2017MNRAS.467..164A -
Mon. Not. R. Astron. Soc., 467, 164-178 (2017/May-1)
On the free precession candidate PSR B1828-11: evidence for increasing deformation.
ASHTON G., JONES D.I. and PRIX R.
Abstract (from CDS):
We observe that the periodic variations in spin-down rate and beamwidth 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 Pfp. We investigate how a precession model can account for such a decrease in Pfp, in terms of an increase over time in the absolute biaxial deformation (|εp| ∼ 10–8) of this pulsar. We perform a Bayesian model comparison against the 'base' precession model (with constant εp) developed in Ashton et al., 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}εp∼10–18 s–1 and odds of 1075 compared to the base model, and (ii) N discrete positive jumps in εp with very similar odds to the linear εp 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.
Abstract Copyright:
© The Authors 2017. Published by Oxford University Press on behalf of The Royal Astronomical Society.
Journal keyword(s):
methods: data analysis - stars: neutron - pulsars: individual: PSR B1828-11 - pulsars: individual: PSR B1828-11
Simbad objects:
3
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