Skip to main content
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 31815

Swift Trigger 1100848 is likely not a GRB
2022-04-02T04:16:01Z (2 years ago)
Tyler Parsotan at UMBC/GSFC/CRESST II <>
A. D'Ai (INAF-IASFPA), S. Dichiara (PSU), S. Laha (GSFC/UMBC),
T. M. Parsotan (GSFC/UMBC/CRESSTII), M. H. Siegel (PSU) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 03:54:42 UT, the Swift Burst Alert Telescope (BAT)  triggered and
located a marginal peak (trigger=1100848). Swift slewed immediately. 
The BAT on-board calculated location is 
RA, Dec 30.692, -61.376 which is 
   RA(J2000) = 02h 02m 46s
   Dec(J2000) = -61d 22' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). 

The XRT began observing the field at 03:56:24.6 UT, 102.1 seconds after
the BAT trigger. No source was detected in 689 s of promptly downlinked
data, which covered 93% of the BAT error circle. We are waiting for the
full dataset to detect and localise the XRT counterpart. 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
318 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 16% of the
BAT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The
8'x8' region for the list of sources generated on-board covers 100% of the BAT
error circle. The list of sources is typically complete to about 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of

Due to the low BAT significance and lack of detection in XRT, we believe that this trigger is not likely an astrophysical event.
Looking for U.S. government information and services? Visit