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X-ray Binaries in Elliptical Galaxies

The globular cluster 47 Tucanae houses a large number of X-ray binaries which can be seen in the inset X-ray image.

Chandra observations of elliptical galaxies have revealed large numbers of neutron star binaries with low mass compansions (called Low Mass X-ray Binaries or LMXBs) and large accretion rates. One possibility is that the companions are evolved red giant stars, expanding and driving accretion onto the neutron stars. In our Galaxy similar systems accrete sporadically as transients due to a thermal instability in their accretion disks. We theoretically follow the evolution of these binaries, and indeed find that they should exhibit transient accretion for at least 75% of their lives. Hopefully, by performing repeated Chandra observations of elliptical galaxies, this hypothesis can be tested. In 2005, we performed observations of a local dwarf galaxy and found binaries which match many of these properties.

Related Links: Pictures of X-ray Binaries - Chandra Public Outreach - What is an Accretion Disk? - What's the difference between an Elliptical and Spiral Galaxy? - Red Giant Stars

"Transient X-Ray Binaries in Elliptical Galaxies," A. L. Piro & L. Bildsten, 2002, Ap. J. L., 571, L103.

NASA ADS - astro-ph

"The Discovery of X-ray Binaries in the Sculptor Dwarf Spheroidal Galaxy," T. J. Maccarone, A. Kundu, S. E. Zepf, A. L. Piro, & L. Bildsten, 2005, M. N. R. A. S. , 364, L61

NASA ADS - astro-ph

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