P. D'Avanzo (INAF-OAB), A. P. Beardmore (U Leicester),
M. G. Bernardini (INAF-OAB), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), A. Y. Lien (GSFC/UMBC),
A. Melandri (INAF-OAB), C. J. Mountford (U Leicester) and
J. L. Racusin (NASA/GSFC) report on behalf of the Swift Team:
At 23:01:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 141225A (trigger=622476). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 138.751, +33.795 which is
RA(J2000) = 09h 15m 00s
Dec(J2000) = +33d 47' 41"
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 30 sec. The peak count rate
was ~1600 counts/sec (15-350 keV), at ~6 sec after the trigger.
The XRT began observing the field at 23:08:10.5 UT, 423.5 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 138.7782, 33.7919 which
is equivalent to:
RA(J2000) = 09h 15m 06.77s
Dec(J2000) = +33d 47' 30.7"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 82 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://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 (1.48 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.6
(+1.62/-1.47) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White
filter starting 440 seconds after the BAT trigger. No credible
afterglow candidate has been found in the initial data products. The
8'x 8' region for the list of sources generated on-board covers 100% of
the XRT error circle. The list of sources is typically complete to
about 18 mag. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.02.
Merry Christmas from the Swift Team!
Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo AT brera.inaf.it).
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.)