Development micro-satellite TSUBAME for polarimetry of gamma-ray bursts

Gamma-ray bursts (GRBs) are the most drastic and intriguing phenomena in high energy astrophysics. The nature of relativistic collimated outflows that bight be generated by gravitational collapses of massive stars is to investigate the physical process just around the central engines by constraining magnetic environment. For this purpose we developed a compact and high sensitive hard x-ray polarimeter aboard a university class micro-satellite "TSUBAME." Unsurprisingly, any micro-satellites have stringent limitations on size, mass, and power consumption restricting the effective area of detectors. However, high luminosities of GRBs allow us to measure their polarizations only if we start observations just after the ignitions. TSUBAME overcomes this problem by using compact an high-torque actuators, control moment gyroscopes, that enable high speed attitude control faster than 6° s -1 . Cooperating with a wide field burst monitor on board for real time position determination of GRBs, TSUBAME can start a pointing observation within ~15 s after the detection for any GRBs in the half-sky field of view of the burst monitor.