TITLE: GCN CIRCULAR
NUMBER: 30734
SUBJECT: GRB 210827A: Swift-XRT observations
DATE: 21/08/28 08:58:36 GMT
FROM: Paolo D'Avanzo at INAF - OAB <paolo.davanzo(a)inaf.it>
J. D. Gropp (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester),
J.P. Osborne (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo
(INAF-OAB), M.G. Bernardini (INAF-OAB), A. Tohuvavohu (U. Toronto) and
P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up …
[View More]observations of the
Swift/BAT-GUANO-detected burst GRB 210827A (James DeLaunay et al. GCN
Circ. 30732), collecting 2.3 ks of Photon Counting (PC) mode data
between T0+44.4 ks and T0+50.4 ks.
One uncatalogued X-ray source has been detected consistent with being
within 296 arcsec of the Swift/BAT-GUANO position, it is below the RASS
limit and shows no definitive signs of fading. Therefore, at the
present time we cannot confirm this as the afterglow. Details of this
source are given below:
Source 3:
RA (J2000.0): 174.9003 = 11:39:36.07
Dec (J2000.0): +55.7239 = +55:43:26.2
Error: 3.8 arcsec (radius, 90% conf. [Enhanced position])
Count-rate: 0.0103 +/- 0.0025 ct s^-1
Distance: 225 arcsec from Swift/BAT-GUANO position.
Flux: (4.8 +/- 1.2)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Four uncatalogued sources were also detected too far from the GRB
position to be likely afterglow candidates.
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/00021461.
This circular is an official product of the Swift-XRT team.
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TITLE: GCN CIRCULAR
NUMBER: 30733
SUBJECT: GRB 210827A: Swift ToO observations
DATE: 21/08/27 22:02:28 GMT
FROM: Phil Evans at U of Leicester <pae9(a)leicester.ac.uk>
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Swift/BAT-GUANO GRB 210827A.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021461
Any uncatalogued X-ray sources detected in this analysis will be
…
[View More]reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT-GUANO 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.
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TITLE: GCN CIRCULAR
NUMBER: 30732
SUBJECT: GRB 210827A: Swift/BAT-GUANO detection and arcminute localization
DATE: 21/08/27 21:41:58 GMT
FROM: Aaron Tohuvavohu at U Toronto <aaron.tohu(a)gmail.com>
James DeLaunay (PSU), Gayathri Raman (PSU), Jamie A. Kennea (PSU),
Aaron Tohuvavohu (U Toronto), report:
Swift/BAT did not trigger on GRB 210827A (T0: 2021-08-27 09:59:24.34
UTC, Fermi/GBM trigger # 651751169, GCN 30724).
The Fermi/GBM notice, distributed in near real-time, …
[View More]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 approximately 10 seconds.
Using the normal BAT imaging technique, we find the location for
the GRB with an SNR of 8.3.
The BAT position is
RA, Dec = 174.9181 +55.7858 deg which is
RA(J2000) = 11h 39m 40.34s
Dec(J2000) = +55d 47′ 08.88″
with an estimated uncertainty of 4 arcmin.
This position is consistent with the Fermi/GBM localization.
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/
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TITLE: GCN CIRCULAR
NUMBER: 30731
SUBJECT: GRB 210820A: CAHA 2.2m Optical Detection
DATE: 21/08/27 18:03:36 GMT
FROM: Alexander Kann at IAA-CSIC <kann(a)iaa.es>
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC,
DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all
HETH/IAA-CSIC), A. Fernandez, and I. Hermelo (all CAHA) report:
We observed GRB 210820A (Swift detection: Beardmore et al., GCN #30664)
with CAFOS mounted on the 2.2m CAHA telescope at Calar …
[View More]Alto, Alemria,
Spain, under inclement conditions (bright moonlight, passing clouds, low
transparency). We obtained 10 x 90 s each in filters B, V, Rc. Stacks
reveal no detection of the afterglow in B (very shallow because of
moonlight) and Rc (shallow because of incoming clouds which also
prevented further observations). However, the afterglow (Beardmore et
al., GCN #30664; Butler et al., GCN #30672; LaPorte & Beardmore, GCN
#30686; Nicuesa Guelbenzu et al., GCN #30695) is clearly detected in V,
somewhat north of a source also seen in Pan-STARRS and in SDSS.
We find the afterglow to be V = 22.43 +/- 0.15 mag (AB mag, derived from
two SDSS field stars transformed to V via the equations of Lupton 2005)
at 0.43868 days after the GRB.
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TITLE: GCN CIRCULAR
NUMBER: 30730
SUBJECT: GRB 210824A: Swift/UVOT Upper Limits
DATE: 21/08/27 15:52:44 GMT
FROM: Sam LaPorte at PSU <sjl5346(a)psu.edu>
GRB 210824A: Swift/UVOT Upper Limits
S. J. LaPorte (PSU) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210824A
311 s after the BAT trigger (Page et al., GCN Circ. 30700).
No optical afterglow consistent with the XRT position
(Goad et al. …
[View More]GCN Circ. 30702)
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) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 311 461 147 >20.8
white 311 4350 364 >20.9
v 467 4760 236 >19.4
b 565 4145 235 >20.1
u 541 5220 83 >19.6
w1 516 5170 236 >20.4
m2 4765 4965 197 >20.3
w2 4356 4555 197 >19.9
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.037 in the direction of the burst
(Schlegel et al. 1998).
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TITLE: GCN CIRCULAR
NUMBER: 30729
SUBJECT: GRB 210826A: Swift/UVOT Upper Limits
DATE: 21/08/27 15:38:05 GMT
FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk>
A. A. Breeveld (UCL-MSSL) and T. Sbarrato (INAF-IASFPA) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210826A 36747 s after the LAT trigger
(Ohno et al., GCN Circ. 30721). No new optical source consistent with the any of the 8 candidate XRT
positions (D'Ai …
[View More]et al., GCN Circ. 30725) 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 initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
v 36747 49716 4869 >20.9
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of
E(B-V) = 0.032 in the direction of the burst (Schlegel et al. 1998).
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TITLE: GCN CIRCULAR
NUMBER: 30728
SUBJECT: POLAR detection of a SGR-like burst
DATE: 21/08/27 13:34:35 GMT
FROM: Hancheng Li at IHEP/POLAR <lihc(a)ihep.ac.cn>
G. Koziol (UniGE), H. C. Li (UniGE), M. Kole (UniGE), Y. H. Wang (IHEP),
N. Produit (UniGE), J. C. Sun (IHEP) and Y. Zhao (IHEP/BNU)
report on behalf of the POLAR collaboration:
During on-ground blind search of archive POLAR data, we found a SGR-like
burst whick took place on 2017-01-18 16:16:25.5 UT (T0). The …
[View More]burst has a
duration (T90) of 0.32 +/- 0.02 seconds, the light curve and data files
(both in ROOT and FITS formats) can be found at:
https://www.astro.unige.ch/polar/content/sgr-candidate-170118
Using the localization method of POLAR (Y. H. Wang et al, 2021),
the location of this event is best fitted as (in J2000):
RA : 33.5 [deg] (l = 136.04)
Dec: +50.7 [deg] (b = -10.06)
Err: 8.1 [deg] (radius, 1 sigma containment, statistical only)
The incident angle in the POLAR local coordinate at T0 is:
Theta: 60.0 [deg]
Phi: 50.0 [deg]
The spectra is better fitted with "bbody+powerlaw" model than Band function
or single powerlaw. The temperature (kT) is 13.85 +/- 0.79 keV with a
normalization of 99.34 +/- 7.93, and the power law index is 1.73 +/- 0.43
with a normalization of 74.21 +/- 182.29. The fluence (50-500 keV) from
T0 to T0 + 1.0 s is (5.09 +/- 1.33) E-06 erg/cm^2, and the average photon
flux (50-500 keV) over this time period is 40 +/- 1 ph/s/cm^2.
The results presented above are preliminary. Refined analyses are ongoing.
Additionally, more burst events are expected to be found in the blind
search of data which was recently started, and to be circulated by GCN.
POLAR was a dedicated Gamma-Ray Burst polarimeter which was launched
on-board the Chinese space laboratory Tiangong-2 (TG-2) on Sep 15, 2016,
and ended operation in April 2017. More information about POLAR can be
found at https://www.astro.unige.ch/polar/ , http://polar.ihep.ac.cn/en/ ,
and http://polar.psi.ch/html/ .
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TITLE: GCN CIRCULAR
NUMBER: 30727
SUBJECT: GRB 210827B: BALROG localization (Fermi Trigger 651751821 / GRB 210827424)
DATE: 21/08/27 10:28:30 GMT
FROM: Jochen Greiner at MPE,Garching <jcg(a)mpe.mpg.de>
J. Burgess, F. Kunzweiler, B. Biltzinger, F. Berlato, & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
651751821 at 10:10:16 on 27 Aug. 2021 were automatically fitted for spectrum
and sky location with BALROG …
[View More](Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 305.1+/-2.9 deg
Decl.(2000.0) = -17.3+/-2.3 deg
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210827424/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210827424/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210827424/json
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TITLE: GCN CIRCULAR
NUMBER: 30726
SUBJECT: GRB 210827B: Fermi GBM Final Real-time Localization
DATE: 21/08/27 10:20:35 GMT
FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov>
The Fermi GBM team reports the detection of a likely LONG GRB
At 10:10:16 UT on 27 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210827B (trigger 651751821.143562 / 210827424).
The on-ground calculated location, using the Fermi GBM trigger data, is RA …
[View More]= 308.8, Dec = -19.3 (J2000 degrees, equivalent to J2000 20h 35m, -19d 18'), with a statistical uncertainty of 2.5 degrees.
The angle from the Fermi LAT boresight is 66.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827424/…
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827424/…
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827424/…
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