GRB 221202A
GCN Circular 33005
Subject
GRB 221202A: Swift detection of a burst
Date
2022-12-02T20:20:01Z (3 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
R. Caputo (GSFC), M. G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB),
P. D'Avanzo (INAF-OAB), S. Dichiara (PSU),
R. A. J. Eyles-Ferris (U Leicester), M. Ferro (INAF-OAB),
J.D. Gropp (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII),
H. A. Krimm (NSF), A. Y. Lien (U Tampa), K. L. Page (U Leicester),
D. M. Palmer (LANL), T. M. Parsotan (GSFC/UMBC/CRESSTII),
C. Salvaggio (INAF-OAB), A. Tohuvavohu (U Toronto) and
M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 20:06:10 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 221202A (trigger=1142997). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 77.095, -59.806 which is
RA(J2000) = 05h 08m 23s
Dec(J2000) = -59d 48' 21"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single peak
structure with a duration of about 20 sec. The peak count rate
was ~1000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 20:07:48.2 UT, 97.6 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 77.08221,
-59.83213 which is equivalent to:
RA(J2000) = 05h 08m 19.73s
Dec(J2000) = -59d 49' 55.7"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 96 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 2.11
x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 101 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag.
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.027.
Burst Advocate for this burst is R. Caputo (regina.caputo 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 33007
Subject
GRB 221202A: MeerLICHT upper limits
Date
2022-12-02T22:14:11Z (3 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT) and P.J. Groot (Radboud/UCT/SAAO) report on behalf of the
MeerLICHT consortium:
Following the detection by Swift of GRB 221202A and its X-ray counterpart
(Caputo et al., GCN 33005), the 0.6m wide-field MeerLICHT telescope,
located at Sutherland, South Africa, obtained 5x300s observations in the
q,z,i,r,g bands beginning at 21:14:34 UT on 2022 December 2, approximately
1.14 hours after the Swift trigger.
We detect no new source at the XRT position (Caputo et al., GCN 33005) in
any of our images down to the following 3-sigma upper limits, in the AB
magnitude system:
q > 21.80 at 21:17:27 UT
z > 20.01 at 21:22:34 UT
i > 21.02 at 21:28:03 UT
r > 21.53 at 21:33:25 UT
g > 21.58 at 21:38:54 UT
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 33008
Subject
GRB 221202A: Enhanced Swift-XRT position
Date
2022-12-02T22:47:18Z (3 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 864 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 221202A, 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 = 77.08299, -59.83246 which is equivalent
to:
RA (J2000): 05h 08m 19.92s
Dec (J2000): -59d 49' 56.9"
with an uncertainty of 2.2 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 33009
Subject
GRB 221202A: LCOGT Optical Upper Limits
Date
2022-12-02T22:51:53Z (3 years ago)
From
Robert Strausbaugh at University of Minnesota <rstrausb@umn.edu>
R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on
behalf of a larger collaboration:
We observed the GRB 221202A (Caputo et al., GCN 33005) field with the LCOGT
1-meter Sinistro instrument at the South African Astronomical Observatory
site, on December 2, from 21:09 to 21:36 (corresponding to 1.05 to 1.5
hours from the GRB trigger time) with the Bessel R and I filters.
We performed a series of 3x280s exposures in each band. We do not detect
any sources in the XRT error region, in either band, consistent with other
optical upper limits (de Wet et al., GCN 33007).
The following upper limits are calculated using the USNO-B.1 catalog as
reference:
R > 20.0
I > 19.0
These magnitudes are not corrected for galactic extinction.
GCN Circular 33010
Subject
GRB 221202A: Swift-XRT refined Analysis
Date
2022-12-03T07:45:52Z (3 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G.
Bernardini (INAF-OAB), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU),
J. D. Gropp (PSU) and R. Caputo report on behalf of the Swift-XRT team:
We have analysed 6.1 ks of XRT data for GRB 221202A (Caputo et al. GCN
Circ. 33005), from 82 s to 27.6 ks after the BAT trigger. The data
comprise 185 s in Windowed Timing (WT) mode (the first 8 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Beardmore
et al. (GCN Circ. 33008).
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.45 (+0.08, -0.07).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.25 (+0.11, -0.10). The
best-fitting absorption column is 3.94 (+0.29, -0.28) x 10^21 cm^-2,
in excess of the Galactic value of 2.1 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.77 (+0.32, -0.29)
and a best-fitting absorption column of 2.1 (+0.8, -0.7) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 2.5 x 10^-11 (5.3 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.1 (+0.8, -0.7) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^20 cm^-2
Excess significance: 4.6 sigma
Photon index: 2.77 (+0.32, -0.29)
If the light curve continues to decay with a power-law decay index of
1.45, the count rate at T+24 hours will be 4.0 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x
10^-14 (2.1 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01142997.
This circular is an official product of the Swift-XRT team.
GCN Circular 33014
Subject
GRB 221202A: VLT/FORS2 Afterglow Discovery
Date
2022-12-03T17:28:59Z (3 years ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
A. Rossi (INAF), G. Pugliese (API, Amsterdam university), D. A. Kann
(Goethe Univ.), B. Schneider (CEA Paris-Saclay), and V. D'Elia (INAF/OAR
and ASI/SSDC) report on behalf of the Stargate collaboration:
We performed photometric observations of the afterglow of GRB 221202A
detected by the Swift Burst Alert Telescope (BAT) at 20:06:10.56 UT
(Caputo et al., GCN 33005; De Wet et al., GCN 33007; Beardmore et al.,
GCN 33008;�� Strausbaugh et al., GCN 33009; Evans et al., GCN 33010) with
the FORS2 instrument at the ESO VLT-UT1 in the R_Special, I_Bessel and
z_Gunn filters (in the following RIz). The observation started at
06:50:29 UT (about 10.73 hours after the BAT detection), and consisted
of 500 s in R, 800 s in I, and 1320 s in z.
We detect a source in the XRT error circle in all filters at position
RA, Dec. (J2000) = 05:08:19.94,-59:49:58.6, astrometrized against Gaia
DR3 field stars. We measure the following photometry, consistent with
the upper limits of MeerLICHT (S. de Wet et al., GCN 33007) and LCOGT
(R. Strausbaugh et al., GCN 33009):
R = 23.10 +/- 0.05 mag,
I = 22.68 +/- 0.06 mag,
z = 22.52 +/- 0.07 mag.
Magnitudes are calibrated against SkyMapper field stars and are in the
AB system. For the R and I bands we use the Lupton formulas to convert
the standard stars to the BVRI photometric system, then convert the
measured magnitudes back to the AB system.
A source at the same position is visible in r'-band images downloaded
and stacked from the Legacy Imaging Survey, with r' ~ 24.3 mag (AB).
Therefore, we conclude that the detected source is dominated by the
afterglow of GRB 221202A and slightly contaminated by the GRB host
galaxy. We derive an X-ray to optical slope beta_OX ~ 0.8, therefore the
afterglow is not dark, just faint.
We acknowledge the support provided by T. C. Emy and the Paranal staff,
in particular Ana Escorza, Ricardo Arrue, Marcela Espinoza, and Michael
Abdul-Masih.
GCN Circular 33015
Subject
GRB 221202A: Swift-BAT refined analysis
Date
2022-12-03T19:01:10Z (3 years ago)
From
Tyler Parsotan at UMBC/GSFC/CRESST II <parsotat@umbc.edu>
S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU),
M. Stamatikos (OSU) (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 221202A (trigger #1142997)
(Caputo et al. GCN Circ. 33005). The BAT ground-calculated position is
RA, Dec = 77.002, -59.836 deg which is
RA(J2000) = 05h 08m 00.5s
Dec(J2000) = -59d 50' 09.0"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 85%.
The mask-weighted light curve shows a single peaked pulse.
T90 (15-350 keV) is 10.34 +- 1.21 sec (estimated error including
systematics).
The time-averaged spectrum from T+1.03 to T+12.44 sec is best fit by a
simple
power-law model. The power law index of the time-averaged spectrum is
1.64 +- 0.25. The fluence in the 15-150 keV band is 3.2 +- 0.6 x 10^-07
erg/cm2.
The 1-sec peak photon flux measured from T+3.31 sec in the 15-150 keV band
is 0.7 +- 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/1142997/BA/
GCN Circular 33016
Subject
GRB 221202A: Swift/UVOT Detection
Date
2022-12-03T21:07:48Z (3 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
Paul Kuin (MSSL-UCL) and R. Caputo (GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 221202A
102 s after the BAT trigger (Caputo et al., GCN Circ. 33005).
A source consistent with the XRT position (Beardmore et al. GCN Circ. 33008)
is detected in the initial UVOT exposures.
Preliminary detections and 3-sigma upper limits 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 102 733 186 20.66 +/- 0.20
v 590 4820 216 >19.9
b 516 709 39 >19.8
u 260 857 285 >19.7
w1 640 832 39 >20.8
m2 615 808 39 >18.1
w2 566 4635 235 >20.0
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.027 in the direction of the burst
(Schlegel et al. 1998).