GRB 060123: Swift detection of a very long, faint burst

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 4584
SUBJECT: GRB 060123: Swift detection of a very long, faint burst
DATE: 06/01/24 23:09:07 GMT
FROM: David Burrows at PSU/Swift dxb15@psu.edu

D. Palmer (LANL), J. Kennea (PSU), J. Cummings (GSFC), D. N. Burrows (PSU), N. Gehrels (GSFC), F. Marshall (GSFC), C. Markwardt (GSFC/UMD), J. A. Nousek (PSU), A. Parsons (GSFC) report on behalf of the Swift team:

At 22:22:40 UT, the Swift Burst Alert Telescope (BAT) located GRB 060123. The burst did not trigger GCN notices because the source was found in a long-term (5 minute) image, for which triggers are not currently enabled. The BAT ground-calculated location is RA,Dec 179.750, +45.513 {11h 59m 00s, +45d 30′ 47″} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 900 +- 100 sec. The peak count rate was ~160 counts/sec (15-50 keV, note the unusual energy interval), at ~300 sec after the trigger. We note that this is a very long duration burst, which suggests the possibility of a high-z event.

At 19:14:14 on Jan 24th, 2006 (75.1 ks after the event) Swift began a target of opportunity observation of this source. Analysis of XRT data reveals a faint, fading, uncataloged point source at the following coordinates:

RA(J2000): 11h 58m 47.9s

Dec(J2000): +45d 30′ 45.5″

with an error circle of 6 arcseconds (90% containment). This position lies 128 arcseconds from the BAT position of this source. The fading X-ray lightcurve of this object strongly suggests that this is a GRB afterglow.

UVOT took a 210 second exposure with the V filter starting at 19:14:14 UT. No source was detected with a 3-sigma upper limit of 20.0 mag. at the XRT position.