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GRB 210422A

GCN Circular 29886

Subject

GRB 210422A: Swift detection of a burst

Date

2021-04-22T23:07:53Z (4 years ago)

From

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

E. Troja (NASA/GSFC/UMCP), C. Gronwall (PSU), A. Y. Lien (GSFC/UMBC)
and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels
Swift Observatory Team:

At 17:47:10 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210422A (trigger=1044678). Due to an observing constraint,
Swift did not slew immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 21.139, +42.110 which is 
   RA(J2000) = 01h 24m 33s
   Dec(J2000) = +42d 06' 36"
with an uncertainty of 3 arcmin (radius, 90% containment, 
including systematic uncertainty). The BAT light curve showed a 
single pulse structure with a duration of about 5 sec.  
The peak count rate was ~1000 counts/sec (15-350 keV), 
at ~0 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT 
position until 2021 June 4. There will thus be no XRT or UVOT data
for this trigger before this time. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)

GCN Circular 29897

Subject

GRB 210422A: Swift-BAT refined analysis

Date

2021-04-25T00:00:01Z (4 years ago)

From

Sibasish Laha at GSFC <sibasish.laha@nasa.gov>

S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210422A (trigger #1044678)
(Troja et al., GCN Circ. 29886Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 21.077, 42.100 deg which is
   RA(J2000)  =  01h 24m 18.6s
   Dec(J2000) = +42d 05' 58.2"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.

The BAT light curve showed a complex structure with a duration of about ~30 sec.
T90 (15-350 keV) is 39.00 +- 7.28 sec (estimated error including systematics).

The time-averaged spectrum from -34.40 s to -20.56 s and -19.40s to 7.59 s is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.70 +- 0.22.  The fluence in the 15-150 keV band is 7.2 +- 1.1 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+0.59 sec in the 15-150 keV band
is 1.3 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/BATbursts/1044678/bascript/top.html