NASA SWIFT detection of a long transient (GRB 050714B?)
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3613
SUBJECT: Swift detection of a long transient (GRB 050714B?)
DATE: 05/07/15 00:25:37 GMT
FROM: Andrew Levan at U.of Leicester anl@star.le.ac.uk
A. Levan, A. Beardmore, K. Page, J. Osborne, E. Rol (U. Leicester) S. Barthelmy, J. Cannizzo (GSFC-UMBC), L. Cominsky (Sonoma State U.), H. Krimm (GSFC), C. Markwardt (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC), C. Gronwall, D. Burrows, P. Roming, J. Kennea (PSU) and N. Gehrels (GSFC) report for the Swift team.
At 22:40:32 UT, Swift-BAT triggered (trigger=145994) and located on-board a source. The flight-determined location is RA,Dec 169.694, -15.528 {+11h 18m 47s, -15d 31′ 39″} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The spacecraft was on target at approximately 150 seconds. This was a very weak 64-sec image-trigger detection right at the image-trigger threshold (10.1 sigma). There are no “peaks” in the BAT lightcurve, which is consistent with a long low-amplitude event, and that it was an image trigger and not a rate trigger. At this early stage in the analysis, we can not distinguish between a long GRB and a hard X-ray transient. However, we do think that it is from a real astrophysical source.
The spacecraft slewed immediately and the XRT began observing the burst at 22:43:00.6 UT (151 s after the BAT trigger). XRT found a bright, uncatalogued, fading X-ray source. The position, calculated with xrtcentroid on the TDRSS postage stamp image, is:
RA: 11h 18m 47.9s (J2000),
Dec: -15d 32′ 55.5″ (J2000).
This position is 76.5 arcseconds from the BAT position. The estimated uncertainty is 6 arcseconds radius (90% containment).
The Swift Ultra Violet/Optical Telescope (UVOT) observations began at 22:43:03 UT, 151 seconds after the BAT trigger. The first data taken after the spacecraft settled was a 100 seconds exposure using the V filter with the midpoint of the observation at 201 seconds after the BAT trigger. There is no new source at the XRT position.
