GRB 211022A

Yi Zhao, S. L. Xiong, S. Xiao, C. Cai, J. J. He, Y. Huang, Z. W. Guo, 
C. Y. Li, X. B. Li, J. C. Liu, X. Y. Song, C. W. Wang, P. Wang, S. L. Xie, W. C. Xue,
Q. B. Yi, Y. Q. Zhang, G. Y. Zhao, X. Y. Zhao, C. Zheng, Y. Q. Du, D. Y. Guo, 
J. Liang, F. J. Lu, Q. Luo, X. Ma, W. X. Peng, R. Qiao, L. M. Song, J. Wang, H. Wu, 
P. Zhang, S. N. Zhang, X. L. Zhang, Z. Zhang, S. J. Zheng (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B was triggered in-flight by a
burst, GRB 211022A, at 2021-10-22T00:47:28.100 UTC (denoted as T0),
which was also observed by KONUS/WIND.

Its alert data was promptly downlinked to the ground through the short
message service of BeiDou Navigation Satellite System (BDS). The time
latency of the first BeiDou message relative to the trigger time is about
1 minute.

According to the BDS alert data, this burst mainly consists of multiple
pulses with duration of about 120 s.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_88562848.png

GECAM-B localized this burst to the following position (J2000): 
Ra: 164.5 deg 
Dec: -50.6 deg
Err: 2.0 deg (1-sigma, statistical only)
The current systematic error of location is estimated to be several degrees 
which could be minimized by the ongoing calibration.

The GECAM preliminary location could be found here: 
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_bdm_88562848_V01.png

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).

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.,
2021, JApA, 42, 73) showed detection of a long GRB 211022A, which was
also detected by GECAM (Zhao et al., GCN 30955
Loading...
 
 ).

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
2021-10-22 00:48:52.0 UT. The measured peak count rate associated with
the burst is 166 (+14, -13) cts/s above the background in the combined
data of four quadrants, with a total of 11186 (+925, -981) cts. The
local mean background count rate was 598 (+1, -1) cts/s. Using
cumulative rates, we measure a T90 of 92 (+63, -9) 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 2021-10-22 00:48:54.1 UT. The
measured peak count rate is 2130 (+71, -86) cts/s above the background
in the combined Veto data of four quadrants, with a total of 159488
(+3241, -5602) cts. The local mean background count rate was 21425 (+3,
-91) cts/s. We measure a T90 of 119 (+5, -10) 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

A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the MGNS/BepiColombo and HEND/Mars Odyssey teams,

J. Benkhoff on behalf of the BepiColombo team,

K. Hurley on behalf of the IPN,

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long-duration GRB 211022A
(GECAM-B detection: Zhao et al., GCN Circ. 30955
Loading...
 
 ;
AstroSat-CZTI detection: Prasad et al., GCN Circ. 30968
Loading...
 
 )
was detected by BepiColombo (MGNS; see introductory GCN Circ. 30949
Loading...
 
 ),
Mars-Odyssey (HEND), GECAM-B, AstroSat (CZTI), Konus-Wind,
INTEGRAL (SPI-ACS), and Swift (BAT), at about 2845 s UT (00:47:25).
The burst was outside the coded field of view of the BAT.

The burst light curves in the energy range 30 keV-1.5 MeV (HEND)
and 250-450 keV (MGNS) exhibit a multi-peaked pulse structure
with a total duration of ~150 s.

We have triangulated GRB 211022A to the following 3 sigma annuli:
------------------------------------------------------------
            R.A.(J2000)  Dec.(J2000)    R      +dR     -dR
                deg         deg        deg     deg     deg
------------------------------------------------------------
MGNS-HEND      30.161     12.392    125.005  +0.096  -0.214
SPI-ACS-HEND  202.386     -8.806     53.850  +0.093  -0.071
Konus-SPI-ACS 193.415    -14.239     44.866  +5.706  -5.232
------------------------------------------------------------
The MGNS-HEND and SPI-ACS-HEND annuli intersect to form two error
boxes one of which is inconsistent with the Konus-SPI-ACS annulus,
the KW ecliptic latitude response, and the GECAM position.

The correct preliminary, 3 sigma error box is:
---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   161.615 (10h 46m 27s) -51.006 (-51d 00' 21")
  Corners:
   160.852 (10h 43m 24s) -50.508 (-50d 30' 29")
   162.525 (10h 50m 06s) -51.893 (-51d 53' 33")
   161.845 (10h 47m 23s) -51.080 (-51d 04' 47")
   160.242 (10h 40m 58s) -49.672 (-49d 40' 19")
  ---------------------------------------------
The error box area is 1026 sq. arcmin, and its maximum
dimension is 2.6 deg (the minimum one is 9.8 arcmin).
The Sun distance was 54 deg.

This box may be improved.

A triangulation maps are posted at:
http://www.ioffe.ru/LEA/GRBs/GRB211022_T02845/IPN

The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.