NOAO >   Observing Info >   Approved Programs >   2011A-0129

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Proposal Information for 2011A-0129


PI: Thomas Maccarone, University of Southampton, tjm@soton.ac.uk
Address: Department of Physics, Southampton, S017 1BJ, United Kingdom

CoI: Arunav Kundu, Eureka Scientific
CoI: Stephen Zepf, Michigan State University
CoI: Katherine Rhode, Indiana University
CoI: Matthew Steele, Michigan State University

Title: Understanding the Variability of the First Globular Cluster Black Hole

Abstract: We proposed in the most recent Chandra round for a 20 kilosecond observation of the globular cluster RZ2109 in NGC 4472, along with a Gemini spectrum of 7.2 hours in duration. This proposal is for banding of the Gemini time awarded by the Chandra TAC. This globular cluster hosts the first black hole X-ray source to be umambiguosly identified in a globular cluster. While other similarly bright globular cluster X-ray sources have been seen, this is the first with strong enough variability to rule out a superposition of bright neutron star X-ray binaries. In the past Chandra cycle, we were awarded time in Feb 2010 to observe the central region of NGC 4472, and did not detect this source which had previously been bright since at least the mid 1990s. On the other hand, our recent Gemini spectra from March 2009 indicate that the cluster was still extremely bright in emission line flux at that time. Our proposed observations with Chandra and Gemini should determine whether this source has truly turned off, in which case the optical emission should fade, or merely went through an episode of very high absorption, in which case the optical emission should change little.


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NOAO >   Observing Info >   Approved Programs >   2011A-0129

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