GRB 210328A

The Fermi GBM team reports the detection of a likely LONG GRB

At 20:45:16 UT on 28 Mar 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210328A (trigger 638657121.97022 / 210328865).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 207.9, Dec = -8.6 (J2000 degrees, equivalent to J2000 13h 51m, -8d 35'), with a statistical uncertainty of 2.1 degrees.

The angle from the Fermi LAT boresight is 79.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210328865/quicklook/glg_skymap_all_bn210328865.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210328865/quicklook/glg_healpix_all_bn210328865.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210328865/quicklook/glg_lc_medres34_bn210328865.gif

B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
 at 20:45:16 on 28 March 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 205.9+/-1.3 deg
Decl.(2000.0) = -11.4+/-1.5 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210328865/?data_version=h00

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/media/data/GRB210328865/data_files/210328_211506727701_GRB210328865_healpix_trigdat_h00.fits

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210328865/json

X. Y. Zhao, S. L. Xiong, X. Y. Song, D. Y. Guo, Y. Huang, S. Xiao,
C. Cai, Y. Zhao, J. C. Liu, Q. B. Yi, Y. Q. Zhang, W. C. Xue, C. Zheng,
Z. W. Guo,�� 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 by a long burst,
GRB 210328A, at 2021-03-28 20:45:17.900 UTC (T0), which was also detected
by Fermi/GBM (GCN #29732
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 )

According to the GECAM-B light curves in about 20 keV - 500 keV,
this burst mainly consists of a broad pulse with duration of about 12 s.

Spectral evolution is clearly seen during the burst, and the emissions
in low energies last longer than that in high energies.

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: 201.9 deg Dec: -2.6 deg
Err: 3.4 deg (1-sgima, statistical only)

The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration.

GECAM location is consistent with the Fermi/GBM and BALROG positions
within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/multiLCvsE_tn210328_204626.pdf

The GECAM preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/tn210328_204626_locSatB.pdf

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).

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 210328A, which was also
detected by Fermi-GBM (GCN #29732
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 , #29733
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 ) and GECAM-B (GCN #29737
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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
2021-03-28 20:45:21.5 UT. The measured peak count rate associated with the
burst is 338 (+48, -45) cts/s above the background in the combined data of
four quadrants, with a total of 4242 (+496, -511) cts. The local mean
background count rate was 528 (+2, -3) cts/s. Using cumulative rates, we
measure a T90 of 39 (+10, -13) 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 2021-03-28 20:45:18.1 UT. The measured
peak count rate is 296 (+85, -28) cts/s above the background in the
combined Veto data of four quadrants, with a total of 3378 (+447, -604)
cts. The local mean background count rate was 1740 (+6, -5) cts/s. We
measure a T90 of 18 (+3, -4) 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. 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.