[vsnet-grb-info 3757] GRB 060923C: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5591
SUBJECT: GRB 060923C: Swift detection of a burst
DATE:    06/09/23 13:48:45 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

M. Stamatikos (NASA/ORAU), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), M. Capalbi (ASDC), M.L. Conciatore (ASDC),
C. Guidorzi (Univ Bicocca&INAF-OAB), S. T. Holland (GSFC/USRA),
J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
M. Perri (ASDC), T. Sakamoto (NASA/ORAU), D. E. Vanden Berk (PSU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:

At 13:33:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060923C (trigger=230711).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA,Dec 346.127, +3.942 {23h 04m 30s, +03d 56' 32"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  This is an image-trigger (88 sec), and as such,
the BAT TDRSS lightcurve does not show significant activity. 

The XRT began observing the field at 13:36:25 UT, 203 seconds after the
BAT trigger. XRT found a bright, fading, uncatalogued X-ray source
located at RA(J2000) = 23h 04m 28.1s, Dec(J2000) = +03d 55' 30.3", with an
estimated uncertainty of 8.1 arcseconds (90% confidence radius). 
This location is 70 arcseconds from the BAT on-board position, within
the BAT error circle. The initial flux in the 2.5s image was
8.5e-10 erg/cm2/s (0.2-10 keV). 

There is a 4th magnitude star 12 arcmin from the XRT error circle. 
Therefore, UVOT will not and can not observe this burst.