GRB 211120A
GCN Circular 31100
Subject
GRB 211120A: GECAM detection
Date
2021-11-21T09:11:34Z (4 years ago)
From
Shuo Xiao at IHEP <xiaoshuo@ihep.ac.cn>
C. Y. Li, S. L. Xie, S. L. Xiong, S. Xiao, C. Cai, X. Y. Zhao, Y. Huang, X. Y. Song,
J. C. Liu, Y. Q. Zhang, Y. Zhao, Z. W. Guo, C. Zheng, W. C. Xue, C. W. Wang,
Q. B. Yi, B. X. Zhang, P. Zhang, W. X. Peng, R. Qiao, D. Y. Guo,
X. B. Li, X. Ma, P. Wang, J. Wang, Z. Zhang, S. J. Zheng, W. Chen, J. J. He,
G. Y. Zhao, Y. Q. Du, H. Wu, J. Liang, Q. Luo, X. L. Zhang,
L. M. Song, F. J. Lu, S. N. Zhang (IHEP), report on behalf of GECAM team:
During the commissioning phase, GECAM-B was triggered in-flight by a long
burst, GRB 211120A, at 2021-11-20T23:05:20.600 UTC (denoted as T0).
GECAM alert data was downlinked to the ground through the short message
service of BeiDou Navigation Satellite System (BDS) within ~60 s after T0.
According to the BDS alert data, this burst mainly consists of a broad pulse
with a duration of about 6 s.
The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_91148720.png
Using the automatic on-ground localization pipeline with the BDS alert data,
GECAM-B localized this burst to the following position (J2000):
Ra: 304.99 deg
Dec: 41.42 deg
Err: 1.34 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_91148720_V01.png
Given that the location is consistent with the Galactic plane, we cannot rule
out the galactic origin of this burst.
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 31104
Subject
GRB 211120A: AstroSat CZTI detection
Date
2021-11-23T05:52:20Z (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.,
2021, JApA, 42, 73) showed detection of a long GRB 211120A, which was
also detected by GECAM (Li et al., GCN 31100).
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
2021-11-20 23:05:22.85 UT. The measured peak count rate associated with
the burst is 1756 (+251, -174) cts/s above the background in the
combined data of two quadrants, with a total of 2263 (+183, -134) cts.
The local mean background count rate was 443 (+4, -8) cts/s. Using
cumulative rates, we measure a T90 of 4.8 (+0.6, -0.2) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range.
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 31105
Subject
GRB 211120A: AGILE detection
Date
2021-11-23T15:05:36Z (4 years ago)
From
Alessandro Ursi at INAF/IAPS <alessandro.ursi@gmail.com>
A. Ursi (INAF/IAPS), C. Pittori (SSDC, and INAF/OAR), A. Trois
(INAF/OA-Cagliari), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A.
Argan, M. Cardillo, C. Casentini, Y. Evangelista, E. Menegoni, L. Foffano,
G. Piano (INAF/IAPS), F. Lucarelli, F. Verrecchia (SSDC, and INAF/OAR), A.
Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N. Parmiggiani
(INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University),
M. Pilia (INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ. Trieste
and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report on behalf of the
AGILE Team:
The AGILE satellite detected the GRB 211120A at T0 = 2021-11-20 23:05:20
(UTC), reported by GECAM (GCN #31100) and AstroSat CZTI (GCN #31104).
The burst is clearly visible in the AGILE scientific ratemeters of the
SuperAGILE (SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and
AntiCoincidence (AC; 50-200 keV) detectors. The event lasted about 6 s and
it released a total number of 821 counts in the SA detector (above a
background rate of 96 Hz), 9275 counts in the MCAL detector (above a
background rate of 1210 Hz), and 23969 counts in the AC detector (above a
background rate of 3440 Hz). The AGILE ratemeter light curves can be found
at http://www.agilescienceapp.it/notices/GRB211120A_AGILE_RM.png .
The event also triggered a partial high time resolution MCAL data
acquisition, covering the main peak of the burst, from T1 = 2021-11-20
23:05:20.0 s +/- 0.5 (UTC) to T2 = 2021-11-20 23:05:26.0 +/- 0.5 s (UTC),
and released 2291 counts in the detector, above a background rate of 710
Hz. The time-integrated spectrum of the burst between T1 and T1+2.43 s can
be fitted in the energy range 0.4-20 MeV with a single power-law with ph.
ind. = -2.43 (-0.34/+0.44), resulting in a reduced chi-squared of 1.09 (62
d.o.f.) and a fluence of 5.9e-06 ergs/cm^2 (90% confidence level), in the
same energy range. The MCAL light curve can be found at:
http://www.agilescienceapp.it/notices/GRB211120A_MCAL.png .
Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html. Please
note that in the MCAL notice #564534599 the T0 was affected by a temporal
shift of about +279 sec due to a temporary ground software problem now
solved.
GCN Circular 31129
Subject
IPN triangulation of GRB 211120A
Date
2021-11-26T13:51:12Z (4 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
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,
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 211120A
(GECAM-B detection: Li et al., GCN Circ. 31100;
AstroSat-CZTI detection: Prasad et al., GCN Circ. 31104;
AGILE-MCAL detection: Ursi et al., GCN Circ. 31105)
was detected by GECAM-B (GRD), AstroSat (CZTI), AGILE (MCAL),
Konus-Wind, Mars-Odyssey (HEND),
and BepiColombo (MGNS; see introductory GCN Circ. 30949)
at about 83120 s UT (23:05:20).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
315.138 (21h 00m 33s) +42.856 (+42d 51' 20")
Corners:
315.108 (21h 00m 26s) +43.024 (+43d 01' 25")
315.128 (21h 00m 31s) +42.774 (+42d 46' 28")
315.185 (21h 00m 44s) +42.640 (+42d 38' 25")
315.164 (21h 00m 39s) +42.890 (+42d 53' 23")
---------------------------------------------
The error box area is 30 sq. arcmin, and its maximum
dimension is 23 arcmin (the minimum one is 0.7 arcmin).
The Sun distance was 95 deg.
This box may be improved.
The distance between the box and the GECAM position
(RA, Dec, Err = 304.99, 41.42, 1.34; GCN 31100) is
7.6 deg, thus it is inconsistent with the box.
The box Galactic latitude is -2.2 deg (noticed by Shaolin XIONG),
so the Galactic origin can not be ruled out
using the burst localization only.
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB211120_T83120/IPN/
The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.
GCN Circular 31130
Subject
Konus-Wind detection of GRB 211120A
Date
2021-11-26T14:31:29Z (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 211120A (GECAM detection: Li et al., GCN 31100;
AstroSat CZTI detection: Prasad et al., GCN 31104;
AGILE detection: Ursi et al., GCN 31105;
IPN localization: Kozyrev et al., GCN 31129)
triggered Konus-Wind (KW) at T0=83120.396 s UT (23:05:20.396).
The burst light curve shows a bright, multi-peaked pulse
which starts at ~T0-1 s and has a total duration of ~8 s.
The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB211120_T83120/
As observed by Konus-Wind, the burst had
a fluence of (3.5 �� 0.4)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 1.984 s,
of (2.4 �� 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+5.120 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 = -0.65 (-0.07,+0.08),
the high energy photon index beta = -2.71 (-0.30,+0.20),
the peak energy Ep = 315 (-24,+24) keV,
chi2 = 113/95 dof.
The spectrum near the peak count rate (measured from T0+0.256
to T0+3.072 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 = -0.55 (-0.10,+0.12),
the high energy photon index beta = -2.48 (-0.28,+0.18),
the peak energy Ep = 325 (-36,+40) keV,
chi2 = 96/84 dof.
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.