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The massive neutron star or low-mass black hole in 2S 0921-630
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Shahbaz, T., Casares, J., Watson, C. A., Charles, P. A., Hynes, R. I., Shih, S. C. and Steeghs, D. (2004) The massive neutron star or low-mass black hole in 2S 0921-630. The Astrophysical Journal, Vol.616 (No.2). L123-L126. doi:10.1086/426504 ISSN 0004-637X.
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Official URL: http://dx.doi.org/10.1086/426504
Abstract
We report on the optical spectroscopy of the eclipsing halo low-mass X-ray binary 2S 0921-630, which reveals the absorption-line radial velocity curve of the K0 III secondary star with a semiamplitude K2 = 92.89 ± 3.84 km s-1, a systemic velocity γ = 34.9 ± 3.3 km s-1, and an orbital period Porb of 9.0035 ± 0.0029 days (1 σ). Given the quality of the data, we find no evidence for the effects of X-ray irradiation. Using the previously determined rotational broadening of the mass donor and applying conservative limits on the orbital inclination, we constrain the compact object mass to be 2.0-4.3 M☉ (1 σ), ruling out a canonical neutron star at the 99% level. Since the nature of the compact object is unclear, this mass range implies that the compact object is either a low-mass black hole with a mass slightly higher than the maximum possible neutron star mass (2.9 M☉) or a massive neutron star. If the compact object is a black hole, it confirms the prediction of the existence of low-mass black holes, while if the object is a massive neutron star, its high mass severely constrains the equation of state of nuclear matter.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QB Astronomy | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Library of Congress Subject Headings (LCSH): | Double stars, Neutron stars, Black holes (Astronomy) | ||||
Journal or Publication Title: | The Astrophysical Journal | ||||
Publisher: | Institute of Physics Publishing, Inc. | ||||
ISSN: | 0004-637X | ||||
Official Date: | 2004 | ||||
Dates: |
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Volume: | Vol.616 | ||||
Number: | No.2 | ||||
Page Range: | L123-L126 | ||||
DOI: | 10.1086/426504 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Open Access (Creative Commons) | ||||
Funder: | Spain. Ministerio de Ciencia y Tecnología (MCT), United States. National Aeronautics and Space Administration (NASA), Smithsonian Astrophysical Observatory | ||||
Grant number: | HF-01150.01-A (NASA) |
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