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Improved mass and radius constraints for quiescent neutron stars in omega Cen and NGC 6397

Improved mass and radius constraints for quiescent neutron stars in omega Cen and NGC 6397
Improved mass and radius constraints for quiescent neutron stars in omega Cen and NGC 6397
We use Chandra and XMM-Newton observations of the globular clusters omega Cen and NGC 6397 to measure the spectrum of their quiescent neutron stars (NSs), and thus to constrain the allowed ranges of mass and radius for each. We also use Hubble Space Telescope photometry of NGC 6397 to identify a potential optical companion to the quiescent NS, and find evidence that the companion lacks hydrogen. We carefully consider a number of systematic problems, and show that the choices of atmospheric composition, interstellar medium abundances, and cluster distances can have important effects on the inferred NS mass and radius. We find that for typical NS masses, the radii of both NSs are consistent with the 10-13 km range favoured by recent nuclear physics experiments. This removes the evidence suggested by Guillot and collaborators for an unusually small NS radius, which relied upon the small inferred radius of the NGC 6397 NS.
1365-2966
443-456
Heinke, Craig O.
d7382ed2-cb85-4e15-b2d9-296fc8b6221d
Cohn, Haldan N.
c20a687d-c882-4ca3-8a8a-3f3fb3525df7
Lugger, Phyllis M.
7b9b6d9b-1f93-4bdd-9828-baee02c80c30
Webb, Natalie A.
f12a5e10-a3fa-4d24-8b44-9855d0b095df
Ho, Wynn C.G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Anderson, Jay
4844205b-bfa1-4321-bad4-057a7f57258d
Campana, Sergio
1c257264-14fc-4242-89e8-e0ea7f328e29
Bogdanov, Slavko
39f20582-4d71-4b1a-ae2a-b266367341ef
Haggard, Daryl
29179449-da8e-4e11-9ea6-33f3e040e354
Cool, Adrienne M.
82278bf4-4092-4a50-b82f-051781a4f704
Grindlay, Josh E.
4f635ffa-272f-4390-98f3-723e825d2bb8
Heinke, Craig O.
d7382ed2-cb85-4e15-b2d9-296fc8b6221d
Cohn, Haldan N.
c20a687d-c882-4ca3-8a8a-3f3fb3525df7
Lugger, Phyllis M.
7b9b6d9b-1f93-4bdd-9828-baee02c80c30
Webb, Natalie A.
f12a5e10-a3fa-4d24-8b44-9855d0b095df
Ho, Wynn C.G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Anderson, Jay
4844205b-bfa1-4321-bad4-057a7f57258d
Campana, Sergio
1c257264-14fc-4242-89e8-e0ea7f328e29
Bogdanov, Slavko
39f20582-4d71-4b1a-ae2a-b266367341ef
Haggard, Daryl
29179449-da8e-4e11-9ea6-33f3e040e354
Cool, Adrienne M.
82278bf4-4092-4a50-b82f-051781a4f704
Grindlay, Josh E.
4f635ffa-272f-4390-98f3-723e825d2bb8

Heinke, Craig O., Cohn, Haldan N., Lugger, Phyllis M., Webb, Natalie A., Ho, Wynn C.G., Anderson, Jay, Campana, Sergio, Bogdanov, Slavko, Haggard, Daryl, Cool, Adrienne M. and Grindlay, Josh E. (2014) Improved mass and radius constraints for quiescent neutron stars in omega Cen and NGC 6397. Monthly Notices of the Royal Astronomical Society, 444 (1), 443-456. (doi:10.1093/mnras/stu1449).

Record type: Article

Abstract

We use Chandra and XMM-Newton observations of the globular clusters omega Cen and NGC 6397 to measure the spectrum of their quiescent neutron stars (NSs), and thus to constrain the allowed ranges of mass and radius for each. We also use Hubble Space Telescope photometry of NGC 6397 to identify a potential optical companion to the quiescent NS, and find evidence that the companion lacks hydrogen. We carefully consider a number of systematic problems, and show that the choices of atmospheric composition, interstellar medium abundances, and cluster distances can have important effects on the inferred NS mass and radius. We find that for typical NS masses, the radii of both NSs are consistent with the 10-13 km range favoured by recent nuclear physics experiments. This removes the evidence suggested by Guillot and collaborators for an unusually small NS radius, which relied upon the small inferred radius of the NGC 6397 NS.

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More information

Accepted/In Press date: 17 July 2014
e-pub ahead of print date: 16 August 2014
Published date: 11 October 2014
Organisations: Applied Mathematics

Identifiers

Local EPrints ID: 367021
URI: http://eprints.soton.ac.uk/id/eprint/367021
ISSN: 1365-2966
PURE UUID: c18b13c8-40b3-4a68-9bf1-092f740a4504
ORCID for Wynn C.G. Ho: ORCID iD orcid.org/0000-0002-6089-6836

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Date deposited: 21 Jul 2014 11:13
Last modified: 14 Mar 2024 17:21

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Contributors

Author: Craig O. Heinke
Author: Haldan N. Cohn
Author: Phyllis M. Lugger
Author: Natalie A. Webb
Author: Wynn C.G. Ho ORCID iD
Author: Jay Anderson
Author: Sergio Campana
Author: Slavko Bogdanov
Author: Daryl Haggard
Author: Adrienne M. Cool
Author: Josh E. Grindlay

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