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The 2009 Fermi Symposium

First Results of Monitoring X-ray Transients with MAXI GSC Onboard ISS

Mutsumi Sugizaki, RIKEN


MAXI (Monitor of All-sky X-ray Image) payload was delivered to the ISS (International Space Station) in July 2009. Since then, the GSC (Gas Slit Camera) on MAXI has been scanning the whole sky every 90 minutes of the ISS orbital period in 2-30 keV band. Transient intensity variations of all the bright X-ray sources over a time scale of the 90-minute orbital period, which includes an outburst from a Be/X-ray binary A0535+26 and a flare from an active star UX Ari, have been detected and monitored successfully so far. It also has a capability to detect a short time variation during a source transit of 40-60 seconds for each scan. The current detection sensitivity per a 90-minute scan cycle is approximately 20-30 mCrab. The instrument-response calibration, background modeling, and the study of the data-processing methods to optimize the sensitivity and to issue fast alerts of new-transient appearances are in progress. We present preliminary results of monitoring X-ray transients for the first two months and the future prospects.