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On the mass of the neutron star in V395 Carinae/2s 0921-630

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Steeghs, D. (Danny), 1972- and Jonker, P. G.. (2007) On the mass of the neutron star in V395 Carinae/2s 0921-630. Astrophysical Journal, Vol.669 (No.2). L85-L88. ISSN 0004-637X

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Official URL: http://dx.doi.org/10.1086/523848

Abstract

We report high-resolution optical spectroscopy of the low-mass X-ray binary V395 Car/2S 0921-630 obtained with the MIKE echelle spectrograph on the Magellan-Clay telescope. Our spectra are obtained near the inferior conjunction of the mass donor star, and we exploit the absorption lines originating from the back side of the K-type object to accurately derive its rotational velocity. Using K0-K1 III templates, we find v sin i = 32.9 +/- 0.8 km s(-1). We show that the choice of template star and the assumed limb-darkening coefficient has little impact on the derived rotational velocity. This value is a significant revision downward compared to previously published values. We derive new system parameter constraints in light of our much lower rotational velocity. We find,, and, where the errors have been estimated M-1 = 1.44 +/- 0.10 M-circle dot, M = 0.35 +/- 0.03 M-circle dot, q = 0.24 +/- 0.02 through a Monte Carlo simulation. A possible remaining systematic effect is the fact that we may be overestimating the orbital velocity of the mass donor due to irradiation effects. However, any correction for this effect will only reduce the compact object mass further, down to a minimum mass of. There is thus M-1 = 1.05 +/- 0.08 M-circle dot. There is thus strong evidence that the compact object in this binary is a neutron star of rather typical mass and that the previously reported mass values of 2-4 M-circle dot were too high due to an overestimate of the rotational broadening.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	X-ray binaries
Journal or Publication Title:	Astrophysical Journal
Publisher:	IOP Publishing
ISSN:	0004-637X
Date:	10 November 2007
Volume:	Vol.669
Number:	No.2
Number of Pages:	4
Page Range:	L85-L88
Identification Number:	10.1086/523848
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access
Funder:	Science and Technology Facilities Council (Great Britain) (STFC), United States. National Aeronautics and Space Administration (NASA)
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URI:	http://wrap.warwick.ac.uk/id/eprint/31177