GCN Circular 37005
Subject
GRB 240730A: Swift-BAT refined analysis
Date
2024-08-01T19:55:22Z (7 months ago)
From
Michael Moss at NASA GSFC <mikejmoss3@gmail.com>
Via
Web form
D. Sadaula (GSFC/UMBC), S. D. Barthelmy (GSFC),
S. B. Cenko (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), T. Sakamoto (AGU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240730A (trigger #1245636)
(Cenko, et al., GCN Circ. 36976). The BAT ground-calculated position is
RA, Dec = 37.841, 59.045 deg which is
RA(J2000) = 02h 31m 21.9s
Dec(J2000) = +59d 02' 43.5"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 98%.
The BAT mask-weighted light curve displays two spectrally soft peaks.
The T90 (15-350 keV) is 50.13 +- 7.60 sec (estimated error including systematics).
The time-averaged spectrum from T-6.06 to T+53.43 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.50 +- 0.19. The fluence in the 15-150 keV band is 6.8 +- 0.9 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+5.80 sec in the 15-150 keV band
is 0.4 +- 0.1 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/1245636
The long duration and proximity to the Galactic plane raised the initial
possibility that this was a Galactic transient. However, its subsequent behavior,
including a lack of later BAT detections, is consistent with a GRB, making the
Galactic transient interpretation less likely.