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῎ ῍ ῑ ῌ

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The Origin of X-Ray Flash Observed by HETE-2

T. SAKAMOTO

The Astroparticle Physics Laboratory, NASA/

Goddard Space Flight Center, Code 661, NASA/

GSFC, Greenbelt, MD 20771

Abstract : We present the detailed and systematic study of the spectral characteristics of X-ray flashes (XRFs) observed by HETE-2. The XRFs show similar characteristics to the long GRBs except for their lower Epeakenergies. One of the key observational relation, EpeakῌEiso

relation, is discussed as a frame work to understand the gamma-ray burst in an unified picture. We emphasis on the importance of the partnership between HETE and Swift for solving the nature of XRFs.

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