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 6 Z. Arzoumanian 7 S. Babak 8 C.G Bassa 9 N.D.R. Bhat 10 P. Brem 8 M. Burgay 11 S. Burke-Spolaor 12 D. Champion 4 S. Chatterjee 13 Ismaël Cognard 14 J. M. Cordes 15 S. Dai 2 P. Demorest 15 G. Desvignes 14 T. Dolch 16 R. D. Ferdman 17 E. Fonseca 18 J. R. Gair 1 M.E. Gonzalez 19 E. Graikou 4 Lucas Guillemot 14 J. w. t. Hessels 20 G Hobbs 21 G. H. Janssen 22 G Jones 23 R Karuppusamy 4 M Keith 24 M Kerr 21 M Kramer 25 M.T Lam 15 P. D. Lasky 21 A Lassus 14 P Lazarus 8 T. J. W. Lazio 5 K.J. Lee 26 L. Levin 24 K. Liu 4 R. S. Lynch 20 D. R. Madison 27 J. Mckee 28 M Mclaughlin 29 S. T. Mcwilliams 29 C.M.F. Mingarelli 30 D.J. Nice 31 S. Osłowski 4 T. Pennucci 32 B. B. P. Perera 24 D. Perrodin 11 A Petiteau 33 P. Possenti 34 S.M. Ransom 27 D Reardon 21 P. A. Rosado 35 S. A. Sanidas 36 A Sesana 8 G. Shaifullah 4 X Siemens 37 R. Smits 22 I. Stairs 38 B. Stappers 24 D.R. Stinebring 39 K. Stowall 40 J.J. Swiggum 41 S.R. Taylor 5 Gilles Theureau 17 C. Tiburzi 11 L Toomey 21 M Vallisneri 5 W. Van Straten 4 A Vecchio 42 J.B. Wang 43 Y. Wang 44 X.P. You 45 W.W. Zhu 14 X.-J Zhu 32
33 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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