GCN Circular 17599
Subject
GRB 150318A: Swift detection of a burst
Date
2015-03-18T07:20:45Z (10 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
C. Pagani (U Leicester), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC),
H. A. Krimm (CRESST/GSFC/USRA), C. J. Mountford (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:
At 07:04:53 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150318A (trigger=635289). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 324.971, -61.477d which is
RA(J2000) = 21h 39m 53s
Dec(J2000) = -61d 28' 35"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
structure with a duration of about 80 sec. The peak count rate
was ~1000 counts/sec (15-350 keV), at ~4 sec after the trigger.
The XRT began observing the field at 07:07:14.5 UT, 141.3 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 325.0056, -61.4559 which is equivalent to:
RA(J2000) = +21h 40m 1.34s
Dec(J2000) = -61d 27' 21.2"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 96 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 164 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. The typical 3-sigma upper limit has been about 19.6 mag.
The 8'x8' 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
0.04.
Burst Advocate for this burst is C. Pagani (cp232 AT star.le.ac.uk).
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.)