GRB 210702A
GCN Circular 30538
Subject
GRB 210702A: MeerKAT radio detection
Date
2021-07-27T22:40:49Z (4 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (University of Bath), S. Buchner (SARAO), S. Legodi (SARAO), K.
D. Alexander (Northwestern), E. Ayache (Bath), E. Berger (Harvard), S.
Bhandari (CSIRO), J. Bright (Northwestern), R. Chornock (UC Berkeley), D.
Coppejans (Northwestern), H. van Eerten (Bath), W. Fong (Northwestern), R.
Margutti (UC Berkeley), C.G. Mundell (Bath), P. Schady (Bath), and G.
Schroeder (Northwestern) report:
"We observed GRB 210702A (Lien et al. GCN 30351) with the MeerKAT radio
telescope array over two epochs beginning on 2021 July 11 12:16 UTC (8.7 d
after the burst) and 2021 July 23 18:16 UTC (21.0 d after the burst),
respectively. Preliminary analysis reveals a brightening radio counterpart
with 1.284 GHz flux density of 123 +/- 12 uJy at 21.0 d at position:
RA (J2000) = 11:14:18.76
Dec (J2000) = -36:44:49.5
with uncertainty ~ 0.4" in each coordinate, consistent with the X-ray
position (D'Elia et al., GCN 30358), optical position (Lien et al., GCN
30351; Kuin et al., GCN 30356), and mm-band position (Laskar & Perley, GCN
30423). Further observations are planned.
The MeerKAT telescope is operated by the South African Radio Astronomy
Observatory, which is a facility of the National Research Foundation, an
agency of the Department of Science and Innovation."
GCN Circular 30479
Subject
GRB 210702A: ALMA detection of mm-band rebrightening
Date
2021-07-22T22:50:41Z (4 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (U. of Bath) reports on behalf of a larger collaboration:
"Following the initial detection of the mm counterpart of GRB 210702A (Lien
et al., GCN 30351) with the Atacama Large Millimeter/Submillimeter Array
(ALMA) on 2021 July 03, 26 h after the burst (Laskar & Perley, GCN 30423),
we have been monitoring this source with ALMA at 97.5 GHz. The mm-band
counterpart was observed to fade to a flux density of ~ 0.3 mJy in
observations taken on 2021 July 11 at a mid-time of 8.3 days after the
burst.
We observed GRB 210702A with ALMA again beginning on 2021 July 20 21:02
UTC. Preliminary analysis reveals a strong (~ 50 sigma) detection at 97.5
GHz with a flux density of ~ 0.8 mJy at a mid-time of 18.1 days after the
burst, implying a significant rebrightening of the mm-band afterglow,
contemporaneous to the radio rebrightening observed at 34, 21.2, and 16.7
GHz with ATCA (Laskar & Bhandari, GCN 30477). Further observations are
planned.
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help
with these observations."
GCN Circular 30477
Subject
GRB 210702A: ATCA detection of radio rebrightening
Date
2021-07-22T22:42:20Z (4 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (U. of Bath) and S. Bhandari (CSIRO) report on behalf of a larger
collaboration:
"Following the initial detection of the radio counterpart of GRB 210702A
(Lien et al., GCN 30351) with the Australia Telescope Compact Array (ATCA)
on 2021 July 06, 3.50 days after the burst (Laskar et al., GCN 30424), we
have been monitoring this source with ATCA at 5.5, 9.0, 16.7, 21.2, and 34
GHz. The 34 GHz radio counterpart was observed to fade, until observations
taken on 2021 July 13 indicated a non-detection with map rms ~ 60 uJy at a
mid-time of 10.3 days after the burst.
We observed GRB 210702A with ATCA again at the above frequencies beginning
on 2021 July 21 07:00 UTC with the array in a hybrid (H168) configuration.
Preliminary analysis reveals a strong (> 10 sigma) detection at 34 GHz with
a flux density of ~ 0.7 mJy at a mid-time of 18.5 days after the burst,
implying a significant rebrightening of the radio afterglow. Similar
rebrightening is observed at 21.2 and 16.7 GHz.
Detailed analysis is ongoing and further observations are planned. We thank
the CSIRO staff for approving and scheduling these observations.
The Australia Telescope Compact Array is part of the Australia Telescope
National Facility which is funded by the Australian Government for
operation as a National Facility managed by CSIRO. We acknowledge the
Gomeroi people as the traditional owners of the Observatory site."
GCN Circular 30424
Subject
GRB 210702A: ATCA detection
Date
2021-07-08T18:32:53Z (4 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (University of Bath), S. Bhandari (CSIRO), K. D. Alexander
(Northwestern), E. Berger (Harvard), R. Chornock (UC Berkeley), D.
Coppejans (Northwestern), M. Drout (U. Toronto), H. van Eerten (University
of Bath), Wen-fai Fong (Northwestern), C. Guidorzi (U. Ferrara), R.
Margutti (UC Berkeley), C. G. Mundell (University of Bath), P. Schady
(University of Bath), and G. Schroeder (Northwestern) report:
"We observed GRB 210702A (Lien et al., GCN 30351) with the Australia
Telescope Compact Array (ATCA) at multiple frequencies beginning on 2021
July 06 05:00 UT. We detect a radio counterpart at 16.7, 21.2, and 34 GHz
at a position consistent with the X-ray position (D'Elia et al., GCN
30358), optical position (Lien et al., GCN 30351; Kuin et al., GCN 30356),
and mm-band position (Laskar et al., GCN 30423) with a flux density of ~
0.8 mJy at 34 GHz at a mid-time of 3.50 days after the burst.
Further observations are planned.
We thank the CSIRO staff for approving and scheduling these observations."
GCN Circular 30423
Subject
GRB 210702A: ALMA detection
Date
2021-07-08T18:26:27Z (4 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (University of Bath) and D. Perley (LJMU) report on behalf of a
larger collaboration:
"We observed GRB 210702A (Lien et al. GCN 30351) with the Atacama Large
Millimeter/Submillimeter Array (ALMA) at 97.5 GHz and 343.5 GHz beginning
on 2021 July 03 21:05:52 UT (26.0 h after the burst). ALMA observations of
this burst were delayed due to uninterruptible scheduled Cycle 8 software
validation at the Observatory.
Preliminary analysis reveals a mm source with flux density of ~ 0.1 mJy at
97.5 GHz and position:
RA (J2000) = 11:14:18.807
Dec (J2000) = -36:44:49.25
with uncertainty ~ 0.03" in each coordinate, consistent with the X-ray
position (D'Elia et al., GCN 30358) and optical position (Lien et al., GCN
30351; Kuin et al., GCN 30356). The spectrum appears strongly self-absorbed
in the mm-band. Further observations are planned.
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help
with these observations."
GCN Circular 30368
Subject
GRB 210702A, Swift-BAT refined analysis
Date
2021-07-04T20:12:21Z (4 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210702A (trigger #1058804)
(Lien et al., GCN Circ. 30351). The BAT ground-calculated position is
RA, Dec = 168.570, -36.741 deg which is
RA(J2000) = 11h 14m 16.8s
Dec(J2000) = -36d -44' -29.2"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 4%.
The mask-weighted light curve shows a single-peaked FRED-like structure
that starts at ~T-4 s, peaks at ~T+1 s, and ends at ~T+370 s. The burst
went out of the BAT field of view at T+452 s. There might be addition
burst emission afterwards. T90 (15-350 keV) is 138.2 +- 47.6 sec
(estimated error including systematics).
The burst occurred at a location with a very low partial coding fraction,
and thus was out of the BAT calibrated field of view until ~T+18 s.
Therefore, the spectral analysis is only available for the burst duration
afterwards. The time-averaged spectrum from T+18.0 to T+369.2 sec is
best fit by a simple power-law model. The power law index of the
time-averaged spectrum is 1.54 +- 0.09. The fluence in the 15-150 keV
band is 9.8 +- 0.5 x 10^-6 erg/cm2. All the quoted errors are at the 90%
confidence level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1058804/BA/
GCN Circular 30367
Subject
GRB 210702A: BOOTES-3/YA optical counterpart observations
Date
2021-07-04T11:59:24Z (4 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, E. Fernandez-Garcia, T.-R. Sun, A. J. Castro-Tirado, M. D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), I. Carrasco and C. Perez del Pulgar (Univ. de Malaga), and R. Querel (NIWA), on behalf of a larger collaboration,
report:
The 60cm BOOTES-3/YA robotic telescope at NIWA Lauder in Otago (New Zealand) automatically responded to the Swift trigger of GRB 210702A (Lien et al. GCNC 30351), which also detected by CALET (Yamaoka et al. GCNC 30362) and AGILE (Ursi et al. GCNC 30363), after the twilight as soon as possible. The first image (clear filter) were obtained starting at 07:00:58 UT (~11.9 hrs after trigger). At the enhanced Swift/XRT position(D'Elia et al. GCNC 30358), we found the optical counterpart reported by MASTER (Lipunov et al. GCNC 30352), MeerLICHT (Groot et al. GCNC 30354), Swift/UVOT (Lien et al. GCNC 30351, Kuin et al. GCNC 30355), VLT (Xu et al. GCNC 30357), iTelescope (Romanov GCNC 30364) and Chilescope (Belkin et al. GCNC 30365) with a magnitude of R = 18.0+-0.1 in the co-added image (10 x 60 s), which calibrated with nearby stars in USNO-B 1.0 catalog. Further analysis is ongoing.
We thank the staff at NIWA for its excellent support.
GCN Circular 30366
Subject
Konus-Wind detection of GRB 210702A
Date
2021-07-03T12:51:56Z (4 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 210702A (Swift detection: Lien et al., GCN 30351;
CALET GRBM detection: Yamaoka et al., GCN 30362;
AGILE detection: Ursi et al., GCN 30363)
triggered Konus-Wind (KW) at T0=68826.870 s UT (19:07:06.870).
The burst light curve shows a bright, FRED-like pulse
which starts at ~T0-4 s, and has a total duration of ~90 s.
The emission is seen up to ~15 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210702_T68826/
As observed by Konus-Wind, the burst had
a fluence of (2.5 �� 0.2)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 7.808 s,
of (3.0 �� 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+86.784 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 = -0.91 (-0.09,+0.10),
the high energy photon index beta = -1.91 (-0.10,+0.08),
the peak energy Ep = 376 (-61,+63) keV,
chi2 = 107/97 dof.
The spectrum near the peak count rate (measured from T0+4.096
to T0+7.936 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.78 (-0.09,+0.11),
the high energy photon index beta = -2.00 (-0.09,+0.08),
the peak energy Ep = 402 (-64,+66) keV,
chi2 = 111/92 dof.
Assuming the redshift z=1.160 (Xu et al., GCN 30357)
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 ~9.3x10^53 erg,
the isotropic luminosity L_iso to ~2.4x10^53 erg/s,
the rest-frame peak energy of the time-integrated spectrum Epi,z to ~812 keV,
and the rest-frame peak energy of the 'peak' spectrum Epp,z to ~870 keV.
With these values, GRB 210702A 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., 2021, ApJ, 908, 83),
see http://www.ioffe.ru/LEA/GRBs/GRB210702_T68826/GRB210702A_rest_frame.pdf
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 30365
Subject
GRB 210702A: Chilescope optical observations
Date
2021-07-03T12:48:04Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Pozanenko (IKI), N. Pankov (HSE, IKI), M. Krugov
(FAI) report on behalf of GRB IKI FuN collaboration:
We observed the field of Swift GRB 210702A (Lien et al., GCN 30351)
with Chilescope RC-1000 starting on 2021-07-02 (UT) 23:40:26 in
r'-filter. Within enhanced XRT position (D'Elia et al., GCN 30358) we
clearly detect the afterglow (Lien et al., GCN 30351; Lipunov et al.,
GCN 30352; Groot et al., GCN 30354; Kuin et al., GCN 30355; Kuin et al.,
GCN 30356; Xu et al., GCN 30357; Romanov et al., GCN 30364).
Preliminary photometry of the afterglow is following
Date UT start t-T0 Filter Exp. OT(AB) Err. UL(AB)
(mid, days) (s)
2021-07-02 23:40:26 0.193202 r' 1*600 17.01 0.05 19.7
The photometry is based on nearby stars from the APASS_DR8
RA DEC r
11:14:16.46880 -36:49:58.2132 15.187
11:14:36.96576 -36:48:30.0132 15.320
GCN Circular 30364
Subject
GRB 210702A: iTelescope optical afterglow observations
Date
2021-07-03T11:42:59Z (4 years ago)
From
Filipp Dmitrievich Romanov at Amateur astronomer <filipp.romanov.27.04.1997@gmail.com>
I observed the field of GRB 210702A (Lien et al., GCN Circ. 30351)
using remote telescope T17 (0.43-m f/6.8 reflector + CCD) of
iTelescope.Net in Siding Spring Observatory (Australia) on 2021-07-03.
Two images were obtained from 09:00:31 UTC and from 09:01:57 UTC with
Sloan I filter (60 seconds exposures, BINx1) and one image was
obtained from 09:04:38 UTC with Sloan R filter (300 seconds exposure,
BINx1).
I detected optical afterglow with UVOT position in stacked image with
SI filter (mid time = 09:01:44 UTC, that is 13h 54m 31s after the
trigger) and in the image with SR filter (mid time = 09:07:08 UTC,
that is 13h 59m 55s after the trigger) and measured the following
magnitudes from comparison to magnitudes of nearby stars from APASS
DR9 catalogue (Henden et al., 2016): 18.6 i' +/- 0.4 and 19.0 r' +/-
0.5.
Magnitudes were not corrected for Galactic extinction.
Images available here: https://www.flickr.com/photos/filipp-romanov/51286698321
GCN Circular 30363
Subject
GRB 210702A: AGILE detection
Date
2021-07-03T10:43:45Z (4 years ago)
From
Alessandro Ursi at INAF/IAPS <alessandro.ursi@gmail.com>
A. Ursi (INAF/IAPS), C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), M.
Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C.
Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and
INAF/OAR), A. Bulgarelli, V. Fioretti, F. Fuschino, N. Parmiggiani
(INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University),
M. Pilia, A. Trois (INAF/OA-Cagliari), F. Longo (Univ. Trieste and INFN
Trieste), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), report on behalf
of the AGILE Team:
The AGILE satellite detected the long GRB 210702A at T0 = 2021-07-02
19:07:13 s (UTC), reported by Swift (GCNs #30351, #30352, #30356, #30358)
and CALET (#30362).
The burst is clearly visible in the AGILE scientific ratemeters of the
SuperAGILE (SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and
AntiCoincidence (AC; 50-200 keV) detectors. The event lasted about ~32 s
and it released a total number of 1630 counts in the SA detector (above a
background rate of 50 Hz), 40500 counts in the MCAL detector (above a
background rate of 1440 Hz), and 74310 counts in the AC detector (above a
background rate of 3610 Hz). The AGILE ratemeter light curves can be found
at http://www.agilescienceapp.it/notices/GRB210702A_AGILE_RM.png . The
event also triggered a partial high time resolution MCAL data acquisition.
Additional analysis of AGILE data is in progress.
GCN Circular 30362
Subject
GRB 210702A: CALET Gamma-Ray Burst Monitor detection
Date
2021-07-03T09:28:11Z (4 years ago)
From
Valentin Pal'shin at AGU <val@phys.aoyama.ac.jp>
K. Yamaoka (Nagoya U),
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), S. Nakahira (RIKEN), Y. Asaoka (ICRR),
S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long bright GRB 210702A (Swift detection: Lien et al., GCN Circ. 30351;
https://gcn.gsfc.nasa.gov/other/210702A.gcn3) triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 19:07:06.474 UTC on 2 July 2021
(http://cgbm.calet.jp/cgbm_trigger/flight/1309287819/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a FRED-like pulse which starts at T+2.1 sec,
peaks at T+6.3 sec,and ends at T+51.3 sec. The T90 and T50 durations
measured by the SGM data are 32.1 +- 4.6 sec and 9.2 +- 0.9 sec
(40-1000 keV), respectively.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1309287819/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.
GCN Circular 30358
Subject
GRB 210702A: Swift-XRT refined Analysis
Date
2021-07-03T08:49:45Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU),
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A.
Melandri (INAF-OAB) and A.Y. Lien report on behalf of the Swift-XRT
team:
We have analysed 6.3 ks of XRT data for GRB 210702A (Lien et al. GCN
Circ. 30351), from 84 s to 38.4 ks after the BAT trigger. The data
comprise 310 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. Using 4559 s of PC mode data and 10 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 = 168.57877, -36.74715
which is equivalent to:
RA (J2000): 11h 14m 18.91s
Dec(J2000): -36d 44' 49.7"
with an uncertainty of 1.9 arcsec (radius, 90% confidence).
The light curve can be modelled with an initial power-law decay with an
index of alpha=1.005 (+0.014, -0.013), followed by a break at T+7161 s
to an alpha of 1.68 (+0.11, -0.10).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.570 (+0.018, -0.015). The
best-fitting absorption column is consistent with the Galactic value
of 1.2 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.95 (+/-0.07) and a best-fitting absorption column
of 1.8 (+/-1.0) x 10^21 cm^-2. The counts to observed (unabsorbed)
0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x
10^-11 (4.5 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.2 x 10^21 cm^-2
Intrinsic column: 1.8 (+/-1.0) x 10^21 cm^-2 at z=1.16
Photon index: 1.95 (+/-0.07)
If the light curve continues to decay with a power-law decay index of
1.68, the count rate at T+24 hours will be 0.044 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x
10^-12 (2.0 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01058804.
This circular is an official product of the Swift-XRT team.
GCN Circular 30357
Subject
GRB 210702A: VLT/X-shooter redshift
Date
2021-07-03T03:58:49Z (4 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
D. Xu (NAOC), L. Izzo (DARK/NBI), A. de Ugarte Postigo (HETH/IAA-CSIC,
DARK/NBI), D. A. Kann (HETH/IAA-CSIC), S. Y. Fu (NAOC), S. Campana
(INAF-OAB), V. D'Elia (ASI/SSDC, INAF/OAR), A. J. Levan (Radboud U.
Nijmegen), B. Milvang-Jensen (DAWN/NBI), D. A. Perley (LJMU), G.
Pugliese (API, Univ. Amsterdam), R. L. C. Starling (Univ. Leicester), N.
R. Tanvir (Univ. Leicester), S. Vergani (CNRS - Observatoire de
Paris/GEPI), and K. Wiersema (Univ. Warwick) report on behalf of the
Stargate Consortium:
We observed the bright afterglow (Lien et al., GCN #30351; Lipunov et
al., GCN #30352; Groot et al., GCN #30354; Kuin et al., GCN #30356) of
GRB 210702A (Lien et al., GCN #30351) using the ESO VLT UT3 (Melipal)
equipped with the X-shooter spectrograph. Our spectra cover the
wavelength range 3000-25000 AA, and consist of 4 exposures of 600 s
each. The observation mid-time was 2021 July 2.997 UT (i.e., 4.80 hr
after the GRB).
In a 20 s image taken with the acquisition camera on July 02.975 UT, we
detect the optical afterglow at r' = 16.91 +/- 0.01 mag (AB system),
measured against three SkyMapper field stars.
In our spectrum, strong continuum is detected over the whole observed
range. We detect a plethora of metallic absorption features, among them
Si II, Si II*, C IV, Fe II, Fe II*, Al II, Ni II, Ni II*, Al III, Zn II,
Mg I, Cr II, Mn II, Mg II, Mg I, and Ca II, all at a common redshift of
z = 1.160. This is about 1.5 sigma lower than, but is broadly consistent
with the value reported by Swift/UVOT (Kuin et al., GCN #30355). No
emission feature is present in the spectrum. The detection of excited
transitions establishes this as the redshift of the GRB.
There is also an intervening system detected at z = 0.538 showing Mg II
and Mg I absorption features.
We acknowledge excellent support from the observing staff at Paranal, in
particular Alain Smette and Bin Yang.
GCN Circular 30356
Subject
GRB 210702A: preliminary Swift/UVOT photometry
Date
2021-07-02T23:31:49Z (4 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
N. P. M. Kuin (UCL-MSSL) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210702A
104 s after the BAT trigger (Lien et al., GCN Circ. 30351).
A source consistent with the XRT position
(Lien et al. GCN Circ. 30351)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 11:14:18.70 = 168.57793 (deg.)
Dec (J2000) = -36:44:50.0 = -36.74723 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).
Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 104 254 147 15.70 +/- 0.02
b 3516 3716 197 15.46 +/- 0.03
u 316 361 44 11.37 +/- 0.05
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.121 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 30355
Subject
GRB 210702A: Swift/UVOT redshift
Date
2021-07-02T23:27:24Z (4 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
N. P. M. Kuin (UCL-MSSL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT obtained a 49s grism spectrum of GRB 210702A
starting 282 s after the BAT trigger (Lien et al., GCN Circ. 30351).
The spectrum shows a clear break at 2011 Angstrom, and absorption features
attributable to Ly-alpha and Ly-beta suggesting
a redshift of z=1.1757+/-0.0093. An possible intervening system is present
at
z=1.050 based on a weaker line seen at 2492A.
The wavelength anchor/zeropoint in the uv grism is uncertain by typically
15A, which translates to an uncertainty as quoted in the redshift above.
GCN Circular 30354
Subject
GRB210702A: MeerLICHT multi-colour photometry
Date
2021-07-02T21:33:49Z (4 years ago)
From
Andrew Levan at U.of Leicester <a.levan@astro.ru.nl>
P.J. Groot (Radboud/UCT/SAAO), S. de Wet (UCT), P.M. Vreeswijk
(Radboud), A.J. Levan (Radboud) report on behalf of the MeerLICHT
consortium:
Following the detection of GRB210702A by Swift and its optical
counterpart (Lien et al., GCN30351), the 0.6m MeerLICHT telescope,
located at Sutherland, South Africa obtained a series of 60s images in
the q,u,q,g,q,r,q,i,q,z,q,u,q,g,q bands, starting at 2021-07-02,
19:23:26.586 UT, 16 minutes after the Swift detection, and 3 minutes
after the distribution of the BAT alert.
The source identified by Swift UVOT is clearly detected as a new
transient at coordinates
RA(ICRS) = 168.57839 = 11:14:18.81 (+/-0.06���)
DEC(ICRS)= -36.74702 = -36:44:49.27 (+/- 0.04���)
MeerLICHT astrometry is calibrated against Gaia DR2.
The first source detections are, at:
q = 12.815 +/- 0.001 +/- 0.018 (19:23:26 UT)
u = 13.585 +/- 0.004 +/- 0.041 (19:25:10 UT)
g = 13.394 +/- 0.002 +/- 0.021 (19:28:46 UT)
r = 13.193 +/- 0.002 +/- 0.015 (19:32:18 UT)
i = 13.096 +/- 0.003 +/- 0.034 (19:35:42 UT)
z = 13.100 +/- 0.004 +/- 0.025 (19:39:25 UT)
where the first uncertainty on the magnitude is the statistical
uncertainty and the second is the uncertainty on the photometric
calibration.
Our repeated q-band observations show decay consistent with a power law
with exponent of approximately -1.2.
Further data taking was suspended due to high winds.
Reference images of the field show no underlying host galaxy down to
the 5-sigma limiting magnitude, at the position of the afterglow, at:
u > 19.54
g > 20.44
q > 21.23
r > 20.20
i > 19.72
z > 18.90
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 30353
Subject
Swift GRB 210702A: Global MASTER-Net observations report
Date
2021-07-02T19:43:25Z (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) was pointed to the Swift GRB 210702A ( A. Y. Lien et al., GCN 30351) errorbox 822 sec after trigger time at 2021-07-02 19:20:56 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 51 deg. The sun altitude is -44.7 deg.
The galactic latitude b = 22 deg., longitude l = 283 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1650622
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
903 | MASTER-SAAO | P\ | 160 | 18.6 |
1084 | MASTER-SAAO | P\ | 180 | 17.9 |
1284 | MASTER-SAAO | P\ | 180 | 17.6 |
The observation and reduction will continue.
The message may be cited.
GCN Circular 30351
Subject
GRB 210702A: Swift detection of a burst with a bright optical counterpart
Date
2021-07-02T19:31:14Z (4 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. A. Kennea (PSU),
N. J. Klingler (GSFC/UMBC/CRESSTII), S. Laha (GSFC/UMBC/CRESST),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 19:07:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210702A (trigger=1058804). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 168.570, -36.741 which is
RA(J2000) = 11h 14m 17s
Dec(J2000) = -36d 44' 28"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
structure with a duration of about 100 sec. The peak count rate
was ~10,000 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 19:08:49.2 UT, 95.5 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 168.5813, -36.7474 which is equivalent to:
RA(J2000) = 11h 14m 19.51s
Dec(J2000) = -36d 44' 50.6"
with an uncertainty of 11.0 arcseconds (radius, 90% containment). No
event data are yet available to determine the column density using
X-ray spectroscopy.
The initial flux in the 2.5 s image was 1.00e-08 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 45 seconds with the U filter starting
315 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 11:14:18.83 = 168.57846
DEC(J2000) = -36:44:48.8 = -36.74690
with a 90%-confidence error radius of about 0.61 arc sec. This position is 8.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
11.72 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.121.
Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)