TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1341
SUBJECT: ASM GRB candidate 020406 refined error box
DATE:    02/04/08 23:24:57 GMT
FROM:    Don Smith at U michigan  <dasmith@rotse2.physics.lsa.umich.edu>

D. A. Smith (U of Michigan) and R. Remillard (MIT) report on behalf of the
RXTE/ASM teams at MIT and NASA/GSFC:

Further RXTE/ASM detections of the event reported in GCN Circ. No. 1332 have
been discovered in the ASM production data, missing from the realtime data
stream available on the day of the event.  Rather than scanning *off* the
source, as we reported, the ASM scan actually moved to put the source *closer*
to the center of the FOV, greatly increasing the detector area exposed to this
source.  The time series data show that the source remained bright, with some
evidence for fading, for at least 100 seconds after the end of the observation
reported in GCN Circ. 1332.  The light curve is strongest in the 5-12 keV band,
with an average count rate during the second dwell of 21.3+-0.7 c/s, as
compared to only 3.0+-0.6 c/s in the 1.5-3 keV band (ASM rates for the Crab are
25.4 and 26.8 in the soft and hard bands, respectively).

Using the strongest detection of this source in each camera, we were able to
greatly refine our error box to a parallelogram roughly 3 arcminutes on a side.
This box is centered on the coordinates 
                R.A.: 19h 01m 45.95s, Decl: 1d 26' 15.7", 
and its corners are located at the following coordinates (all coordinates in
epoch J2000.0):

R.A.      Decl.
285.4381 1.4150
285.3389 1.4563
285.4472 1.4595
285.5416 1.4201

This refined localization appears to rule out the counterpart candidate
proposed by Durig & McDermott in GCN #1138.

A background-subtracted 5-12 keV light curve and the four ASM localizations of
this event can be seen at http://xte.mit.edu/grb/grb020406/