## SUMMARY OF PROPOSAL 81405

#### MR. KAZUTAKA YAMAOKA YAMAOKA@astro.isas.jaxa.jp

ISAS
3-1-1, YOSHINODAI
SAGAMIHARA
KANAGAWA JAPAN 229-8510
Tel: 042-759-8136 Fax: 042-759-8455
Medium: CD ROM
Subject: X-RAY BINARIES

#### ABSTRACT

We propose simultaneous X-ray and $\gamma$-ray observations of microquasar GRS~1915+105 with ASCA and CGRO over a week. The purpose of this observation is to make the singularity of microquasars clear by understanding the origin of $\gamma$-ray continuum, so-called 'hard tail' and the origin of highly ionized plasma which produces resonance absorption lines. GRS~1915+105 is one of the most brightest and variable X-ray sources, whose time scale of the variability is between several micro seconds and several months, but no one has investigated the long intensity variation in the multi-wavelength yet. This observation will be last possible opportunity for long, coordinated, broadband coverage. So we think that ASCA has to take the leadership of this campaign.