Submitted on February 13, 2003
Accepted on April 4, 2003
Formation of a Black Hole in the Dark
I. Félix Mirabel 1*
Irapuan Rodrigues 2
1 Service d'Astrophysique-CEA-Saclay, 91191 Gif-sur-Yvette, France; Instituto de Astronomí a y Fí sica del Espacio/Conicet. Bs As, Argentina.
2 Service d'Astrophysique-CEA-Saclay, 91191 Gif-sur-Yvette, France.
* To whom correspondence should be addressed. E-mail: fmirabel{at}cea.fr.
We show that the black hole in the x-ray binary Cygnus X-1 was formed in situ and did not receive an energetic trigger from a nearby supernova. The progenitor of the black hole had an initial mass higher than 40 solar masses and during the collapse to form the ~10 solar mass black hole of Cygnus X-1, the upper limit for the mass that could have been suddenly ejected is ~1 solar mass, much less than the mass ejected in a supernova. The observations suggest that high-mass stellar black holes may form promptly, when massive stars disappear silently.
