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16 results on '"Toomey, L."'

1. A pulsar-based time-scale from the International Pulsar Timing Array

Author

Hobbs, G, Guo, L, Caballero, RN, Coles, W, Lee, KJ, Manchester, RN, Reardon, DJ, Matsakis, D, Tong, ML, Arzoumanian, Z, Bailes, M, Bassa, CG, Bhat, NDR, Brazier, A, Burke-Spolaor, S, Champion, DJ, Chatterjee, S, Cognard, I, Dai, S, Desvignes, G, Dolch, T, Ferdman, RD, Graikou, E, Guillemot, L, Janssen, GH, Keith, MJ, Kerr, M, Kramer, M, Lam, MT, Liu, K, Lyne, A, Lazio, TJW, Lynch, R, McKee, JW, McLaughlin, MA, Mingarelli, CMF, Nice, DJ, Osłowski, S, Pennucci, TT, Perera, BBP, Perrodin, D, Possenti, A, Russell, CJ, Sanidas, S, Sesana, A, Shaifullah, G, Shannon, RM, Simon, J, Spiewak, R, Stairs, IH, Stappers, BW, Swiggum, JK, Taylor, SR, Theureau, G, Toomey, L, van Haasteren, R, Wang, JB, Wang, Y, and Zhu, XJ

Subjects
time, pulsars: general, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract

We have constructed a new time-scale, TT(IPTA16), based on observations of radio pulsars presented in the first data release from the International Pulsar Timing Array (IPTA). We used two analysis techniques with independent estimates of the noise models for the pulsar observations and different algorithms for obtaining the pulsar time-scale. The two analyses agree within the estimated uncertainties and both agree with TT(BIPM17), a post-corrected time-scale produced by the Bureau International des Poids et Mesures (BIPM). We show that both methods could detect significant errors in TT(BIPM17) if they were present. We estimate the stability of the atomic clocks from which TT(BIPM17) is derived using observations of four rubidium fountain clocks at the US Naval Observatory. Comparing the power spectrum of TT(IPTA16) with that of these fountain clocks suggests that pulsar-based time-scales are unlikely to contribute to the stability of the best time-scales over the next decade, but they will remain a valuable independent check on atomic time-scales. We also find that the stability of the pulsar-based time-scale is likely to be limited by our knowledge of solar-system dynamics, and that errors in TT(BIPM17) will not be a limiting factor for the primary goal of the IPTA, which is to search for the signatures of nano-Hertz gravitational waves.

Published
2020

2. Comparison of pulsar positions from timing and very long baseline astrometry

Author

Wang, JB, Coles, WA, Hobbs, G, Shannon, RM, Manchester, RN, Kerr, M, Yuan, JP, Wang, N, Bailes, M, Bhat, NDR, Dai, S, Dempsey, J, Keith, MJ, Lasky, PD, Levin, Y, Osłowski, S, Ravi, V, Reardon, DJ, Rosado, PA, Russell, CJ, Spiewak, R, van Straten, W, Toomey, L, Wen, L, You, X-P, and Zhu, X-J

Subjects
methods: data analysis, techniques: interferometric, astrometry, reference systems, pulsars: general, Astronomical and Space Sciences, Astronomy & Astrophysics
Published
2017

3. Wide-band profile domain pulsar timing analysis

Author

Lentati, L, Kerr, M, Dai, S, Hobson, MP, Shannon, RM, Hobbs, G, Bailes, M, Bhat, ND Ramesh, Burke-Spolaor, S, Coles, W, Dempsey, J, Lasky, PD, Levin, Y, Manchester, RN, Osłowski, S, Ravi, V, Reardon, DJ, Rosado, PA, Spiewak, R, van Straten, W, Toomey, L, Wang, J, Wen, L, You, X, and Zhu, X

Subjects
methods: data analysis, pulsars: general, pulsars: individual, Astronomical and Space Sciences, Astronomy & Astrophysics
Published
2017

4. THE DISTURBANCE OF A MILLISECOND PULSAR MAGNETOSPHERE

Author

Shannon, RM, Lentati, LT, Kerr, M, Bailes, M, Bhat, NDR, Coles, WA, Dai, S, Dempsey, J, Hobbs, G, Keith, MJ, Lasky, PD, Levin, Y, Manchester, RN, Osłowski, S, Ravi, V, Reardon, DJ, Rosado, PA, Spiewak, R, van Straten, W, Toomey, L, Wang, J-B, Wen, L, You, X-P, and Zhu, X-J

Subjects
pulsars: general, pulsars: individual, stars: neutron, Astronomical and Space Sciences, Astronomy & Astrophysics
Published
2016

5. From spin noise to systematics: stochastic processes in the first International Pulsar Timing Array data release

Author

Lentati, L, Shannon, RM, Coles, WA, Verbiest, JPW, van Haasteren, R, Ellis, JA, Caballero, RN, Manchester, RN, Arzoumanian, Z, Babak, S, Bassa, CG, Bhat, NDR, Brem, P, Burgay, M, Burke-Spolaor, S, Champion, D, Chatterjee, S, Cognard, I, Cordes, JM, Dai, S, Demorest, P, Desvignes, G, Dolch, T, Ferdman, RD, Fonseca, E, Gair, JR, Gonzalez, ME, Graikou, E, Guillemot, L, Hessels, JWT, Hobbs, G, Janssen, GH, Jones, G, Karuppusamy, R, Keith, M, Kerr, M, Kramer, M, Lam, MT, Lasky, PD, Lassus, A, Lazarus, P, Lazio, TJW, Lee, KJ, Levin, L, Liu, K, Lynch, RS, Madison, DR, McKee, J, McLaughlin, M, McWilliams, ST, Mingarelli, CMF, Nice, DJ, Osłowski, S, Pennucci, TT, Perera, BBP, Perrodin, D, Petiteau, A, Possenti, A, Ransom, SM, Reardon, D, Rosado, PA, Sanidas, SA, Sesana, A, Shaifullah, G, Siemens, X, Smits, R, Stairs, I, Stappers, B, Stinebring, DR, Stovall, K, Swiggum, J, Taylor, SR, Theureau, G, Tiburzi, C, Toomey, L, Vallisneri, M, van Straten, W, Vecchio, A, Wang, J-B, Wang, Y, You, XP, Zhu, WW, and Zhu, X-J

Subjects
methods: data analysis, pulsars: general, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract

We analyse the stochastic properties of the 49 pulsars that comprise the first International Pulsar Timing Array (IPTA) data release. We use Bayesian methodology, performing model selection to determine the optimal description of the stochastic signals present in each pulsar. In addition to spin-noise and dispersion-measure (DM) variations, these models can include timing noise unique to a single observing system, or frequency band. We show the improved radio-frequency coverage and presence of overlapping data from different observing systems in the IPTA data set enables us to separate both system and band-dependent effects with much greater efficacy than in the individual pulsar timing array (PTA) data sets. For example, we show that PSR J1643-1224 has, in addition to DM variations, significant band-dependent noise that is coherent between PTAs which we interpret as coming from time-variable scattering or refraction in the ionized interstellar medium. Failing to model these different contributions appropriately can dramatically alter the astrophysical interpretation of the stochastic signals observed in the residuals. In some cases, the spectral exponent of the spin-noise signal can vary from 1.6 to 4 depending upon the model, which has direct implications for the long-term sensitivity of the pulsar to a stochastic gravitational-wave (GW) background. By using a more appropriate model, however, we can greatly improve a pulsar's sensitivity to GWs. For example, including system and band-dependent signals in the PSR J0437-4715 data set improves the upper limit on a fiducial GW background by ~60 per cent compared to a model that includes DM variations and spin-noise only.

Published
2016

6. Timing analysis for 20 millisecond pulsars in the Parkes Pulsar Timing Array

Author

Reardon, DJ, Hobbs, G, Coles, W, Levin, Y, Keith, MJ, Bailes, M, Bhat, NDR, Burke-Spolaor, S, Dai, S, Kerr, M, Lasky, PD, Manchester, RN, Osłowski, S, Ravi, V, Shannon, RM, van Straten, W, Toomey, L, Wang, J, Wen, L, You, XP, and Zhu, X-J

Subjects
astrometry, ephemerides, parallaxes, proper motions, pulsars: general, Astronomical and Space Sciences, Astronomy & Astrophysics
Published
2016

7. PULSAR OBSERVATIONS OF EXTREME SCATTERING EVENTS

Author

Coles, WA, Kerr, M, Shannon, RM, Hobbs, GB, Manchester, RN, You, X-P, Bailes, M, Bhat, NDR, Burke-Spolaor, S, Dai, S, Keith, MJ, Levin, Y, Osłowski, S, Ravi, V, Reardon, D, Toomey, L, van Straten, W, Wang, JB, Wen, L, and Zhu, XJ

Subjects
ISM: structure, pulsars: general, turbulence, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

Extreme scattering events (ESEs) in the interstellar medium (ISM) were first observed in regular flux measurements of compact extragalactic sources. They are characterized by a flux variation over a period of weeks, suggesting the passage of a "diverging plasma lens" across the line of sight (LOS). Modeling the refraction of such a lens indicates that the structure size must be of the order of AU and the electron density of the order of 10s of cm-3. Similar structures have been observed in measurements of pulsar intensity scintillation and group delay. Here we report observations of two ESEs, showing increases in both intensity scintillation and dispersion made with the Parkes Pulsar Timing Array. These allow us to make more complete models of the ESE, including an estimate of the "outer-scale" of the turbulence in the plasma lens. These observations clearly show that the ESE structure is fully turbulent on an AU scale. They provide some support for the idea that the structures are extended along the LOS, such as would be the case for a scattering shell. The dispersion measurements also show a variety of AU scale structures that would not be called ESEs, yet involve electron density variations typical of ESEs and likely have the same origin.

Published
2015

8. A study of multifrequency polarization pulse profiles of millisecond pulsars

Author

Dai, S, Hobbs, G, Manchester, RN, Kerr, M, Shannon, RM, van Straten, W, Mata, A, Bailes, M, Bhat, NDR, Burke-Spolaor, S, Coles, WA, Johnston, S, Keith, MJ, Levin, Y, Osłowski, S, Reardon, D, Ravi, V, Sarkissian, JM, Tiburzi, C, Toomey, L, Wang, HG, Wang, J-B, Wen, L, Xu, RX, Yan, WM, and Zhu, X-J

Subjects
polarization, radiation mechanisms: non-thermal, pulsars: general, radio continuum: general, Astronomical and Space Sciences, Astronomy & Astrophysics
Published
2015

9. Searching for gravitational wave memory bursts with the Parkes Pulsar Timing Array

Author

Wang, JB, Hobbs, G, Coles, W, Shannon, RM, Zhu, XJ, Madison, DR, Kerr, M, Ravi, V, Keith, MJ, Manchester, RN, Levin, Y, Bailes, M, Bhat, NDR, Burke-Spolaor, S, Dai, S, Oslowski, S, van Straten, W, Toomey, L, Wang, N, and Wen, L

Subjects
gravitational waves, methods: data analysis, pulsars: general, Astronomical and Space Sciences, Astronomy & Astrophysics
Published
2015

10. An all-sky search for continuous gravitational waves in the Parkes Pulsar Timing Array data set

Author

Zhu, X-J, Hobbs, G, Wen, L, Coles, WA, Wang, J-B, Shannon, RM, Manchester, RN, Bailes, M, Bhat, NDR, Burke-Spolaor, S, Dai, S, Keith, MJ, Kerr, M, Levin, Y, Madison, DR, Osłowski, S, Ravi, V, Toomey, L, and van Straten, W

Subjects
gravitational waves, methods: data analysis, pulsars: general, galaxies: evolution, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract

We present results of an all-sky search in the Parkes Pulsar Timing Array (PPTA) Data Release 1 data set for continuous gravitational waves (GWs) in the frequency range from 5 × 10-9 to 2 × 10-7 Hz. Such signals could be produced by individual supermassive binary black hole systems in the early stage of coalescence.We phase up the pulsar timing array data set to form, for each position on the sky, two data streams that correspond to the twoGWpolarizations and then carry out an optimal search for GW signals on these data streams. Since no statistically significant GWs were detected, we place upper limits on the intrinsic GW strain amplitude h0 for a range of GW frequencies. For example, at 10-8 Hz our analysis has excluded with 95 per cent confidence the presence of signals with h0 ≥ 1.7 × 10-14. Our new limits are about a factor of 4 more stringent than those of Yardley et al. based on an earlier PPTA data set and a factor of 2 better than those reported in the recent Arzoumanian et al. paper.We also present PPTA directional sensitivity curves and find that for the most sensitive region on the sky, the current data set is sensitive to GWs from circular supermassive binary black holes with chirp masses of 109M⊙ out to a luminosity distance of about 100 Mpc. Finally, we set an upper limit of 4 × 10-3 Mpc-3 Gyr-1 at 95 per cent confidence on the coalescence rate of nearby (z ≲ 0.1) supermassive binary black holes in circular orbits with chirp masses of 1010M⊙.

Published
2014

11. Limitations in timing precision due to single-pulse shape variability in millisecond pulsars

Author

Shannon, RM, Osłowski, S, Dai, S, Bailes, M, Hobbs, G, Manchester, RN, van Straten, W, Raithel, CA, Ravi, V, Toomey, L, Bhat, NDR, Burke-Spolaor, S, Coles, WA, Keith, MJ, Kerr, M, Levin, Y, Sarkissian, JM, Wang, J-B, Wen, L, and Zhu, X-J

Subjects
methods: data analysis, stars: neutron, pulsars: general, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract

High-sensitivity radio-frequency observations of millisecond pulsars usually show stochastic, broad-band, pulse-shape variations intrinsic to the pulsar emission process. These variations induce jitter noise in pulsar timing observations; understanding the properties of this noise is of particular importance for the effort to detect gravitational waves with pulsar timing arrays. We assess the short-term profile and timing stability of 22 millisecond pulsars that are part of the Parkes Pulsar Timing Array sample by examining intraobservation arrival time variability and single-pulse phenomenology. In 7 of the 22 pulsars, in the band centred at approximately 1400 MHz, we find that the brightest observations are limited by intrinsic jitter. We find consistent results, either detections or upper limits, for jitter noise in other frequency bands. PSR J1909-3744 shows the lowest levels of jitter noise, which we estimate to contribute ~10 ns root mean square error to the arrival times for hour-duration observations. Larger levels of jitter noise are found in pulsars with wider pulses and distributions of pulse intensities. The jitter noise in PSR J0437-4715 decorrelates over a bandwidth of ∼2 GHz. We show that the uncertainties associated with timing pulsar models can be improved by including physically motivated jitter uncertainties. Pulse-shape variations will limit the timing precision at future, more sensitive, telescopes; it is imperative to account for this noise when designing instrumentation and timing campaigns for these facilities. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Published
2014

12. From spin noise to systematics: stochastic processes in the first International Pulsar Timing Array data release

Author

R. van Haasteren, Scott M. Ransom, S. Babak, Antoine Petiteau, Paul Demorest, L. Toomey, Gemma H. Janssen, Alberto Sesana, Marjorie Gonzalez, Sourav Chatterjee, A. Lassus, Ryan Shannon, Justin A. Ellis, Glenn Jones, E. Graikou, J. W. McKee, Kang Liu, Kejia Lee, Matthew Kerr, Sarah Burke-Spolaor, William A. Coles, Maura McLaughlin, G. Shaifullah, Stephen Taylor, Weiwei Zhu, P. Lazarus, S. A. Sanidas, D. J. Champion, Delphine Perrodin, R. N. Caballero, Kevin Stovall, Joris P. W. Verbiest, Benetge Perera, Richard N. Manchester, C. G. Bassa, Emmanuel Fonseca, Jonathan R. Gair, George Hobbs, D. R. Madison, R. Smits, Alberto Vecchio, Daniel R. Stinebring, Michael T. Lam, Daniel J. Reardon, X. P. You, Zaven Arzoumanian, Paul D. Lasky, Yue-Fei Wang, Lucas Guillemot, R. S. Lynch, Pablo Rosado, Lina Levin, Xing-Jiang Zhu, Chiara M. F. Mingarelli, L. Lentati, Benjamin Stappers, A. Possenti, T. J. W. Lazio, Robert D. Ferdman, Stefan Oslowski, J. K. Swiggum, X. Siemens, Gregory Desvignes, Gilles Theureau, Ramesh Karuppusamy, Ismaël Cognard, M. Burgay, Timothy T. Pennucci, Michele Vallisneri, J. B. Wang, James M. Cordes, Sean T. McWilliams, David J. Nice, P. Brem, W. van Straten, Caterina Tiburzi, N. D. R. Bhat, Shi Dai, Jason W. T. Hessels, Ingrid H. Stairs, Timothy Dolch, Michael Kramer, Michael Keith, Lentati, L, Shannon, R, Coles, W, Verbiest, J, van Haasteren, R, Ellis, J, Caballero, R, Manchester, R, Arzoumanian, Z, Babak, S, Bassa, C, Bhat, N, Brem, P, Burgay, M, Burke-Spolaor, S, Champion, D, Chatterjee, S, Cognard, I, Cordes, J, Dai, S, Demorest, P, Desvignes, G, Dolch, T, Ferdman, R, Fonseca, E, Gair, J, Gonzalez, M, Graikou, E, Guillemot, L, Hessels, J, Hobbs, G, Janssen, G, Jones, G, Karuppusamy, R, Keith, M, Kerr, M, Kramer, M, Lam, M, Lasky, P, Lassus, A, Lazarus, P, Lazio, T, Lee, K, Levin, L, Liu, K, Lynch, R, Madison, D, Mckee, J, Mclaughlin, M, Mcwilliams, S, Mingarelli, C, Nice, D, Osłowski, S, Pennucci, T, Perera, B, Perrodin, D, Petiteau, A, Possenti, A, Ransom, S, Reardon, D, Rosado, P, Sanidas, S, Sesana, A, Shaifullah, G, Siemens, X, Smits, R, Stairs, I, Stappers, B, Stinebring, D, Stovall, K, Swiggum, J, Taylor, S, Theureau, G, Tiburzi, C, Toomey, L, Vallisneri, M, van Straten, W, Vecchio, A, Wang, J, Wang, Y, You, X, Zhu, W, Zhu, X, High Energy Astrophys. & Astropart. Phys (API, FNWI), Cavendish Laboratory, University of Cambridge [UK] (CAM), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of California, University of California (UC), Max-Planck-Institut für Radioastronomie (MPIFR), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), NASA Goddard Space Flight Center (GSFC), Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), Max-Planck-Gesellschaft, Netherlands Institute for Radio Astronomy (ASTRON), Curtin University [Perth], Planning and Transport Research Centre (PATREC), INAF - Osservatorio Astronomico di Cagliari (OAC), Istituto Nazionale di Astrofisica (INAF), National Radio Astronomy Observatory (NRAO), Center for Radiophysics and Space Research [Ithaca] (CRSR), Cornell University [New York], 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), Department of Astronomy [Ithaca], Department of Physics, Hillsdale College, 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), University of British Columbia (UBC), Vancouver Coastal Health, Department of Nuclear Medicine, Netherlands Institute for Radio Astronomy ( ASTRON ), ARC Centre of Excellence for Coral Reef Studies (CoralCoE), James Cook University (JCU), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Vrije Universiteit Medical Centre (VUMC), Vrije Universiteit Amsterdam [Amsterdam] (VU), Kavli Institute for Astronomy and Astrophysics [Beijing] (KIAA-PKU), Peking University [Beijing], National Radio Astronomy Observatory [Green Bank] (NRAO), Jodrell Bank Centre for Astrophysics (JBCA), Department of Physics, West Virginia University, West Virginia University, Theoretical Astrophysics [Pasadena] (TAPIR), California Institute of Technology (CALTECH), Physics Department, Lafayette College, Lafayette College [Easton], Department of Astronomy [Charlottesville], University of Virginia, APC - Gravitation (APC-Gravitation), 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)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-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)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), Max-Planck-Gesellschaft-Max-Planck-Gesellschaft, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre for Astrophysics and Supercomputing [Swinburne] (CAS), Swinburne University of Technology [Melbourne], Anton Pannekoek Institute for Astronomy, University of Amsterdam [Amsterdam] (UvA), University of Wisconsin - Milwaukee, Department of Physics and Astronomy, University of British Columbia, Department of Physics and Astronomy [Oberlin], Oberlin College, Institute of Meteoritics [Albuquerque] (IOM), The University of New Mexico [Albuquerque], Department of Physics and Astronomy, West Virginia University, West Virginia University [Morgantown], Birmingham City University (BCU), Xinjiang Astronomical Observatory, Chinese Academy of Sciences [Beijing] (CAS), Huazhong University of Science and Technology [Wuhan] (HUST), School of Physical Science and Technology, Southwest University [Chongqing], Australian Research Council Discovery Project DP140102578NASA through Einstein Fellowship grant PF3-140116West Light Foundation of CAS XBBS201322 and NSFC project no.11403086National Science Fundation of China (NSFC) award number 11503007NNSF of China (U1231120) and FRFCU (XDJK2015B012), European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), European Project: 227947,EC:FP7:ERC,ERC-2008-AdG,LEAP(2009), European Project: 610058,EC:FP7:ERC,ERC-2013-SyG,BLACKHOLECAM(2014), Cornell University, 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), Division of Physics, Mathematics and Astronomy [Pasadena], California Institute of Technology (CALTECH)-California Institute of Technology (CALTECH), 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)-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)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), 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)-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)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI), California Institute of Technology (CALTECH)-NASA, 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), University of Virginia [Charlottesville], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut ) (AEI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, data analysis, pulsars: general [methods], FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Methods: Data analysi, Astrophysics, Astronomy & Astrophysics, general [pulsars], 01 natural sciences, General Relativity and Quantum Cosmology, pulsars:individual, Binary pulsar, Pulsar, 0103 physical sciences, data analysis [methods], Coherence (signal processing), Sensitivity (control systems), Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Stochastic process, Noise (signal processing), Model selection, Pulsars: General, Astronomy and Astrophysics, methods: data analysis, LIGO, Computational physics, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astronomical and Space Sciences
Abstract

We analyse the stochastic properties of the 49 pulsars that comprise the first International Pulsar Timing Array (IPTA) data release. We use Bayesian methodology, performing model selection to determine the optimal description of the stochastic signals present in each pulsar. In addition to spin-noise and dispersion-measure (DM) variations, these models can include timing noise unique to a single observing system, or frequency band. We show the improved radio-frequency coverage and presence of overlapping data from different observing systems in the IPTA data set enables us to separate both system and band-dependent effects with much greater efficacy than in the individual PTA data sets. For example, we show that PSR J1643$-$1224 has, in addition to DM variations, significant band-dependent noise that is coherent between PTAs which we interpret as coming from time-variable scattering or refraction in the ionised interstellar medium. Failing to model these different contributions appropriately can dramatically alter the astrophysical interpretation of the stochastic signals observed in the residuals. In some cases, the spectral exponent of the spin noise signal can vary from 1.6 to 4 depending upon the model, which has direct implications for the long-term sensitivity of the pulsar to a stochastic gravitational-wave (GW) background. By using a more appropriate model, however, we can greatly improve a pulsar's sensitivity to GWs. For example, including system and band-dependent signals in the PSR J0437$-$4715 data set improves the upper limit on a fiducial GW background by $\sim 60\%$ compared to a model that includes DM variations and spin-noise only., Comment: 29 pages. 16 figures. Accepted for publication in MNRAS

Published
2016
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13. A pulsar-based time-scale from the International Pulsar Timing Array

Author

Sourav Chatterjee, Daniel J. Reardon, Ismaël Cognard, Gemma H. Janssen, Sarah Burke-Spolaor, Zaven Arzoumanian, Michael T. Lam, Kejia Lee, Michael Kramer, Benetge Perera, J. B. Wang, L. Guo, Renée Spiewak, Ryan Shannon, David J. Nice, Richard N. Manchester, N. D. R. Bhat, D. Matsakis, E. Graikou, Joseph Simon, Ingrid H. Stairs, R. N. Caballero, Shi Dai, Matthew Bailes, Christopher J. Russell, Alberto Sesana, Robert D. Ferdman, Lucas Guillemot, Delphine Perrodin, Xing-Jiang Zhu, Andrew Lyne, Chiara M. F. Mingarelli, C. G. Bassa, Benjamin Stappers, A. Brazier, R. van Haasteren, Timothy T. Pennucci, J. W. McKee, Yue-Fei Wang, Maura McLaughlin, Michael Keith, L. Toomey, Matthew Kerr, William A. Coles, Timothy Dolch, Stefan Oslowski, M. L. Tong, Stephen Taylor, D. J. Champion, Kang Liu, S. A. Sanidas, George Hobbs, J. K. Swiggum, Gregory Desvignes, Gilles Theureau, A. Possenti, T. J. W. Lazio, R. S. Lynch, G. Shaifullah, 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)-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), Unité Scientifique de la Station de Nançay (USN), 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), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Hobbs, G, Guo, L, Caballero, R, Coles, W, Lee, K, Manchester, R, Reardon, D, Matsakis, D, Tong, M, Arzoumanian, Z, Bailes, M, Bassa, C, Bhat, N, Brazier, A, Burke-Spolaor, S, Champion, D, Chatterjee, S, Cognard, I, Dai, S, Desvignes, G, Dolch, T, Ferdman, R, Graikou, E, Guillemot, L, Janssen, G, Keith, M, Kerr, M, Kramer, M, Lam, M, Liu, K, Lyne, A, Lazio, T, Lynch, R, Mckee, J, Mclaughlin, M, Mingarelli, C, Nice, D, Osłowski, S, Pennucci, T, Perera, B, Perrodin, D, Possenti, A, Russell, C, Sanidas, S, Sesana, A, Shaifullah, G, Shannon, R, Simon, J, Spiewak, R, Stairs, I, Stappers, B, Swiggum, J, Taylor, S, Theureau, G, Toomey, L, van Haasteren, R, Wang, J, Wang, Y, Zhu, X, 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), 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), 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), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), ITA, USA, GBR, FRA, DEU, AUS, CAN, NLD, CHN, and HUN

Subjects
Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astronomy & Astrophysics, 01 natural sciences, Stability (probability), general [pulsars], Pulsar, Millisecond pulsar, Observatory, pulsars: general, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, time, Physics, 010308 nuclear & particles physics, Gravitational wave, Spectral density, Astronomy and Astrophysics, Atomic clock, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics - Instrumentation and Methods for Astrophysics, Noise (radio), Astronomical and Space Sciences
Abstract

We have constructed a new timescale, TT(IPTA16), based on observations of radio pulsars presented in the first data release from the International Pulsar Timing Array (IPTA). We used two analysis techniques with independent estimates of the noise models for the pulsar observations and different algorithms for obtaining the pulsar timescale. The two analyses agree within the estimated uncertainties and both agree with TT(BIPM17), a post-corrected timescale produced by the Bureau International des Poids et Mesures (BIPM). We show that both methods could detect significant errors in TT(BIPM17) if they were present. We estimate the stability of the atomic clocks from which TT(BIPM17) is derived using observations of four rubidium fountain clocks at the US Naval Observatory. Comparing the power spectrum of TT(IPTA16) with that of these fountain clocks suggests that pulsar-based timescales are unlikely to contribute to the stability of the best timescales over the next decade, but they will remain a valuable independent check on atomic timescales. We also find that the stability of the pulsar-based timescale is likely to be limited by our knowledge of solar-system dynamics, and that errors in TT(BIPM17) will not be a limiting factor for the primary goal of the IPTA, which is to search for the signatures of nano-Hertz gravitational waves., Comment: accepted by MNRAS

Published
2020
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14. THE DISTURBANCE OF A MILLISECOND PULSAR MAGNETOSPHERE

Author

Renée Spiewak, Yuri Levin, L. Toomey, Stefan Oslowski, Linqing Wen, Ryan Shannon, W. van Straten, Xing-Jiang Zhu, Daniel J. Reardon, Matthew Bailes, N. D. R. Bhat, Lindley Lentati, Shi Dai, Pablo Rosado, Michael Keith, James Dempsey, Paul D. Lasky, George Hobbs, Richard N. Manchester, Matthew Kerr, William A. Coles, Vikram Ravi, X. P. You, and J. B. Wang

Subjects
astro-ph.SR, Astrophysics::High Energy Astrophysical Phenomena, individual (PSR J1643-1224) [pulsars], Magnetosphere, FOS: Physical sciences, Astrophysics, Astronomy & Astrophysics, Rotation, 01 natural sciences, general [pulsars], neutron [stars], Pulsar, Millisecond pulsar, 0103 physical sciences, individual [pulsars], Variation (astronomy), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, 010308 nuclear & particles physics, Gravitational wave, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Pulse (physics), Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, Noise (radio), Astronomical and Space Sciences
Abstract

Pulsar timing has enabled some of the strongest tests of fundamental physics. Central to the technique is the assumption that the detected radio pulses can be used to accurately measure the rotation of the pulsar. Here we report on a broad-band variation in the pulse profile of the millisecond pulsar J1643-1224. A new component of emission suddenly appears in the pulse profile, decays over 4 months, and results in a permanently modified pulse shape. Profile variations such as these may be the origin of timing noise observed in other millisecond pulsars. The sensitivity of pulsar-timing observations to gravitational radiation can be increased by accounting for this variability., Accepted to ApJ Letters

Published
2016
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15. Timing analysis for 20 millisecond pulsars in the Parkes Pulsar Timing Array

Author

X. P. You, Matthew Kerr, William A. Coles, Vikram Ravi, Yuri Levin, Michael Keith, Paul D. Lasky, Xing-Jiang Zhu, Matthew Bailes, George Hobbs, Jiali Wang, Linqing Wen, Ryan Shannon, W. van Straten, L. Toomey, Stefan Oslowski, Sarah Burke-Spolaor, Richard N. Manchester, N. D. R. Bhat, Shi Dai, and Daniel J. Reardon

Subjects
FOS: Physical sciences, Astrophysics, Astronomy & Astrophysics, general [pulsars], 01 natural sciences, Pulsar timing array, Pulsar, proper motions, Millisecond pulsar, pulsars: general, 0103 physical sciences, ephemerides, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, Orbital elements, High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, 010308 nuclear & particles physics, Astronomy, Static timing analysis, Astronomy and Astrophysics, Astrometry, Shapiro delay, Space and Planetary Science, parallaxes, astrometry, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Astronomical and Space Sciences, Noise (radio), astro-ph.IM
Abstract

We present timing models for 20 millisecond pulsars in the Parkes Pulsar Timing Array. The precision of the parameter measurements in these models has been improved over earlier results by using longer data sets and modelling the non-stationary noise. We describe a new noise modelling procedure and demonstrate its effectiveness using simulated data. Our methodology includes the addition of annual dispersion measure (DM) variations to the timing models of some pulsars. We present the first significant parallax measurements for PSRs J1024-0719, J1045-4509, J1600-3053, J1603-7202, and J1730-2304, as well as the first significant measurements of some post-Keplerian orbital parameters in six binary pulsars, caused by kinematic effects. Improved Shapiro delay measurements have resulted in much improved pulsar mass measurements, particularly for PSRs J0437-4715 and J1909-3744 with $M_p=1.44\pm0.07$ $M_\odot$ and $M_p=1.47\pm0.03$ $M_\odot$ respectively. The improved orbital period-derivative measurement for PSR J0437-4715 results in a derived distance measurement at the 0.16% level of precision, $D=156.79\pm0.25$ pc, one of the most fractionally precise distance measurements of any star to date., Comment: 21 pages, 5 figures, 7 tables. Accepted for publication in MNRAS

Published
2015
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16. Pulsar Observations of Extreme Scattering Events

Author

W. van Straten, Matthew Bailes, Daniel J. Reardon, Yuri Levin, Stefan Oslowski, Xing-Jiang Zhu, Sarah Burke-Spolaor, George Hobbs, Linqing Wen, Richard N. Manchester, Ryan Shannon, N. D. R. Bhat, Shi Dai, X. P. You, Michael Keith, Matthew Kerr, William A. Coles, Jing Wang, Vikram Ravi, and L. Toomey

Subjects
Electron density, astro-ph.SR, ISM: structure, FOS: Physical sciences, Astrophysics, Astronomy & Astrophysics, Physical Chemistry, general [pulsars], Atomic, Pulsar timing array, Particle and Plasma Physics, Pulsar, pulsars: general, Nuclear, Solar and Stellar Astrophysics (astro-ph.SR), astro-ph.HE, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Scintillation, Line-of-sight, Scattering, turbulence, Molecular, Astronomy and Astrophysics, Refraction, Interstellar medium, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, structure [ISM], Astrophysics - High Energy Astrophysical Phenomena, Astronomical and Space Sciences, Physical Chemistry (incl. Structural)
Abstract

Extreme scattering events (ESEs) in the interstellar medium (ISM) were first observed in regular flux measurements of compact extragalactic sources. They are characterized by a flux variation over a period of weeks, suggesting the passage of a "diverging plasma lens" across the line of sight. Modeling the refraction of such a lens indicates that the structure size must be of order AU and the electron density of order 10s of cm^{-3}. Similar structures have been observed in measurements of pulsar intensity scintillation and group delay. Here we report observations of two ESEs showing increases in both intensity scintillation and dispersion made with the Parkes Pulsar Timing Array (PPTA). These allow us to make more complete models of the ESE, including an estimate of the "outer-scale" of the turbulence in the plasma lens. These observations show clearly that the ESE structure is fully turbulent on an AU scale. They provide some support for the idea that the structures are extended along the line of sight, such as would be the case for a scattering shell. The dispersion measurements also show a variety of AU scale structures which would not be called ESEs, yet involve electron density variations typical of ESEs and likely have the same origin., Comment: Accepted by ApJ

Published
2015
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