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  1. AU="Reardon, D. J."
  2. AU=Snchez-Calvo Beatriz
  3. AU="Odent, M."
  4. AU="Lyu, Xiaojun"
  5. AU="Semkova, Jordanka"
  6. AU="Stancáková, Alena"
  7. AU="Gerhard P. Püschel"
  8. AU="Rubino, Carlotta"
  9. AU="Pérez-Oliveira, Sergio"
  10. AU="Bunzel, Eli W"
  11. AU="Doan, Andrew H"
  12. AU="Mittal, Vikas"
  13. AU="Nørredam, Marie"
  14. AU="Kamienkowski, Juan E."
  15. AU="Caceres, Silvia"
  16. AU="Wang, Rui-Juan"
  17. AU="Adriaans, Ingrid E"
  18. AU="Potenza, Duilio M"
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  21. AU="Phelps, Robert"
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  28. AU="Lisfeld, Jasmin"
  29. AU="Al-Otaibi, Maha J"
  30. AU="Chechetkin, Vladimir R."
  31. AU="Suresh Kumar Meena Kumari, Madhusoodhanan"
  32. AU="Gu, Zheng"
  33. AU=D'Angelo Maximiliano A.
  34. AU="Maddestra, Nicola"
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  36. AU="Crann, Sara"
  37. AU="Ottino-González, Jonatan"
  38. AU="Klok, Peter F"
  39. AU="Bárbara Ayala-Orozco"
  40. AU=Goudsmit Jaap AU=Goudsmit Jaap
  41. AU="Qian, Junbin"
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  1. Book ; Online: An insight into chromatic behaviour of jitter in pulsars and its modelling

    Kulkarni, A. D. / Shannon, R. M. / Reardon, D. J. / Miles, M. T. / Bailes, M. / Shamohammadi, M.

    A case study of PSR J0437$-$4715

    2024  

    Abstract: Pulse-to-pulse profile shape variations introduce correlations in pulsar times of arrival (TOAs) across radio frequency measured at the same observational epoch. This leads to a broadband noise in excess of radiometer noise, which is termed pulse jitter ... ...

    Abstract Pulse-to-pulse profile shape variations introduce correlations in pulsar times of arrival (TOAs) across radio frequency measured at the same observational epoch. This leads to a broadband noise in excess of radiometer noise, which is termed pulse jitter noise. The presence of jitter noise limits the achievable timing precision and decreases the sensitivity of pulsar-timing data sets to signals of interest such as nanohertz-frequency gravitational waves. Current white noise models used in pulsar timing analyses attempt to account for this, assuming complete correlation of uncertainties through the arrival times collected in a unique observation and no frequency dependence of jitter (which corresponds to a rank-one covariance matrix). However, previous studies show that the brightest millisecond pulsar at decimetre wavelengths, PSR J0437$-$4715, shows decorrelation and frequency dependence of jitter noise. Here we present a detailed study of the decorrelation of jitter noise in PSR J0437$-$4715 and implement a new technique to model it. We show that the rate of decorrelation due to jitter can be expressed as a power-law in frequency. We analyse the covariance matrix associated with the jitter noise process and find that a higher-rank-approximation is essential to account for the decorrelation and to account for frequency dependence of jitter noise. We show that the use of this novel method significantly improves the estimation of other chromatic noise parameters such as dispersion measure variations. However, we find no significant improvement in errors and estimation of other timing model parameters suggesting that current methods are not biased for other parameters, for this pulsar due to this misspecification. We show that pulse energy variations show a similar decorrelation to the jitter noise, indicating a common origin for both observables.

    Comment: 10 pages; 7 figures; Accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS)
    Keywords Astrophysics - High Energy Astrophysical Phenomena ; Astrophysics - Instrumentation and Methods for Astrophysics
    Subject code 612
    Publishing date 2024-01-07
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Book ; Online: The MeerTime Pulsar Timing Array -- A Census of Emission Properties and Timing Potential

    Spiewak, R. / Bailes, M. / Miles, M. T. / Parthasarathy, A. / Reardon, D. J. / Shamohammadi, M. / Shannon, R. M. / Bhat, N. D. R. / Buchner, S. / Cameron, A. D. / Camilo, F. / Geyer, M. / Johnston, S. / Karastergiou, A. / Keith, M. / Kramer, M. / Serylak, M. / van Straten, W. / Theureau, G. /
    Krishnan, V. Venkatraman

    2022  

    Abstract: MeerTime is a five-year Large Survey Project to time pulsars with MeerKAT, the 64-dish South African precursor to the Square Kilometre Array. The science goals for the programme include timing millisecond pulsars (MSPs) to high precision (< 1 $\mu$s) to ... ...

    Abstract MeerTime is a five-year Large Survey Project to time pulsars with MeerKAT, the 64-dish South African precursor to the Square Kilometre Array. The science goals for the programme include timing millisecond pulsars (MSPs) to high precision (< 1 $\mu$s) to study the Galactic MSP population and to contribute to global efforts to detect nanohertz gravitational waves with the International Pulsar Timing Array (IPTA). In order to plan for the remainder of the programme and to use the allocated time most efficiently, we have conducted an initial census with the MeerKAT "L-band" receiver of 189 MSPs visible to MeerKAT and here present their dispersion measures, polarization profiles, polarization fractions, rotation measures, flux density measurements, spectral indices, and timing potential. As all of these observations are taken with the same instrument (which uses coherent dedispersion, interferometric polarization calibration techniques, and a uniform flux scale), they present an excellent resource for population studies. We used wideband pulse portraits as timing standards for each MSP and demonstrated that the MeerTime Pulsar Timing Array (MPTA) can already contribute significantly to the IPTA as it currently achieves better than 1 $\mu$s timing accuracy on 89 MSPs (observed with fortnightly cadence). By the conclusion of the initial five-year MeerTime programme in July 2024, the MPTA will be extremely significant in global efforts to detect the gravitational wave background with a contribution to the detection statistic comparable to other long-standing timing programmes.

    Comment: Accepted to PASA. 27 figures. Data to be made available under the DOI 10.5281/zenodo.5347875 at the time of publication
    Keywords Astrophysics - High Energy Astrophysical Phenomena
    Subject code 551
    Publishing date 2022-04-08
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Book ; Online: Identifying and mitigating noise sources in precision pulsar timing data sets

    Goncharov, Boris / Reardon, D. J. / Shannon, R. M. / Zhu, Xing-Jiang / Thrane, Eric / Bailes, M. / Bhat, N. D. R. / Dai, S. / Hobbs, G. / Kerr, M. / Manchester, R. N. / Osłowski, S. / Parthasarathy, A. / Russell, C. J. / Spiewak, R. / Thyagarajan, N. / Wang, J. B.

    2020  

    Abstract: Pulsar timing array projects measure the pulse arrival times of millisecond pulsars for the primary purpose of detecting nanohertz-frequency gravitational waves. The measurements include contributions from a number of astrophysical and instrumental ... ...

    Abstract Pulsar timing array projects measure the pulse arrival times of millisecond pulsars for the primary purpose of detecting nanohertz-frequency gravitational waves. The measurements include contributions from a number of astrophysical and instrumental processes, which can either be deterministic or stochastic. It is necessary to develop robust statistical and physical models for these noise processes because incorrect models diminish sensitivity and may cause a spurious gravitational wave detection. Here we characterise noise processes for the 26 pulsars in the second data release of the Parkes Pulsar Timing Array using Bayesian inference. In addition to well-studied noise sources found previously in pulsar timing array data sets such as achromatic timing noise and dispersion measure variations, we identify new noise sources including time-correlated chromatic noise that we attribute to variations in pulse scattering. We also identify "exponential dip" events in four pulsars, which we attribute to magnetospheric effects as evidenced by pulse profile shape changes observed for three of the pulsars. This includes an event in PSR J1713$+$0747, which had previously been attributed to interstellar propagation. We present noise models to be used in searches for gravitational waves. We outline a robust methodology to evaluate the performance of noise models and identify unknown signals in the data. The detection of variations in pulse profiles highlights the need to develop efficient profile domain timing methods.

    Comment: 18 pages, 7 figures, 5 tables
    Keywords Astrophysics - High Energy Astrophysical Phenomena ; Astrophysics - Instrumentation and Methods for Astrophysics ; General Relativity and Quantum Cosmology
    Subject code 551
    Publishing date 2020-10-12
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Gravitational waves from binary supermassive black holes missing in pulsar observations.

    Shannon, R M / Ravi, V / Lentati, L T / Lasky, P D / Hobbs, G / Kerr, M / Manchester, R N / Coles, W A / Levin, Y / Bailes, M / Bhat, N D R / Burke-Spolaor, S / Dai, S / Keith, M J / Osłowski, S / Reardon, D J / van Straten, W / Toomey, L / Wang, J-B /
    Wen, L / Wyithe, J S B / Zhu, X-J

    Science (New York, N.Y.)

    2015  Volume 349, Issue 6255, Page(s) 1522–1525

    Abstract: Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. ...

    Abstract Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrained the characteristic amplitude of this background, A(c,yr), to be <1.0 × 10(-15) with 95% confidence. This limit excludes predicted ranges for A(c,yr) from current models with 91 to 99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments and that higher-cadence and shorter-wavelength observations would be more sensitive to gravitational waves.
    Language English
    Publishing date 2015-09-25
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 128410-1
    ISSN 1095-9203 ; 0036-8075
    ISSN (online) 1095-9203
    ISSN 0036-8075
    DOI 10.1126/science.aab1910
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Book ; Online: Comparing recent PTA results on the nanohertz stochastic gravitational wave background

    The International Pulsar Timing Array Collaboration / Agazie, G. / Antoniadis, J. / Anumarlapudi, A. / Archibald, A. M. / Arumugam, P. / Arumugam, S. / Arzoumanian, Z. / Askew, J. / Babak, S. / Bagchi, M. / Bailes, M. / Nielsen, A. -S. Bak / Baker, P. T. / Bassa, C. G. / Bathula, A. / Bécsy, B. / Berthereau, A. / Bhat, N. D. R. /
    Blecha, L. / Bonetti, M. / Bortolas, E. / Brazier, A. / Brook, P. R. / Burgay, M. / Burke-Spolaor, S. / Burnette, R. / Caballero, R. N. / Cameron, A. / Case, R. / Chalumeau, A. / Champion, D. J. / Chanlaridis, S. / Charisi, M. / Chatterjee, S. / Chatziioannou, K. / Cheeseboro, B. D. / Chen, S. / Chen, Z. -C. / Cognard, I. / Cohen, T. / Coles, W. A. / Cordes, J. M. / Cornish, N. J. / Crawford, F. / Cromartie, H. T. / Crowter, K. / Curyło, M. / Cutler, C. J. / Dai, S. / Dandapat, S. / Deb, D. / DeCesar, M. E. / DeGan, D. / Demorest, P. B. / Deng, H. / Desai, S. / Desvignes, G. / Dey, L. / Dhanda-Batra, N. / Di Marco, V. / Dolch, T. / Drachler, B. / Dwivedi, C. / Ellis, J. A. / Falxa, M. / Feng, Y. / Ferdman, R. D. / Ferrara, E. C. / Fiore, W. / Fonseca, E. / Franchini, A. / Freedman, G. E. / Gair, J. R. / Garver-Daniels, N. / Gentile, P. A. / Gersbach, K. A. / Glaser, J. / Good, D. C. / Goncharov, B. / Gopakumar, A. / Graikou, E. / Grießmeier, J. -M. / Guillemot, L. / Gültekin, K. / Guo, Y. J. / Gupta, Y. / Grunthal, K. / Hazboun, J. S. / Hisano, S. / Hobbs, G. B. / Hourihane, S. / Hu, H. / Iraci, F. / Islo, K. / Izquierdo-Villalba, D. / Jang, J. / Jawor, J. / Janssen, G. H. / Jennings, R. J. / Jessner, A. / Johnson, A. D. / Jones, M. L. / Joshi, B. C. / Kaiser, A. R. / Kaplan, D. L. / Kapur, A. / Kareem, F. / Karuppusamy, R. / Keane, E. F. / Keith, M. J. / Kelley, L. Z. / Kerr, M. / Key, J. S. / Kharbanda, D. / Kikunaga, T. / Klein, T. C. / Kolhe, N. / Kramer, M. / Krishnakumar, M. A. / Kulkarni, A. / Laal, N. / Lackeos, K. / Lam, M. T. / Lamb, W. G. / Larsen, B. B. / Lazio, T. J. W. / Lee, K. J. / Levin, Y. / Lewandowska, N. / Littenberg, T. B. / Liu, K. / Liu, T. / Liu, Y. / Lommen, A. / Lorimer, D. R. / Lower, M. E. / Luo, J. / Luo, R. / Lynch, R. S. / Lyne, A. G. / Ma, C. -P. / Maan, Y. / Madison, D. R. / Main, R. A. / Manchester, R. N. / Mandow, R. / Mattson, M. A. / McEwen, A. / McKee, J. W. / McLaughlin, M. A. / McMann, N. / Meyers, B. W. / Meyers, P. M. / Mickaliger, M. B. / Miles, M. / Mingarelli, C. M. F. / Mitridate, A. / Natarajan, P. / Nathan, R. S. / Ng, C. / Nice, D. J. / Niţu, I. C. / Nobleson, K. / Ocker, S. K. / Olum, K. D. / Osłowski, S. / Paladi, A. K. / Parthasarathy, A. / Pennucci, T. T. / Perera, B. B. P. / Perrodin, D. / Petiteau, A. / Petrov, P. / Pol, N. S. / Porayko, N. K. / Possenti, A. / Prabu, T. / Leclere, H. Quelquejay / Radovan, H. A. / Rana, P. / Ransom, S. M. / Ray, P. S. / Reardon, D. J. / Rogers, A. F. / Romano, J. D. / Russell, C. J. / Samajdar, A. / Sanidas, S. A. / Sardesai, S. C. / Schmiedekamp, A. / Schmiedekamp, C. / Schmitz, K. / Schult, L. / Sesana, A. / Shaifullah, G. / Shannon, R. M. / Shapiro-Albert, B. J. / Siemens, X. / Simon, J. / Singha, J. / Siwek, M. S. / Speri, L. / Spiewak, R. / Srivastava, A. / Stairs, I. H. / Stappers, B. W. / Stinebring, D. R. / Stovall, K. / Sun, J. P. / Surnis, M. / Susarla, S. C. / Susobhanan, A. / Swiggum, J. K. / Takahashi, K. / Tarafdar, P. / Taylor, J. / Taylor, S. R. / Theureau, G. / Thrane, E. / Thyagarajan, N. / Tiburzi, C. / Toomey, L. / Turner, J. E. / Unal, C. / Vallisneri, M. / van der Wateren, E. / van Haasteren, R. / Vecchio, A. / Krishnan, V. Venkatraman / Verbiest, J. P. W. / Vigeland, S. J. / Wahl, H. M. / Wang, S. / Wang, Q. / Witt, C. A. / Wang, J. / Wang, L. / Wayt, K. E. / Wu, Z. / Young, O. / Zhang, L. / Zhang, S. / Zhu, X. -J. / Zic, A.

    2023  

    Abstract: The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational wave background (GWB). Given that each PTA made different ... ...

    Abstract The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within $1\sigma$. The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we "extended" each PTA's data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the Hellings and Downs correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA's Data Release 3, which will involve not just adding in additional pulsars, but also including data from all three PTAs where any given pulsar is timed by more than as single PTA.

    Comment: 21 pages, 9 figures, submitted to ApJ
    Keywords Astrophysics - High Energy Astrophysical Phenomena ; General Relativity and Quantum Cosmology
    Subject code 551
    Publishing date 2023-09-01
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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