GRB 201021C
GCN Circular 28730
Subject
GRB 201021C: Swift detection of a burst with an optical counterpart
Date
2020-10-21T20:40:16Z (5 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
A. Y. Lien (GSFC/UMBC), M. G. Bernardini (INAF-OAB),
D. N. Burrows (PSU), P. D'Avanzo (INAF-OAB), J.D. Gropp (PSU),
J. A. Kennea (PSU), N. J. Klingler (PSU), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC),
A. Melandri (INAF-OAB), M. J. Moss (GWU), T. Sakamoto (AGU),
T. Sbarrato (INAF-OAB) and B. Sbarufatti (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:
At 20:27:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 201021C (trigger=1001130). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 12.550, -55.839 which is
RA(J2000) = 00h 50m 12s
Dec(J2000) = -55d 50' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single-peaked
structure with a duration of about 25 sec. The peak count rate
was ~1200 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 20:29:00.6 UT, 102.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 12.53057, -55.86729 which
is equivalent to:
RA(J2000) = 00h 50m 07.34s
Dec(J2000) = -55d 52' 02.2"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 109 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.05
x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 105 seconds after the BAT trigger. There is a candidate afterglow in
the list of sources generated on-board at
RA(J2000) = 00:50:06.85 = 12.52855
DEC(J2000) = -55:51:56.7 = -55.86576
with a 90%-confidence error radius of about 1.10 arc sec. This position is 2.8
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.19. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.02.
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/)
GCN Circular 28733
Subject
GRB 201021C: MASTER optical synchronously observation
Date
2020-10-21T21:46:25Z (5 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, V.Kornilov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, A.Kuznetsov,K.Zhirkov, F.Balakin,
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov, A.Pozdnyakov,
V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-SAAO started GRB 201021C (Lien et al. GCN 28730) observation by
MASTER-II (2x4sq.deg.) in 2020-10-21 20:31:04UT and also detected OT at
Swift-UVOT position (Lien et al. GCN 28730)
in 2 polarization filters.
MASTER very wide field cameras (Lipunov et al. 2010, Advances in Astronomy, vol.2010, 30L)
observed this GRB _synchronously_ .
Observation and reduction will continue.
GCN Circular 28736
Subject
GRB 201021C: Enhanced Swift-XRT position
Date
2020-10-22T01:22:09Z (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 742 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 201021C, 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 = 12.52888, -55.86549 which is equivalent
to:
RA (J2000): 00h 50m 6.93s
Dec (J2000): -55d 51' 55.8"
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 28739
Subject
GRB 201021C: VLT/X-shooter redshift
Date
2020-10-22T08:45:59Z (5 years ago)
From
Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>
J.-B. Vielfaure (GEPI - Paris Observatory), D. Xu (NAO/CAS), J. Palmerio
(GEPI - Paris Observatory), P. D'Avanzo (INAF-OAB), D. B. Malesani (DTU Space),
J. P. U. Fynbo (DAWN/NBI), V. D'Elia (ASI/SSDC), D. A. Kann (HETH/IAA-CSIC) and
N. R. Tanvir (Univ. Leicester) report on behalf of the Stargate collaboration:
We observed the optical afterglow of GRB 201021C (Lien et al., GCN
28730; Lipunov et al., GCN 28733) using the ESO VLT UT3 (Melipal) equipped
with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA,
and consist of 4 exposures by 600 s each. The observation started at 03:29:00 UT on
2020 Oct 22 (7.02 hr after the GRB).
In a 30 s image taken with the acquisition camera on Oct 22.14 UT, we detect the optical
afterglow, for which we measure a magnitude r = 19.97 +/- 0.02 (AB, calibrated against
nearby stars from the SkyMapper catalog; Wolf et al. 2018, PASA, 35, 010).
We clearly detect continuum over the whole X-shooter spectrum.
From detection of multiple absorption features, which we interpret as
due to Si II, Al II, Al III, Fe II and Mg II, we infer a redshift z = 1.070.
In particular, weak fine structure lines from Fe II* are visible, which
confirm the association of the absorption system with the GRB.
We also detect Mg II and Mg I absorption features from an intervening
system at z = 0.805.
We acknowledge excellent support from the ESO observing staff in
Paranal, in particular Bin Yang and Fernando Selman.
GCN Circular 28745
Subject
GRB 201021C: Swift/UVOT Detection
Date
2020-10-22T13:16:47Z (5 years ago)
From
Samantha Oates at MSSL <samantha.oates@alumni.ucl.ac.uk>
S. R. Oates (U.Birmingham) 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 201021C
105 s after the BAT trigger (Lien et al., GCN Circ. 28730).
A source consistent with the XRT position
(Beardmore et al. GCN Circ. 28736)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 00:50:06.93 = 12.52886 (deg.)
Dec (J2000) = -55:51:56.8 = -55.86577 (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) 105 255 147 16.66 +/- 0.03
white 598 617 19 16.22 +/- 0.05
v 647 667 19 16.49 +/- 0.16
b 573 593 20 16.80 +/- 0.10
u (FC) 317 567 246 15.76 +/- 0.03
u 722 742 19 16.06 +/- 0.10
uvm2 672 692 19 16.43 +/- 0.24
uvw2 623 643 19 16.68 +/- 0.22
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 28748
Subject
GRB 201021C: Fermi GBM detection
Date
2020-10-22T15:41:24Z (5 years ago)
From
Stephen Lesage at Fermi-GBM Team <sjl0014@uah.edu>
S. Lesage (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 20:27:21.92 UT on 21 October 2020, the Fermi Gamma-Ray Burst Monitor
(GBM)
triggered and located GRB 201021C (trigger 625004846 / 201021852)
which was also detected by the Swift/BAT (A. Y. Lien et al. 2020, GCN
28730).
The Fermi GBM on-ground localization is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is ~59
degrees.
The GBM light curve shows a single bright peak
with a duration (T90) of about 35.3 s (50-300 keV).
The time-averaged spectrum from T0-5.9 s to T0+29.4 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.1 +/- 0.2 and
the cutoff energy, parameterized as Epeak, is 131.1 +/- 28.2 keV.
The event fluence (10-1000 keV) in this time interval is
(1.7 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0-1.9 s in the 10-1000 keV band
is 1.82 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support
Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 28754
Subject
GRB 201021C: Swift-XRT refined Analysis
Date
2020-10-22T20:40:03Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester), P. D'Avanzo (INAF-OAB), M.G.
Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , J. D. Gropp (PSU),
J.A. Kennea (PSU) and A.Y. Lien report on behalf of the Swift-XRT team:
We have analysed 4.3 ks of XRT data for GRB 201021C (Lien et al. GCN
Circ. 28730), from 105 s to 58.8 ks after the BAT trigger. The data
comprise 62 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. 28736).
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.22 (+0.07, -0.06).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.62 (+0.19, -0.16). The
best-fitting absorption column is 5 (+21, -5) x 10^20 cm^-2, at a
redshift of 1.07, in addition to the Galactic value of 2.0 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 (4.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 2.0 x 10^20 cm^-2
Intrinsic column: 5 (+21, -5) x 10^20 cm^-2 at z=1.07
Photon index: 1.62 (+0.19, -0.16)
If the light curve continues to decay with a power-law decay index of
1.22, the count rate at T+24 hours will be 2.7 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (1.1 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/01001130.
This circular is an official product of the Swift-XRT team.
GCN Circular 28755
Subject
GRB 201021C: Swift-BAT refined analysis
Date
2020-10-22T22:30:34Z (5 years ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 201021C (trigger #1001130)
(Lien, et al., GCN Circ. 28730). The BAT ground-calculated position is
RA, Dec = 12.503, -55.862 deg which is
RA(J2000) = 00h 50m 00.6s
Dec(J2000) = -55d 51' 44.0"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 80%.
The mask-weighted light curve shows a single peak running from ~T-5 sec to
T+20 sec, with a broad peak around T+3 sec. T90 (15-350 keV) is 24.38 +- 6.76 sec
(estimated error including systematics).
The time-averaged spectrum from T-4.19 to T+27.95 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.63 +- 0.15. The fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-3.62 sec in the 15-150 keV band
is 1.0 +- 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/1001130/BA/
GCN Circular 31752
Subject
GRB 201021C: TAROT Reunion observatory optical light curve
Date
2022-03-13T22:08:20Z (3 years ago)
From
Alain Klotz at IRAP-CNRS-OMP <Alain.Klotz@free.fr>
A. Klotz (CNRS-OMP-IRAP),
M. Fortune, R. Augerai (Universite de la Renuion),
P. Thierry�� (AGORA),
L. Eymar, S. Antier, M. Boer, A. de Ugarte Postigo (CNRS-OCA-ARTEMIS),
We analyzed archive images of the SWIFT trigger 1001130 (GRB 201021C,
BAT detection by�� Lien et al. GCN Circ. 28730,
early optical ground observations by Lipunov et al. GCN Circ. 28733,
redshift by Vielfaure et al. GCN Circ. 28739)
with the TAROT robotic telescope (D=18cm) located
at Les Makes Observatory, Reunion Island, France.
Images were acquired without any filter, camera FLI PL16803
and Takahashi Epsilon 180ED.
According the reference star NOMAD-1 0340-0006028 R=13.85
we give the photometry of the GRB optical transient:
��t1(s) t2(s)�������� R�� dmag
���� 813���� 993 15.92�� 0.04
�� 1003�� 1183 16.02�� 0.03
�� 1190�� 1370 16.24�� 0.05
�� 1388�� 1568 16.28�� 0.04
�� 1575�� 1755 16.52�� 0.06
�� 1762�� 1942 16.62�� 0.06
�� 2048�� 2228 16.80�� 0.08
�� 2236�� 2416 16.92�� 0.09
�� 2425�� 3178 17.12�� 0.06
�� 3198�� 4132 17.54�� 0.09
�� 4139�� 9462 17.82�� 0.10
t1 and t2 are start and stop acquisition since the trigger.
Magnitudes are not corrected for Galactic dust extinction.