Speaker
Felix Mirabel
Description
I will present the multiple strands of observational
evidence for the formation of black holes in X-
ray binaries and binary stellar black holes, the first
sources of gravitational waves detected by
LIGO. It is believed that stellar black holes (BHs) can be
formed in two different ways: Either a
massive star collapses directly into a BH without a
supernova (SN) explosion, or an explosion
occurs in a proto-neutron star, but the energy is too low to
completely unbind the stellar envelope,
and a large fraction of it falls back onto the short-lived
neutron star (NS), leading to the delayed
formation of a BH. Theoretical models set progenitor masses
for BH formation by implosion,
namely, by complete or almost complete collapse, but
observational evidences have been elusive.
Here are reviewed the observational insights on BHs formed
by implosion without large natal kicks
from: (1) the kinematics in three dimensions of space of
five Galactic BH X-ray binaries (BH-
XRBs), (2) the diversity of optical and infrared
observations of massive stars that collapse in the
dark, with no luminous SN explosions, possibly leading to
the formation of BHs, and (3) the
sources of gravitational waves produced by mergers of
stellar BHs so far detected with LIGO. The
multiple insights of BH formation without ejection of a
significant amount of matter and with no
natal kicks obtained from these different areas of
observational astrophysics, and the recent
observational confirmation of the expected dependence of BH
formation on metallicity and redshift,
are qualitatively consistent with the high merger rates of
binary black holes (BBHs) inferred from
the first detections with LIGO.
