TITLE:   GCN CIRCULAR
NUMBER:  37956
SUBJECT: GRB 241030A: Swift detection of a burst with a bright optical counterpart
DATE:    24/10/30 06:05:42 GMT
FROM:    Simone Dichiara at Pennsylvania State University <sbd5667@psu.edu>

N. J. Klingler (GSFC/UMBC/CRESSTII), S. Dichiara (PSU),
R. Gupta (NASA GSFC), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 05:48:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 241030A (trigger=1263718).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 343.033, +80.439 which is 
   RA(J2000) = 22h 52m 08s
   Dec(J2000) = +80d 26' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of at least 180 sec.  The peak count rate
was ~12000 counts/sec (15-350 keV), at ~162 sec after the trigger.

The XRT began observing the field at 05:49:16.6 UT, 73.5 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 343.1400, 80.4482 which is equivalent to:
   RA(J2000)  = 22h 52m 33.60s
   Dec(J2000) = +80d 26' 53.5"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 72 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	22:52:33.57 = 343.13987
  DEC(J2000) = +80:26:59.9  =  80.44996
with a 90%-confidence error radius of about 0.61 arc sec. This position is 6.3
arc sec. from the center of the XRT error circle. The estimated magnitude is
15.42 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.131.

Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)