Colloq Abstract - Hailey

by Hubertus Intema last modified Oct 06, 2017 by Lori Appel

Oct 6

11:00am Mountain


Chuck Hailey (Columbia)


Observations of the central parsec of the Milky Way with NuSTAR and Chandra



NuSTAR recently discovered the diffuse, central hard X-ray emission (CHXE)  within ~ 10 pc of Sgr A*, the supermassive black hole at the center of the Milky Way. The CHXE was attributed to the unresolved emission of massive, magnetized, accreting white dwarfs. But due to its limited angular resolution, NuSTAR was silent on the question of whether there might be another population of sources, which could exist much closer to Sgr A*.  In particular, a cusp of black holes, never observed, but a fundamental prediction of galactic stellar dynamics, should lead to substantial numbers of transient, X-ray emitting black hole binaries in the central parsec. But only one firm black hole transient is known in the central parsec. Here I report NuSTAR spectroscopic observations of two more Swift-discovered transients in the central parsec, whose spectra are suggestive of black hole binaries. In addition, I describe a remarkable cluster of quiescent X-ray binaries in the central parsec, identified with Chandra, and whose properties, numbers and distribution indicate the presence of the long sought black hole cusp. I discuss the implications of this cusp for both galactic stellar dynamics and binary accretion theory.