GRB 211130A
GCN Circular 31196
Subject
GRB 211130A: MeerLICHT identification of possible afterglow candidate
Date
2021-12-10T09:16:11Z (4 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), A.J. Levan (Radboud),
P.M. Vreeswijk (Radboud), report on behalf of the MeerLICHT consortium:
We observed the field of the Fermi/GBM long GRB candidate GRB 211130A
(Fermi GBM Team, GCN 31151) with the 0.6m wide-field MeerLICHT
optical telescope located at Sutherland, South Africa, starting at
2021-11-30,
18:31:26 UT, approximately 3 hours 15 minutes after the GRB trigger.
With a field of view of 2.7 square degrees, 72 MeerLICHT pointings were
required to cover the GBM sky map to a probability level of 90%. We
observed 67 out of the 72 fields three times on the first night of
observations.
The remaining 5 fields were observed once. All observations were conducted
in the q-band (g+r) with a 60s exposure time. The average 5-sigma full-frame
limiting magnitude was q = 20.79 across the observations.
Following the IPN triangulation of GRB 211130A (Kozyrev et al., GCN 31161),
a refined search for transient candidates in our data reveals a single
promising
afterglow candidate at coordinates:
RA (J2000) = 01:24:52.46 (21.2186d)
Dec (J2000) = -27:41:57.48 (-27.6993d)
calibrated against Gaia DR2. The candidate is, however, located just North
of
the IPN triangulation region, an angular distance of 8.7' from the centre
of the
IPN region and still consistent with the Konus-Wind/GBM triangulation
region.
The candidate was detected at three epochs and appears to show fading
behaviour, with 5-sigma AB magnitudes at time post-trigger of:
q = 19.83 +/- 0.07 at 3.74 hours
q = 20.05 +/- 0.10 at 5.57 hours
q = 20.66 +/- 0.20 at 7.05 hours.
No underlying source is visible in PanSTARRS and Legacy Survey DR9 images
at this position.
MeerLICHT is built and run by a consortium consisting of Radboud
University,
University of Cape Town, the South African Astronomical Observatory, the
University of Oxford, the University of Manchester and the University of
Amsterdam.
GCN Circular 31162
Subject
Konus-Wind detection of GRB 211130A
Date
2021-12-03T17:19:17Z (4 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 211130A
(Fermi GBM Final Real-time localization: The Fermi GBM team, GCN 31151;
BALROG localization: Kunzweiler et al., GCN 31152;
IPN triangulation: Kozyrev et al., GCN 31161)
triggered Konus-Wind at T0=54992.505 s UT (15:16:32.505).
The burst light curve starts with a smooth pulse, which was followed,
after a period of low-level emission, by a more intense, multi-peaked
emission complex. The total burst duration is ~21.4 s.
The emission is seen up to ~6 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB211130_T54992/
As observed by Konus-Wind, the burst
had a fluence of 9.57(-0.68,+0.75)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+13.456 s,
of 8.39(-2.23,+2.99)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 6 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.54(-0.24,+0.27)
and Ep = 164(-15,+19) keV (chi2 = 82/75 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.5
(chi2 = 82/74).
The spectrum near the maximum count rate
(measured from T0+8.448 to T0+16.640 s)
is best fit in the 20 keV - 6 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.40(-0.34,+0.47),
the high energy photon index beta = -2.69(-1.55,+0.43),
the peak energy Ep = 177(-31,+34) keV
(chi2 = 56/73 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 31161
Subject
IPN triangulation of GRB 211130A
Date
2021-12-03T14:20:30Z (4 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@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,
A. Ridnaia, D. Frederiks, D. Svinkin, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,
K. Hurley, on behalf of the IPN,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and
A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team, report:
The long-duration GRB 211130A
(Fermi GBM Final Real-time localization: The Fermi GBM team, GCN 31151