Revealing the spectral/temporal evolution of Cyg X-1 under Suzaku & MAXI collaboration
Abstract
Over the past 3 decades, the Low/Hard state of black hole binaries has remained rather poorly understood. This limitation is now being overcome by the wide-band capability of Suzaku. In fact, a Suzaku observation of Cyg X-1 in the Low/Hard state led to a view that an optically- thick disk partially intrudes into a hot corona, the disk is truncated at 10 gravitational radii, and the corona is highly inhomogeneous (Makishima+08). From 2005 to 2009, Cyg X-1 was observed 25 times with Suzaku. The source meanwhile stayed mostly in the Low/Hard state, but approached the Soft state on June 2009. We applied a unified spectral and timing analysis to all these data sets. The results suggest that, as the 2-10 keV luminosity increases, (1) the corona shrinks, (2) the inner radius of the optically-thick disk decreases, and (3) the disk intrudes deeper into the corona. These results will be much enhanced through a collaboration between MAXI and Suzaku. For example, we may select a transition phase from the Low/Hard state to the High/Soft state, and examine how the Comptonized hard continuum in the former state turns into the enigmatic steeper hard-tail emission which is seen in the latter state.
- Publication:
-
The First Year of MAXI: Monitoring Variable X-ray Sources
- Pub Date:
- December 2010
- Bibcode:
- 2010fym..confP...8T