[29.03] First Results on X-Ray Flashes from Swift

AAS 206th Meeting, 29 May - 2 June 2005
Session 29 X-Ray Flashes
Topical Session, Tuesday, 2:30-4:00pm, 4:15-6:00pm, May 31, 2005, 102 E

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[29.03] First Results on X-Ray Flashes from Swift

T. Sakamoto (GSFC/NRC), Swift Team

Gamma-ray bursts (GRBs), whose energy fluence in the X-ray energy band S_X (2--30 keV) is larger than their energy fluence in the gamma-ray S_\gamma (30--400 keV), have received increasing attention. These events are so-called X-ray flashes (XRFs) and X-ray-rich GRBs (XRRs) depending on their hardness, and have been studied in detail by Ginga, BeppoSAX, and the HETE-2 satellite. The recent studies of BeppoSAX and HETE-2 suggest that XRFs, XRRs, and GRBs arise from the same phenomenon.

The Swift satellite, which was successfully launched on November 20, 2004, has an unprecedented capability to study the nature of XRF afterglows. Once the burst is detected by the Burst Alert Telescope (BAT) or by another satellite, Swift can slew to the burst location within seconds, and can start to observe an afterglow in the X-ray (X-Ray Telescope; XRT) and ultraviolet/optical (UV/Optical Telescope; UVOT) bands. BAT has a good capability for observing XRFs with its relatively low energy coverage from 15 keV to 150 keV. An XRF observed by Swift and HETE-2 on February 15, 2005 (XRF050215b) has the fastest and the longest XRF follow-up observation so far. XRT and UVOT detected the very faint X-ray afterglow. We highlight the recent XRF observations by Swift in the scope of its prompt and afterglow emission properties.

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