- GCN Circular #29508
Yuhan Yao (Caltech), Daniel Perley (LJMU), Anna Ho (UCB) on behalf of the
Zwicky Transient Facility (ZTF) collaboration:
We report the discovery two nights ago of the fast optical transient
ZTF21aakruew/AT2021cwd in Zwicky Transient Facility (ZTF, Bellm et al.
2019, Graham et al. 2019) data at coordinates (J2000):
RA = 10:24:42.16 (156.17566 deg)
Dec = +11:36:40.98 (+11.61138 deg)
ZTF21aakruew was first detected at g=19.64+/-0.10 mag in an image obtained
at 2021-02-12 08:52.4 UT as part of the 2-day cadence public survey, and
passed a filter designed to find fast transients (Ho et al. 2020, ApJ, 905,
2). The most recent upper limit was one night prior: r > 20.93 mag on
2021-02-11 07:59.6 UT in an image obtained for reference construction.
Liverpool Telescope (LT) follow-up photometry showed that the source faded
by ~2.1 mag in r-band in the next 0.9 days. The transient was most recently
detected in an LT image on 2021-02-13 22:49 UT at r = 22.42 +/- 0.21 mag.
The color appears to be red, with g-r~0.9 on 2021-02-13 and low extinction
along the line of sight (E(B-V)=0.04 mag; Planck Collaboration et al.,
2015).
There do not appear to be any reported GRBs consistent with the position of
ZTF21aakruew during the interval between the last non-detection and the
first detection. No counterpart is visible in deep Legacy Survey
pre-imaging (>24 mag; Dey et al. 2019, ApJ, 157, 5).
We encourage spectroscopic classification and multi-wavelength follow-up of
ZTF21aakruew.
ZTF is supported by the National Science Foundation under Grant No.
AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann
Institute for Science, the Oskar Klein Center at Stockholm University, the
University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt
University, the TANGO Consortium of Taiwan, the University of Wisconsin at
Milwaukee, Trinity College Dublin, Lawrence Livermore National
Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and
UW. Alert distribution service provided by DIRAC@UW (Patterson et al.
2019). Alert database searches are performed using Kowalski (Duev et al.
2019).
- GCN Circular #29511
D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
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
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, report:
The long-duration GRB 210212B has been detected by
Konus-Wind, in the waiting mode, INTEGRAL (SPI-ACS), and
Swift (BAT), so far, at about 9477 s UT (02:37:57).
The burst was likely 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
---------------------------------
Corners:
159.26 +24.95
100.54 +38.07
96.30 +19.08
163.83 +2.39
---------------------------------
This box may be improved.
The optical transient ZTF21aakruew/AT2021cwd (Yao et al., GCN Circ.
29508) 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/GRB210212_T09477/IPN/
The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.
- GCN Circular #29512
A. Pozanenko (IKI), S. Belkin (IKI), V. Kim (FAI, Pulkovo Observatory),
Y. Aimuratov (FAI), M. Krugov (FAI), N.Pankov (HSE) report on behalf of
GRB IKI FuN
We observed the optical transient of ZTF21aakruew/AT2021cwd (Yao et al.,
GCN 29508) which is probably an afterglow of GRB 210212B (Svinkin et
al., GCN 29511) with AZT-20 telescope of Assy-Turgen observatory
starting on 2021-02-15 (UT) 17:33:23. The optical transient is
marginally detected in a stacked image in r'-filter.
Preliminary photometry of the object is following
Date UT start t-T0 Filter Exp. OT S/N Err. UL(3sigma)
(mid, days) (s)
2021-02-15 17:33:23 3.64231 r' 59*60 23.8 2.5 0.5 23.6
The photometry is based on nearby SDSS-DR12 stars
RA DEC r dr
10:24:36.66048 +11:35:29.6088 18.206 0.008
10:24:34.08528 +11:36:05.0220 17.486 0.006
10:24:47.98080 +11:38:11.0832 15.153 0.003
The midtime value (t-T0) given in the table above was counted from GRB
trigger of 2021-02-12 (UT) 02:37:57 (Svinkin et al., GCN 29511).
The power-law index of the light curve (alpha ~ 1.7) is consistent with
an afterglow after jet break. The light curve can be found in
http://grb.rssi.ru/GRB210212B/GRB210212B_LC.png
- GCN Circular #29513
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the IPN GRB 210212B.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021423
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 IPN 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 #29514
D. Svinkin, S. Golenetskii, D. Frederiks, M. Ulanov,
A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 210212B
(ZTF OT detection: Yao et al., GCN Circ. 29508;
IPN triangulation: Svinkin et al., GCN Circ. 29511)
was detected by Konus-Wind (KW) in the waiting mode.
The burst light curve shows a single emission episode
which starts at about T0=9479 s UT (02:37:59)
and has the total duration of ~48 s.
The K-W light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB210212_T09477/
As observed by Konus-Wind, the burst had a fluence of
8.7(-1.1,+1.7)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0, of 6.7(-1.6,+4.8)x10^-7 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The K-W 3-channel time-integrated spectrum
(from T0 to T0+48 s) is well described by
a cutoff power-law model with
alpha = -1.24(-0.23,+0.33) and Ep = 208(-46,+84) keV.
All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.
- GCN Circular #29528
A. Nicuesa Guelbenzu and S. Klose (both TLS Tautenburg) report:
We observed the field of the optical transient ZTF21aakruew/AT2021cwd (Yao
et al., GCN 29508) that was located inside the error box of GRB 210212B
(Svinkin et al., GCN 29511) with GROND (Greiner et al. 2008, PASP 120,
405) mounted at the 2.2m MPG telescope at the ESO La Silla Observatory
(Chile).
Observations were performed at 5:00 UT (midtime) on February 15, 2021,
about 3.1 days after the GRB 210212B trigger. They were executed at an
average seeing of 1.15 arcsec and at an average airmass of 1.3.
The optical transient is detected in the optical but not in the NIR bands.
Based on a 33 min exposure in g'r'i'z' and 30 min in JHK, and we measure
the following preliminary AB magnitudes and upper limits (3 sigma):
g' = 24.16 +/- 0.14,
r' = 23.63 +/- 0.12,
i' = 23.41 +/- 0.21,
z' > 23.3,
J > 21.7,
H > 21.1,
K > 18.1,
calibrated against SDSS and 2MASS field stars. The observed r'-band
magnitude is formally consistent with the observations reported by
Pozanenko et al. (GCN 29512).
After correction for Galactic extinction (E(B-V)=0.04 mag; Ho et al., GCN
29508), the data are in agreement with an SED that follows a power law. We
consider this as evidence that the transient was indeed afterglow light,
confirming its suggested association with GRB 210212B (Svinkin et al., GCN
29511; Svinkin et al., GCN 29514).
We thank R. Lechaume (PUC) for performing the observations.
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