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

L Lentati 1 R. M. Shannon 2 W. A. Coles 3 J. P. W. Verbiest 4 R van Haasteren 5 J.A. Ellis 5 R. N. Caballero 4 R. N. Manchester 2 Z. Arzoumanian 6 S. Babak 7 C.G Bassa 8 N.D.R. Bhat 9 P. Brem 7 M. Burgay 10 S. Burke-Spolaor 11 D. Champion 4 S. Chatterjee 12 Ismaël Cognard 13 J. M. Cordes 14 S. Dai 2 P. Demorest 14 G. Desvignes 13 T. Dolch 15 R. D. Ferdman 16 E. Fonseca 17 J. R. Gair 1 M.E. Gonzalez 18 E. Graikou 4 Lucas Guillemot 13 J. w. t. Hessels 19 G Hobbs 20 G. H. Janssen 21 G Jones 22 R Karuppusamy 4 M Keith 23 M Kerr 20 M Kramer 24 M.T Lam 14 P. D. Lasky 20 A Lassus 13 P Lazarus 7 T. J. W. Lazio 5 K.J. Lee 25 L. Levin 23 K. Liu 4 R. S. Lynch 19 D. R. Madison 26 J. Mckee 27 M Mclaughlin 28 S. T. Mcwilliams 28 C.M.F. Mingarelli 29 D.J. Nice 30 S. Osłowski 4 T. Pennucci 31 B. B. P. Perera 23 D. Perrodin 10 A Petiteau 32 P. Possenti 33 S.M. Ransom 26 D Reardon 20 P. A. Rosado 34 S. A. Sanidas 35 A Sesana 7 G. Shaifullah 4 X Siemens 36 R. Smits 21 I. Stairs 37 B. Stappers 23 D.R. Stinebring 38 K. Stowall 39 J.J. Swiggum 40 S.R. Taylor 5 Gilles Theureau 16 C. Tiburzi 10 L Toomey 20 M Vallisneri 5 W. van Straten 4 A Vecchio 41 J.B. Wang 42 Y. Wang 43 X.P. You 44 W.W. Zhu 13 X.-J Zhu 31
32 APC-Gravitation - APC - Gravitation
APC - UMR 7164 - AstroParticule et Cosmologie, AEI - Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut )
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 ∼ 60% compared to a model that includes DM variations and spin-noise only.
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L Lentati, R. M. Shannon, W. A. Coles, J. P. W. Verbiest, R van Haasteren, et al.. From spin noise to systematics: stochastic processes in the first International Pulsar Timing Array data release. Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2016, 458 (2), pp.2161-2187. ⟨10.1093/mnras/stw395⟩. ⟨insu-01327914⟩

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