GRB 201128A
GCN Circular 28958
Subject
GRB 201128A: Swift detection of a burst
Date
2020-11-28T06:44:21Z (5 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. Y. Lien (GSFC/UMBC), E. Ambrosi (INAF-IASFPA),
A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC), J.D. Gropp (PSU),
J. A. Kennea (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Neil Gehrels
Swift Observatory Team:
At 06:27:58 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 201128A (trigger=1009679). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 223.136, +26.678 which is
RA(J2000) = 14h 52m 33s
Dec(J2000) = +26d 40' 41"
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 10 sec. The peak count rate
was ~600 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 06:30:04.8 UT, 126.6 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 223.1083, 26.6844 which
is equivalent to:
RA(J2000) = 14h 52m 26.00s
Dec(J2000) = +26d 41' 03.8"
with an uncertainty of 2.6 arcseconds (radius, 90% containment). This
location is 92 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. We
cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 3.53
x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 130 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 none of
the XRT error circle. 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 0.03.
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 28959
Subject
GRB 201128A: DDOTI Observations
Date
2020-11-28T15:11:50Z (5 years ago)
From
Alan M Watson at UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara
(GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Oc��lotl Lopez
(UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and
Eleonora Troja (GSFC/UMD) report:
We observed the field of GRB 201128A (Lien et al., GCN Circ. 28958) with with
the DDOTI/OAN wide-field imager at the Observatorio Astron��mico Nacional on
Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of
2020-11-28 UTC.
We observed from 2020-11-30 12:45 to 13:07 (from 6.3 to 6.7 hours after the
trigger) obtaining a total of 960 seconds exposure in the w filter. We calibrate
our images against the APASS catalog. Our 5-sigma limiting magnitude is w =
20.4.
Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogs, we
detect no uncatalogued sources in the Swift/XRT error region (Lien et al., GCN
Circ. 28958 to our 5-sigma limit.
We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.
GCN Circular 28960
Subject
GRB 201128A: Enhanced Swift-XRT position
Date
2020-11-28T15:58:08Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1017 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 201128A, 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 = 223.10767, +26.68502 which is equivalent
to:
RA (J2000): 14h 52m 25.84s
Dec (J2000): +26d 41' 06.1"
with an uncertainty of 2.0 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 28962
Subject
GRB 201128A: Swift-XRT refined Analysis
Date
2020-11-28T22:44:04Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri
(ASDC), V. D'Elia (ASDC), J.A. Kennea (PSU), A. Tohuvavohu (U.
Toronto), B. Sbarufatti (PSU), P.A. Evans (U. Leicester), J.P. Osborne
(U. Leicester) and A.Y. Lien report on behalf of the Swift-XRT team:
We have analysed 9.4 ks of XRT data for GRB 201128A (Lien et al. GCN
Circ. 28958), from 133 s to 46.1 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Evans et al. (GCN Circ. 28960).
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.58 (+/-0.04).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.09 (+0.23, -0.21). The
best-fitting absorption column is 1.6 (+0.7, -0.6) x 10^21 cm^-2, in
excess of the Galactic value of 3.5 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 3.3 x 10^-11 (4.0 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.6 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 3.5 x 10^20 cm^-2
Excess significance: 3.4 sigma
Photon index: 2.09 (+0.23, -0.21)
If the light curve continues to decay with a power-law decay index of
0.58, the count rate at T+24 hours will be 0.014 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.6 x
10^-13 (5.5 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/01009679.
This circular is an official product of the Swift-XRT team.
GCN Circular 28963
Subject
GRB 201128A: Swift-BAT refined analysis
Date
2020-11-29T03:42:15Z (5 years ago)
From
Sibasish Laha at GSFC <sibasish.laha@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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 201128A (trigger #1009679)
(Lien et al., GCN Circ. 28958). The BAT ground-calculated position is
RA, Dec = 223.091, 26.716 deg which is
RA(J2000) = 14h 52m 21.9s
Dec(J2000) = +26d 42' 58.6"
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.
The BAT light curve showed a complex structure with a duration of about 30 sec.
T90 (15-350 keV) is 5.41 +- 3.22 sec (estimated error including systematics).
The time-averaged spectrum from T-0.44 to T+8.74 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.37 +- 0.37. The fluence in the 15-150 keV band is 2.0 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+4.21 sec in the 15-150 keV band
is 0.4 +- 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/1009679/BA/
GCN Circular 28970
Subject
GRB 201128A: Swift/UVOT Upper Limits
Date
2020-11-30T23:24:56Z (5 years ago)
From
Alexander Belles at PSU/Swift <aub1461@psu.edu>
GRB 201128A: Swift/UVOT Upper Limits
A. Belles (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 201128A
130 s after the BAT trigger (Lien et al., GCN Circ. 28958).
No optical afterglow consistent with the XRT position
(Lien et al. GCN Circ. 28958)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposures and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 130 280 147 >20.0
u_FC 289 538 246 >19.3
white 130 761 186 >20.0
v 619 639 19 >17.4
b 544 737 39 >18.6
u 289 538 246 >19.3
w1 668 688 19 >18.3
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).