GCN Circular 40487

T. Sakamoto (AGU), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester),
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), (i.e. the Swift-BAT team):

Using the data set from T-240 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 250516A (trigger #1314210)
(Beardmore et al., GCN Circ. 40467
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 ).  The BAT ground-calculated position is
RA, Dec = 334.612, -9.120 deg which is
   RA(J2000)  =  22h 18m 26.8s
   Dec(J2000) = -09d 07' 11.9"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 61%.

The mask-weighted light curve shows a multi-peaked structure that starts at
~T-20 s and ends at ~T+23 s. The highest peak occurs at ~T+20 s. T90
(15-350 keV) is 30.04 +- 6.01 sec (estimated error including systematics).

The time-averaged spectrum from T-19.96 to T+22.70 sec is best fit by a
simple power-law model.  The power law index of the time-averaged spectrum
is 1.69 +- 0.08.  The fluence in the 15-150 keV band is 2.3 +- 0.1 x 10^-06
erg/cm2. The 1-sec peak photon flux measured from T+19.39 sec in the 15-150
keV band is 3.8 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90%
confidence level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1314210