ON THE MAXIMUM MASS OF STELLAR BLACK HOLES
- Los Alamos National Lab, P.O. Box 1663, MS 466, Los Alamos, NM 87545 (United States)
- Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw (Poland)
- Department of Astronomy, New Mexico State University, 1320 Frenger Mall, Las Cruces, NM 88003 (United States)
- Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)
- Armagh Observatory, College Hill, Armagh BT61, 9DG, Northern Ireland (United Kingdom)
We present the spectrum of compact object masses: neutron stars and black holes (BHs) that originate from single stars in different environments. In particular, we calculate the dependence of maximum BH mass on metallicity and on some specific wind mass loss rates (e.g., Hurley et al. and Vink et al.). Our calculations show that the highest mass BHs observed in the Galaxy M{sub bh} {approx} 15 M{sub sun} in the high metallicity environment (Z = Z{sub sun} = 0.02) can be explained with stellar models and the wind mass loss rates adopted here. To reach this result we had to set luminous blue variable mass loss rates at the level of {approx}10{sup -4} M{sub sun} yr{sup -1} and to employ metallicity-dependent Wolf-Rayet winds. With such winds, calibrated on Galactic BH mass measurements, the maximum BH mass obtained for moderate metallicity (Z = 0.3 Z{sub sun} = 0.006) is M{sub bh,max} = 30 M{sub sun}. This is a rather striking finding as the mass of the most massive known stellar BH is M{sub bh} = 23-34 M{sub sun} and, in fact, it is located in a small star-forming galaxy with moderate metallicity. We find that in the very low (globular cluster-like) metallicity environment the maximum BH mass can be as high as M{sub bh,max} = 80 M{sub sun} (Z = 0.01 Z{sub sun} = 0.0002). It is interesting to note that X-ray luminosity from Eddington-limited accretion onto an 80 M{sub sun} BH is of the order of {approx}10{sup 40} erg s{sup -1} and is comparable to luminosities of some known ultra-luminous X-ray sources. We emphasize that our results were obtained for single stars only and that binary interactions may alter these maximum BH masses (e.g., accretion from a close companion). This is strictly a proof-of-principle study which demonstrates that stellar models can naturally explain even the most massive known stellar BHs.
- OSTI ID:
- 21448853
- Journal Information:
- Astrophysical Journal, Vol. 714, Issue 2; Other Information: DOI: 10.1088/0004-637X/714/2/1217; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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