[vsnet-grb-info 22819] GRB 190630B, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24918
SUBJECT: GRB 190630B, Swift-BAT refined analysis
DATE:    19/06/30 16:01:10 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm at nsf.gov>

J. R. Cummings (CPI), S. D. Barthelmy (GSFC),  H. A. Krimm (NSF),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), F. Marshall (GSFC),
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-240 to T+50 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 190630B (trigger #912102)
(Krimm, et al., GCN Circ. 24913).  The BAT ground-calculated position is
RA, Dec = 223.729, 41.528 deg which is 
  RA(J2000)  =  14h 54m 55.0s 
  Dec(J2000) = +41d 31' 42.4" 
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a single, weak pulse with a FRED-like
shape, starting from T-3 sec, peaking at T+1 sec and fading to background by
T+6 sec.  We note that data is available until approximately T+250 sec.  However,
after T+50 sec, the background cannot be properly subtracted due to high 
background levels arising from Swift’s entry into the SAA.  Therefore we only
use data prior to T+50 sec for analysis.  The raw light curve shows no sign of any
burst activity after the initial pulse.  T90 (15-350 keV) is 5.6 +- 0.9 sec 
(estimated error including systematics).

The time-averaged spectrum from T-1.7 to T+4.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.36 +- 0.24.  The fluence in the 15-150 keV band is 2.8 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.19 sec in the 15-150 keV band
is 1.1 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 

In the initial circular for GRB 190630B (Krimm, et al., GCN Circ. 24913), this event
was reported as a possible burst.   After the more complete analysis carried out here,
we conclude that Swift trigger 912102 is indeed a GRB.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/912102/BA/