Black hole candidates

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Astronomers Find 26 Possible Black Holes in Andromeda Galaxy

An international group of astronomers using NASA’s Chandra X-ray Observatory has reported the detection of 26 black hole candidates in Messier 31, also known as the Andromeda Galaxy.


R. Barnard, and M.R. Garcia
Harvard-Smithsonian Center for Astrophysics (CFA), Cambridge MA 02138
S. S. Murray
Johns Hopkins University, Baltimore, Maryland; CFA
Draft version May 1, 2013



We have previously identified 10 M31 black hole candidates (BHCs) in M31, from their X-ray properties alone. They exhibit “hard state” emission spectra that are seen at luminosities [less-than or approx.-equal-to]10% Eddington in X-ray binaries (XBs) containing a neutron star (NS) or black hole (BH), at luminosities that significantly exceed the NS threshold. Nine of these are associated with globular clusters (GCs);hence, these are most likely low mass X-ray binaries (LMXBs); eight are included in this survey. We have recently discovered that analysis of the long term 0.5–4.5 keV variability of XBs via structure functions allows us to separate XBs from AGN, even though the emission spectra are often similar; this has enabled us to search for BHCs outside of GCs. We have identified 26 new BHCs (12 strong, 14 plausible) within 20′ of the M31 nucleus (M31*), using 152 Chandra observations spaced over ∼13 years; some of our classifications were enhanced with XMM-Newton observations. Of these, 7 appear within 100′′ of M31*; this supports the theory suggesting that this region experiences enhanced XB production via dynamical processes similar to those seen in GCs. W e have found a parameter space where our black hole candidates are separated from Galactic neutron star binaries: we show that modelling a simulated hard state spectrum with a disk blackbody + blackbody model yields parameters that lie outside the space occupied by neutron star binaries that are modeled this way. The probability that our BHCs all lie within the NS parameter space is ∼ 3 × 10−29.
Subject headings: x-rays: general — x-rays: binaries — black hole physics

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Fig.1. The M100 galaxy, with supernova remnant SN 1979C indicated
NASA's Chandra Finds Youngest Nearby Black Hole:
Chandra Mission Multimedia
Nov. 15, 2010
“Astronomers using NASA's Chandra X-ray Observatory have found evidence of the youngest black hole known to exist in our cosmic neighborhood. The 30-year-old black hole provides a unique opportunity to watch this type of object develop from infancy. —See Fig. 1.

Youngest-Ever Nearby Black Hole Discovered

NASA Sciene News
Nov. 14, 2010
“Astronomers using NASA's Chandra X-ray Observatory have found evidence of the youngest black hole known to exist in our cosmic neighborhood. The 30-year-old object provides a unique opportunity to watch a black hole develop from infancy.
The black hole is a remnant of SN 1979C, a supernova in the galaxy M100 approximately 50 million light years from Earth. Data from Chandra, NASA's Swift satellite, the European Space Agency's XMM-Newton and the German ROSAT observatory revealed a bright source of X-rays that has remained steady during observation from 1995 to 2007. This suggests the object is a black hole being fed either by material falling into it from the supernova or a binary companion.
“Although the evidence points to a newly formed black hole in SN 1979C, another intriguing possibility exists: A young, rapidly spinning neutron star with a powerful wind of high energy particles could be responsible for the X-ray emission. This would make the object in SN 1979C the youngest and brightest example of such a "pulsar wind nebula" and the youngest known neutron star. The Crab pulsar, the best-known example of a bright pulsar wind nebula, is about 950 years old. More observations will either confirm or rule out this alternate explanation; for now, however, the black hole hypothesis appears to be more compelling.

A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence