GRB 201128B

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie Kennea (PSU) report:

Swift/BAT did not trigger on GRB 201128B (T0: 2020-11-28 17:54:11 UTC,
Fermi/GBM TRIGGER 628278856).

The Fermi/GBM notice, distributed in near real-time triggered the
Swift Mission Operations Center operated Gamma-ray Urgent Archiver for
Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).

Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from
[-50,+150] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.

The burst is detected in BAT with a duration of ~15 seconds. This was
a weak and slow burst that occurred during a rapid part of a Swift
slew. The position of the burst was found with a novel and
uncalibrated slew image mosaicing procedure, and so the positional
uncertainty is not yet well characterized.


The BAT position is
RA, Dec = 339.354, -49.246 deg which is
   RA(J2000)  = 22h 37m 24.96s
   Dec(J2000) =  -49d 14��� 45.6���
with an estimated uncertainty of at least 5 arcmin.

This position is consistent with the Fermi GBM localization
(https://gcn.gsfc.nasa.gov/other/628278856.fermi).

XRT and UVOT follow-up has been requested. Results of follow-up
observations will be reported in future circulars.

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Swift/BAT GRB 201128B. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021044

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 Swift/BAT 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.

M. Perri (ASDC), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Tohuvavohu
(U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Swift/BAT-detected burst GRB 201128B (James DeLaunay et al. GCN Circ.
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 ), collecting 5.0 ks of Photon Counting (PC) mode data between
T0+246.0 ks and T0+303.8 ks. 

Ten uncatalogued X-ray sources have been detected, however none of them
is above the RASS limit or shows definitive signs of fading. Therefore,
at the present time we cannot identify which, if any, is the afterglow.
Details of these sources are given below:

Source 1:
  RA (J2000.0):  339.4164  =  22:37:39.94
  Dec (J2000.0): -49.2698  =  -49:16:11.1
  Error: 5.1 arcsec (radius, 90% conf.)
  Count-rate: (3.32 [+1.13, -0.93])e-3 ct s^-1	 
  Distance: 169 arcsec from Swift/BAT position.
  Flux: (1.67 [+0.57, -0.47])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:
  RA (J2000.0):  339.0250  =  22:36:5.99
  Dec (J2000.0): -49.1319  =  -49:07:54.7
  Error: 5.2 arcsec (radius, 90% conf.)
  Count-rate: (4.7 [+2.8, -2.0])e-3 ct s^-1   
  Distance: 876 arcsec from Swift/BAT position.

Source 4:
  RA (J2000.0):  339.5648  =  22:38:15.55
  Dec (J2000.0): -49.2141  =  -49:12:50.9
  Error: 7.7 arcsec (radius, 90% conf.)
  Count-rate: (2.35 [+1.05, -0.81])e-3 ct s^-1	 
  Distance: 508 arcsec from Swift/BAT position.
  Flux: (7.8 [+3.5, -2.7])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 5:
  RA (J2000.0):  339.4267  =  22:37:42.42
  Dec (J2000.0): -49.1173  =  -49:07:02.2
  Error: 5.3 arcsec (radius, 90% conf.)
  Count-rate: (1.36 [+0.77, -0.57])e-3 ct s^-1	 
  Distance: 494 arcsec from Swift/BAT position.
  Flux: (9.5 [+5.4, -4.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 6:
  RA (J2000.0):  339.2905  =  22:37:9.71
  Dec (J2000.0): -49.3858  =  -49:23:08.7
  Error: 5.1 arcsec (radius, 90% conf.)
  Count-rate: (6.6 [+2.0, -1.6])e-3 ct s^-1   
  Distance: 524 arcsec from Swift/BAT position.
  Flux: (1.69 [+0.50, -0.42])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 7:
  RA (J2000.0):  339.2768  =  22:37:6.43
  Dec (J2000.0): -49.1392  =  -49:08:21.0
  Error: 4.9 arcsec (radius, 90% conf.)
  Count-rate: (4.7 +/- 1.3)e-3 ct s^-1	 
  Distance: 425 arcsec from Swift/BAT position.
  Flux: (2.03 +/- 0.55)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 8:
  RA (J2000.0):  339.2888  =  22:37:9.31
  Dec (J2000.0): -49.1961  =  -49:11:45.9
  Error: 7.2 arcsec (radius, 90% conf.)
  Count-rate: (2.17 [+0.97, -0.77])e-3 ct s^-1	 
  Distance: 236 arcsec from Swift/BAT position.
  Flux: (1.84 [+0.83, -0.65])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 9:
  RA (J2000.0):  339.2747  =  22:37:5.92
  Dec (J2000.0): -49.1221  =  -49:07:19.5
  Error: 9.8 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (3.04 [+1.19, -0.95])e-3 ct s^-1	 
  Distance: 483 arcsec from Swift/BAT position.
  Flux: (7.4 [+2.9, -2.3])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 10:
  RA (J2000.0):  339.5188  =  22:38:4.51
  Dec (J2000.0): -49.1801  =  -49:10:48.4
  Error: 6.9 arcsec (radius, 90% conf.)
  Count-rate: (1.89 [+0.94, -0.72])e-3 ct s^-1	 
  Distance: 454 arcsec from Swift/BAT position.
  Flux: (3.0 [+1.5, -1.1])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 11:
  RA (J2000.0):  339.5043  =  22:38:1.04
  Dec (J2000.0): -49.3084  =  -49:18:30.2
  Error: 5.2 arcsec (radius, 90% conf.)
  Count-rate: (2.14 [+1.07, -0.81])e-3 ct s^-1	 
  Distance: 418 arcsec from Swift/BAT position.
  Flux: (1.04 [+0.52, -0.39])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

A catalogued source was also detected.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021044.

This circular is an official product of the Swift-XRT team.