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GCN Circular 24330

Subject

GRB 190427A, Swift-BAT refined analysis

Date

2019-04-28T15:40:56Z (6 years ago)

From

Amy Lien at GSFC <amy.y.lien@nasa.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), A. Tohuvavohu (PSU)
(i.e. the Swift-BAT team):

Using the data set from T-61 to T+242 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 190427A (trigger #900730)
(Tohuvavohu et al., GCN Circ. 24261Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 280.217, 40.304 deg which is
   RA(J2000)  =  18h 40m 52.0s
   Dec(J2000) = +40d 18' 15.6"
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 68%.

The mask-weighted light curve shows a double-peaked structure that starts
from ~ T0 and ends at ~T+0.3. The main peak occurs at ~T0, followed by a
weaker peak at ~T+0.2 s. T90 (15-350 keV) is 0.3 +- 0.1 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.0 to T+0.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.17 +- 0.21.  The fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-7
erg/cm2.
The 1-sec peak photon flux measured from T-0.33 sec in the 15-150 keV band
is 1.6 +- 0.3 ph/cm2/sec.  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/900730/BA/