GRB 210401A
GCN Circular 29739
Subject
GRB 210401A: Fermi GBM Final Real-time Localization
Date
2021-04-01T23:27:12Z (4 years ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
The Fermi GBM team reports the detection of a likely LONG GRB
At 23:17:04 UT on 1 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210401A (trigger 639011829.029182 / 210401970).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 263.1, Dec = -31.6 (J2000 degrees, equivalent to J2000 17h 32m, -31d 36'), with a statistical uncertainty of 1.8 degrees.
The angle from the Fermi LAT boresight is 98.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210401970/quicklook/glg_skymap_all_bn210401970.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/bn210401970/quicklook/glg_healpix_all_bn210401970.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210401970/quicklook/glg_lc_medres34_bn210401970.gif
GCN Circular 29740
Subject
Fermi GRB 210401A: Global MASTER-Net observations report
Date
2021-04-02T21:00:17Z (4 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin,
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov, D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova
(Irkutsk State University, API),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko
(Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210401A ( Fermi GBM team, GCN 29739) errorbox 77156 sec after notice time and 77165 sec after trigger time at 2021-04-02 20:43:09 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 80 deg. The sun altitude is -51.3 deg.
The galactic latitude b = 0 deg., longitude l = 357 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1581695
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
77256 | 2021-04-02 20:43:09 | MASTER-SAAO | (17h 29m 04.89s , -34d 09m 47.6s) | C | 180 | 17.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 29744
Subject
Konus-Wind detection of GRB 210401A
Date
2021-04-02T23:19:00Z (4 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, D. Frederiks, S. Golenetskii, A.Lysenko,
A. Ridnaya, A. Tsvetkova, M. Ulanov, and T. Cline, report:
The long-duration GRB 210401A (Fermi-GBM detection: The Fermi GBM team,
GCN Circ. 29739) was detected by Konus-Wind (KW) in the waiting mode.
A Bayesian block analysis of the KW waiting mode data in
the 20-1500 keV band reveals a count rate increase over background
in the interval from ~T0-500 s to ~T0+340 s,
where T0 = T0(GBM) = 83824 (23:17:04) UT.
The total duration of ~840 s makes this burst an ultra-long GRB candidate.
On the other hand, the proximity of the burst localization (GCN 29739)
to the Galactic center may suggest that the burst is a galactic transient.
The KW light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB210401A/
Modeling the KW 3-channel time-integrated spectrum
(measured from T0-499.335 s to T0+339.705 s)
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.40(-0.10,+0.12) and Ep = 240(-35,+45) keV.
A CPL fit to the spectrum near the peak count rate,
measured from T0+248.441 s to T0+254.329 s, gives
alpha -1.25(-0.12,+0.13), and Ep = 413(-78,+122) keV.
In the 10 keV -10 MeV band, the total burst fluence
is (1.46 +/- 0.18)x10^-4 erg/cm^2, and the 2.944 s peak energy flux,
measured in the interval starting from T0+248.441 s,
is (1.73 +/- 0.22)x10^-6 erg/cm^2.
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
[GCN OPS NOTE(03apr21), Per author's request, the typo in the SUBJECT:-line
was changed from 210104A to 210401A.]
GCN Circular 29758
Subject
GRB 210401A: GECAM detection
Date
2021-04-04T15:01:13Z (4 years ago)
From
Wangchen Xue at IHEP <xuewc@ihep.ac.cn>
W. C. Xue, S. L. Xiong, X. Y. Song, Y. Huang, S. Xiao, C. Cai, Y. Zhao,
J. C. Liu, Q. B. Yi, Y. Q. Zhang, C. Zheng, Z. W. Guo, X. Y. Zhao,
P. Wang, X. B. Li, W. X. Peng, R. Qiao, D. Y. Guo, 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 very long burst,
GRB 210401A, at 2021-04-01 23:17:08.000 UTC (T0), which was also detected
by Fermi/GBM (GCN #29739) and Konus-Wind (GCN #29744).
According to the GECAM-B light curves in about 10 keV - 500 keV,
this burst mainly consists of multiple pulses with duration of about 800 s.
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: 275.3 deg Dec: -29.2 deg
Err: 5.8 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.
GECAM location is consistent with that of Fermi/GBM within the error.
The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/71018228.0energys.pdf
The GECAM preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/tn210401_232014_locationSatB_map.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).