GCN Circular 45713
GRB 260924A: Swift detection of a burst
From: Jimmy DeLaunay at PSU
Issued: 2026-09-24 01:41 UTC

V. D'Elia (SSDC & INAF-OAR), J. J. DeLaunay (PSU),
R. Gupta (NASA GSFC), A. Y. Lien (U Tampa), K. L. Page (U Leicester),
D. M. Palmer (LANL), T. M. Parsotan (GSFC) and
B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 01:13:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 260924A (trigger=1513082). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec (133.740, +12.046) which is
RA(J2000) = 08h 54m 58s
Dec(J2000) = +12d 02' 44"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The available BAT light curve (cut off at T+8s
while still active) showed a complex structure with a duration of at least
20 sec. The peak count rate was ~3700 counts/sec (15-350 keV), at ~0 sec
after the trigger.

The XRT began observing the field at 01:15:18.8 UT, 110.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 133.7620, 12.0455 which is equivalent to:
RA(J2000) = 08h 55m 2.88s
Dec(J2000) = +12d 02' 43.8"
with an uncertainty of 5.1 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.

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 123 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image processing
FAILED because of no aspect solution. Results from the list of sources
generated on-board are not available at this time. No correction has been made
for the expected extinction corresponding to E(B-V) of 0.041.

Burst Advocate for this burst is V. D'Elia (valerio.delia AT ssdc.asi.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: Welcome to the Neil Gehrels Swift Observatory (swift.psu.edu))

Filter: gamma-ray bursts are posted only if in the top 10% of the past year's — by fluence (total energy received per cm², from Fermi GBM, Konus-Wind, GECAM and similar circulars; now ≥ 3.9×10^-5 erg/cm²) or by the number of GCN Circulars about the burst (now ≥ 14). Thresholds are recalculated monthly.
Relayed automatically from NASA's General Coordinates Network.