------------------------------------------------------------------------
 transients.tex ApJL submitted
From: Michael Muno <mmuno@astro.UCLA.EDU>
To: gcnews@aoc.nrao.edu
Content-Transfer-Encoding: 7bit
Message-Id: <3C2EDD95-507F-11D9-87A1-000A957B1F54@astro.ucla.edu>
X-Mailer: Apple Mail (2.553)
X-MailScanner-Information: Please contact postmaster@aoc.nrao.edu for more information
X-MailScanner: Found to be clean
X-MailScanner-SpamCheck: not spam, SpamAssassin (score=-5.4, required 7,
	BAYES_01 -5.40, USER_AGENT_APPLEMAIL 0.00)

%astro-ph/0412492

\documentclass[12pt,preprint]{aastex}
\begin{document}

\title{An Overabundance of Transient X-ray Binaries within 1 pc of
the Galactic Center}

\author{M. P. Muno,\altaffilmark{1,2} E. Pfahl,\altaffilmark{3}
W. N. Brandt, \altaffilmark{5}
J. Lu,\altaffilmark{1}

California,
Los Angeles, CA 90095; mmuno@astro.ucla.edu}
\altaffiltext{2}{Hubble Fellow}
\altaffiltext{3}{Chandra Fellow, Department of Astronomy, University of
Virginia, Charlottesville, VA 22904}
\altaffiltext{4}{Kavli Institute for Astrophysics and Space Research,
Massachusetts Institute of Technology, Cambridge, MA 02139}
\altaffiltext{5}{Department of Astronomy and Astrophysics,
The Pennsylvania State University, University Park, PA 16802}

\begin{abstract}
During five years of Chandra observations, we have identified
seven X-ray transients located within 23 pc of \sgrastar.
These sources each vary in luminosity by more than a factor of 10, and
have peak X-ray luminosities greater than $5 \times 10^{33}$ \ergs,
which strongly suggests that they are accreting black holes or
neutron stars. The peak luminosities of the transients are intermediate
between those typically considered
outburst and quiescence for X-ray binaries. Remarkably four of these
transients lie within only 1 pc of \sgrastar. This implies that, 
compared
to the numbers of similar systems located between 1 and 23 pc,
transients are over-abundant by a factor of $\approx 20$ per unit 
stellar
mass within 1 pc of \sgrastar.
It is likely that the excess transient X-ray sources are
low-mass X-ray binaries that were produced, as in the cores of globular
clusters, by three-body
interactions between binary star systems and either black holes or
neutron stars that have been concentrated in the central parsec through
dynamical friction. Alternatively, they could be high-mass X-ray
binaries that formed among the young stars that are present in the
central parsec.
\end{abstract}

\end{document}