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On the free-precession candidate PSR B1828-11: Evidence for increasing deformation

Ashton, G., Jones, D. I., & Prix, R. (2017). On the free-precession candidate PSR B1828-11: Evidence for increasing deformation. Monthly Notices of the Royal Astronomical Society: Letters, 465(3), 164-178. doi:10.1093/mnras/stx060.

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Creators:
Ashton, G., Author
Jones, D. I., Author
Prix, Reinhard1, 2, Author
Affiliations:
1Observational Relativity and Cosmology, AEI-Hannover, MPI for Gravitational Physics, Max Planck Society, ou_24011
2Searching for Continuous Gravitational Waves, AEI-Hannover, MPI for Gravitational Physics, Max Planck Society, Hannover, DE, ou_2630691

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Free keywords: Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
Abstract: We observe that the periodic variations in spin-down rate and beam-width of the radio pulsar PSR B1828-11 are getting faster. In the context of a free precession model, this corresponds to a decrease in the precession period $P_{\mathrm{fp}}$. We investigate how a precession model can account for such a decrease in $P_{\mathrm{fp}}$, in terms of an increase over time in the absolute biaxial deformation ($|\epsilon_{\mathrm{p}}|{\sim}10^{-8}$) of this pulsar. We perform a Bayesian model comparison against the 'base' precession model (with constant $\epsilon_{\mathrm{p}}$) developed in Ashton et al (2016), and we obtain decisive odds in favour of a time-varying deformation. We study two types of time-variation: (i) a linear drift with a posterior estimate of $\dot{\epsilon}_{\mathrm{p}}{\sim}10^{-18}\,\mathrm{s}^{-1}$ and odds of $10^{75}$ compared to the base-model, and (ii) $N$ discrete positive jumps in $\epsilon_{\mathrm{p}}$ with very similar odds to the linear $\epsilon_{\mathrm{p}}$-drift model. The physical mechanism explaining this behaviour is unclear, but the observation could provide a crucial probe of the interior physics of neutron stars. We also place an upper bound on the rate at which the precessional motion is damped, and translate this into a bound on a dissipative mutual friction-type coupling between the star's crust and core.

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Dates: 2016-10-112017-01-162017
Publication Status: Published in print
Pages: 14 pages, 12 figures. Updated to incorporate referee comments, including new appendix discussing differences in contributions from the two data sets employed. Accepted by MNRAS. (Identical to v2 aside from this comment line)
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Rev. Method: -
Identifiers: arXiv: 1610.03508
DOI: 10.1093/mnras/stx060
URI: http://arxiv.org/abs/1610.03508
Degree: -

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Title: Monthly Notices of the Royal Astronomical Society: Letters
Other : Mon. Not. Roy. Astron. Soc.: Letters
Source Genre: Journal
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Publ. Info: Oxford : Blackwell Science
Pages: - Volume / Issue: 465 (3) Sequence Number: - Start / End Page: 164 - 178 Identifier: ISSN: 1745-3925
CoNE: /journals/resource/1000000000021470