TITLE:   GCN CIRCULAR
NUMBER:  34434
SUBJECT: GRB 230815A: Swift detection of a burst
DATE:    23/08/15 11:25:59 GMT
FROM:    K.L. Page at U Leicester <klp5@leicester.ac.uk>


N. J. Klingler (GSFC/UMBC/CRESSTII), C. Gronwall (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
T. M. Parsotan (GSFC/UMBC/CRESSTII) report on behalf of the Neil
Gehrels Swift Observatory Team:

At 10:49:55 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 230815A (trigger=1185505).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 184.772, -58.065 which is 
   RA(J2000) = 12h 19m 05s
   Dec(J2000) = -58d 03' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 2 sec.  The peak count rate
was ~6000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 10:52:04.0 UT, 128.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 184.72347, -58.05386 which
is equivalent to:
   RA(J2000)  = 12h 18m 53.63s
   Dec(J2000) = -58d 03' 13.9"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (4.94 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 7.8
(+3.75/-3.24) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 2.07e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 155 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. Because of the density of catalogued stars, further
analysis is required to report an upper limit for any afterglow in the
sub-image. Data from the list of sources generated on-board are not available
at this time. No correction has been made for the large, but uncertain,
extinction expected. 

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/)