (AMI-LA, 15.5 GHz) began one day post-burst and lasted nearly 200 d. We used complementary data from Swift X-Ray Telescope (XRT), which ran to 100 d post-burst. We detected a likely forward shock component with both MeerKAT and XRT up to over 100 d post-burst. Conversely, the AMI-LA light curve appears to be dominated by reverse shock emission until around 70 d post-burst when the afterglow flux drops below the level of the host galaxy. We also present previously unpublished observations of the other H.E.S.S.-detected GRB, GRB 180720B from AMI-LA, which shows likely forward shock emission that fades in less than 10 d. We present a comparison between the radio emission from the three GRBs with detected very high energy (VHE) gamma-ray emission and a sensitivity-limited radio afterglow sample. GRB 190829A has the lowest isotropic radio luminosity of any GRB in our sample, but the distribution of luminosities is otherwise consistent, as expected, with the VHE GRBs being drawn from the same parent distribution as the other radio-detected long GRBs. [ABSTRACT FROM AUTHOR]

Published
2020
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20. Type Ia supernovae from non-accreting progenitors.

Author

Antoniadis, J., Chanlaridis, S., Gräfener, G., and Langer, N.

Subjects
*TYPE I supernovae, *B stars, *STELLAR mass, *ELECTRON capture, *WHITE dwarf stars, *NUCLEAR energy
Abstract

Type Ia supernovae (SNe Ia) are manifestations of stars that are deficient in hydrogen and helium, and disrupt in a thermonuclear runaway. While explosions of carbon-oxygen white dwarfs are thought to account for the majority of events, part of the observed diversity may be due to varied progenitor channels. We demonstrate that helium stars with masses between~1.8 and 2.5 M may evolve into highly degenerate cores with near-Chandrasekhar mass and helium-free envelopes that subsequently ignite carbon and oxygen explosively at densities of~(1.8-5.9) × 109 g cm-3. This occurs either due to core growth from shell burning (when the core has a hybrid CO/NeO composition), or following ignition of residual carbon triggered by exothermic electron captures on 24Mg (for a NeOMg-dominated composition). We argue that the resulting thermonuclear runaway is likely to prevent core collapse, leading to the complete disruption of the star. The available nuclear energy at the onset of explosive oxygen burning suffices to create ejecta with a kinetic energy of~1051 erg, as in typical SNe Ia. Conversely, if these runaways result in partial disruptions, the corresponding transients would resemble SN Iax events similar to SN 2002cx. If helium stars in this mass range indeed explode as SNe Ia, then the frequency of events would be comparable to the observed SN Ib/c rates, thereby sufficing to account for the majority of SNe Ia in star-forming galaxies. [ABSTRACT FROM AUTHOR]

Published
2020
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22. Improving timing sensitivity in the microhertz frequency regime: limits from PSR J1713+0747 on gravitational waves produced by supermassive black hole binaries.

Author

Perera, B B P, Stappers, B W, Babak, S, Keith, M J, Antoniadis, J, Bassa, C G, Caballero, R N, Champion, D J, Cognard, I, Desvignes, G, Graikou, E, Guillemot, L, Janssen, G H, Karuppusamy, R, Kramer, M, Lazarus, P, Lentati, L, Liu, K, Lyne, A G, and McKee, J W

Subjects
GRAVITATIONAL waves, SUPERMASSIVE black holes, ASTRONOMICAL observations, BAYESIAN analysis, PULSARS
Abstract

We search for continuous gravitational waves (CGWs) produced by individual supermassive black hole binaries in circular orbits using high-cadence timing observations of PSR J1713+0747. We observe this millisecond pulsar using the telescopes in the European Pulsar Timing Array with an average cadence of approximately 1.6 d over the period between 2011 April and 2015 July, including an approximately daily average between 2013 February and 2014 April. The high-cadence observations are used to improve the pulsar timing sensitivity across the gravitational wave frequency range of 0.008−5 $\mu$ Hz. We use two algorithms in the analysis, including a spectral fitting method and a Bayesian approach. For an independent comparison, we also use a previously published Bayesian algorithm. We find that the Bayesian approaches provide optimal results and the timing observations of the pulsar place a 95 per cent upper limit on the sky-averaged strain amplitude of CGWs to be ≲3.5 × 10−13 at a reference frequency of 1  $\mu$ Hz. We also find a 95 per cent upper limit on the sky-averaged strain amplitude of low-frequency CGWs to be ≲1.4 × 10−14 at a reference frequency of 20 nHz. [ABSTRACT FROM AUTHOR]

Published
2018
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23. The relativistic pulsar-white dwarf binary PSR J1738+0333 - I. Mass determination and evolutionary history

Author

Antoniadis, J., van Kerkwijk, M. H., Koester, D., Freire, P. C. C., Wex, N., Tauris, T. M., Kramer, M., and Bassa, C. G.

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics - Solar and Stellar Astrophysics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, General Relativity and Quantum Cosmology
Abstract

PSR J1738+0333 is one of the four millisecond pulsars known to be orbited by a white dwarf companion bright enough for optical spectroscopy. Of these, it has the shortest orbital period, making it especially interesting for a range of astrophysical and gravity related questions. We present a spectroscopic and photometric study of the white dwarf companion and infer its radial velocity curve, effective temperature, surface gravity and luminosity. We find that the white dwarf has properties consistent with those of low-mass white dwarfs with thick hydrogen envelopes, and use the corresponding mass-radius relation to infer its mass; M_WD = 0.181 +/- +0.007/-0.005 solar masses. Combined with the mass ratio q=8.1 +/- 0.2 inferred from the radial velocities and the precise pulsar timing ephemeris, the neutron star mass is constrained to M_PSR = 1.47 +/- +0.07/-0.06 solar masses. Contrary to expectations, the latter is only slightly above the Chandrasekhar limit. We find that, even if the birth mass of the neutron star was only 1.20 solar masses, more than 60% of the matter that left the surface of the white dwarf progenitor escaped the system. The accurate determination of the component masses transforms this system in a laboratory for fundamental physics by constraining the orbital decay predicted by general relativity. Currently, the agreement is within 1 sigma of the observed decay. Further radio timing observations will allow precise tests of white dwarf models, assuming the validity of general relativity., Article published in Monthly Notices of the Royal Astronomical Society v.3: Updated references

Published
2012
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24. Cool white dwarf companions to four millisecond pulsars.

Author

Bassa, C. G., Antoniadis, J., Camilo, F., Cognard, I., Koester, D., Kramer, M., Ransom, S. R., and Stappers, B. W.

Subjects
*SUPERNOVA remnants, *NEUTRON stars, *DWARF galaxies, *RADIATION sources, *LUMINESCENCE
Abstract

We report on photometric and spectroscopic observations of white dwarf companions to four binary radio millisecond pulsars, leading to the discovery of companions to PSRs J0614--3329, J1231--1411 and J2017+0603. We place limits on the brightness of the companion to PSR J0613--0200. Optical spectroscopy of the companion to PSR J0614--3329 identifies it as a DA-type white dwarf with a temperature of Teff = 6460 ± 80 K, a surface gravity log g = 7.0 ± 0.2 cgs and a mass of MWD = 0.24 ± 0.04 M☉. We find that the distance to PSR J0614--3329 is smaller than previously estimated, removing the need for the pulsar to have an unrealistically high γ -ray efficiency. Comparing the photometry with predictions from white dwarf cooling models allows us to estimate temperatures and cooling ages of the companions to PSRs J0613--0200, J1231--1411 and J2017+0603. We find that the white dwarfs in these systems are cool Teff < 4000 K and old ≳5 Gyr. Thin hydrogen envelopes are required for these white dwarfs to cool to the observed temperatures, and we suggest that besides hydrogen shell flashes, irradiation driven mass loss by the pulsar may have been important. [ABSTRACT FROM AUTHOR]

Published
2016
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25. The timescale of low-mass proto-helium white dwarf evolution.

Author

Istrate, A. G., Langer, N., Tauris, T. M., and Antoniadis, J.

Subjects
HELIUM, WHITE dwarf stars, BINARY systems (Astronomy), X-ray binaries, STELLAR evolution
Abstract

Context. A large number of low-mass (≲0.20 M☉) helium white dwarfs (He WDs) have recently been discovered. The majority of these are orbiting another WD or a millisecond pulsar (MSP) in a close binary system; a few examples are found to show pulsations or to have a main-sequence star companion. There appear to be discrepancies between the current theoretical modelling of such lowmass He WDs and a number of key observed cases, indicating that their formation scenario yet remains to be fully understood. Aims. Here we investigate the formation of detached proto-He WDs in close-orbit low-mass X-ray binaries (LMXBs). Our prime focus is to examine the thermal evolution and the contraction phase towards the WD cooling track and investigate how this evolution depends on the WD mass. Our calculations are then compared to the most recent observational data. Methods. Numerical calculations with a detailed stellar evolution code were used to trace the mass-transfer phase in a large number of close-orbit LMXBs with different initial values of donor star mass, neutron star mass, orbital period, and strength of magnetic braking. Subsequently, we followed the evolution of the detached low-mass proto-He WDs, including stages with residual shell hydrogen burning and vigorous flashes caused by unstable CNO burning. Results. We find that the time between Roche-lobe detachment until the low-mass proto-He WD reaches the WD cooling track is typically Δtproto = 0.5-2 Gyr, depending systematically on the WD mass and therefore on its luminosity. The lowest WD mass for developing shell flashes is ∼0.21 M☉ for progenitor stars of mass M2 ⩽ 1.5 M☉ (and ∼0.18 M☉for M2 = 1.6 M☉). Conclusions. The long timescale of low-mass proto-He WD evolution can explain a number of recent observations, including some MSP systems hosting He WD companions with very low surface gravities and high effective temperatures. We find no evidence for Δtproto to depend on the occurrence of flashes and thus question the suggested dichotomy in thermal evolution of proto-WDs. [ABSTRACT FROM AUTHOR]

Published
2014
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26. A white dwarf companion to the relativistic pulsar PSR J1141−6545.

Author

Antoniadis, J., Bassa, C. G., Wex, N., Kramer, M., and Napiwotzki, R.

Subjects
*DWARF stars, *PULSARS, *PHYSICS laboratories, *GENERAL relativity (Physics), *EQUATIONS of state, *BIG bang theory, *GRAVITATIONAL fields
Abstract

Pulsars with compact companions in close eccentric orbits are unique laboratories for testing general relativity and alternative theories of gravity. Moreover, they are excellent targets for future gravitational wave experiments like LISA and they are also highly important for understanding the equation of state of superdense matter and the evolution of massive binaries. Here we report on optical observations of the 1.02 M companion to the pulsar PSR J6545. We detect an optical counterpart with apparent magnitudes and , consistent with the timing position of the pulsar. We demonstrate that our results are in agreement with a white dwarf companion. However the latter is redder than expected and the inferred values are not consistent with the theoretical cooling tracks, preventing us from deriving the exact age. Our results confirm the importance of the PSR J6545 system for gravitational experiments. [ABSTRACT FROM AUTHOR]

Published
2011
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27. An ingress and a complete transit of HD 80606 b.

Author

Hidas, M. G., Tsapras, Y., Mislis, D., Ramaprakash, A. N., Barros, S. C. C., Street, R. A., Schmitt, J. H. M. M., Steele, I., Pollacco, D., Ayiomamitis, A., Antoniadis, J., Nitsos, A., Seiradakis, J. H., and Urakawa, S.

Subjects
TELESCOPES, PLANETS, STARS, MARKOV processes, MONTE Carlo method, ASTRONOMICAL observations
Abstract

We have used four telescopes at different longitudes to obtain near-continuous light-curve coverage of the star HD 80606 as it was transited by its ∼4- MJup planet. The observations were performed during the predicted transit windows around 2008 October 25 and 2009 February 14. Our data set is unique in that it simultaneously constrains the duration of the transit and the planet's period. Our Markov Chain Monte Carlo analysis of the light curves, combined with constraints from radial-velocity data, yields system parameters consistent with previously reported values. We find a planet-to-star radius ratio marginally smaller than previously reported, corresponding to a planet radius of . [ABSTRACT FROM AUTHOR]

Published
2010
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28. Common-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: inferences in the stochastic gravitational-wave background search

Author

Cees Bassa, J. W. McKee, A.-S. Bak Nielsen, E. van der Wateren, J. Wang, Antoine Petiteau, Andrea Possenti, Mitchell B. Mickaliger, Alberto Sesana, Kejia Lee, Delphine Perrodin, E. Graikou, Lan Wang, A. Chalumeau, R. N. Caballero, Kang Liu, Caterina Tiburzi, N. K. Porayko, Siyuan Chen, H. Xu, Alberto Vecchio, H. Hu, M. Falxa, Gemma H. Janssen, X. J. Liu, Ramesh Karuppusamy, John Antoniadis, David Champion, Ismaël Cognard, Michael Kramer, Benetge Perera, Gregory Desvignes, Stanislav Babak, Aditya Parthasarathy, Gilles Theureau, Y J Guo, L. Speri, Lucas Guillemot, Robert D. Ferdman, S. A. Sanidas, Paulo C. C. Freire, Michael Keith, Ben Stappers, J. Jang, Jonathan R. Gair, A. Berthereau, Andrew Lyne, G. Shaifullah, A. Samajdar, R. A. Main, M. Burgay, Joris P. W. Verbiest, RUS, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), ANR-18-CE31-0015,PTA-France,Recherche d'ondes gravitationnelles avec un réseau de pulsars en France(2018), Chen, S, Caballero, R, Guo, Y, Chalumeau, A, Liu, K, Shaifullah, G, Lee, K, Babak, S, Desvignes, G, Parthasarathy, A, Hu, H, Van Der Wateren, E, Antoniadis, J, Bak Nielsen, A, Bassa, C, Berthereau, A, Burgay, M, Champion, D, Cognard, I, Falxa, M, Ferdman, R, Freire, P, Gair, J, Graikou, E, Guillemot, L, Jang, J, Janssen, G, Karuppusamy, R, Keith, M, Kramer, M, Liu, X, Lyne, A, Main, R, Mckee, J, Mickaliger, M, Perera, B, Perrodin, D, Petiteau, A, Porayko, N, Possenti, A, Samajdar, A, Sanidas, S, Sesana, A, Speri, L, Stappers, B, Theureau, G, Tiburzi, C, Vecchio, A, Verbiest, J, Wang, J, Wang, L, and Xu, H

Subjects
Spatial correlation, General relativity, Astronomy, Astrophysics, 01 natural sciences, Gravitational wave background, Pulsar, Millisecond pulsar, pulsars: general, 0103 physical sciences, gravitational wave, 010303 astronomy & astrophysics, Physics, Spectral index, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astronomy and Astrophysics, methods: data analysis, European Pulsar Timing Array, Amplitude, gravitational waves, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics - High Energy Astrophysical Phenomena, methods: data analysi, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We present results from the search for a stochastic gravitational-wave background (GWB) as predicted by the theory of General Relativity using six radio millisecond pulsars from the Data Release 2 (DR2) of the European Pulsar Timing Array (EPTA) covering a timespan up to 24 years. A GWB manifests itself as a long-term low-frequency stochastic signal common to all pulsars, a common red signal (CRS), with the characteristic Hellings-Downs (HD) spatial correlation. Our analysis is performed with two independent pipelines, \eprise{} and \tn{}+\ftwo{}, which produce consistent results. A search for a CRS with simultaneous estimation of its spatial correlations yields spectral properties compatible with theoretical GWB predictions, but does not result in the required measurement of the HD correlation, as required for GWB detection. Further Bayesian model comparison between different types of CRSs, including a GWB, finds the most favoured model to be the common uncorrelated red noise described by a power-law with $A = 5.13_{-2.73}^{+4.20} \times 10^{-15}$ and $\gamma = 3.78_{-0.59}^{+0.69}$ (95\% credible regions). Fixing the spectral index to $\gamma=13/3$ as expected from the GWB by circular, inspiralling supermassive black-hole binaries results in an amplitude of $A =2.95_{-0.72}^{+0.89} \times 10^{-15}$. We implement three different models, BAYESEPHEM, LINIMOSS and EPHEMGP, to address possible Solar-system ephemeris (SSE) systematics and conclude that our results may only marginally depend on these effects. This work builds on the methods and models from the studies on the EPTA DR1. We show that under the same analysis framework the results remain consistent after the data set extension., Comment: 25 pages, 10 figures, 7 tables, 2 appendix tables and 1 appendix figure

Published
2021
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29. Improving timing sensitivity in the microhertz frequency regime: limits from PSR J1713$+$0747 on gravitational waves produced by super-massive black-hole binaries

Author

John Antoniadis, Gregory Desvignes, R. N. Caballero, Benjamin Stappers, Gilles Theureau, James Mckee, G. Shaifullah, E. Graikou, Andrew Lyne, Cees Bassa, Stefan Oslowski, Sotirios A. Sanidas, L. Lentati, Lucas Guillemot, Benetge Perera, Ramesh Karuppusamy, Ismaël Cognard, Michael Kramer, Delphine Perrodin, Joris P. W. Verbiest, Stephen Taylor, Michael Keith, Kang Liu, P. Lazarus, Gemma H. Janssen, Alberto Sesana, S Babak, D. J. Champion, AstroParticule et Cosmologie ( APC - UMR 7164 ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace ( LPC2E ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Unité Scientifique de la Station de Nançay ( USN ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Univers et Théories ( LUTH ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), ITA, USA, GBR, FRA, DEU, AUS, NLD, RUS, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Perera, B, Stappers, B, Babak, S, Keith, M, Antoniadis, J, Bassa, C, Caballero, R, Champion, D, Cognard, I, Desvignes, G, Graikou, E, Guillemot, L, Janssen, G, Karuppusamy, R, Kramer, M, Lazarus, P, Lentati, L, Liu, K, Lyne, A, Mckee, J, Osłowski, S, Perrodin, D, Sanidas, S, Sesana, A, Shaifullah, G, Theureau, G, Verbiest, J, Taylor, S, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], FOS: Physical sciences, Astrophysics, 01 natural sciences, Bayesian, stars: neutron, neutron, Pulsar, Millisecond pulsar, 0103 physical sciences, Quasars: Supermassive black hole, black hole, 010303 astronomy & astrophysics, orbit, quasars: supermassive, pulsar, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Supermassive black hole, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Gravitational wave, stars, quasars: supermassive black holes, Astrophysics::Instrumentation and Methods for Astrophysics, gravitational radiation, Astronomy and Astrophysics, sensitivity, black holes, Black hole, Orbit, European Pulsar Timing Array, Amplitude, binaries: general, gravitational waves, black hole: binary, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], frequency, spectral, Stars: Black hole, pulsars: individual: PSR J1713+0747, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], stars: black holes
Abstract

We search for continuous gravitational waves (CGWs) produced by individual super-massive black-hole binaries (SMBHBs) in circular orbits using high-cadence timing observations of PSR J1713$+$0747. We observe this millisecond pulsar using the telescopes in the European Pulsar Timing Array (EPTA) with an average cadence of approximately 1.6 days over the period between April 2011 and July 2015, including an approximately daily average between February 2013 and April 2014. The high-cadence observations are used to improve the pulsar timing sensitivity across the GW frequency range of $0.008-5$ $\mu$Hz. We use two algorithms in the analysis, including a spectral fitting method and a Bayesian approach. For an independent comparison, we also use a previously published Bayesian algorithm. We find that the Bayesian approaches provide optimal results and the timing observations of the pulsar place a 95 per cent upper limit on the sky-averaged strain amplitude of CGWs to be $\lesssim3.5\times10^{-13}$ at a reference frequency of 1 $\mu$Hz. We also find a 95 per cent upper limit on the sky-averaged strain amplitude of low-frequency CGWs to be $\lesssim1.4\times10^{-14}$ at a reference frequency of 20~nHz., Comment: 12 pages, 4 figures. Accepted for publication in MNRAS

Published
2018
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30. Noise analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search

Author

A Chalumeau, S Babak, A Petiteau, S Chen, A Samajdar, R N Caballero, G Theureau, L Guillemot, G Desvignes, A Parthasarathy, K Liu, G Shaifullah, H Hu, E van der Wateren, J Antoniadis, A-S Bak Nielsen, C G Bassa, A Berthereau, M Burgay, D J Champion, I Cognard, M Falxa, R D Ferdman, P C C Freire, J R Gair, E Graikou, Y J Guo, J Jang, G H Janssen, R Karuppusamy, M J Keith, M Kramer, K J Lee, X J Liu, A G Lyne, R A Main, J W McKee, M B Mickaliger, B B P Perera, D Perrodin, N K Porayko, A Possenti, S A Sanidas, A Sesana, L Speri, B W Stappers, C Tiburzi, A Vecchio, J P W Verbiest, J Wang, L Wang, H Xu, Chalumeau, A, Babak, S, Petiteau, A, Chen, S, Samajdar, A, Caballero, R, Theureau, G, Guillemot, L, Desvignes, G, Parthasarathy, A, Liu, K, Shaifullah, G, Hu, H, van der Wateren, E, Antoniadis, J, Bak Nielsen, A, Bassa, C, Berthereau, A, Burgay, M, Champion, D, Cognard, I, Falxa, M, Ferdman, R, Freire, P, Gair, J, Graikou, E, Guo, Y, Jang, J, Janssen, G, Karuppusamy, R, Keith, M, Kramer, M, Lee, K, Liu, X, Lyne, A, Main, R, Mckee, J, Mickaliger, M, Perera, B, Perrodin, D, Porayko, N, Possenti, A, Sanidas, S, Sesana, A, Speri, L, Stappers, B, Tiburzi, C, Vecchio, A, Verbiest, J, Wang, J, Wang, L, Xu, H, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ITA, USA, GBR, FRA, DEU, CAN, GRC, NLD, CHN, RUS, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and ANR-18-CE31-0015,PTA-France,Recherche d'ondes gravitationnelles avec un réseau de pulsars en France(2018)

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, methods: data analysis, 01 natural sciences, gravitational waves, Space and Planetary Science, pulsars: general, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), gravitational wave, methods: data analysi
Abstract

The European Pulsar Timing Array (EPTA) collaboration has recently released an extended data set for six pulsars (DR2) and reported evidence for a common red noise signal. Here we present a noise analysis for each of the six pulsars. We consider several types of noise: (i) radio frequency independent, "achromatic", and time-correlated red noise; (ii) variations of dispersion measure and scattering; (iii) system and band noise; and (iv) deterministic signals (other than gravitational waves) that could be present in the PTA data. We perform Bayesian model selection to find the optimal combination of noise components for each pulsar. Using these custom models we revisit the presence of the common uncorrelated red noise signal previously reported in the EPTA DR2 and show that the data still supports it with a high statistical significance. Next, we confirm that there is no preference for or against the Hellings-Downs spatial correlations expected for the stochastic gravitational-wave background. The main conclusion of the EPTA DR2 paper remains unchanged despite a very significant change in the noise model of each pulsar. However, modelling the noise is essential for the robust detection of gravitational waves and its impact could be significant when analysing the next EPTA data release, which will include a larger number of pulsars and more precise measurements., 21 pages, 11 figures, 7 tables, 1 appendix figure and 1 appendix table, accepted for publication to MNRAS

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31. Second Data Release from the European Pulsar Timing Array: Challenging the Ultralight Dark Matter Paradigm.

Author

Smarra C, Goncharov B, Barausse E, Antoniadis J, Babak S, Nielsen AB, Bassa CG, Berthereau A, Bonetti M, Bortolas E, Brook PR, Burgay M, Caballero RN, Chalumeau A, Champion DJ, Chanlaridis S, Chen S, Cognard I, Desvignes G, Falxa M, Ferdman RD, Franchini A, Gair JR, Graikou E, Grießmeier JM, Guillemot L, Guo YJ, Hu H, Iraci F, Izquierdo-Villalba D, Jang J, Jawor J, Janssen GH, Jessner A, Karuppusamy R, Keane EF, Keith MJ, Kramer M, Krishnakumar MA, Lackeos K, Lee KJ, Liu K, Liu Y, Lyne AG, McKee JW, Main RA, Mickaliger MB, Niţu IC, Parthasarathy A, Perera BBP, Perrodin D, Petiteau A, Porayko NK, Possenti A, Leclere HQ, Samajdar A, Sanidas SA, Sesana A, Shaifullah G, Speri L, Spiewak R, Stappers BW, Susarla SC, Theureau G, Tiburzi C, van der Wateren E, Vecchio A, Krishnan VV, Wang J, Wang L, and Wu Z

Abstract

Pulsar Timing Array experiments probe the presence of possible scalar or pseudoscalar ultralight dark matter particles through decade-long timing of an ensemble of galactic millisecond radio pulsars. With the second data release of the European Pulsar Timing Array, we focus on the most robust scenario, in which dark matter interacts only gravitationally with ordinary baryonic matter. Our results show that ultralight particles with masses 10^{-24.0}  eV≲m≲10^{-23.3}  eV cannot constitute 100% of the measured local dark matter density, but can have at most local density ρ≲0.3  GeV/cm^{3}.

Published
2023
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32. A massive pulsar in a compact relativistic binary.

Author

Antoniadis J, Freire PC, Wex N, Tauris TM, Lynch RS, van Kerkwijk MH, Kramer M, Bassa C, Dhillon VS, Driebe T, Hessels JW, Kaspi VM, Kondratiev VI, Langer N, Marsh TR, McLaughlin MA, Pennucci TT, Ransom SM, Stairs IH, van Leeuwen J, Verbiest JP, and Whelan DG

Abstract

Many physically motivated extensions to general relativity (GR) predict substantial deviations in the properties of spacetime surrounding massive neutron stars. We report the measurement of a 2.01 ± 0.04 solar mass (M⊙) pulsar in a 2.46-hour orbit with a 0.172 ± 0.003 M⊙ white dwarf. The high pulsar mass and the compact orbit make this system a sensitive laboratory of a previously untested strong-field gravity regime. Thus far, the observed orbital decay agrees with GR, supporting its validity even for the extreme conditions present in the system. The resulting constraints on deviations support the use of GR-based templates for ground-based gravitational wave detectors. Additionally, the system strengthens recent constraints on the properties of dense matter and provides insight to binary stellar astrophysics and pulsar recycling.

Published
2013
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33. Cardiac interbeat interval increment for the identification of obstructive sleep apnea.

Author

Roche F, Duverney D, Court-Fortune I, Pichot V, Costes F, Lacour JR, Antoniadis JA, Gaspoz JM, and Barthelemy JC

Subjects
Adult, Aged, Electrocardiography, Ambulatory, Female, Humans, Male, Middle Aged, Polysomnography, Predictive Value of Tests, Prospective Studies, ROC Curve, Sensitivity and Specificity, Sleep Apnea, Obstructive physiopathology, Heart Rate, Sleep Apnea, Obstructive diagnosis
Abstract

The prevalence of obstructive sleep apnea syndrome (OSAS) is high in developed countries but its diagnosis is costly. Based on physiological evidence, the frequency component of heart rate variability (HRV) was evaluated as a simple and inexpensive diagnostic tool in OSAS. The predictive accuracy of frequency-domain HRV variables obtained from 24-hour ECG Holter monitoring (the power spectral density of the interbeat interval increment of very low frequencies, "VLFIpsd," and its percentage over the total power spectral density, "% VLFI"), and of established time-domain HRV variables were analyzed by comparison with respiratory disturbances indexes assessed by complete polysomnography in 124 consecutive patients (98 men aged 53.8 +/- 11.2 years) with clinically suspected OSAS. OSAS was present in 54 (43.5%) patients according to standard criteria. Using receiver operating characteristic curve analysis, two of the three most powerful predictors were frequency-domain variables: % VLFI (W = 0.80, P < 0.0001), and VL-FIpsd (W = 0.79, P < 0.0001). Using a multiple logistic regression analysis, %VLFI was the most strongly associated with diseased status (adjusted OR: 8.4; 95% CI: 3.4-19.5). Using an appropriate threshold, %VLFI demonstrated a diagnostic sensitivity of 87%. A 3-month continuous positive airway pressure treatment significantly improved the same parameter. Frequency-domain analysis of the interbeat interval increment appears as a powerful tool for OSAS diagnosis and follow-up. The simplicity of its analysis and of its use makes of it a well-suited variable for mass screening of OSAS patients.

Published
2002
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