TITLE: GCN CIRCULAR NUMBER: 32603 SUBJECT: GRB 220930A: Swift detection of a burst DATE: 22/09/30 11:36:03 GMT FROM: Kim Page at U.of Leicester klp5@leicester.ac.uk
S. B. Cenko (GSFC), A. P. Beardmore (U Leicester), C. Gronwall (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester) and T. M. Parsotan (GSFC/UMBC/CRESSTII) report on behalf of the Neil Gehrels Swift Observatory Team:
At 11:11:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220930A (trigger=1125809). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 64.737, +13.352 which is RA(J2000) = 04h 18m 57s Dec(J2000) = +13d 21' 06" 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 20 sec and a secondary peak at about 70 seconds after the trigger time. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 11:14:42.1 UT, 170.0 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 64.7149, 13.3500 which is equivalent to: RA(J2000) = 04h 18m 51.58s Dec(J2000) = +13d 21' 00.0" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 77 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 3.09e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 179 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 0.639.
Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). 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/)