[vsnet-grb-info 27872] GRB 210509A: Swift-BAT refined analysis
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Mon May 10 13:33:56 JST 2021
TITLE: GCN CIRCULAR
NUMBER: 29975
SUBJECT: GRB 210509A: Swift-BAT refined analysis
DATE: 21/05/10 04:33:00 GMT
FROM: Amy Lien at GSFC <amy.y.lien at nasa.gov>
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210509A (trigger #1047531)
(Page et al., GCN Circ. 29970). The BAT ground-calculated position is
RA, Dec = 350.363, 6.650 deg which is
RA(J2000) = 23h 21m 27.2s
Dec(J2000) = +06d 39' 01.1"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 95%.
The mask-weighted light curve shows several overlapping pulses that
start at ~T-2 s and end at ~T+8 s. The burst went out of the BAT FOV
at ~T+77 s. T90 (15-350 keV) is 8.22 +- 0.75 sec (estimated error
including systematics).
The time-averaged spectrum from T-1.65 to T+7.63 sec is best fit by
a power law with an exponential cutoff. This fit gives a photon
index 0.76 +- 1.00, and Epeak of 33.0 +- 8.3 keV (chi squared 70.16
for 56 d.o.f.). For this model the total fluence in the 15-150 keV band
is 3.1 +- 0.4 x 10^-7 erg/cm2 and the 1-sec peak flux measured from
T+3.24 sec in the 15-150 keV band is 1.2 +- 0.2 ph/cm2/sec. A fit to
a simple power law gives a photon index of 2.18 +- 0.17 (chi squared
78.23 for 57 d.o.f.). All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1047531/BA/
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