GRB 210330A

D. Y. Guo, Y. Huang, S. L. Xiong, S. Xiao, C. Cai, Y. Zhao, J. C. Liu,
Q. B. Yi, Y. Q. Zhang, W. C. Xue, C. Zheng, Z. W. Guo, X. Y. Zhao,
X. Y. Song, P. Wang, X. B. Li, W. X. Peng, R. Qiao, C. W. Wang,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. 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,�� D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long burst,
GRB 210330A, at 2021-03-30T12:45:46.600 UTC (denoted as T0).

GECAM 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
a broad pulses with duration of about 20 s.

An automatic on-ground localization was calculated using the light curves
and counts spectrum in the BDS alert data.
Although the in-flight calibration of energy response and localization
has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):
Ra: 164.3 deg Dec: -55.6 deg
Err: 5.1 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.

Given that the location is close to the galactic plane, we cannot rule out
the possibility that this burst originated from a galactic source.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_70807546.png

The GECAM preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_70807546_V01.png

As the detailed science data are downloaded, all analyses would be improved.

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. Lipunov, A.Chasovnikov, F.Balakin, V.Kornilov, E.Gorbovskoy,P.Balanutsa, V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, 
N.Tiurina, I.Gorbunov, D.Zimnukhov, V.Senik, V.Topolev, D.Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)
started GECAM  GRB 210330A (D.Y.Guo et al. GCN 29739
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 , Ttrigger=12:45:46.600 UTC, R.A.Dec.: 164.3d,-55.6d, er.-b.=5.1d) 
optical observations at MASTER-SAAO (located in South African Astronomical Observatory) 
17496 sec after trigger time at 2021-03-30 17:37:23 UT at sunset, with 
upper limit up to  18.7 mag.

Observations started at zenith distance = 43 deg. The sun  altitude was -13.6 deg.

The galactic latitude b =  4 deg., longitude l = 288 deg.

Real time updated cover map and OT,that can be discovered, will be available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1580304

There are the following upper limits of the first images

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
    17587 | 2021-03-30 17:37:23 |         MASTER-SAAO | (10h 57m 26.66s , -55d 35m 44.3s) |   C |   180 | 18.7 |
    17787 | 2021-03-30 17:40:43 |         MASTER-SAAO | (10h 57m 26.36s , -55d 34m 44.9s) |   C |   180 | 18.6 |
    17986 | 2021-03-30 17:44:02 |         MASTER-SAAO | (11h 05m 32.80s , -55d 35m 42.8s) |   C |   180 | 18.6 |
Filter C is a clear (unfiltred) band.


The observation and reduction will continue.
The message may be cited.

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(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 long GRB 210330A, which was also
detected by GECAM (GCN #29736
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 ).

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
2021-03-30 12:45:46.50 UT. The measured peak count rate associated with the
burst is 262 (+45, -46) cts/s above the background in the combined data of
four quadrants, with a total 1367 (+248, -267) cts. The local mean
background count rate was 510 (+3, -3) cts/s. Using cumulative rates, we
measure a T90 of 13 (+2, -7) s.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. 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.