A 15.65-solar-mass black hole in an eclipsing binary in the nearby spiral galaxy M 33

Jerome A. Orosz, Jeffrey E. McClintock, Ramesh Narayan, Charles D. Bailyn, Joel D. Hartman, Lucas MacRi, Jiefeng Liu, Wolfgang Pietsch, Ronald A. Remillard, Avi Shporer, Tsevi Mazeh

Research output: Contribution to journalArticlepeer-review

170 Scopus citations


Stellar-mass black holes are found in X-ray-emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty producing black holes in close binaries with masses more than ten times that of the Sun (>10M ref. 4), which is consistent with the fact that the most massive stellar black holes known so far all have masses within one standard deviation of 10M . Here we report a mass of (15.65 ± 1.45)M for the black hole in the recently discovered system M 33 X-7, which is located in the nearby galaxy Messier 33 (M 33) and is the only known black hole that is in an eclipsing binary. To produce such a massive black hole, the progenitor star must have retained much of its outer envelope until after helium fusion in the core was completed. On the other hand, in order for the black hole to be in its present 3.45-day orbit about its (70.0 ± 6.9)M companion, there must have been a 'common envelope' phase of evolution in which a significant amount of mass was lost from the system. We find that the common envelope phase could not have occurred in M 33 X-7 unless the amount of mass lost from the progenitor during its evolution was an order of magnitude less than what is usually assumed in evolutionary models of massive stars.

Original languageEnglish (US)
Pages (from-to)872-875
Number of pages4
Issue number7164
StatePublished - Oct 18 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General


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