ON THE DYNAMICAL FORMATION OF VERY YOUNG, X-RAY EMITTING BLACK HOLE BINARIES IN DENSE STAR CLUSTERS

Journal Article · Fri Aug 10 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/755/1/49· OSTI ID:22039150

Garofali, Kristen ^[1]; Converse, Joseph M; Chandar, Rupali; Rangelov, Blagoy ^[2]

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1. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
2. Department of Physics and Astronomy, University of Toledo, 2801 W Bancroft Street, Toledo, OH 43606 (United States)

We recently discovered a population of very young ({tau} {approx}< 6-8 Myr), X-ray emitting black hole binaries (BHBs) in the nearby starburst galaxy NGC 4449. These BHBs are located within or near to very young star clusters, indicating that they form within the clusters, but that some fraction are dynamically ejected. Here we present results from a suite of N-body simulations of N = 16,384 ({approx}6000 M{sub Sun }) star clusters, similar to the masses of BHB hosts in NGC 4449, through the first 10 Myr of their lives. Our goal is to determine whether dynamical interactions are responsible for the observed population of BHBs in NGC 4449. Our simulations span a wide range of initial size and density profiles, both with and without primordial mass segregation, testing both realistic initial conditions and extreme ones. We find that clusters without primordial mass segregation only dynamically produce BHBs within 10 Myr when they are extremely compact and centrally concentrated. Preliminary results that include primordial binaries support this conclusion. The introduction of strong primordial mass segregation, however, greatly increases the rapidity with which the binaries form, although these are still not tight enough that they will emit X-rays. We conclude that X-ray emitting BHBs are unlikely to form dynamically in clusters of this mass under realistic conditions. Instead, they probably originate from binaries that contain two massive stars with small orbital separations, which are present from the cluster's birth.

• OSTI ID: 22039150
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 755; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
BINARY STARS
BLACK HOLES
COMPUTERIZED SIMULATION
GALAXIES
GAMMA ASTRONOMY
MASS
PHOTON EMISSION
SEGREGATION
STAR CLUSTERS
X RADIATION