[AGN, Quasars, Black Holes -- Oral ]

The HETGS View of the Microquasar GRS 1915+105: Fast Spectral Variability and the Disk-Jet Connection

Joseph Neilsen, Harvard University, CfA
Julia C. Lee (Harvard/CfA), Ron Remillard (MIT)

Over the last decade, Chandra has observed the enigmatic microquasar GRS 1915+105 eleven times at high time resolution using the high spectral resolution of the HETGS. We will present the results of both long-term and fast spectral variability studies of these observations, which provide new and powerful probes of the connection between relativistic jets and the accretion disk around this stellar-mass black hole. Our study of the long-term spectral variability of GRS 1915+105 shows that spectrally hard states (known for their production of optically thick jets) exhibit broad iron emission lines, while softer states produce an accretion disk wind. We use this gradient in behavior to argue that Comptonization mediates the disk-jet interaction in GRS 1915+105. Our fast timing and spectral analysis of the same observations is designed to identify the geometry of the Comptonizing medium and its role in photoionization of the accretion flow. We show how strong absorption lines from highly ionized iron appear and disappear on timescales of 5 seconds or less, and relate this evolution to changes in the broadband X-ray continuum. These results underscore Chandra's phenomenal capabilitiesand show that the HETGS can compete with RXTE in timing analysis of bright X-ray sources.