TITLE:   GCN CIRCULAR
NUMBER:  32239
SUBJECT: GRB 220618A: Swift-BAT refined analysis
DATE:    22/06/21 12:26:59 GMT
FROM:    Tyler Parsotan at UMBC/GSFC/CRESST II  <parsotat@umbc.edu>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC), 

H. A. Krimm (NSF), S. Laha (GSFC/UMBC),

A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),

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 220618A (trigger #1110821)

(Troja, et al., GCN Circ. 1110821).  The BAT ground-calculated position is

RA, Dec = 38.986, 55.218 deg which is 

   RA(J2000)  =  02h 35m 56.6s 

   Dec(J2000) = +55d 13' 05.0" 

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

The partial coding was 21%.

 

The BAT light curve showed a single peak structure with a duration of about 40 sec. 

T90 (15-350 keV) is 96.00 +- 65.97 sec (estimated error including systematics).

 

The time-averaged spectrum from -15.264 to 128.736 sec is best fit by a power law

with an exponential cutoff.  This fit gives a photon index 0.26 +- 0.85, 

and Epeak of 65.0 +- 16.9 keV (chi squared 53.40 for 56 d.o.f.).  For this

model the total fluence in the 15-150 keV band is 2.2 +- 0.3 x 10^-06 erg/cm2

and the 1-sec peak flux measured from T+8.24 sec in the 15-150 keV band is

0.8 +- 0.4 ph/cm2/sec.  A fit to a simple power law gives a photon index

of 1.61 +- 0.16 (chi squared 63.41 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/1110821/BA/