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GCN Circular 23389

Subject
GRB 181030A: Swift detection of a burst with a possible optical counterpart
Date
2018-10-30T01:50:20Z (6 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
E. Sonbas (Adiyaman Univ.), J.D. Gropp (PSU), J. A. Kennea (PSU),
A. Y. Lien (GSFC/UMBC), M. J. Moss (George Washington University),
K. L. Page (U Leicester), M. H. Siegel (PSU) and A. Tohuvavohu (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 01:27:22 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 181030A (trigger=869494).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 146.922, +14.658 which is 
   RA(J2000) = 09h 47m 41s
   Dec(J2000) = +14d 39' 28"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual with an image trigger, the available
BAT light curve shows no significant structure. 

The XRT began observing the field at 01:29:44.2 UT, 142.1 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 146.9251, 14.6582 which is equivalent to:
   RA(J2000)  = 09h 47m 42.02s
   Dec(J2000) = +14d 39' 29.5"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 10 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. 

The initial flux in the 2.5 s image was 5.25e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 118 seconds with the White
filter  starting 151 seconds after the BAT trigger. There is a
possible afterglow in the  rapidly available 2.7'x2.7' sub-image near
the position of the XRT afterglow. A  precise position is unavailable
due to a failed aspect correction.  The estimated magnitude is 18.94
with a 1-sigma error of about  0.22. 

Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.com). 
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/too.html.)