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Title: Constraining the mass and radius of neutron stars in globular clusters

In this paper, we analyse observations of eight quiescent low-mass X-ray binaries in globular clusters and combine them to determine the neutron star mass–radius 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. Finally, 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.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ; ORCiD logo [5] ; ORCiD logo [6] ;  [7]
  1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Physics Division
  2. Univ. of Alberta, Edmonton, AB (Canada). Dept. of Physics
  3. Columbia Univ., New York, NY (United States). Columbia Astrophysics Lab.
  4. Univ. of Alberta, Edmonton, AB (Canada). Dept. of Physics; Chinese Academy of Sciences (CAS), Beijing (China). Key Lab. for Particle Astrophysics. Inst. of High Energy Physics
  5. Univ. of Southampton (United Kingdom). Mathematical Sciences, Physics & Astronomy. STAG Research Centre
  6. Univ. of Alberta, Edmonton, AB (Canada). Dept. of Physics; Michigan State Univ., East Lansing, MI (United States). Dept. of Physics and Astronomy
  7. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
Publication Date:
Grant/Contract Number:
AC05-00OR22725; PHY1554876
Type:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 476; Journal Issue: 1; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Univ. of Alberta, Edmonton, AB (Canada); Univ. of Southampton (United Kingdom)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); National Science Foundation (NSF); Natural Sciences and Engineering Research Council of Canada (NSERC); Science and Technology Facilities Council (STFC) (United Kingdom)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; dense matter; neutron stars; globular clusters; X-rays; binaries
OSTI Identifier:
1460181