[vsnet-grb-info 2747] GRB 060123: Swift detection of a very long, faint burst

[GCN Circulars]

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 at 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.