TITLE:   GCN CIRCULAR
NUMBER:  32069
SUBJECT: GRB 220518A: Swift-BAT refined analysis
DATE:    22/05/19 22:19:52 GMT
FROM:    Tyler Parsotan at UMBC/GSFC/CRESST II  <parsotat@umbc.edu>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), 

H. A. Krimm (NSF), A. Y. Lien (U Tampa), 

C. B. Markwardt (GSFC), D. M. Palmer (LANL), 

T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), 

M. Stamatikos (OSU), (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 220518A (trigger #1107050)

(Gropp et al., GCN 32060).  The BAT ground-calculated position is

RA, Dec = 55.340, -47.593 deg which is 

   RA(J2000)  =  03h 41m 21.6s 

   Dec(J2000) = -47d 35' 36.3" 

with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).

The partial coding was 51%.

 

The light curve has a peak at the trigger time and potential precursor 

emission occuring slightly before the BAT trigger time. 

T90 (15-350 keV) is 12.29 +- 3.07 sec (estimated error including systematics).

The time-averaged spectrum from T-8.36 to T+7.58 sec is best fit by a simple

power-law model.  The power law index of the time-averaged spectrum is

1.71 +- 0.21.  The fluence in the 15-150 keV band is 5.7 +- 0.8 x 10^-07 erg/cm2.

The 1-sec peak photon flux measured from T+0.07 sec in the 15-150 keV band

is 1.8 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence

level. 

 

The results of the batgrbproduct analysis are available at

http://gcn.gsfc.nasa.gov/notices_s/1107050/BA/