B. Sbarufatti (PSU), H. A. Krimm (NSF/USRA),
F. E. Marshall (NASA/GSFC) and A. Tohuvavohu (PSU) report on behalf of
the Neil Gehrels Swift Observatory Team:
At 19:04:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180823A (trigger=855434). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 210.349, +14.884 which is
RA(J2000) = 14h 01m 24s
Dec(J2000) = +14d 53' 03"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve, which is superimposed
on a declining background, shows a double-peaked structure with a
duration of about 40 sec. The peak count rate was ~2000 counts/sec
(15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 19:06:02.2 UT, 89.2 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 210.35630, 14.89029 which
is equivalent to:
RA(J2000) = 14h 01m 25.51s
Dec(J2000) = +14d 53' 25.0"
with an uncertainty of 5.4 arcseconds (radius, 90% containment). This
location is 34 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. We
cannot determine whether the source is fading at the present time. No
spectrum from the promptly downlinked event data is yet available to
determine the column density.
The initial flux in the 2.5 s image was 3.10e-09 erg cm^-2 s^-1 (0.2-10
UVOT took a finding chart exposure of 37 seconds with the White
filter starting 379 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 is expected to be about 18.5 mag. No correction
has been made for the expected extinction corresponding to E(B-V) of
Burst Advocate for this burst is B. Sbarufatti (bxs60 AT psu.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/too.html.)