GCN Circular 45834
GRB 261005B: Swift-BAT refined analysis
From: Amy
Issued: 2026-10-07 13:05 UTC
S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha
(GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss
(GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T.
Sakamoto (AGU) (i.e. the Swift-BAT team):
Using the data set from T-179 to T+200 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 261005B (trigger #1515414)
(Parsotan et al., GCN Circ. 45812). The BAT ground-calculated position is
RA, Dec = 255.322, 1.584 deg which is
RA(J2000) = 17h 01m 17.3s
Dec(J2000) = +01d 35' 02.3"
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The
partial coding was 93%.
The mask-weighted light curve shows a multi-peaked structure that starts at
~T0 and ends at ~T+100 s. The two main peaks occur at ~T+4 s and ~T+21 s,
respectively. T90 (15-350 keV) is 94.00 +- 20.10 sec (estimated error
including systematics).
The time-averaged spectrum from T+1.78 to T+106.78 sec is best fit by a
simple power-law model. The power law index of the time-averaged spectrum
is 1.37 +- 0.27. The fluence in the 15-150 keV band is 7.9 +- 1.3 x 10^-07
erg/cm2. The 1-sec peak photon flux measured from T+3.78 sec in the 15-150
keV band is 0.7 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90%
confidence level.
The results of the batgrbproduct analysis are available at
batgrbproduct analysis for trigger=1515414 (swift.gsfc.nasa.gov)
Every one of the gamma-ray bursts GCN reports is posted here.
Relayed automatically from NASA's General Coordinates Network.
Transient Alerts » in reply to GRB 261005B
In plain words Routine
On the evening of 5 October 2026 (UTC), two space telescopes, NASA's Swift and Fermi, both caught a burst of gamma rays (the most energetic form of light) from a spot in the sky near the border of the constellations Ophiuchus and Hercules. The burst flickered with several peaks and lasted somewhere between about 20 and 90 seconds, depending on which instrument and energy range measured it. Swift's X-ray telescope found a fading X-ray afterglow and pinned its position to within about 2 arcseconds, but ultraviolet, optical and infrared searches hours later found no visible afterglow. No distance has been reported, so how far away it is remains unknown. It looks like an ordinary long gamma-ray burst, the kind usually linked to the death of a massive star.
How unusual is it? This is a typical gamma-ray burst: moderate brightness, an X-ray afterglow found, no visible-light afterglow and no distance measured. A redshift (distance) measurement or a supernova or other counterpart found later would make it more notable.
Written by an AI model (claude-sonnet-5-5) from the official reports in this thread; last updated . It may contain mistakes: the reports themselves are the authority.
GRB 261005B: Swift-BAT refined analysis