GRB 210822A
GCN Circular 30744
Subject
GRB 210822A: CALET Gamma-Ray Burst Monitor detection
Date
2021-08-30T07:06:23Z (4 years ago)
From
Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>
K. Kobayashi (Waseda U),
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka (ICRR), S. Torii, Y. Akaike (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long GRB 210822A (Swift detection: Page et al., GCN Circ. 30677, Lien
et al., GCN Circ. 30689; GECAM detection: Wang et al., GCN Circ. 30678,
30696; Fermi-LAT detection: Ohno et al., GCN Circ. 30687; AstroSat CZTI
detection: Prasad et al., GCN Circ. 30693; Konus-Wind detection:
Frederiks et al., GCN Circ. 30694; GRBAlpha detection: Ohno et al.,
GCN Circ. 30697; https://gcn.gsfc.nasa.gov/other/210822A.gcn3)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 09:18:18.162 UTC
on 22 August 2021. The burst signal was seen by all CGBM detectors.
Because of a problem in one of the ground alert processing script,
the GCN notice was not distributed automatically for this event.
The burst light curve shows a multi-peaked structure which starts at
T-0.2 sec, peaks at T+0.1 sec and ends at T+11.0 sec.
The T90 and T50 durations measured by the SGM data are 10.1 +- 0.5 sec
and 5.8 +- 0.4 sec (40-1000 keV), respectively.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1313658800/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.
GCN Circular 30723
Subject
GRB 210822A: CAHA 2.2m observations
Date
2021-08-27T00:27:10Z (4 years ago)
From
Alexander Kann at IAA-CSIC  <kann@iaa.es>
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), A. Fernandez, I. Hermelo, and P. Martin (all CAHA) 
report:
We observed the bright GRB 210822A (Swift detection: Page et al., GCN 
#30677; GECAM detection: Wang et al., GCN #30678; Fermi-LAT detection: 
Ohno et al., GCN #30687;  AstroSat CZTI detection: Prasad et al., GCN 
#30693; Konus-Wind detection: Frederiks et al., GCN #30694; GRBAlpha 
detection: Ohno et al., GCN #30697) at a redshift of z = 1.736 (Zhu et 
al., GCN #30692) with CAFOS mounted on the 2.2m CAHA telescope at Calar 
Alto, Alemria, Spain. The first epoch was obtained under very inclement 
conditions (almost overcast), and one 60 s as well as four 90 s images 
were useful. The second epoch, two nights later, was obtained under 
significantly improved (but still not really good) conditions, and 31 x 
30 s images were obtained.
The optical afterglow (Page et al., GCN #30677; Zheng et al., GCN 
#30679; Butler et al., GCN #30680; Fu et al., GCN #30684; Zhu  et al., 
GCN #30692; Romanov & Lane, GCN #30701; Nicuesa Guelbenzu et al., GCN 
#30703; Siegel et al., GCN #30710; Belkin  et al., GCN #30712; Belkin  
et al., GCN #30714) is faintly detected in the first epoch, but not 
detected in the second epoch.
Against three nearby Pan-STARRS comparison stars, we measure (AB 
magnitudes):
i' = 18.56 +/- 0.14 mag at 0.43283 days after the GRB, and
i' > 21.5 mag at 2.5206 mag after the GRB.
GCN Circular 30714
Subject
GRB 210822A: TSHAO continued optical observation
Date
2021-08-25T16:34:52Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Kusakin (FAP), I. Reva (FAP),  Pozanenko (IKI), N. 
Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:
We continue observations of GRB 210822A (Page et al., GCN  30677;  Wang 
et al., GCN 30678; Prasad  et al., GCN  30693; Frederiks et al., GCN 
30694) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory. 
on Aug. 22 (UT) 15:48:55 -- 18:48:47. We obtained series  in R-filter 
starting on  2021-08-24 (UT) 16:47:35.
The optical afterglow (Page et al., GCN  30677; Zheng et al., GCN 30679; 
Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu  et al., GCN 30692; 
Romanov  et al., GCN 30701; Guelbenzu et al., GCN 30703; Siegel et al., 
GCN 30710; Belkin  et al., GCN 30712) at the redshift of z = 1.736 (Zhu 
  et al., GCN 30692) is detected in stacked image. Preliminary 
photometry of the afterglow in a stacked image is following.
Date       UT start t-T0    Filter  Exp.  OT    Err.  UL(3 sigma)
                     (mid, days)     (s)
2021-08-24 16:47:35 2.33041  R      3180  21.60 0.26  22.0
The photometry is based on nearby USNO-B1.0 stars.
USNO-B1.0
RA Dec R2
20:18:06.64416 +05:17:24.1404 12.33
20:17:59.55288 +05:18:19.5912 13.05
GCN Circular 30713
Subject
GRB 210822A: VLA detection
Date
2021-08-25T14:47:06Z (4 years ago)
From
Tanmoy Laskar at U of Bath  <tanmoylaskar@gmail.com>
T. Laskar (University of Bath), K. D. Alexander (Northwestern), E. Berger
(Harvard), R. Chornock (UC Berkeley), W. Fong (Northwestern), R. Margutti
(UC Berkeley), C. G. Mundell (University of Bath), P. Schady (University of
Bath), and G. Schroeder (Northwestern) report on behalf of a larger
collaboration:
"We observed GRB 210822A (Page et al. GCN 30677) with the Karl G. Jansky
Very Large Array (VLA) beginning on 2021 August 24 at 05:30 UT (1.9 d after
the burst). At a mean frequency of 14.8 GHz, we detect a radio source with
a preliminary flux density of ~ 0.4 mJy at the position:
RA (J2000) = 20:17:44.992 +/- 0.001
Dec (J2000) = 05:16:59.53 +/- 0.02
consistent with the position of the optical afterglow (Page et al., GCN
30677) and the Swift/XRT afterglow (Evans al., GCN 30682). Follow-up
observations are planned.
We thank the VLA staff for rapidly executing these observations."
GCN Circular 30712
Subject
GRB 210822A: TSHAO optical observation
Date
2021-08-25T09:49:39Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Kusakin (FAP), I. Reva (FAP),  Pozanenko (IKI), N. 
Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:
We observed GRB 210822A (Page et al., GCN  30677;  Wang et al., GCN 
30678; Prasad  et al., GCN  30693; Frederiks et al., GCN 30694) with 
Zeiss-1000 telescope of Tien Shan Astronomical Observatory on Aug. 22 
(UT) 15:48:55 -- 18:48:47. We obtained series with 20 and 30 sec 
exposition in R-filter.
The optical afterglow (Page et al., GCN  30677; Zheng et al., GCN 30679; 
Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu  et al., GCN 30692; 
Romanov  et al., GCN 30701; Guelbenzu et al., GCN 30703; Siegel et al., 
GCN 30710) at redshift z = 1.736 (Zhu  et al., GCN 30692) is detected in 
stacked images. Preliminary photometry of the afterglow in a stacked 
image of the second series is following.
Date       UT start t-T0    Filter  Exp.  OT    Err.  UL(3 sigma)
                     (mid, days)     (s)
2021-08-22 17:26:41 0.36184  R      196*20 18.63 0.03 21.0
The photometry is based on nearby USNO-B1.0 stars.
USNO-B1.0
RA Dec R2
20:18:06.64416 +05:17:24.1404 12.33
20:17:59.55288 +05:18:19.5912 13.05
GCN Circular 30710
Subject
GRB 210822A: Swift/UVOT Detection
Date
2021-08-25T06:21:36Z (4 years ago)
From
Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>
M. H. Siegel (PSU) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210822A
85 s after the BAT trigger (Page et al., GCN Circ. 30677).
A fading source consistent with the XRT position (Page et al.
GCN Circ. 30677) and the previously reported UVOT source is 
is detected in the initial UVOT exposures.
Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag
white (fc)          86          236          147      13.63+/-1.10
white              577         1200          205      15.35+/-0.02
white             4965         5058           91      17.43+/-0.05
white            34405        35230          804      19.15+/-0.05
white           149533       190336         1894      20.64+/-0.11
v                  627         1250           77      15.07+/-0.05
v                27494        28215          702      18.68+/-0.13
b                  553         1176           58      15.31+/-0.04
b                 4760         4960          196      17.56+/-0.06
b                33493        34400          885      19.18+/-0.08
u (fc)             298          548          245      13.78+/-0.03
u                  700         1304           39      14.86+/-0.05
u                 4555         4755          196      16.85+/-0.05
u                57947        58635          670      19.73+/-0.19
uvw1               676         1299           77      15.28+/-0.07
uvw1             39434        96567         1775      19.90+/-0.22
uvm2               824         1274           38            >17.66
uvm2             92215        93015          788            >20.06
uvw2               602         1225           77      17.21+/-0.18
uvw2             21659        64335         1469      20.40+/-0.34
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.162 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 30703
Subject
GRB 210822A: GROND observations
Date
2021-08-24T15:19:39Z (4 years ago)
From
Ana Nicuesa at TLS Tautenburg  <ana@tls-tautenburg.de>
A. Nicuesa Guelbenzu, S. Klose (both TLS Tautenburg) and
A. Rau (MPE Garching) report:
We observed the field of GRB 210822A (Swift trigger #1069788; Page et al.,
GCN 30677) with GROND mounted at the 2.2m MPG telescope at La Silla
Observatory (Chile).
Observations started at 02:54 UT on August 23, about 17.6 hr after the GRB
trigger. They were performed at an average seeing of 2.2 arcsec and at an
average airmass of 1.2.
Based on combined images with 10 min total exposure, at a mid-time of
03:02 UT on 2021-08-23 for the afterglow (Page et al., GCN 30677; Zheng &
Filippenko, GCN 30679; Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu
et al., GCN 30692; Romanov & Lane, GCN 30701) we derive the following
AB magnitudes:
g' = 20.37 +/- 0.09,
r' = 20.10 +/- 0.05,
i' = 19.92 +/- 0.05.
Given magnitudes are calibrated against Pan-STARRS and   are not corrected
for the expected Galactic foreground extinction corresponding to a
reddening of E(B-V) = 0.14 mag in the direction of the burst (Schlegel et
al. 1998).
We thank Angela Hempel for excellent support and for performing the
observations.
GCN Circular 30701
Subject
GRB 210822A: Abbey Ridge Observatory optical afterglow observation
Date
2021-08-24T06:49:06Z (4 years ago)
From
Filipp Dmitrievich Romanov at Amateur astronomer  <filipp.romanov.27.04.1997@gmail.com>
Filipp D. Romanov (Russia) and David J. Lane (Saint Mary's University,
Canada) report:
Filipp Romanov observed optical afterglow of GRB 210822A (Page et al.,
GCN Circ. 30677) remotely using 0.355-m f/6.2 Schmidt-Cassegrain
telescope of Abbey Ridge Observatory (it is owned by Dave Lane) in
Canada, on 2021-08-23.
Four images (with exposures: 720, 720, 600 and 720 seconds) were
obtained with Cousins R filter from 00:54:39 to 02:17:30 UTC. Faint
(SNR = 5) optical afterglow (with UVOT position) is visible in the
stacked image (mid time =  01:36:04 UTC, that is 16.296 hours after
the trigger). Romanov measured its magnitude comparing to transformed
(using formula Rc=r���-0.22 from Dymock & Miles, 2009) r' magnitudes of
nearby stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016).
The measured magnitude = 20.1 +/- 0.3. Magnitude was not corrected for
Galactic extinction.
Stacked image available here:
http://abbeyridgeobservatory.ca/images/grb210822a.jpg
GCN Circular 30697
Subject
GRB 210822A: Detection by GRBAlpha
Date
2021-08-23T15:42:18Z (4 years ago)
From
Masanori Ohno at Hiroshima U  <ohno@astro.hiroshima-u.ac.jp>
M. Ohno (Eotvos U./Konkoly Observatory/Hiroshima U.), J. Ripa (Masaryk U.),
 H. Takahashi (Hiroshima U.), A. Pal, L. Meszaros, B. Csak (Konkoly
Observatory), N. Werner, M. Topinka, F. Munz, F. Hroch (Masaryk U.), T.
Urbanec, M. Kasal,  A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus,
M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M.
Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner
Research Center/Eotvos U.), Yuusuke Uchida, Helen Poon, H. Matake, N.
Uchida (Hiroshima U.), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T.
Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa,
K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.),
K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory),  T. Mizuno
(Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J.
Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.) -- the GRBAlpha
collaboration.
The long duration GRB 210822A (Swift-BAT detection; Page et al. GCN Circ.
 30677, GECAM detection; Wang et al. GCN Circ. 30678, Fermi-LAT detection;
Ohno et al. GCN Circ. 30687) was detected by the GRBAlpha 1U CubeSat (Pal
et al. Proc. SPIE 2020).
The light curve shows a strong spike structure with a high significance of
a SNR ~ 45. The observed total duration was about 12 sec. GRBAlpha was
leaving the outer Van Allen radiation belt and thus GRB 210822A is
superimposed on a high background due to trapped electrons.
The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB210822A_GCN.pdf
GRBAlpha is a demonstration mission for a future CubeSats constellation
(Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75
x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy
range from ~50 keV to ~1000 keV. GRBAlpha was launched on 2021 March 22
from Baikonur. After its commissioning phase, the scientific observations
are now under way. To increase the duty cycle and the downlink rate, the
upgrade of the on-board data acquisition software stack is in progress. The
ground segment is also supported by the radio amateur community and it
takes advantage of the SatNOGS network for increased data downlink volume.
GCN Circular 30696
Subject
GRB 210822A: GECAM refined analysis
Date
2021-08-23T15:00:34Z (4 years ago)
From
Chenwei Wang at IHEP  <cwwang@ihep.ac.cn>
C. W. Wang, S. L. Xiong, X. Y. Zhao, X. Y. Song, C. Cai, C. Y. Li,
Y. Huang, S. L. Xie, J. C. Liu, Y. Q. Zhang,  Y. Zhao, Z. W. Guo, C. Zheng,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li,
X. H. Liang, J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, 
Q. Luo, X. Ma, G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi, 
L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, J. Z. Wang,X. L. Zhang, 
W. C. Xue, X. Y. Wen, S. Xiao, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, 
Q. B. Yi, B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, 
H. M. Zhang, K. Zhang, P. Wang, P. Zhang, S. N. Zhang, Z. Zhang, 
S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP), report on behalf of GECAM team:
At 2021-08-22T09:18:18.00 UTC(denoted as T0), GECAM-B was triggered in-flight 
by a long bright burst, GRB 210822A, which is also observed by Swift/BAT (GCN #30677). 
The spectrum was calculated using the GECAM-B trigger data. 
The time-integrated spectrum (measured from T0 to T0+15) 
is best fit in the 20 keV - 5 MeV range 
by a power law with high energy exponential rolloff model:
dN/dE ~ (E^alpha)*exp(-E/beta)
with  alpha = -0.8595 +/- 0.029,
and beta = 394.9867 +/- 23.466 keV.
The event fluence (10-1000 keV) in this time interval is
(7.54 +0.10/-0.19)E-05 erg/cm^2. 
Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).
GCN Circular 30694
Subject
Konus-Wind detection of GRB 210822A
Date
2021-08-23T12:38:10Z (4 years ago)
From
Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 210822A (Swift detection: Page et al., GCN 30677;
GECAM detection: Wang et al., GCN 30678;
Fermi-LAT detection: Ohno et al., GCN 30687;
AstroSat CZTI detection: Ohno et al., GCN 30693)
triggered Konus-Wind (KW) at T0=33502.974 s UT (09:18:22.974).
The burst light curve shows a bright, multi-peaked pulse
which starts at ~T0-1 s and has a total duration of ~12 s,
followed by a weaker decaying emission visible up to ~T0+50 s.
The emission in the main pulse is seen up to ~15 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210822_T33502/
As observed by Konus-Wind, the burst had
a fluence of (1.20 �� 0.11)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.320 s,
of (3.25 �� 0.28)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+18.176 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.64 (-0.06,+0.07),
the high energy photon index beta = -2.39 (-0.15,+0.12),
the peak energy Ep = 398 (-29,+30) keV,
chi2 = 124/96 dof.
The spectrum near the peak count rate (measured from T0+4.096
to T0+7.936 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.59 (-0.15,+0.18),
the high energy photon index beta = -2.08 (-0.18,+0.12),
the peak energy Ep = 429 (-83,+108) keV,
chi2 = 75/63 dof.
Assuming the redshift z=1.736 (Zhu et al., GCN 30692)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the isotropic energy release E_iso to (9.5 �� 0.8)x10^53 erg,
the isotropic luminosity L_iso to (7.0 �� 0.6)x10^53 erg/s,
the rest-frame peak energy of the time-integrated spectrum Epi,z to (1090 �� 80) keV,
and the rest-frame peak energy of the 'peak' spectrum Epp,z to (1175 �� 250) keV.
With these values, GRB 210822A lies within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., 2021, ApJ, 908, 83),
see http://www.ioffe.ru/LEA/GRBs/GRB210702_T68826/GRB210822A_rest_frame.pdf
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 30693
Subject
GRB 210822A: AstroSat CZTI detection
Date
2021-08-23T09:13:47Z (4 years ago)
From
Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>
V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat
CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al,
2020, arxiv:2011.07067) showed detection of a bright long GRB 210822A,
which was also detected by Swift (Page et al., GCN 30677), GECAM (Wang
et al., GCN 30678), and Fermi-LAT (Ohno et al., GCN 30687). 
The source was clearly detected in the 20-200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2021-08-22 09:18:17.50 UT. The measured peak count rate associated with
the burst is 2190 (+85, -91) cts/s above the background in the combined
data of four quadrants, with a total of 12961 (+301, -314) cts. The
local mean background count rate was 530 (+2, -3) cts/s. Using
cumulative rates, we measure a T90 of 10 (+0.2, -0.2) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed multiple peaks
of emission with the strongest peak at 2021-08-22 09:18:18.97 UT. The
measured peak count rate is 3587 (+117, -127) cts/s above the background
in the combined Veto data of four quadrants, with a total of 24196
(+541, -655) cts. The local mean background count rate was 1799 (+4, -4)
cts/s. We measure a T90 of 12 (+0.5, -0.5) s from the cumulative Veto
light curve.
CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC
and PRL. The Indian Space Research Organisation funded, managed and
facilitated the project. 
Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 30692
Subject
GRB 210822A: NOT photometry and spectroscopy
Date
2021-08-23T08:25:52Z (4 years ago)
From
Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>
Z.P. Zhu (NAOC, HUST), L. Izzo (DARK/NBI), S.Y.Fu, D. Xu (NAOC), J.P.U. 
Fynbo (DAWN/NBI), E. Paraskeva, S. Vitali (NOT), report on behalf of a 
larger collaboration:
We observed the bright optical afterglow of GRB 210822A (Page et al., 
GCN 30677; Wang et al., GCN 30678; Ohno et al., GCN 30687) using the 
Nordic Optical Telescope (NOT) equipped with the ALFOSC camera.
We obtained 3x120s frames in the Sloan r-filter, starting at 23:11:50 UT 
on 2021-08-22 (i.e., ~ 13.89 hr after the BAT trigger). The previously 
reported optical afterglow (e.g., Page et al., GCN 30677; Zheng & 
Filippenko, GCN 30679; Butler et al., GCN 30680; Lipunov et al., GCN 
30681; Fu et al., GCN 30684) has decayed to m(r) = 19.71 +/- 0.02, 
calibrated with the PS1 field.
Subsequently 4x1200 s spectroscopy was carried out. A continuum is 
detected over the whole wavelength range of 3700-9500 AA, superimposed 
with some absorption features, among which prominent Fe II, Mg II, Mg I, 
and Al III lines were identified at a common redshift of z = 1.736. We 
conclude that this is the redshift of the burst.
GCN Circular 30691
Subject
GRB 210822A: Swift-XRT refined Analysis
Date
2021-08-23T08:08:50Z (4 years ago)
From
Phil Evans at U of Leicester  <pae9@leicester.ac.uk>
M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai
(INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N.
Burrows (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester)
and K.L. Page report on behalf of the Swift-XRT team:
We have analysed 7.3 ks of XRT data for GRB 210822A (Page et al. GCN
Circ. 30677), from 64 s to 58.6 ks after the  BAT trigger. The data
comprise 1.2 ks in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 30682