Gamma-ray Burst 210422A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #29886
  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 #29887
  V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
  R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
  R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
  D. Buckley (South African Astronomical Observatory),
  O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
  A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
  V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
  MASTER-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB210422.74 (trigger No 1044678,01h 24m 33.36s , +42d 06m 36.0s, R=0.05) errorbox 39 sec after notice time and 23084 sec after trigger time at 2021-04-23 00:11:54 UT, with upper limit up to 16.3 mag. The observations began at zenith distance = 84 deg. The sun altitude is -24.0 deg.
  The galactic latitude b = -20 deg., longitude l = 130 deg.
  Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1599524
  We obtain a following upper limits.

  Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
  _________|_____________________|_____|_______|______|________
  
     23175 |      MASTER-Tavrida |   C |   180 | 16.2 |        
     23374 |      MASTER-Tavrida |   C |   180 | 16.3 |        
  

  Filter C is a clear (unfiltred) band.
  The observation and reduction will continue. The message may be cited.
• GCN Circular #29897
  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. 29886). 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