GRB 210204A
GCN Circular 29541
Subject
uGMRT radio detection of GRB 210204A
Date
2021-02-22T11:21:18Z (5 years ago)
From
Poonam Chandra at TIFR <poonam@ncra.tifr.res.in>
Poonam Chandra (NCRA-TIFR), Varun Bhalerao (IIT-B), Kuntal Misra (ARIES)
and G. C. Anupama (IIA) report on behalf of a larger collaboration:
We carried out radio observations of GRB 210204A (GCN#29390) with the
upgraded Giant Metrewave Radio Telescope (uGMRT) in uGMRT band 5
(1000-1450 MHz). The observations were taken on 2021 Feb 20 and the
preliminary flux at at a position RA, Dec(J2000) 07:48:19.345, 11:24:33.91
is ~140 uJy. The uncertainty in the measurements is ~20 uJy.
Further observations are planned. We thank GMRT staff for making these
observations possible.
GCN Circular 29520
Subject
GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Assy and Mondy optical observations
Date
2021-02-17T22:55:05Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Pozanenko (IKI), V. Kim (FAI, Pulkovo Observatory),
E. Klunko (ISTP), N. Pankov (HSE), M. Krugov (FAI) report on behalf of
GRB IKI FuN:
We continued observation of the ZTF21aagwbjr/AT2021buv transient (Kool
et al., GCN 29405) at the redshift of 0.876 (Xu et al., GCN 29432) which
is an afterglow (Kennea et al., GCN 29413; Teja et al., GCN 29414;
Belkin et al., GCNs 29417, 29438, 29499; Rossi et al., GCN 29433;
Gupta et al., GCN 29490) of GRB 210204A (Fermi GBM team, GCN 29390; Li
et al., GCN 29392; Hurley et al., GCN 29408; Waratkar et al., GCN 29410;
Frederiks et al., GCN 29415). Images in R-filter were obtained at
AZT-33IK telescope of Sayan observatory (Mondy) on Feb.12, 16 and in
r'-filter at AZT-22 telescope of Assy-Turgen observatory on Feb.15, 16.
Preliminary photometry of the optical transient in combined images is
following
Date UT start t-T0 Filter Exp. OT Err. UL(3s) Telescope
(mid, days) (s)
2021-02-12 16:11:09 8.41787 R 20*120 21.66 0.09 22.9 AZT-33IK
2021-02-15 15:40:01 11.40667 r' 70*60 21.86 0.15 23.6 AZT-20
2021-02-16 14:39:53 12.36212 R 31*120 21.8 0.4 21.8 AZT-33IK
2021-02-16 16:57:06 12.44700 r' 32*60 22.18 0.14 23.3 AZT-20
The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00
and the same stars from SDSS-DR12
SDSS-DR12
RA DEC g dg r dr
117.03151400 +11.42180300 17.036 0.005 15.624 0.005
117.07973400 +11.41971200 17.909 0.006 17.191 0.006
The updated light curve can be found in
http://grb.rssi.ru/GRB210204A/GRB210204A_lc.png
GCN Circular 29499
Subject
GRB 210204A (ZTF21aagwbjr/AT2021buv): continued CrAO and AbAO optical observations
Date
2021-02-12T23:18:51Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), R. Ya.
Inasaridze (AbAO), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We continued observation of the ZTF21aagwbjr/AT2021buv transient (Kool
et al., GCN 29405) at the redshift of 0.876 (Xu et al., GCN 29432) which
is an afterglow (Kennea et al., GCN 29413; Teja et al., GCN 29414;
Belkin et al., GCNs 29417, 29438; Rossi et al., GCN 29433; Gupta et
al., GCN 29490) of GRB 210204A (Fermi GBM team, GCN 29390; Li et al.,
GCN 29392; Hurley et al., GCN 29408; Waratkar et al., GCN 29410;
Frederiks et al., GCN 29415). Images in R-filter were taken with AS-32
telescope of Abastumani observatory (AbAO) and ZTSh 2.6m telescope of
CrAO observatory on 2021-02-09 and 2021-02-11.
Preliminary photometry of the afterglow in combined images is following
Date UT start t-T0 Filter Exp. OT Err. UL(3s) Telescope
(mid, days) (s)
2021-02-09 18:41:28 5.52572 R 25*120 21.09 0.08 22.6 ZTSh
2021-02-09 19:28:42 5.55610 R 43*60 21.4 0.2 22.5 AS-32
2021-02-11 18:18:20 7.50966 R 50*60 21.8 0.2 22.5 AS-32
2021-02-11 21:32:47 7.64817 R 30*120 21.6 0.3 21.8 ZTSh
The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00
A light curve can be found in
http://grb.rssi.ru/GRB210204A/GRB210204A_lc.png
Our photometry confirms suggested jet-break (Rossi et al. GCN 29433;
Gupta et al., GCN 29490).
GCN Circular 29490
Subject
GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
Date
2021-02-12T12:06:31Z (5 years ago)
From
Rahul Gupta at ARIES, India <rahulbhu.c157@gmail.com>
R. Gupta, S. B. Pandey, A. Kumar, Dimple, A. Ghosh, A. Aryan, K. Misra
(ARIES), D. Bhattacharya (IUCAA), V. Bhalerao (IITB), A. Pozanenko (IKI),
and D. Buckley (SAAO) as a part of larger BRICS collaboration:
GRB 210204A was triggered by the Fermi-GBM at 06:29:25 UT on 4 Feb 2021
(GCNs 29390, and 29393) and the prompt emission was also detected by other
space-based facilities like GECAM (29392), AstroSat (GCN 29410), and
Konus-Wind (GCNC 29415) up to MeV energies. So, we searched for extended
GeV emission for a temporal window of 50 ks since GBM trigger-based on
available LAT data, however, we do not find detection of any GeV photons
with a probability greater than 50 % to be associated with the source.
The optical counterpart associated with this burst was independently
discovered by Kool et al., 2021 using the ZTF telescope (GCN 29405) and
later follow-up observations were continued by several ground-based
facilities (GCNs 29411, 29414, 29417, 29432, 29433, and 29438). Xu et al.
2021 report a redshift value of 0.876 for this burst using
VLT/X-shooter observations
(GCN 29411).
We performed late time follow-up observations of the optical counterpart
using the 4Kx4K CCD Imager (Pandey et al. 2017, arXiv:1711.05422v1) mounted
at the axial port of the 3.6m Devasthal Optical Telescope of ARIES Nainital
starting ~ 58 hours after the burst. Multiple frames were taken in various
broad-band filters including B, V, R, and I bands. A fading afterglow
candidate was clearly seen in individual frames decayed around ~ 0.6 mags
in R Band during our observing run. We report the preliminary brightness of
the afterglow to be R= 20.19 +/- 0.03 mag ~ 58 hours after the GBM trigger.
The magnitude value reported is calibrated against UNSO B1 nearby stars.
Our R-band light curve along with early data published by Kool et al., 2021
(GCN 29405) is well-described with a broken power-law model. We found that
the temporal decay index before break time (~ 36 hours post burst) is 0.55
+/- 0.03 steepen to 1.43 +/- 0.09 at later epochs. Considering this break
as a jet break (as reported in GCN 29433), we calculated the optical
spectral index (using BVRI data at ~ 58 hours) \beta_O to be 1.08 +/- 0.10.
Considering the closure relations after the jet break (both for ISM and
WIND like a medium, without energy injection), the optical emission could
be better described with spectral regime \nu > \nu_c for WIND medium
demanding electron energy index value $p$ equal to 2.16 +/- 0.20 for the
available data-set so far.
This circular maybe cited. 3.6m Devasthal Optical Telescope (DOT) is a
recently commissioned facility in the Northern Himalayan region of India
(long:79 41 04E, lat:29 21 40N, alt:2540m) owned and operated by the
Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital (
https://www.aries.res.in). Authors of this GCN circular thankfully
acknowledge consistent support from the staff members to run and maintain
the 3.6m DOT.
GCN Circular 29438
Subject
GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
Date
2021-02-09T12:40:35Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE)
report on behalf of GRB IKI FuN:
We continued observation of the ZTF21aagwbjr/AT2021buv transient (Kool
et al., GCN 29405) at the redshift of 0.876 (Xu et al., GCN 29432) which
is an afterglow (Kennea et al., GCN 29413; Teja et al., GCN 29414) of
GRB 210204A (Fermi GBM team, GCN 29390; Li et al., GCN 29392; Hurley
et al., GCN 29408; Waratkar et al., GCN 29410; Frederiks et al., GCN
29415). Images in R-filter were taken in AZT-33IK telescope of Sayan
observatory (Mondy) on Feb.7 and Feb.8.
Preliminary photometry of the optical transient in combined images in
two epochs is following
Date UT start t-T0 Filter Exp. OT Err. UL(3s) Telescope
(mid, days) (s)
2021-02-07 13:43:58 3.32260 R 60*60 20.61 0.04 22.8 AZT-33IK
2021-02-08 15:22:01 4.39035 R 59*60 20.92 0.05 22.7 AZT-33IK
The photometry does not contradict a possible jet-break suggested by
Rossi et al (GCN 29433).
The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00
GCN Circular 29433
Subject
GRB 210204A: LBT observations and jet break
Date
2021-02-08T19:23:12Z (5 years ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
A. Rossi (INAF-OAS Bologna), A. Melandri (INAF-OAB) report on behalf of
the CIBO collaboration:
We observed the field of GRB210204A (Fermi GBM team, GCN 29390; Li et
al., GCN 29392; Hurley et al., GCN 29408; Waratkar et al., GCN 29410;
Frederiks et al., GCN 29415) simultaneously in the g'r'i' and z' bands
with the LBC imager mounted on LBT (Mt Graham, AZ, USA). We obtained
20min of imaging for each band at the midtime 08:20 UT on 2021-02-07,
3.08 days after the burst trigger.
We clearly detect the afterglow (Kool et al., GCN 29405) and we
preliminary measure the following AB magnitudes:
g = 21.1 +- 0.1
r = 20.7 +- 0.1
i = 20.4 +- 0.1
z = 20.2 +- 0.1
calibrated against SDSS field stars.
Modelling the observations available (Kool et al., GCN29405 ; Belkin et
al., GCN29417; Teja et al., GCN 29414) with a broken power-law, we find
that the light curve first decays with index alpha_1=0.60+-0.05, then
breaks at t_b=2.2+-0.2 days, and afterwards it is described by a decay
index alpha_2~1.7+-0.5. The last one is constrained only by the LBT
detection, but is ~0.4 magnitude fainter than the brightness predicted
extrapolating the pre-break decay.
We acknowledge the excellent support from the LBTO and LBT-INAF staff,
particularly B. Rothberg, F. Cusano and D. Paris, in obtaining these
observations.
GCN Circular 29432
Subject
GRB 210204A: redshift revision of ZTF21aagwbjr/AT2021buv (correction to GCN 29411)
Date
2021-02-08T18:20:17Z (5 years ago)
From
Daniele B Malesani at DTU Space <malesani@space.dtu.dk>
D. Xu (NAOC), L. Izzo (DARK/NBI), J. P. U. Fynbo (DAWN/NBI), D. A. Kann
(HETH/IAA-CSIC), S. D. Vergani (GEPI, Observatoire de Paris), D. B.
Malesani (DTU Space), M. Arabsalmani (ICRAR/UWA), A. Rossi (INAF-OAS),
G. Pugliese (API, Univ. Amsterdam), J.-B. Vielfaure (APC), report on
behalf of the Stargate consortium:
Off-line reanalysis of our data of GRB 210204A (ZTF21aagwbjr/AT2021buv;
Kool et al., GCN 29405) made us realise that we had used an incorrect
data set for our previous GCN circular (Izzo et al., GCN 29411). We
report here the correct analysis and results, and urge users to
disregard GCN 29411. We regret for any confusion created by this mishap.
Our data of GRB 210204A were acquired with the X-shooter spectrograph
installed on the ESO VLT UT3 (Melipal) telescope. Four spectra by 600 s
each were secured, starting on 2021 Feb 6.08 UT (1.79 days after the
trigger) and covering the wavelength range 3000-21000 AA.
Continuum is clearly detected across the entire trace. A number of
absorption features are detected; we identify, among others, Al II, Zn
II, Fe II, Mg II, Mg I, Ca II H and K at a common redshift z = 0.876. In
particular, fine-structure lines from Fe II* are also visible, which
confirms the association of this absorption system with the GRB.
Emission lines due to [O II], [O III], H beta and H alpha are also
detected at z = 0.876.
We thus conclude that ZTF21aagwbjr/AT2021buv is at redshift z = 0.876.
Three intervening Mg II absorbers are also detected, at redshift 0.71,
0.66, and 0.57.
The revision of the redshift value does not affect our previous
conclusion that ZTF21aagwbjr/AT2021buv is the likely afterglow of GRB
210204A (Fermi GBM Team, GCN 29390; Li et al., GCN 29392; Hurley et al.,
GCN 29408; Waratkar et al., GCN 29410): at z = 0.876, the transient
reached an absolute magnitude of ~ -26.7 (Kool et al., GCN 29405),
within the range of long GRB afterglows. The set of absorption features
(including those due to fine-structure transitons) is also typical of
GRB environments.
We recompute the isotropic-equivalent gamma-ray energy using the fluence
reported by Konus-Wind (Frederiks, GCN 29424) and the correct redshift
value, which turns to be ~8.7*10^52 erg.
We acknowledge the observing staff at Paranal, in particular Zahed Wahhaj.
GCN Circular 29424
Subject
Konus-Wind detection of GRB 210204A (correction to GCN 29415)
Date
2021-02-08T11:35:19Z (5 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, on behalf of the Konus-Wind team:
The KW spectral data and energetics of GRB 210204A
reported in Frederiks et al., GCN 29415 contain errors due to an
incorrect detector response matrix used in the calculations.
The correct spectra and energetics are provided below,
we are sorry for the inconvenience.
The burst time-integrated spectrum (measured from T0 to T0+49.408 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.45 (-0.08,+0.09),
the high energy photon index beta = -2.63 (-0.41,+0.20),
the peak energy Ep = 136 (-16,+21) keV,
chi2 = 76/97 dof.
The spectrum near the peak count rate (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.12 (-0.18,+0.34),
the high energy photon index beta = -2.45 (-0.46,+0.26),
the peak energy Ep = 175 (-42,+34) keV,
chi2 = 104/96 dof.
As observed by Konus-Wind, the burst had
a fluence of (7.0 �� 0.9)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+2.304,
of (5.2 �� 0.9)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
Assuming the redshift z=1.466 (Izzo et al., GCN 29411)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the isotropic energy release E_iso to ~3.9x10^53 erg,
the isotropic luminosity L_iso to ~7.1x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~333 keV.
With these values, GRB 210204A is within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., ApJ, in press),
see http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/GRB210204A_rest_frame.pdf
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 29417
Subject
GRB 210204A (ZTF21aagwbjr/AT2021buv): Mondy and AbAO optical observations
Date
2021-02-07T16:34:13Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze
(AbAO), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We observed the ZTF21aagwbjr/AT2021buv transient (Kool et al., GCN
29405) at the redshift of 1.466 (Izzo et al., GCN 29411) which is most
probably is an afterglow (Kennea et al., GCN 29413; Teja et al., GCN
29414) of GRB 210204A (Fermi GBM team, GCN 29390; Li et al., GCN 29392;
Hurley et al., GCN 29408; Waratkar et al., GCN 29410; Frederiks et al.,
GCN 29415). Images in R-filter were taken in AZT-33IK telescope of Sayan
observatory (Mondy) and AS-32 telescope of Abastumani observatory (AbAO).
Preliminary photometry of the optical transient in a combined image is
following
Date UT start t-T0 Filter Exp. OT Err. UL(3s) Telescope
(mid, days) (s)
2021-02-06 12:33:10 2.26579 R 38*60 19.94 0.09 21.7 AZT-33IK
2021-02-06 16:50:17 2.44748 R 47*60 20.1 0.4 20.1 AS-32
The photometry is based on the nearby USNO-B1.0 stars.
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00
GCN Circular 29415
Subject
Konus-Wind detection of GRB 210204A / ZTF21aagwbjr
Date
2021-02-07T14:27:40Z (5 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 210204A (Fermi GBM detection: Bissaldi, GCN 29393;
GECAM detection: Li et al, GCN 29392;
IPN triangulation: Hurley et al., GCN 24908;
AstroSat CZTI Detection: Waratkar et al., GCN 29410),
associated with the fast optical transient ZTF21aagwbjr/AT2021buv
(Kool et al., GCN 29405),
triggered Konus-Wind (KW) at T0=23570.576 s UT (06:32:50.576).
The burst light shows a bright, multi-peaked pulse, which starts
at ~T0-30 s and has a duration of ~80 s.
A weaker precursor is clearly visible in the KW waiting
mode data around ~T0-165 s.
The emission in the main pulse is seen up to ~3 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/
As observed by Konus-Wind, the burst had
a fluence of (5.7 �� 0.9)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+2.304,
of (5.0 �� 0.7)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+49.408 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.04 (-0.12,+0.18),
the high energy photon index beta = -2.43 (-0.18,+0.31),
the peak energy Ep = 137 (-25,+22) keV,
chi2 = 79/97 dof.
The spectrum near the peak count rate (measured from T0
to T0+8.448 s) is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.28 (-0.54,+0.64),
the high energy photon index beta = -2.12 (-0.24,+0.11),
the peak energy Ep = 123 (-24,+49) keV,
chi2 = 109/97 dof.
Assuming the redshift z=1.466 (Izzo et al., GCN 29411)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the isotropic energy release E_iso to ~2.3x10^53 erg,
the isotropic luminosity L_iso to ~7.1x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~340 keV.
With these values, GRB 210204A is within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., ApJ, in press),
see http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/GRB210204A_rest_frame.pdf
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 29414
Subject
GRB 210204A: Optical Observations from HCT
Date
2021-02-07T04:46:24Z (5 years ago)
From
Anirban Dutta at Indian Inst. of Astrophysics <anirban.dutta@iiap.res.in>
Teja, R.S.; Dutta, Anirban (IIA, Bengaluru); Kumar, Harsh (IIT, Bombay);
Sujith, D.S.; Sahu, D.K.; Anupama, G.C.; Barway, Sudhansu (IIA,
Bengaluru); Bhalerao, Varun (IIT, Bombay)
We observed the field of GRB 210204A / ZTF21aagwbjr (Fermi-GBM, GCN
#29390; Li et al., GCN #29392; Izzo et al., GCN #29411) with the
Himalayan Faint Object Spectrograph and Camera (HFOSC) mounted on the
2-m Himalayan Chandra Telescope (IAO, Hanle, India). Multiple frames
(each 300 sec) of the GRB field in Bessell R and I bands were obtained
with an average airmass of 1.21 under good seeing conditions.
Preliminary PSF photometry on the stacked images was performed and
calibrated against USNO-B1 catalogue. We clearly detected an OT in the
stacked images in both the bands. The estimated magnitudes of the OT
(not corrected for the Galactic extinction) are as under -
-------------------------------------------------------------------------------------
Date | UT (mean) | Filter | Exp. time x No. of frames | Magnitude (err)
-------------------------------------------------------------------------------------
2021-02-06 15:11:11 R 300 sec x 4 20.07
(0.13)
2021-02-06 15:40:29 I 300 sec X 4 19.79
(0.15)
-------------------------------------------------------------------------------------
The observations were carried out under the ToO program HCT-2021-C1-P2.
We thank the staff at IAO and CREST for helping us with the
observations.
GCN Circular 29413
Subject
GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
Date
2021-02-06T16:22:25Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M.
Perri (SSDC & INAF-OAR), A. Tohuvavohu (U. Toronto), B. Sbarufatti
(PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of ZTF21aagwbjr (Kool et
al., 29405), which may be related to the Fermi/GBM / GECAM / IPN
detected burst GRB 210204A (GCN Circ., 29390, GCN Circ. 29392, GCN
Circ. 29408), collecting 2.9 ks of Photon Counting (PC) mode data
between T0+160.9 ks and T0+173.2 ks.
An uncatalogued X-ray source is detected consistent with being within 1
arcsec of the ZTF position and is believed to be the afterglow, or at
least, the X-ray counterpart of the ZTF21aagwbjr. Using 2886 s of PC
mode data and 6 UVOT images, we find an enhanced XRT position (using
the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue): RA, Dec = 117.08071, +11.40951 which is equivalent to:
RA (J2000): 07h 48m 19.37s
Dec(J2000): +11d 24' 34.2"
with an uncertainty of 1.7 arcsec (radius, 90% confidence). This
position is 0.7 arcsec from the ZTF position. The light curve is
consistent with a constant source of mean count rate 9.1e-02 ct/sec.
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.73 (+0.31, -0.29). The
best-fitting absorption column is 1.7 (+1.3, -1.1) x 10^21 cm^-2, in
excess of the Galactic value of 3.5 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 4.0 x 10^-11 (4.9 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.7 (+1.3, -1.1) x 10^21 cm^-2
Galactic foreground: 3.5 x 10^20 cm^-2
Excess significance: 2.0 sigma
Photon index: 1.73 (+0.31, -0.29)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00014055. The results of the full
analysis of the XRT observations are available at
https://www.swift.ac.uk/ToO_GRBs/00014055.
This circular is an official product of the Swift-XRT team.
GCN Circular 29412
Subject
GRB 210204A: Swift ToO observations
Date
2021-02-06T11:56:02Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/GBM GRB 210204A.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00014055
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/GBM event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 29411
Subject
VLT/X-shooter redshift of 1.466 for ZTF21aagwbjr/AT2021buv, strengthening its association with GRB 210204A
Date
2021-02-06T11:15:41Z (5 years ago)
From
Maryam Arabsalmani at University of Melbourne <mar.arabsalmani@gmail.com>
L. Izzo (DARK/NBI), J. P. U. Fynbo (DAWN/NBI), D. A. Kann (HETH/IAA-CSIC),
S. D. Vergani (GEPI, Observatoire de Paris), D. B. Malesani (DTU Space), M.
Arabsalmani (ICRAR/UWA), A. Rossi (INAF-OAS), G. Pugliese (API, Univ.
Amsterdam), D. Xu (NAOC), report on behalf of the Stargate consortium:
We observed the fast optical transient ZTF21aagwbjr/AT2021buv (Kool et al.,
GCN 29405), likely associated with the Fermi, GECAM, and IPN GRB 210204A
(The Fermi GBM team, GCN 29390; F. Kunzweiler et al., GCN 29391; Li et al.,
GCN 29392; Hurley et al., GCN 29408) using the ESO VLT UT3 (Melipal)
equipped with the X-shooter spectrograph. Spectroscopic observations
started at 01:38 UT on 06 February 2021, i.e. ~1.8 days after the burst
detection and they consisted of 4 x 600 s exposures. In the resulting
spectrum, we find a series of strong absorption lines that we identify as
Mg II, Si IV, C IV, and Ca II at a common redshift of 1.466. At this
redshift, we also detect emission lines of [O II], [O III] and H-alpha
Balmer line. We therefore conclude that z = 1.466 is the redshift of
ZTF21aagwbjr/AT2021buv.
The measured redshift implies a high intrinsic brightness (absolute
magnitude ~ 28 at an epoch of 45 min after the GRB; Kool et al., GCN
29405), which is typical of long GRB afterglows. This, coupled with the
observed absorption lines set, typical of long GRB environments, further
strengthens the association between ZTF21aagwbjr/AT2021buv and GRB 210204A.
Further analysis is undergoing.
We acknowledge support from the ESO observing staff at Paranal, in
particular Zahed Wahhaj.
GCN Circular 29410
Subject
GRB 210204A: AstroSat CZTI Detection
Date
2021-02-06T10:46:42Z (5 years ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
G. Waratkar (IITB), V. Shenoy (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), P. Sawant (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 bright long GRB 210204A,
which was also detected by Fermi-GBM (GCN #29390, #29393) and GECAM-B
(GCN #29392).
The source was clearly detected in the 20-200 keV energy range. The
light curve showed two isolated emission peaks with the stronger peak at
2021-02-04 06:32:45 UT in all four quadrants. The measured peak count
rate associated with the burst is 789 (+58, -61) cts/s above the
background in the combined data of four quadrants, with a total of 18141
(+1631, -1364) cts. The initial fainter peak contributed to about 6% of
the reported total counts. The local mean background count rate was 480
(+2, -3) cts/s. Using cumulative rates, we measure a T90 of 200 (+7,
-10) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed two isolated
peaks of emission with the stronger peak at 2021-02-04 06:32:45 UT. The
initial fainter peak contributed less than 5% of total counts and hence
was excluded from the following analysis. The measured peak count rate
is 754 (+76, -80) cts/s above the background in the combined Veto data
of four quadrants, with a total of 15971 (+827, -996) cts. The local
mean background count rate was 1575 (+2, -3) cts/s. We measure a T90 of
57 (+7, -5) 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.
GCN Circular 29408
Subject
IPN triangulation of GRB 210204A
Date
2021-02-05T23:27:45Z (5 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
K. Hurley, on behalf of the IPN,
I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,
D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT 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 210204A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29390;
Bissaldi, GCN Circ. 29393;
BALROG localization: Kunzweileret al., GCN Circ. 29391;
GECAM detection: Li, GCN Circ. 29392)
has been detected by Fermi (GBM trigger 634112970), INTEGRAL (SPI-ACS),
Konus-Wind, Mars-Odyssey (HEND), and Swift (BAT), so far,
at about 23365 s UT (06:29:25).
The burst was outside the coded field of view of the BAT.
We have triangulated it to a preliminary, error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
118.116 (07h 52m 28s) +15.249 (+15d 14' 57")
Corners:
120.374 (08h 01m 30s) +23.758 (+23d 45' 30")
115.277 (07h 41m 07s) +4.395 ( +4d 23' 43")
114.946 (07h 39m 47s) +4.455 ( +4d 27' 16")
120.017 (08h 00m 04s) +23.825 (+23d 49' 30")
---------------------------------------------
The error box area is 6.7 sq. deg, and its maximum
dimension is 20.0 deg (the minimum one is 20 arcmin).
The Sun distance was 155 deg.
This box may be improved.
The IPN localization is consistent with, but reduces the area of, the
Fermi RoboBA and BALROG localizations (GCN Circ. 29390 and 29391).
The optical transient ZTF21aagwbjr/AT2021buv (Kool et al., GCN Circ. 29405)
is inside the box, lending support to the association of the transient and
the burst.
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/IPN/
The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.
GCN Circular 29395
Subject
Fermi GRB 210204A: Global MASTER-Net observations report
Date
2021-02-05T01:45:09Z (5 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 210204A ( Fermi GBM team, GCN 29390) errorbox 60315 sec after notice time and 60380 sec after trigger time at 2021-02-04 23:15:45 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 53 deg. The sun altitude is -41.7 deg.
The galactic latitude b = 10 deg., longitude l = 207 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1539740
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
60410 | 2021-02-04 23:15:45 | MASTER-SAAO | (07h 36m 18.07s , +12d 00m 15.6s) | C | 60 | 19.5 |
60650 | 2021-02-04 23:19:45 | MASTER-SAAO | (07h 33m 16.34s , +10d 00m 28.3s) | C | 60 | 19.4 |
61528 | 2021-02-04 23:34:23 | MASTER-SAAO | (07h 36m 15.36s , +12d 02m 18.2s) | C | 60 | 19.3 |
62007 | 2021-02-04 23:42:22 | MASTER-SAAO | (07h 33m 06.36s , +10d 00m 56.4s) | C | 60 | 19.4 |
62087 | 2021-02-04 23:43:42 | MASTER-SAAO | (07h 37m 16.25s , +10d 01m 05.7s) | C | 60 | 19.4 |
62845 | 2021-02-04 23:56:20 | MASTER-SAAO | (07h 36m 14.47s , +12d 01m 44.5s) | C | 60 | 19.4 |
63325 | 2021-02-05 00:04:21 | MASTER-SAAO | (07h 33m 07.78s , +10d 02m 43.9s) | C | 60 | 19.4 |
63503 | 2021-02-05 00:07:18 | MASTER-SAAO | (07h 37m 07.26s , +10d 03m 31.2s) | C | 60 | 19.4 |
64498 | 2021-02-05 00:23:53 | MASTER-SAAO | (07h 37m 02.39s , +10d 02m 11.3s) | C | 60 | 19.0 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 29392
Subject
GRB 210204A: GECAM detection
Date
2021-02-04T07:51:58Z (5 years ago)
From
Shaolin Xiong at IHEP <xiongsl@ihep.ac.cn>
C. Y. Li, S. L. Xiong, S. Xiao, C. Cai, Y. Huang, Y. Zhao, J. C. Liu,
J. J. He, Q. B. Yi, B. X. Zhang, Y. Q. Zhang, S. Y. Zhao, C. Zheng,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, B. Li,
C. Li, J. H. Li, Q. X. Li, X. B. 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, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi, L. M. Song,
X. Y. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, C. W. Wang, J. Z. Wang,
P. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, W. C. Xue, S. Yang, M. Yao,
C. Y. Zhang,D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, X. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:
During the commissioning phase, GECAM-B in-flight triggered (Trig#
66119400) a long burst, GRB 210204A, at 2021-02-04T06:30:00.600 UTC (T0),
which was also reported by Fermi/GBM (GCN 29390) and
CALET/CGBM (Trig# 1296455384).
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
multiple pulses, while the later bright pulse is evident in the alert data
although it falls in the last wide time bin.
The burst spectrum extends above about 400 keV.
An automatic on-ground localization was calculated using the light curves
and spectrum in the 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: 121.7 deg�� Dec: 1.5 deg
Err: 7.5 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-B location is consistent with the Fermi/GBM position (GCN 29390,
29391) within error.
The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_66119400.png
The GECAM preliminary on-ground location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_bdm_66119400_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).
GCN Circular 29391
Subject
GRB 210204A: BALROG localization (Fermi Trigger 634112970 / GRB 210204270)
Date
2021-02-04T06:59:58Z (5 years ago)
From
Jochen Greiner at MPE,Garching <jcg@mpe.mpg.de>
F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
634112970 at 06:29:25 on 04 Feb. 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) = 118.6+/-3.1 deg
Decl.(2000.0) = 12.0+/-3.1 deg
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210204270/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210204270/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210204270/json
GCN Circular 29390
Subject
GRB 210204A: Fermi GBM Final Real-time Localization
Date
2021-02-04T06:39:48Z (5 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 06:29:25 UT on 4 Feb 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210204A (trigger 634112970.655966 / 210204270).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 109.1, Dec = 9.7 (J2000 degrees, equivalent to J2000 07h 16m, 9d 41'), with a statistical uncertainty of 4.0 degrees.
The angle from the Fermi LAT boresight is 57.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210204270/quicklook/glg_skymap_all_bn210204270.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/bn210204270/quicklook/glg_healpix_all_bn210204270.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210204270/quicklook/glg_lc_medres34_bn210204270.gif