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Title: The radius of the quiescent neutron star in the globular cluster M13

X-ray spectra of quiescent low-mass X-ray binaries containing neutron stars can be fit with atmosphere models to constrain the mass and the radius. Mass-radius constraints can be used to place limits on the equation of state of dense matter. In this paper, we perform fits to the X-ray spectrum of a quiescent neutron star in the globular cluster M13, utilizing data from ROSAT, Chandra, and XMM–Newton, and constrain the mass–radius relation. Assuming an atmosphere composed of hydrogen and a 1.4 M neutron star, we find the radius to be R NS = 12.2 +1.5 -1.1 km, a significant improvement in precision over previous measurements. Incorporating an uncertainty on the distance to M13 relaxes the radius constraints slightly and we find R NS = 12.3 +1.9 -1.7 km (for a 1.4M neutron star with a hydrogen atmosphere), which is still an improvement in precision over previous measurements, some of which do not consider distance uncertainty. Finally, we also discuss how the composition of the atmosphere affects the derived radius, finding that a helium atmosphere implies a significantly larger radius.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ; ORCiD logo [5] ;  [4] ;  [6]
  1. Univ. of Alberta, Edmonton, AB (Canada). Dept. of Physics
  2. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Physics Division
  3. INAF Brera Astronomical Observatory, Milan (Italy)
  4. Indiana Univ., Bloomington, IN (United States). Dept. of Astronomy
  5. Haverford College, PA (United States). Dept. of Physics and Astronomy; Univ. of Southampton (United Kingdom). Mathematical Sciences, Physics & Astronomy. STAG Research Centre
  6. Paris Diderot Univ., Meudon (France). PSL Research Univ. Paris Observatory. Lab. for the Universe and Theory (LUTH)
Publication Date:
Grant/Contract Number:
AC05-00OR22725; PHY1554876; ST/M000931/1
Type:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 476; Journal Issue: 4; 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; 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; neutron stars; globular clusters; X-rays; binaries
OSTI Identifier:
1460182

Shaw, A. W., Heinke, C. O., Steiner, A. W., Campana, S., Cohn, H. N., Ho, W. C. G., Lugger, P. M., and Servillat, M.. The radius of the quiescent neutron star in the globular cluster M13. United States: N. p., Web. doi:10.1093/mnras/sty582.
Shaw, A. W., Heinke, C. O., Steiner, A. W., Campana, S., Cohn, H. N., Ho, W. C. G., Lugger, P. M., & Servillat, M.. The radius of the quiescent neutron star in the globular cluster M13. United States. doi:10.1093/mnras/sty582.
Shaw, A. W., Heinke, C. O., Steiner, A. W., Campana, S., Cohn, H. N., Ho, W. C. G., Lugger, P. M., and Servillat, M.. 2018. "The radius of the quiescent neutron star in the globular cluster M13". United States. doi:10.1093/mnras/sty582.
@article{osti_1460182,
title = {The radius of the quiescent neutron star in the globular cluster M13},
author = {Shaw, A. W. and Heinke, C. O. and Steiner, A. W. and Campana, S. and Cohn, H. N. and Ho, W. C. G. and Lugger, P. M. and Servillat, M.},
abstractNote = {X-ray spectra of quiescent low-mass X-ray binaries containing neutron stars can be fit with atmosphere models to constrain the mass and the radius. Mass-radius constraints can be used to place limits on the equation of state of dense matter. In this paper, we perform fits to the X-ray spectrum of a quiescent neutron star in the globular cluster M13, utilizing data from ROSAT, Chandra, and XMM–Newton, and constrain the mass–radius relation. Assuming an atmosphere composed of hydrogen and a 1.4 M⊙ neutron star, we find the radius to be RNS = 12.2+1.5-1.1 km, a significant improvement in precision over previous measurements. Incorporating an uncertainty on the distance to M13 relaxes the radius constraints slightly and we find RNS = 12.3+1.9-1.7 km (for a 1.4M⊙ neutron star with a hydrogen atmosphere), which is still an improvement in precision over previous measurements, some of which do not consider distance uncertainty. Finally, we also discuss how the composition of the atmosphere affects the derived radius, finding that a helium atmosphere implies a significantly larger radius.},
doi = {10.1093/mnras/sty582},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 4,
volume = 476,
place = {United States},
year = {2018},
month = {3}
}