GRB 210207B
GCN Circular 29759
Subject
GRB 210207B: Prompt and very late time observations with HCT.
Date
2021-04-04T16:50:36Z (5 years ago)
From
Firoza Sutaria at Indian Inst. of Astrophysics <fsutaria@iiap.res.in>
F. Sutaria (IIA, Bangalore, India) and A. Ray (TIFR /HBCSE, Mumbai,
India) report on the observations of the optical counterpart of GRB
210207B (Lien et al., GCN #29420; Strausbaugh, R, GCN #29441 and
references therein) taken with the Himalyan Chandra telescope (HCT) on
two epochs.
The first observation was on MJD 59254.91163194 -- i.e 48.0103 hr after
the Swift/BAT trigger. The field of the GRB was observed in the Bessel
R filter. We stacked 12 frames to achieve a total exposure time of 570
s. The photometry was carried out using standard IRAF utilities for
faint objects in relatively uncrowded fields. The instrumental
magnitudes were calibrated against photometric standards in the field
of PG0918+029, taken on the same and on the previous night, resulting in
an average atmospheric extinction coefficient of 0.087(\pm 0.0208) /mag
in this filter. At the position of the GRB (18:02:32.40 +53:40:56.0) we
find a faint optical source with apparent magnitude R=22.0 \pm 0.1,
uncorrected for galactic extinction.
We observed the same field once again on 17th Mar. 2021 (MJD
59290.91730324), in the same filter. A stacked exposure of 10 frames
leading to a total exposure time of 600s did not reveal any source at
the location of the GRB, down to a 3-sigma limiting magnitude of R=
23.66. We thus conclude that there was no contribution from the host
galaxy in the previous detection. Our results are also tabulated below.
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
MJD Filter Detected? Magnitude
(uncorrected for galactic
extinction)
-------------------------------------------------------------------------------
59254.9116 R Yes 22.0 \pm 0.1
59290.9173 R No. < 23.66 (3-sigma)
-------------------------------------------------------------------------------
We note that the galactic extinction for the CTIO R filter in this
direction is estimated at A_R = 0.087 mag [Schlafly E. F. & Finkbeiner
D., 2011, ApJ, 737, 103], based on a SDSS dust map. However, the IRAS
and COBE/DIRBE survey [D.J. Schlegel, D.P. Finkbeiner, & M. Davis,
1998, ApJ, 500, 525] sets it at A_R=0.109 mag.
This GCN may be cited.
We thank the staff of IAO, Hanle and CREST, Hosakote, that made these
observations possible. The facilities at IAO and CREST are operated by
the Indian Institute of Astrophysics, Bangalore.
GCN Circular 29486
Subject
GRB 210207B: GECAM detection
Date
2021-02-12T03:32:43Z (5 years ago)
From
Zhao Yi at POLAR <yizhao@ihep.ac.cn>
Y. Zhao, X. Y. Song, S. Xiao, C. Cai, S. L. Xiong, Y. Huang, C. Y. Li,
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,
J. C. Liu, 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, the ground search of GECAM-B data found
a long burst, GRB 210207B, at 2021-02-07T21:52:14.050 UTC (T0), which
was also reported by Swift/BAT (GCN #29420, #29435), Konus/Wind (GCN #29426),
AGILE (GCN #29428) and Insight-HXMT/HE (GCN #29434).
The later bright pulse also triggered GECAM-B in-flight.
According to the GECAM-B light curves in about 8 keV-4 MeV, this burst
mainly consists of multiple pulses with a duration (T90) of 45.0 +/- 4.5 s
starting from T0 - 1.8 s. The 1-s peak counts rate is about 1300 cps
while the total counts is about 4600 counts.
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: 275.00 deg Dec: 51.57 deg
Err: 8.23 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.
This position is consistent with Swift (GCN #29420) within the error.
The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/GECAM-B-tn210207_215215.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).
GCN Circular 29441
Subject
GRB 210207B: Continued LCO Observations
Date
2021-02-09T16:35:12Z (5 years ago)
From
Robert Strausbaugh at U. of the Virgin Islands <robert.strausbaugh@uvi.edu>
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:
We performed a second set of observations on Swift GRB 210207B (Lien, GCN 29420) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on February 9, from 11:19 to 11:24 UT (corresponding to 37.23 to 37.31 hours from the GRB trigger time) with the Bessel R filter.
We performed a second series of 4x60s exposures in R band. We no longer detect a source at the location consistent with other optical detections (Lien, GCN 29420; Kumar, GCN ; Zheng, GCN 29430; Strausbaugh, GCN 29431). Using the USNO-B.1 catalog as reference, we calculate the following upper limit:
R > 21.42
These magnitudes are not corrected for galactic extinction. This lack of a detection provides further evidence for the transient nature of this source. As a correction to GCN 29431, the series of exposures in R and I bands were 4x60s, not the originally reported 5x60s.
R.S. is funded by NSF AST grant #1831682
GCN Circular 29437
Subject
GRB 210207B: AstroSat CZTI detection
Date
2021-02-09T11:42:14Z (5 years ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
G. Waratkar (IITB), D. Nadella (NITK), 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 210207B,
which was also detected by Swift (BAT - GCN #29420, #29435, XRT -
#29422, #29427) Konus-Wind (GCN #29426), AGILE-MCAL (GCN #29428) and
Insight-HXMT/HE (GCN #29434).
The source was clearly detected in the 20-200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2021-02-07 21:52:49 UT in all four quadrants. The measured peak count
rate associated with the burst is 517 (+52, -57) cts/s above the
background in the combined data of four quadrants, with a total of 3408
(+384, -451) cts. The local mean background count rate was 560 (+3, -3)
cts/s. Using cumulative rates, we measure a T90 of 42 (+10, -2) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed multiple peaks
of emission with the strongest peak at 2021-02-07 21:52:48 UT. The
measured peak count rate is 994 (+88, -93) cts/s above the background in
the combined Veto data of four quadrants, with a total of 6364 (+849,
-894) cts. The local mean background count rate was 1931.8 (+5, -5)
cts/s. We measure a T90 of 44 (+9, -4) 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 29436
Subject
GRB 210207B: Swift/UVOT Detection
Date
2021-02-09T07:45:09Z (5 years ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
M. H. Siegel (PSU) 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 210207B
82 s after the BAT trigger (Lien et al., GCN Circ. 29420).
A source consistent with the XRT position
(Lien et al. GCN Circ. 29420) is detected in the initial UVOT exposures,
as reported in the initial circular and confirmed by ARIES (Kumar et al.,
GCN Circ. 29421), KAIT (Zheng & Filippenko, GCN Circ. 29430) and LCO
(Strausbaugh & Cucchiara, GCN Circ. 29431). We note that the lack
of detection in the two bluer NUV passbands is suggestive of a redshift in
the 1.4-1.9 range.
The preliminary UVOT position is:
RA (J2000) = 18:02:32.40 = 270.63500 (deg.)
Dec (J2000) = +53:40:55.8 = 53.68217 (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 (fc) 83 233 147 13.66+/-1.13
white 4081 5717 393 17.91+/-0.04
white 61938 62307 361 21.06+/-0.32
v 4492 4692 196 17.61+/-0.10
v 9433 10341 885 18.54+/-0.09
v 56912 74907 1297 >19.84
b 3876 5512 393 17.95+/-0.05
b 44686 45593 885 >20.99
b 61025 79012 1770 20.79+/-0.18
u (fc) 295 410 113 14.42+/-0.03
u 5106 5306 196 17.80+/-0.09
u 43773 44680 885 20.47+/-0.26
u 51795 69087 612 >19.80
uvw1 4901 5101 196 18.23+/-0.18
uvw1 11254 11428 171 >18.90
uvw1 39917 40544 616 >19.72
uvw1 50889 68646 1771 >20.53
uvm2 4697 4896 196 >19.12
uvm2 10346 11246 885 >20.23
uvw2 4287 5871 342 >19.39
uvw2 56005 74346 1771 >20.68
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.041 in the direction of the burst
(Schlegel et al. 1998).
[GCN OPS NOTE: Per author's request the rerferece to Circ 294311
was changed to the correct value Circ 29431.]
GCN Circular 29435
Subject
GRB 210207B: Swift-BAT refined analysis
Date
2021-02-09T01:29:50Z (5 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
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 210207B (trigger #1031297)
(Lien et al., GCN Circ. 29420). The BAT ground-calculated position is
RA, Dec = 270.614, 53.700 deg which is
RA(J2000) = 18h 02m 27.3s
Dec(J2000) = +53d 42' 01.1"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 56%.
The mask-weighted light curve shows a multi-peaked structure that
starts at ~T0 and ends at ~T+106 s. The main peak occurs at ~T+43 s.
T90 (15-350 keV) is 95.69 +- 4.52 sec (estimated error including
systematics).
The time-averaged spectrum from T-0.25 to T+106.40 sec is best fit by a
simple
power-law model. The power law index of the time-averaged spectrum is
1.20 +- 0.07. The fluence in the 15-150 keV band is 4.3 +- 0.2 x 10^-6
erg/cm2.
The 1-sec peak photon flux measured from T+43.16 sec in the 15-150 keV band
is 3.1 +- 0.2 ph/cm2/sec. 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/1031297/BA/
GCN Circular 29434
Subject
GRB 210207B: Insight-HXMT/HE detection
Date
2021-02-09T01:22:58Z (5 years ago)
From
Chao Zheng at IHEP <zhengchao97@ihep.ac.cn>
C. Zheng, C. Cai, J. C. Liu, Q. Luo, S. Xiao,
W. C. Xue, Q. B. Yi, Y. Q. Zhang, Y. Huang, C. K. Li,
G. Li, X. B. Li, J. Y. Liao, X. Y. Song, S. L. Xiong, C. Z. Liu,
X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang,
X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU),
T. P. Li (IHEP/THU), F. J. Lu, L. M. Song,
M. Wu, Y. P. Xu, S. N. Zhang (IHEP),
report on behalf of the Insight-HXMT team:
At 2021-02-07T21:52:49.600 (T0), Insight-HXMT/HE detected
GRB 210207B (trigger ID: HEB210207911) in a routine search of the data,
which also triggered Swift/BAT (A. Y. Lien et al. , GCN #29420).
The Insight-HXMT/HE light curve mainly consists of a single
pulse with a duration (T90) of 2.03 s measured from T0+0.24 s.
The 1-ms peak rate, measured from T0+1.829 s, is 3687 cnts/sec.
The total counts from this burst is 5247 counts.
URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210207911_lc.jpg
All measurements above are made with the CsI detectors operating in the
GRB mode with the energy range of about 250-3000 keV (deposited energy).
Only gamma-rays with energy greater than about 200 keV can penetrate
the spacecraft and leave signals in the CsI detectors installed inside
of the telescope.
Insight-HXMT is the first Chinese space X-ray telescope, which was
funded jointly by the China National Space Administration (CNSA) and
the Chinese Academy of Sciences (CAS).
More information about it could be found at:
http://www.hxmt.org.
GCN Circular 29431
Subject
GRB 210207B: LCO Optical Afterglow Detection
Date
2021-02-08T16:56:16Z (5 years ago)
From
Robert Strausbaugh at U. of the Virgin Islands <robert.strausbaugh@uvi.edu>
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:
We observed Swift GRB 210207B (Lien, GCN 29420) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on February 8, from 11:23 to 11:34 UT (corresponding to 13.30 to 13.48 hours from the GRB trigger time) with the Bessel R and I filters.
We performed a series of 5x60s exposures in R and I. We clearly detect an optical source in R and I band in stacked images at a location consistent the initial UVOT detection (Lien, GCN 29420). Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:
R = 20.24 +/- 0.13
I = 20.56 +/- 0.24
These magnitudes are not corrected for galactic extinction. A quick catalog search found no galaxies at this brightness at this location. Further observations are encouraged.
R.S. is funded by NSF AST grant #1831682
GCN Circular 29430
Subject
GRB 210207B: KAIT Optical Observations
Date
2021-02-08T16:12:38Z (5 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to the Swift GRB 210207B (Lien et al.,
GCN 29420) starting at ~0.657 days after the trigger.
A total of 20x60s images were obtained in the clear (roughly R) filters.
We marginally detect the optical afterglow (Lien et al., GCN 29420;
Kumar et al., GCN 29421) in the coadd image with a mag of 20.3 +/- 0.3,
calibrated to the Pan-STARRS1 catalog.
GCN Circular 29428
Subject
GRB 210207B: AGILE observations
Date
2021-02-08T13:45:28Z (5 years ago)
From
Alessandro Ursi at INAF/IAPS <alessandro.ursi@gmail.com>
A. Ursi (INAF/IAPS), F. Longo (Univ. Trieste and INFN Trieste), 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), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), report
on behalf of the AGILE Team:
The AGILE satellite detected GRB 210207B, reported by Swift (GCNs #29420,
#29422, #29427) and Konus-Wind (GCN #29426) at T0 = 2021-02-07 21:52:08
(UT).
The AGILE Mini-CALorimeter (MCAL; 0.4-100 MeV) scientific ratemeters
clearly detected the main peak of the burst, which occurred at T0 + 40 s,
as reported by Swift/BAT. The episode lasted ~4 s and released 7950 counts
in the MCAL detector, above a background rate of 1250 Hz. The AGILE
ratemeters light curve can be found at:
http://www.agilescienceapp.it/notices/GRB210207B_AGILE_RM.png . The event
was 160�� off-axis.
Additional analysis of AGILE data is in progress.
GCN Circular 29427
Subject
GRB 210207B: Swift-XRT refined Analysis
Date
2021-02-08T13:40:11Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K.L. Page (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC &
INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (PSU), D.N.
Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester), P.A.
Evans (U. Leicester) and A.Y. Lien report on behalf of the Swift-XRT
team:
We have analysed 6.8 ks of XRT data for GRB 210207B (Lien et al. GCN
Circ. 29420), from 80 s to 45.6 ks after the BAT trigger. The data
comprise 329 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Beardmore et al. (GCN Circ. 29422).
The late-time light curve (from T0+3.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.37 (+0.07, -0.06).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.99 (+/-0.04). The
best-fitting absorption column is 1.38 (+/-0.13) x 10^21 cm^-2, in
excess of the Galactic value of 3.5 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.78 (+0.11, -0.10)
and a best-fitting absorption column of 7.2 (+2.9, -2.6) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.7 x 10^-11 (4.2 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 7.2 (+2.9, -2.6) x 10^20 cm^-2
Galactic foreground: 3.5 x 10^20 cm^-2
Excess significance: 2.3 sigma
Photon index: 1.78 (+0.11, -0.10)
If the light curve continues to decay with a power-law decay index of
1.37, the count rate at T+24 hours will be 0.021 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.7 x
10^-13 (8.7 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01031297.
This circular is an official product of the Swift-XRT team.
GCN Circular 29426
Subject
Konus-Wind detection of GRB 210207B
Date
2021-02-08T13:36:32Z (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 210207B (Swift detection: Lien et al., GCN 29420)
triggered Konus-Wind (KW) at T0=78768.813 s UT (21:52:48.813).
The burst light shows a multi-peaked emission complex,
which starts at ~T0-50 s, peaks at ~T0, and has the total duration of ~110 s.
The emission in is seen up to ~2.5 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210207_T78768/
As observed by Konus-Wind, the burst had
a fluence of (2.4 �� 0.8)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+1.472,
of (4.5 �� 0.8)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum (measured from T0 to T0+65.792 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.85(-0.34,+0.44) and Ep = 334(-97,+237) keV (chi2 = 91/97 dof).
Fitting this spectrum by a Band function yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.15
(chi2 =67/97 dof).
The spectrum near the peak count rate (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range by the CPL model
with alpha = -0.46(-0.22,+0.25) and Ep = 497(-84,+120) keV (chi2 = 76/97 dof).
Fitting this spectrum by a Band function yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.33
(chi2 =76/96 dof).
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 29423
Subject
GRB 210207B: AbAO optical upper limit
Date
2021-02-08T10:54:56Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), V. R.
Ayvazian (AbAO), G. V. Kapanadze (AbAO), N. Pankov (HSE, IKI) report
on behalf of IKI-GRB-FuN:
We observed the field of GRB 210207B (Lien et al., GCN 29420) with
AS-32 telescope of Abastumani observatory (AbAO) in R-filter starting on
2021-02-08 (UT) 02:14:17. The optical afterglow (Lien et al., GCN
29420; Kumar et al., GCN 29421) is not detected in stacked image.
Date UT start t-T0 Filter Exp. OT Err. UL(3sigma)
(mid, days) (s)
2021-02-08 02:14:17 0.19837 R 47*60 n/d n/d 18.7
The photometry is based on nearby USNO-B1.0 stars
USNO-B1.0_id R2
1436-0267956 15.29
1436-0268040 15.52
The non-detection of the afterglow implies a jet break somewhere before
of our observations, or the source of the GRB 210207B is highly redshifted.
GCN Circular 29422
Subject
GRB 210207B: Enhanced Swift-XRT position
Date
2021-02-08T02:08:50Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1993 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 210207B, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 270.63474, +53.68210 which is equivalent
to:
RA (J2000): 18h 02m 32.34s
Dec (J2000): +53d 40' 55.5"
with an uncertainty of 1.7 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 29421
Subject
GRB 210207B: optical detection with 3.6m Devasthal Optical Telescope
Date
2021-02-07T23:39:21Z (5 years ago)
From
Amit Kumar at ARIES, India <amitkundu515@gmail.com>
Amit Kumar (ARIES), Shashi B. Pandey (ARIES), Rahul Gupta (ARIES), Ankur
Ghosh (ARIES), Dimple (ARIES), Amar Aryan (ARIES), Brajesh Kumar (ARIES),
and Kuntal Misra (ARIES) report:
We observed the Swift detected GRB 210207B (Lien et al., GCN 29420) using
the 4Kx4K CCD Imager (Pandey et al. 2018, 2018BSRSL..87...42P) mounted at
the axial port of the 3.6m Devasthal Optical Telescope (DOT) of ARIES
Nainital. The observations were carried out on 2021-02-07 in Bessel
UBVRI-bands starting from UT 22:32:31.875 (corresponding to 40.38 minutes
after the burst). We clearly detect the optical transient reported by Lien
et al., GCN 29420. In the first I band image the afterglow has a I band
magnitude of 15.61+/-0.01 mag. Further processing of the data is in
progress.
The quoted magnitude is calibrated with the nearby USNO-B1 stars and not
corrected for Galactic extinction in the direction of the GRB.
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. This circular may be
cited.
GCN Circular 29420
Subject
GRB 210207B: Swift detection of a burst with a bright optical counterpart
Date
2021-02-07T22:03:29Z (5 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
A. Y. Lien (GSFC/UMBC), E. Ambrosi (INAF-IASFPA),
S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC),
J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
S. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), A. Tohuvavohu (U Toronto) and
E. Troja (NASA/GSFC/UMCP) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 21:52:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210207B (trigger=1031297). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 270.582, +53.694 which is
RA(J2000) = 18h 02m 20s
Dec(J2000) = +53d 41' 39"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a multi-peaked
structure with a duration of about 100 sec. The peak count rate
was ~2500 counts/sec (15-350 keV), at ~45 sec after the trigger.
The XRT began observing the field at 21:53:22.0 UT, 73.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 270.6356, 53.6836 which is equivalent to:
RA(J2000) = 18h 02m 32.54s
Dec(J2000) = +53d 41' 01.0"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 120 arcseconds from the BAT onboard position, within the
BAT error circle. 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 1.09e-08 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 18:02:32.40 = 270.63501
DEC(J2000) = +53:40:56.0 = 53.68223
with a 90%-confidence error radius of about 0.74 arc sec. This position is 5.1
arc sec. from the center of the XRT error circle. The estimated magnitude is
13.72 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.041.
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/)