Galactic black holes in the hard state, a multiwavelength view of accretion and ejection

Abstract

The canonical hard state is associated with emission from all three fundamental accretion components: the accretion disk, the hot accretion disk corona and the jet. On top of these, the hard state also hosts very rich temporal variability properties (low frequency QPOs in the PDS, time lags, long time scale evolution). Our group has been working on the major questions of the hard state both observationally (with multi-wavelength campaigns using RXTE, SWIFT, SUZAKU, SPITZER, VLA, ATCA, SMARTS) and theoretically (through jet models that can fit entire SEDs). Through spectral and temporal analysis we seek to determine the geometry of accretion components, and relate the geometry to the formation and emission from a jet. In this presentation I will review the recent contributions of our group to the field, including the SWIFT results on the disk geometry at low accretion rates, the jet model fits to the hard state SEDs (including SPITZER data) of GRO J 1655-40, and the final results on the evolution of spectral (including X-ray, radio and infrared) and temporal properties of selected black holes in the hard states. I will also talk about impact of ASTROSAT to the science objectives of our group.