Shahbaz, T., Casares, J., Watson, C. A., Charles, P. A., Hynes, R. I., Shih, S. C. and Steeghs, D. (Danny), 1972-. (2004) The massive neutron star or low-mass black hole in 2S 0921-630. The Astrophysical Journal, Vol.616 (No.2). L123-L126. ISSN 0004-637X

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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
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of 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
Date:	2004
Volume:	Vol.616
Number:	No.2
Page Range:	L123-L126
Identification Number:	10.1086/426504
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access
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)
References:	Akmal, A., Pandharipande, V. R., & Ravenhall, D. G. 1998, Phys. Rev. C, 58, 1804 Barziv O., Kaper L., van Kerkwijk M. H., Telting J. H., van Paradijs J., 2001, A&A, 377, 925 Branduardi-Raymont, G., Corbet, R. H. D., Mason, K. O., Parmar, A. N., Murdin, P. G., & White, N. E. 1983, MNRAS, 205, 403 Brown G. E., Weingartner J. C., Wijers Ralph A. M. J., 1996, ApJ, 463, 297. Casares, J., Charles, P. A., & Kuulkers, E. 1998, ApJ, 493, L39 Casares, J., Dubus, G., Shahbaz, T., Zurita, C., & Charles, P. A. 2002, MNRAS, 329, 29 Casares, J., Steeghs, D., Hynes, R. I., Charles, P. A., & O’Brien, K. 2003, ApJ, 590, 1041 Charles P.A., Coe M., in Compact Stellar X–ray Sources, ed. W. H. G. Lewin & M. van der Klis, Cambridge University Press, astro-ph/0308020 Chevalier, C. & Ilovaisky, S. A. 1982, A&A, 112, 68 Chevalier, C. & Ilovaisky, S. A. 1981, A&A, 94, L3 Clark, J. S., Goodwin, S. P., Crowther, P. A., Kaper, L., Fairbairn, M., Langer, N., & Brocksopp, C. 2002, A&A, 392, 909 Cowley, A. P., Crampton, D., & Hutchings, J. B. 1982, ApJ, 256, 605 Dehnen, W. & Binney, J. 1998, MNRAS, 294, 429 Fryer, C. L. & Kalogera, V. 2001, ApJ, 554, 548 Gray, D. F. 1992, Cambridge Astrophysics Series, Cambridge: Cambridge University Press, 1992, 2nd ed. Horne, K. 1986, PASP, 98, 609 Horne, K., Wade, R. A., & Szkody, P. 1986, MNRAS, 219, 791 Kahabka, P. & van den Heuvel, E. P. J. 1997, ARA&A, 35, 69 Kallman, T. R., Angelini, L., Boroson, B., & Cottam, J. 2003, ApJ, 583, 861 Kalogera, V. & Baym, G. 1996, ApJ, 470, L61 King, A. R. & Ritter, H. 1999, MNRAS, 309, 253 Li, F. K., Clark, G. W., Jernigan, J. G., Laustsen, S., Zuiderwijk, E. J., & van Paradijs, J. A. 1978, Nature, 276, 799 Kolb, U. 1998, MNRAS, 297, 419 Marsh, T. R., Robinson, E. L., & Wood, J. H. 1994, MNRAS, 266, 137 Mason, K. O., Branduardi-Raymont, G., Codova, F. A., & Corbet, R. H. D. 1987, MNRAS, 226, 423 Miller, M. C., Lamb, F. K., & Psaltis, D. 1998a, ApJ, 508, 791 Miller, J. C., Shahbaz, T., & Nolan, L. A. 1998b, MNRAS, 294, L25 Nelemans, G., Tauris, T. M., & van den Heuvel, E. P. J. 1999, A&A, 352, L87 Orosz J. A., Kuulkers E., 1999, MNRAS, 305, 132. Phillips, S. N., Shahbaz, T., & Podsiadlowski, P. 1999, MNRAS, 304, 839 Shahbaz, T., Kuulkers, E., Charles, P. A., van der Hooft, F., Casares, J., & van Paradijs, J. 1999, A&A, 344, 101 Shahbaz, T., Groot, P., Phillips, S. N., Casares, J., Charles, P. A., & van Paradijs, J. 2000, MNRAS, 314, 747 Shahbaz, T., Zurita, C., Casares, J., Dubus, G., Charles, P. A., Wagner, R. M., & Ryan, E. 2003, ApJ, 585, 443 Thorstensen, J. R. & Charles, P. A. 1979, BAAS, 11, 721 Titarchuk, L. & Shaposhnikov, N. 2002, ApJ, 570, L25 Tonry, J. & Davis, M. 1979, AJ, 84, 1511 Torres, M. A. P., Casares, J., Mart´ınez-Pais, I. G., & Charles, P. A. 2002, MNRAS, 334, 233 van Kerkwijk, M. H. 2001, in Black Holes in Binaries and Galactic Nuclei, ed. L. Kaper, E. P. J. van den Heuvel, & P. A. Woudt (Berlin: Springer), 39 White, N. E. & Mason, K. O. 1985, Space Science Reviews, 40, 167 White, N. E., Nagase, F., Paramar, A. N., 1995, X-ray Binaries, eds. W.H.G. Lewin, J. van Paradijs, and E.P.J. van den Heuvel (Cambridge: Cambridge Univ. Press), p. 1 Zhang W., Strohmayer T. E., Swank J. H., 1997, ApJ, 482, L167.
URI:	http://wrap.warwick.ac.uk/id/eprint/50096

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