LMXBs in their hard state: studies with Suzaku, MAXI, and ASTRO-H
Abstract
Low-Mass X-ray binaries (LMXBs) are known to have soft and hard states, like Black Hole Binaries (BHBs). Since LMXBs are similar to BHBs in many respects, comparison between them will help us to understand their accretion mechanisms. With this in mind, we analyzed archival Suzaku data of the recurrent transient LMXB Aql X-1. The data were obtained on 7 occasions during an outburst, covering both the hard and soft states. The soft-state data gave consistent results with previous studies (Mitsuda+1984, Makishima+1986). In the hard state, the source was detected up to 100 keV with the HXD, and the accretion geometry became much clearer than before. Currently, more than 20 LMXBs are being detected with MAXI, and some of them (e.g., 4U 1646- 53 and Cyg X-2) clearly exhibit semi-periodic ( a few months) state transitions. By monitoring their MAXI light curves, we can select their low-state periods, and perform scheduled Suzaku observations. To better qualify the high-energy cutoff in the hard state of LMXBs, and to search for any hidden non-thermal signals, a significant jump will be provided by the ASTRO-H SGD.
- Publication:
-
The First Year of MAXI: Monitoring Variable X-ray Sources
- Pub Date:
- December 2010
- Bibcode:
- 2010fym..confP..24S