Constraining the mass and radius of neutron stars in globular clusters
Abstract
We analyse observations of eight quiescent lowmass Xray binaries in globular clusters and combine them to determine the neutron star massradius curve and the equation of state of dense matter. We determine the effect that several uncertainties may have on our results, including uncertainties in the distance, the atmosphere composition, the neutron star maximum mass, the neutron star mass distribution, the possible presence of a hotspot on the neutron star surface, and the prior choice for the equation of state of dense matter. The distance uncertainty is implemented in a new Gaussian blurring method that can be directly applied to the probability distribution over mass and radius. We find that the radius of a 1.4 solar mass neutron star is most likely from 10 to 14 km and that tighter constraints are only possible with stronger assumptions about the nature of the neutron stars, the systematics of the observations, or the nature of dense matter. Strong phase transitions in the equation of state are preferred, and in this case, the radius is likely smaller than 12 km. However, radii larger than 12 km are preferred if the neutron stars have uneven temperature distributions.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 May 2018
 DOI:
 10.1093/mnras/sty215
 arXiv:
 arXiv:1709.05013
 Bibcode:
 2018MNRAS.476..421S
 Keywords:

 dense matter;
 stars: neutron;
 globular clusters: general;
 Xrays: binaries;
 Astrophysics  High Energy Astrophysical Phenomena;
 Astrophysics  Solar and Stellar Astrophysics;
 Nuclear Theory
 EPrint:
 16 pages, 12 figures