Ashley L. King, Jon M. Miller, John Raymond, Andy C. Fabian, Chris S. Reynolds, Tim R. Kallman, Dipankar Maitra, Edward M. Cackett, Michael P. Rupen
Chandra spectroscopy of transient stellar-mass black holes in outburst has
clearly revealed accretion disk winds in soft, disk-dominated states, in
apparent anti-correlation with relativistic jets in low/hard states. These disk
winds are observed to be highly ionized, dense, and to have typical velocities
of ~1000 km/s or less projected along our line of sight. Here, we present an
analysis of two Chandra High Energy Transmission Grating spectra of the
Galactic black hole candidate IGR J17091-3624 and contemporaneous EVLA radio
observations, obtained in 2011. The second Chandra observation reveals an
absorption line at 6.91+/-0.01 keV; associating this line with He-like Fe XXV
requires a blue-shift of 9300^{+500}_{-400} km/s (0.03c, or the escape velocity
at 1000 R_{Schw}). This projected outflow velocity is an order of magnitude
higher than has previously been observed in stellar-mass black holes, and is
broadly consistent with some of the fastest winds detected in active galactic
nuclei. Potential features at 7.07 keV and 7.32 keV, if due to Fe XXV and Fe
XXVI, would imply a velocity of ~15,400 km/s (0.05c), but these putative
features are marginal. Photoionization modeling suggests that the accretion
disk wind in IGR J17091-3624 may originate within 43,300 Schwarzschild radii of
the black hole, and may be expelling more gas than accretes. The
contemporaneous EVLA observations strongly indicate that jet activity was
indeed quenched at the time of our Chandra observations. We discuss the results
in the context of disk winds, jets, and basic accretion disk physics in
accreting black hole systems.
View original:
http://arxiv.org/abs/1112.3648
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