Gamma-ray Burst 210827A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 27 Aug 21 09:59:48 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     651751169
GRB_RA:           97.917d {+06h 31m 40s} (J2000),
                  98.604d {+06h 34m 25s} (current),
                  96.326d {+06h 25m 18s} (1950)
GRB_DEC:         +73.767d {+73d 46' 00"} (J2000),
                 +73.749d {+73d 44' 58"} (current),
                 +73.801d {+73d 48' 04"} (1950)
GRB_ERROR:       22.63 [deg radius, statistical plus systematic]
GRB_INTEN:       49 [cnts/sec]
DATA_SIGNIF:     4.60 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19453 TJD;   239 DOY;   21/08/27
GRB_TIME:        35964.34 SOD {09:59:24.34} UT
GRB_PHI:         282.00 [deg]
GRB_THETA:        65.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.06
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   1%  Solar Flare
DETECTORS:       0,0,0, 1,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       156.23d {+10h 24m 56s}   +9.91d {+09d 54' 34"}
SUN_DIST:         71.77 [deg]   Sun_angle= 3.8 [hr] (West of Sun)
MOON_POSTN:       31.61d {+02h 06m 26s}   +9.91d {+09d 54' 42"}
MOON_DIST:        74.16 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      140.77, 24.61 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       93.46, 50.42 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827416/quicklook/glg_lc_medres34_bn210827416.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 82.13,-7.92 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 27 Aug 21 10:00:06 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      58
TRIGGER_NUM:     651751169
GRB_RA:           91.640d {+06h 06m 34s} (J2000),
                  92.213d {+06h 08m 51s} (current),
                  90.316d {+06h 01m 16s} (1950)
GRB_DEC:         +67.830d {+67d 49' 48"} (J2000),
                 +67.826d {+67d 49' 33"} (current),
                 +67.835d {+67d 50' 05"} (1950)
GRB_ERROR:       12.93 [deg radius, statistical only]
DATA_SIGNIF:     5.00 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        19453 TJD;   239 DOY;   21/08/27
GRB_TIME:        35964.34 SOD {09:59:24.34} UT
GRB_PHI:         284.00 [deg]
GRB_THETA:        71.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       156.23d {+10h 24m 56s}   +9.91d {+09d 54' 33"}
SUN_DIST:         71.20 [deg]   Sun_angle= 4.3 [hr] (West of Sun)
MOON_POSTN:       31.61d {+02h 06m 27s}   +9.91d {+09d 54' 46"}
MOON_DIST:        70.01 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      146.28, 20.91 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       90.87, 44.40 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827416/quicklook/glg_lc_medres34_bn210827416.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_651751169.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 27 Aug 21 10:08:47 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     651751169
GRB_RA:          138.280d {+09h 13m 07s} (J2000),
                 138.697d {+09h 14m 47s} (current),
                 137.312d {+09h 09m 15s} (1950)
GRB_DEC:         +60.180d {+60d 10' 48"} (J2000),
                 +60.090d {+60d 05' 23"} (current),
                 +60.386d {+60d 23' 10"} (1950)
GRB_ERROR:       20.17 [deg radius, statistical only]
GRB_DATE:        19453 TJD;   239 DOY;   21/08/27
GRB_TIME:        35964.34 SOD {09:59:24.34} UT
GRB_PHI:         304.00 [deg]
GRB_THETA:        60.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       156.24d {+10h 24m 57s}   +9.91d {+09d 54' 26"}
SUN_DIST:         51.87 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:       31.68d {+02h 06m 43s}   +9.94d {+09d 56' 33"}
MOON_DIST:        89.66 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      155.24, 40.70 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      119.78, 41.63 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827416/quicklook/glg_lc_medres34_bn210827416.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827416/quicklook/glg_locplot_all_bn210827416.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.

GCN Circular #30724
The Fermi GBM team reports the detection of a likely LONG GRB
At 09:59:24 UT on 27 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210827A (trigger 651751169.343218 / 210827416).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 138.3, Dec = 60.2 (J2000 degrees, equivalent to J2000 09h 13m, 60d 12'), with a statistical uncertainty of 20.2 degrees.
The angle from the Fermi LAT boresight is 60.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827416/quicklook/glg_skymap_all_bn210827416.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827416/quicklook/glg_healpix_all_bn210827416.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827416/quicklook/glg_lc_medres34_bn210827416.gif
GCN Circular #30732
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, 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/
GCN Circular #30733
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 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.
GCN Circular #30734
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 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.

GCN Circular #30736
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210827A ( Fermi GBM team, GCN 30724) errorbox 30492 sec after notice time and 30537 sec after trigger time at 2021-08-27 18:28:21 UT, with upper limit up to 18.1 mag. The observations began at zenith distance = 70 deg. The sun altitude is -25.3 deg.
The galactic latitude b = 41 deg., longitude l = 155 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1701371
We obtain a following upper limits.

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   11650 | 2021-08-27 13:13:33 |             MASTER- | (11h 12m 36.70s , +67d 11m 16.1s) |   C |     1 | 13.4 |        
   11918 | 2021-08-27 13:17:59 |             MASTER- | (11h 46m 32.91s , +55d 47m 35.7s) |   C |     5 | 13.7 |        
   11947 | 2021-08-27 13:18:27 |             MASTER- | (11h 55m 02.70s , +57d 44m 41.4s) |   C |     5 | 14.1 |        
   12173 | 2021-08-27 13:22:14 |             MASTER- | (10h 01m 20.63s , +69d 03m 02.1s) |   C |     5 | 15.1 |        
   12194 | 2021-08-27 13:22:35 |             MASTER- | (09h 45m 27.80s , +65d 14m 47.8s) |   C |     5 | 14.9 |        
   12211 | 2021-08-27 13:22:52 |             MASTER- | (09h 52m 33.30s , +67d 08m 02.1s) |   C |     5 | 14.8 |        
   12228 | 2021-08-27 13:23:09 |             MASTER- | (11h 00m 38.41s , +70d 57m 53.9s) |   C |     5 | 15.5 |        
   12254 | 2021-08-27 13:23:32 |             MASTER- | (10h 22m 38.11s , +65d 14m 38.6s) |   C |    10 | 15.2 |        
   12274 | 2021-08-27 13:23:53 |             MASTER- | (10h 32m 28.63s , +67d 09m 16.9s) |   C |    10 | 14.9 |        
   12306 | 2021-08-27 13:24:25 |             MASTER- | (10h 44m 58.15s , +69d 03m 57.8s) |   C |    10 | 15.4 |        
   12332 | 2021-08-27 13:24:51 |             MASTER- | (11h 20m 42.93s , +72d 54m 50.1s) |   C |    10 | 15.5 |        
   12357 | 2021-08-27 13:25:16 |             MASTER- | (10h 14m 37.53s , +63d 20m 51.7s) |   C |    10 | 15.0 |        
   12383 | 2021-08-27 13:25:42 |             MASTER- | (09h 32m 58.63s , +59d 31m 17.2s) |   C |    10 | 14.7 |        
   12415 | 2021-08-27 13:26:14 |             MASTER- | (10h 03m 32.71s , +59d 31m 40.8s) |   C |    10 | 14.7 |        
   12441 | 2021-08-27 13:26:40 |             MASTER- | (09h 30m 48.25s , +57d 33m 40.2s) |   C |    10 | 14.2 |        
   12467 | 2021-08-27 13:27:05 |             MASTER- | (11h 28m 35.54s , +69d 03m 40.2s) |   C |    10 | 15.7 |        
   12487 | 2021-08-27 13:27:26 |             MASTER- | (11h 46m 30.04s , +74d 48m 24.7s) |   C |    10 | 15.5 |        
   12515 | 2021-08-27 13:27:53 |             MASTER- | (09h 04m 11.03s , +51d 49m 54.5s) |   C |    10 | 13.6 |        
   12550 | 2021-08-27 13:28:28 |             MASTER- | (09h 29m 10.43s , +53d 47m 35.1s) |   C |    10 | 14.7 |        
   12576 | 2021-08-27 13:28:55 |             MASTER- | (09h 59m 46.06s , +57d 36m 24.2s) |   C |    10 | 14.2 |        
   12596 | 2021-08-27 13:29:15 |             MASTER- | (09h 36m 05.99s , +61d 24m 19.6s) |   C |    10 | 15.0 |        
   12622 | 2021-08-27 13:29:41 |             MASTER- | (09h 29m 46.69s , +55d 40m 55.7s) |   C |    10 | 14.7 |        
   12655 | 2021-08-27 13:30:13 |             MASTER- | (10h 08m 27.79s , +61d 23m 46.2s) |   C |    10 | 15.1 |        
   12686 | 2021-08-27 13:30:45 |             MASTER- | (10h 59m 45.12s , +65d 13m 05.6s) |   C |    10 | 15.3 |        
   12710 | 2021-08-27 13:31:08 |             MASTER- | (09h 40m 15.47s , +63d 17m 48.7s) |   C |    10 | 13.3 |        
   12738 | 2021-08-27 13:31:34 |             MASTER- | (11h 12m 47.15s , +67d 08m 17.3s) |   C |    15 | 15.4 |        
   12738 | 2021-08-27 13:31:34 |             MASTER- | (11h 33m 48.90s , +68d 29m 16.4s) |   C |    15 | 14.1 |        
   12780 | 2021-08-27 13:32:16 |             MASTER- | (09h 06m 01.09s , +49d 57m 40.5s) |   C |    15 | 14.4 |        
   12780 | 2021-08-27 13:32:16 |             MASTER- | (09h 18m 00.30s , +51d 19m 06.1s) |   C |    15 | 12.7 |        
   12806 | 2021-08-27 13:32:42 |             MASTER- | (09h 56m 59.13s , +55d 40m 23.3s) |   C |    15 | 14.7 |        
   12806 | 2021-08-27 13:32:42 |             MASTER- | (10h 10m 59.95s , +57d 01m 11.1s) |   C |    15 | 13.2 |        
   12836 | 2021-08-27 13:33:12 |             MASTER- | (11h 48m 50.32s , +70d 59m 28.3s) |   C |    15 | 15.7 |        
   12910 | 2021-08-27 13:34:26 |             MASTER- | (10h 40m 39.02s , +61d 26m 55.2s) |   C |    15 | 15.3 |        
   12910 | 2021-08-27 13:34:26 |             MASTER- | (10h 57m 34.22s , +62d 46m 02.2s) |   C |    15 | 13.3 |        
   12940 | 2021-08-27 13:34:54 |             MASTER- | (09h 29m 11.96s , +51d 52m 23.5s) |   C |    20 | 14.8 |        
   12940 | 2021-08-27 13:34:54 |             MASTER- | (09h 41m 50.47s , +53d 10m 58.8s) |   C |    20 | 12.8 |        
   13025 | 2021-08-27 13:36:19 |             MASTER- | (10h 49m 17.27s , +63d 20m 37.8s) |   C |    20 | 15.5 |        
   13025 | 2021-08-27 13:36:19 |             MASTER- | (11h 07m 11.77s , +64d 40m 09.6s) |   C |    20 | 13.5 |        
   13062 | 2021-08-27 13:36:52 |             MASTER- | (12h 13m 57.24s , +72d 56m 00.0s) |   C |    25 | 14.4 |        
   13200 | 2021-08-27 13:39:09 |             MASTER- | (11h 46m 38.50s , +55d 46m 53.8s) |   C |    30 | 15.4 |        
   13200 | 2021-08-27 13:39:09 |             MASTER- | (12h 00m 55.06s , +57d 06m 14.3s) |   C |    30 | 13.9 |        
   13242 | 2021-08-27 13:39:48 |             MASTER- | (11h 55m 06.51s , +57d 41m 00.0s) |   C |    35 | 16.4 |        
   13914 | 2021-08-27 13:50:53 |             MASTER- | (10h 05m 07.14s , +66d 32m 23.8s) |   C |    50 | 14.4 |        
   13988 | 2021-08-27 13:52:03 |             MASTER- | (10h 13m 32.56s , +68d 26m 04.6s) |   C |    55 | 14.0 |        
   14071 | 2021-08-27 13:53:26 |             MASTER- | (11h 26m 13.82s , +72d 18m 56.3s) |   C |    55 | 14.7 |        
   14142 | 2021-08-27 13:54:36 |             MASTER- | (10h 22m 46.72s , +65d 13m 18.1s) |   C |    60 | 14.4 |        
   14223 | 2021-08-27 13:55:57 |             MASTER- | (10h 32m 39.17s , +67d 06m 40.3s) |   C |    60 | 15.1 |        
   14305 | 2021-08-27 13:57:18 |             MASTER- | (10h 45m 10.68s , +69d 01m 17.8s) |   C |    60 | 14.9 |        
   14305 | 2021-08-27 13:57:18 |             MASTER- | (11h 08m 24.23s , +70d 21m 59.0s) |   C |    60 | 14.6 |        
   14461 | 2021-08-27 13:59:55 |             MASTER- | (10h 32m 48.00s , +64d 38m 12.2s) |   C |    60 | 14.3 |        
   14547 | 2021-08-27 14:01:20 |             MASTER- | (09h 48m 55.04s , +60d 49m 31.6s) |   C |    60 | 13.8 |        
   14617 | 2021-08-27 14:02:31 |             MASTER- | (10h 03m 35.61s , +59d 29m 02.7s) |   C |    60 | 13.0 |        
   15032 | 2021-08-27 14:09:26 |             MASTER- | (09h 42m 24.32s , +55d 06m 08.6s) |   C |    60 | 14.5 |        
   15103 | 2021-08-27 14:10:37 |             MASTER- | (10h 00m 00.22s , +57d 32m 08.8s) |   C |    60 | 14.1 |        
   15267 | 2021-08-27 14:13:21 |             MASTER- | (09h 43m 39.34s , +57d 00m 17.0s) |   C |    60 | 14.6 |        
   15267 | 2021-08-27 14:13:21 |             MASTER- | (09h 29m 51.06s , +55d 38m 39.9s) |   C |    60 | 16.0 |        
   15337 | 2021-08-27 14:14:32 |             MASTER- | (10h 08m 42.40s , +61d 22m 46.0s) |   C |    55 | 13.7 |        
   15412 | 2021-08-27 14:15:51 |             MASTER- | (11h 19m 12.19s , +66d 33m 52.9s) |   C |    50 | 15.0 |        
   15475 | 2021-08-27 14:16:54 |             MASTER- | (09h 58m 16.72s , +64d 35m 36.7s) |   C |    50 | 14.1 |        
   15475 | 2021-08-27 14:16:54 |             MASTER- | (09h 40m 29.81s , +63d 14m 20.6s) |   C |    50 | 15.9 |        
   15556 | 2021-08-27 14:18:12 |             MASTER- | (11h 13m 03.21s , +67d 05m 51.4s) |   C |    55 | 12.4 |        
   15638 | 2021-08-27 14:19:34 |             MASTER- | (10h 11m 12.98s , +57d 00m 30.2s) |   C |    55 | 14.4 |        
   15638 | 2021-08-27 14:19:34 |             MASTER- | (09h 57m 16.48s , +55d 38m 20.8s) |   C |    55 | 14.8 |        
   15708 | 2021-08-27 14:20:44 |             MASTER- | (12h 14m 11.05s , +72d 18m 07.1s) |   C |    55 | 15.0 |        
   15708 | 2021-08-27 14:20:44 |             MASTER- | (11h 49m 02.98s , +70d 57m 13.0s) |   C |    55 | 14.9 |        
   15949 | 2021-08-27 14:24:42 |             MASTER- | (09h 41m 57.90s , +53d 11m 40.0s) |   C |    60 | 13.6 |        
   16123 | 2021-08-27 14:27:42 |             MASTER- | (10h 49m 44.99s , +63d 17m 26.4s) |   C |    50 | 14.2 |        
   16192 | 2021-08-27 14:28:45 |             MASTER- | (12h 14m 20.14s , +72d 52m 25.9s) |   C |    60 | 13.6 |        
   16595 | 2021-08-27 14:35:39 |             MASTER- | (11h 46m 34.30s , +55d 44m 13.6s) |   C |    40 | 15.1 |        
   16644 | 2021-08-27 14:36:28 |             MASTER- | (12h 10m 25.31s , +58d 58m 20.1s) |   C |    40 | 13.5 |        
   16755 | 2021-08-27 14:38:29 |             MASTER- | (11h 41m 24.68s , +58d 58m 33.2s) |   C |    20 | 13.7 |        
   16755 | 2021-08-27 14:38:29 |             MASTER- | (11h 26m 19.64s , +57d 38m 07.6s) |   C |    20 | 14.7 |        
   16787 | 2021-08-27 14:39:01 |             MASTER- | (12h 05m 35.42s , +59d 34m 15.7s) |   C |    20 | 15.6 |        
   16852 | 2021-08-27 14:40:06 |             MASTER- | (11h 04m 34.20s , +59d 33m 06.4s) |   C |    20 | 16.1 |        
   16959 | 2021-08-27 14:41:53 |             MASTER- | (11h 53m 15.95s , +55d 10m 45.9s) |   C |    20 | 13.8 |        
   16959 | 2021-08-27 14:41:53 |             MASTER- | (11h 39m 38.11s , +53d 49m 19.8s) |   C |    20 | 15.7 |        
   17022 | 2021-08-27 14:42:56 |             MASTER- | (11h 33m 29.78s , +57d 03m 39.7s) |   C |    20 | 13.4 |        
   17022 | 2021-08-27 14:42:56 |             MASTER- | (11h 19m 19.52s , +55d 42m 47.1s) |   C |    20 | 15.0 |        
   17331 | 2021-08-27 14:48:05 |             MASTER- | (12h 05m 29.24s , +59d 32m 27.7s) |   C |    20 | 15.6 |        
   17407 | 2021-08-27 14:49:21 |             MASTER- | (11h 20m 40.57s , +60d 51m 48.6s) |   C |    20 | 13.2 |        
   17407 | 2021-08-27 14:49:21 |             MASTER- | (11h 04m 44.06s , +59d 32m 05.8s) |   C |    20 | 15.8 |        
   17437 | 2021-08-27 14:49:51 |             MASTER- | (11h 51m 08.81s , +60d 51m 10.7s) |   C |    20 | 13.7 |        
   17498 | 2021-08-27 14:50:52 |             MASTER- | (11h 53m 13.08s , +55d 11m 34.7s) |   C |    20 | 13.6 |        
   17498 | 2021-08-27 14:50:52 |             MASTER- | (11h 39m 43.02s , +53d 50m 41.5s) |   C |    20 | 16.1 |        
   17671 | 2021-08-27 14:53:45 |             MASTER- | (11h 33m 36.97s , +57d 02m 27.0s) |   C |    20 | 13.4 |        
   17671 | 2021-08-27 14:53:45 |             MASTER- | (11h 19m 27.44s , +55d 42m 15.9s) |   C |    20 | 15.8 |        
   17700 | 2021-08-27 14:54:13 |             MASTER- | (11h 41m 33.01s , +58d 56m 46.1s) |   C |    20 | 13.0 |        
   17700 | 2021-08-27 14:54:13 |             MASTER- | (11h 26m 33.07s , +57d 35m 35.3s) |   C |    20 | 15.5 |        
   17731 | 2021-08-27 14:54:44 |             MASTER- | (12h 05m 41.38s , +59d 32m 22.8s) |   C |    20 | 15.7 |        
   17838 | 2021-08-27 14:56:31 |             MASTER- | (11h 51m 09.60s , +60d 51m 57.3s) |   C |    20 | 13.4 |        
   17909 | 2021-08-27 14:57:43 |             MASTER- | (11h 53m 25.45s , +55d 09m 54.2s) |   C |    20 | 13.4 |        
   17910 | 2021-08-27 14:57:43 |             MASTER- | (11h 39m 53.42s , +53d 49m 25.3s) |   C |    20 | 14.4 |        
   18101 | 2021-08-27 15:00:55 |             MASTER- | (11h 30m 26.09s , +62d 46m 41.0s) |   C |    20 | 13.3 |        
   18101 | 2021-08-27 15:00:55 |             MASTER- | (11h 13m 32.12s , +61d 24m 19.9s) |   C |    20 | 15.3 |        
   18289 | 2021-08-27 15:04:03 |             MASTER- | (10h 50m 08.24s , +60d 49m 28.9s) |   C |    20 | 13.2 |        
   18289 | 2021-08-27 15:04:03 |             MASTER- | (10h 34m 30.40s , +59d 27m 37.8s) |   C |    20 | 15.0 |        
   18320 | 2021-08-27 15:04:34 |             MASTER- | (11h 12m 38.32s , +58d 55m 08.8s) |   C |    20 | 13.1 |        
   18320 | 2021-08-27 15:04:34 |             MASTER- | (10h 57m 47.86s , +57d 33m 14.5s) |   C |    20 | 15.4 |        
   18362 | 2021-08-27 15:05:15 |             MASTER- | (11h 06m 20.08s , +57d 01m 27.5s) |   C |    20 | 13.0 |        
   18362 | 2021-08-27 15:05:15 |             MASTER- | (10h 52m 19.20s , +55d 40m 37.6s) |   C |    20 | 15.6 |        
   18392 | 2021-08-27 15:05:46 |             MASTER- | (10h 28m 58.66s , +57d 34m 29.6s) |   C |    20 | 15.1 |        
   18425 | 2021-08-27 15:06:18 |             MASTER- | (11h 30m 27.14s , +62d 43m 49.0s) |   C |    20 | 13.7 |        
   18425 | 2021-08-27 15:06:19 |             MASTER- | (11h 13m 38.18s , +61d 21m 52.5s) |   C |    20 | 15.4 |        
   18457 | 2021-08-27 15:06:51 |             MASTER- | (11h 27m 12.37s , +55d 10m 55.6s) |   C |    20 | 14.0 |        
   18457 | 2021-08-27 15:06:51 |             MASTER- | (11h 13m 56.70s , +53d 48m 49.0s) |   C |    20 | 15.9 |        
   18501 | 2021-08-27 15:07:35 |             MASTER- | (10h 24m 46.08s , +55d 38m 36.4s) |   C |    20 | 14.5 |        
   18534 | 2021-08-27 15:08:07 |             MASTER- | (11h 42m 11.95s , +64d 40m 53.6s) |   C |    20 | 13.5 |        
   18534 | 2021-08-27 15:08:07 |             MASTER- | (11h 24m 23.30s , +63d 18m 59.1s) |   C |    20 | 16.2 |        
   18565 | 2021-08-27 15:08:39 |             MASTER- | (10h 34m 31.63s , +59d 27m 03.1s) |   C |    20 | 15.1 |        
   18609 | 2021-08-27 15:09:23 |             MASTER- | (12h 02m 46.48s , +62d 45m 03.1s) |   C |    20 | 13.9 |        
   18609 | 2021-08-27 15:09:23 |             MASTER- | (11h 45m 56.18s , +61d 22m 25.8s) |   C |    20 | 15.6 |        
   18641 | 2021-08-27 15:09:55 |             MASTER- | (11h 12m 40.13s , +58d 56m 25.2s) |   C |    20 | 12.6 |        
   18641 | 2021-08-27 15:09:55 |             MASTER- | (10h 57m 54.03s , +57d 33m 53.4s) |   C |    20 | 14.1 |        
   18670 | 2021-08-27 15:10:23 |             MASTER- | (11h 06m 17.28s , +57d 02m 08.4s) |   C |    20 | 13.2 |        
   18670 | 2021-08-27 15:10:23 |             MASTER- | (10h 52m 11.20s , +55d 40m 04.5s) |   C |    20 | 15.7 |        
   18699 | 2021-08-27 15:10:53 |             MASTER- | (10h 29m 08.31s , +57d 31m 46.3s) |   C |    20 | 15.6 |        
   18741 | 2021-08-27 15:11:35 |             MASTER- | (11h 30m 22.56s , +62d 46m 13.4s) |   C |    20 | 13.2 |        
   18741 | 2021-08-27 15:11:35 |             MASTER- | (11h 13m 42.26s , +61d 23m 06.9s) |   C |    20 | 15.1 |        
   18773 | 2021-08-27 15:12:07 |             MASTER- | (11h 27m 03.50s , +55d 08m 24.0s) |   C |    20 | 13.5 |        
   18773 | 2021-08-27 15:12:07 |             MASTER- | (11h 13m 46.34s , +53d 46m 13.3s) |   C |    20 | 15.3 |        
   18806 | 2021-08-27 15:12:40 |             MASTER- | (10h 24m 53.25s , +55d 40m 46.0s) |   C |    20 | 15.4 |        
   18850 | 2021-08-27 15:13:24 |             MASTER- | (11h 24m 28.50s , +63d 18m 00.7s) |   C |    20 | 15.5 |        
   18882 | 2021-08-27 15:13:56 |             MASTER- | (10h 49m 58.75s , +60d 47m 44.8s) |   C |    20 | 13.1 |        
   18882 | 2021-08-27 15:13:56 |             MASTER- | (10h 34m 27.05s , +59d 25m 47.8s) |   C |    20 | 15.1 |        
   18916 | 2021-08-27 15:14:30 |             MASTER- | (12h 02m 45.53s , +62d 45m 44.1s) |   C |    20 | 14.1 |        
   18916 | 2021-08-27 15:14:30 |             MASTER- | (11h 46m 11.43s , +61d 23m 24.9s) |   C |    20 | 15.8 |        
   19029 | 2021-08-27 15:16:23 |             MASTER- | (10h 29m 12.51s , +57d 33m 18.2s) |   C |    20 | 14.8 |        
   19114 | 2021-08-27 15:17:48 |             MASTER- | (11h 13m 46.37s , +53d 48m 10.8s) |   C |    20 | 14.8 |        
   19148 | 2021-08-27 15:18:22 |             MASTER- | (10h 24m 59.00s , +55d 39m 36.6s) |   C |    20 | 15.3 |        
   19148 | 2021-08-27 15:18:22 |             MASTER- | (10h 38m 47.02s , +57d 01m 12.7s) |   C |    20 | 13.3 |        
   19181 | 2021-08-27 15:18:54 |             MASTER- | (11h 24m 25.91s , +63d 15m 26.2s) |   C |    20 | 16.0 |        
   19181 | 2021-08-27 15:18:54 |             MASTER- | (11h 42m 09.52s , +64d 37m 52.2s) |   C |    20 | 13.5 |        
   19263 | 2021-08-27 15:20:17 |             MASTER- | (12h 02m 45.57s , +62d 45m 12.2s) |   C |    20 | 13.3 |        
   19263 | 2021-08-27 15:20:17 |             MASTER- | (11h 46m 03.30s , +61d 24m 27.2s) |   C |    20 | 14.6 |        
   20984 | 2021-08-27 15:48:58 |             MASTER- | (11h 58m 41.13s , +63d 18m 47.7s) |   C |    20 | 15.2 |        
   20984 | 2021-08-27 15:48:58 |             MASTER- | (12h 16m 23.96s , +64d 38m 13.6s) |   C |    20 | 13.7 |        
   21198 | 2021-08-27 15:52:31 |             MASTER- | (12h 18m 28.25s , +61d 25m 56.1s) |   C |    20 | 16.0 |        
   21243 | 2021-08-27 15:53:17 |             MASTER- | (11h 37m 13.80s , +65d 11m 07.4s) |   C |    20 | 15.6 |        
   21243 | 2021-08-27 15:53:17 |             MASTER- | (11h 56m 11.10s , +66d 31m 57.7s) |   C |    20 | 14.3 |        
   21413 | 2021-08-27 15:56:06 |             MASTER- | (11h 58m 50.70s , +63d 16m 39.0s) |   C |    20 | 15.5 |        
   21413 | 2021-08-27 15:56:06 |             MASTER- | (12h 16m 49.59s , +64d 37m 34.9s) |   C |    20 | 13.7 |        
   21628 | 2021-08-27 15:59:42 |             MASTER- | (12h 18m 20.92s , +61d 24m 54.9s) |   C |    20 | 15.4 |        
   21659 | 2021-08-27 16:00:13 |             MASTER- | (11h 37m 37.23s , +65d 12m 07.7s) |   C |    20 | 16.2 |        
   21659 | 2021-08-27 16:00:13 |             MASTER- | (11h 56m 49.55s , +66d 33m 14.8s) |   C |    20 | 13.8 |        
   21747 | 2021-08-27 16:01:41 |             MASTER- | (11h 58m 58.79s , +63d 16m 33.4s) |   C |    20 | 15.5 |        
   21810 | 2021-08-27 16:02:44 |             MASTER- | (12h 14m 37.59s , +65d 11m 02.4s) |   C |    20 | 15.1 |        
   21916 | 2021-08-27 16:04:30 |             MASTER- | (11h 53m 19.32s , +67d 06m 12.1s) |   C |    20 | 15.4 |        
   21916 | 2021-08-27 16:04:30 |             MASTER- | (12h 14m 25.09s , +68d 26m 50.1s) |   C |    20 | 13.5 |        
   21991 | 2021-08-27 16:05:45 |             MASTER- | (11h 37m 35.11s , +65d 10m 53.9s) |   C |    20 | 16.2 |        
   22134 | 2021-08-27 16:08:08 |             MASTER- | (12h 14m 42.20s , +65d 12m 17.2s) |   C |    20 | 15.3 |        
   22240 | 2021-08-27 16:09:54 |             MASTER- | (11h 53m 38.72s , +67d 04m 55.2s) |   C |    20 | 15.5 |        
   22455 | 2021-08-27 16:13:29 |             MASTER- | (12h 14m 38.21s , +65d 11m 15.0s) |   C |    20 | 15.1 |        
   22564 | 2021-08-27 16:15:17 |             MASTER- | (11h 53m 25.23s , +67d 03m 34.6s) |   C |    20 | 15.3 |        
   22564 | 2021-08-27 16:15:17 |             MASTER- | (12h 14m 26.56s , +68d 25m 29.5s) |   C |    20 | 13.1 |        
   30567 | 2021-08-27 18:28:21 |   MASTER-Kislovodsk | (06h 19m 12.16s , +65d 20m 16.3s) |   C |    60 | 17.8 |        
   30567 | 2021-08-27 18:28:21 |   MASTER-Kislovodsk | (06h 09m 28.58s , +65d 45m 46.2s) |   C |    60 | 17.2 |        
   30647 | 2021-08-27 18:29:41 |   MASTER-Kislovodsk | (05h 59m 00.90s , +69d 08m 32.6s) |   C |    60 | 17.9 |        
   30728 | 2021-08-27 18:31:01 |   MASTER-Kislovodsk | (06h 09m 43.61s , +67d 15m 56.9s) |   C |    60 | 17.8 |        
   30728 | 2021-08-27 18:31:02 |   MASTER-Kislovodsk | (05h 59m 11.65s , +67d 41m 30.7s) |   C |    60 | 17.3 |        
   30808 | 2021-08-27 18:32:21 |   MASTER-Kislovodsk | (06h 42m 26.91s , +69d 08m 09.5s) |   C |    60 | 18.0 |        
   30808 | 2021-08-27 18:32:21 |   MASTER-Kislovodsk | (06h 30m 58.61s , +69d 33m 45.3s) |   C |    60 | 17.5 |        
   30968 | 2021-08-27 18:35:02 |   MASTER-Kislovodsk | (06h 34m 19.20s , +71d 02m 14.1s) |   C |    60 | 18.1 |        
   30968 | 2021-08-27 18:35:02 |   MASTER-Kislovodsk | (06h 20m 50.93s , +71d 28m 30.0s) |   C |    60 | 17.5 |        
   31048 | 2021-08-27 18:36:22 |   MASTER-Kislovodsk | (06h 49m 41.09s , +67d 15m 25.5s) |   C |    60 | 17.9 |        
   31048 | 2021-08-27 18:36:22 |   MASTER-Kislovodsk | (06h 38m 26.91s , +67d 41m 30.2s) |   C |    60 | 17.3 |        
   31289 | 2021-08-27 18:40:23 |   MASTER-Kislovodsk | (07h 02m 22.14s , +63d 26m 32.4s) |   C |    60 | 17.7 |        
   31289 | 2021-08-27 18:40:23 |   MASTER-Kislovodsk | (06h 53m 18.49s , +63d 52m 02.4s) |   C |    60 | 17.2 |        
   31530 | 2021-08-27 18:44:23 |   MASTER-Kislovodsk | (06h 19m 19.21s , +65d 22m 04.8s) |   C |    60 | 17.7 |        
   31530 | 2021-08-27 18:44:23 |   MASTER-Kislovodsk | (06h 09m 33.40s , +65d 47m 39.7s) |   C |    60 | 17.3 |        
   31610 | 2021-08-27 18:45:44 |   MASTER-Kislovodsk | (05h 58m 59.89s , +69d 10m 29.9s) |   C |    60 | 17.8 |        
   31690 | 2021-08-27 18:47:04 |   MASTER-Kislovodsk | (06h 09m 43.67s , +67d 16m 29.4s) |   C |    60 | 17.8 |        
   31690 | 2021-08-27 18:47:04 |   MASTER-Kislovodsk | (05h 59m 09.68s , +67d 42m 07.1s) |   C |    60 | 17.3 |        
   31770 | 2021-08-27 18:48:24 |   MASTER-Kislovodsk | (06h 42m 33.83s , +69d 10m 02.7s) |   C |    60 | 17.8 |        
   31770 | 2021-08-27 18:48:24 |   MASTER-Kislovodsk | (06h 31m 02.76s , +69d 35m 44.1s) |   C |    60 | 17.4 |        
   31930 | 2021-08-27 18:51:04 |   MASTER-Kislovodsk | (06h 34m 27.39s , +71d 01m 52.5s) |   C |    60 | 17.9 |        
   31930 | 2021-08-27 18:51:04 |   MASTER-Kislovodsk | (06h 20m 59.22s , +71d 28m 15.0s) |   C |    60 | 17.5 |        
   32010 | 2021-08-27 18:52:24 |   MASTER-Kislovodsk | (06h 49m 46.79s , +67d 15m 06.0s) |   C |    60 | 17.8 |        
   32010 | 2021-08-27 18:52:24 |   MASTER-Kislovodsk | (06h 38m 32.52s , +67d 41m 16.8s) |   C |    60 | 17.3 |        
   32250 | 2021-08-27 18:56:24 |   MASTER-Kislovodsk | (07h 02m 18.77s , +63d 27m 17.3s) |   C |    60 | 17.5 |        
   32250 | 2021-08-27 18:56:24 |   MASTER-Kislovodsk | (06h 53m 14.25s , +63d 52m 52.2s) |   C |    60 | 17.2 |        
   32330 | 2021-08-27 18:57:44 |   MASTER-Kislovodsk | (07h 03m 30.23s , +63d 27m 18.2s) |   C |    60 | 12.9 |        
   32330 | 2021-08-27 18:57:44 |   MASTER-Kislovodsk | (06h 53m 55.14s , +63d 52m 53.5s) |   C |    60 | 12.6 |        
   32455 | 2021-08-27 19:00:09 |             MASTER- | (12h 14m 44.53s , +68d 57m 28.0s) |   C |    20 | 13.7 |        
   32490 | 2021-08-27 19:00:24 |   MASTER-Kislovodsk | (06h 19m 27.91s , +65d 20m 04.7s) |   C |    60 | 17.6 |        
   32491 | 2021-08-27 19:00:24 |   MASTER-Kislovodsk | (06h 09m 05.21s , +65d 46m 08.9s) |   C |    60 | 17.2 |        
   32571 | 2021-08-27 19:01:45 |   MASTER-Kislovodsk | (05h 59m 19.02s , +69d 08m 32.7s) |   C |    60 | 17.7 |        
   32570 | 2021-08-27 19:02:04 |             MASTER- | (12h 27m 03.52s , +66d 38m 29.9s) |   C |    20 | 12.9 |        
   32651 | 2021-08-27 19:03:05 |   MASTER-Kislovodsk | (06h 10m 01.33s , +67d 16m 04.2s) |   C |    60 | 17.6 |        
   32651 | 2021-08-27 19:03:05 |   MASTER-Kislovodsk | (05h 58m 46.72s , +67d 42m 11.9s) |   C |    60 | 17.3 |        
   32671 | 2021-08-27 19:03:45 |             MASTER- | (12h 28m 10.18s , +69d 57m 04.0s) |   C |    20 | 13.6 |        
   32731 | 2021-08-27 19:04:25 |   MASTER-Kislovodsk | (06h 42m 44.87s , +69d 07m 44.1s) |   C |    60 | 17.8 |        
   32731 | 2021-08-27 19:04:25 |   MASTER-Kislovodsk | (06h 30m 31.28s , +69d 33m 55.1s) |   C |    60 | 17.4 |        
   32892 | 2021-08-27 19:07:06 |   MASTER-Kislovodsk | (06h 34m 34.94s , +71d 02m 29.4s) |   C |    60 | 17.9 |        
   32892 | 2021-08-27 19:07:06 |   MASTER-Kislovodsk | (06h 21m 06.53s , +71d 28m 55.4s) |   C |    60 | 17.4 |        
   32905 | 2021-08-27 19:07:39 |             MASTER- | (06h 25m 59.85s , +64d 20m 01.2s) |   C |    20 | 13.1 |        
   32935 | 2021-08-27 19:08:09 |             MASTER- | (06h 54m 15.07s , +66d 15m 32.0s) |   C |    20 | 12.0 |        
   32972 | 2021-08-27 19:08:26 |   MASTER-Kislovodsk | (06h 49m 56.53s , +67d 15m 38.0s) |   C |    60 | 17.7 |        
   32972 | 2021-08-27 19:08:26 |   MASTER-Kislovodsk | (06h 38m 41.88s , +67d 41m 52.3s) |   C |    60 | 17.3 |        
   33212 | 2021-08-27 19:12:26 |   MASTER-Kislovodsk | (06h 52m 59.48s , +63d 52m 14.5s) |   C |    60 | 17.2 |        
   33213 | 2021-08-27 19:12:26 |   MASTER-Kislovodsk | (07h 02m 38.65s , +63d 26m 18.4s) |   C |    60 | 17.5 |        
   97622 | 2021-08-28 13:06:25 |             MASTER- | (11h 33m 38.59s , +55d 20m 48.5s) |   C |     1 | 12.5 |

Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.

GCN Circular #30738
S. Lesage (UAH), R. Dunwoody (UCD), J. Mangan (UCD) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 09:59:24 UT on 27 August 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210827A (trigger 651751169/210827416) which was also detected by Swift/BAT-GUANO (James DeLaunay et al. 2021, GCN 30732). The Fermi GBM Final Real-time Localization (GCN 30724) is consistent with the Swift/BAT-GUANO position.
The angle from the Fermi LAT boresight is 42 degrees.
The GBM light curve consists of a single emission episode with a duration (T90) of about 9 s (10-1000 keV). The time-averaged spectrum from T0-2.0 to T0+4.1 s is best fit by a simple power law function with index -1.6 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is (7 +/- 1)E-07 erg/cm^2. The 1-sec peak photon flux measured starting from T0-2.5 s in the 10-1000 keV band is 1.7 +/- 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 #30742
Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado and M.D. Caballero-Garcia (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar and I. Carrasco (UMA), I. H. Park (SKKU) on behalf of a larger collaboration, report:
We triggered the 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) for the Fermi trigger of GRB 210827A (Fermi GBM team, GCNC 30724) in order to monitor the Swift/BAT-GUANO error region (DeLaunay et al. GCNC 30732) on 28 Aug 05:25 UT (~ 0.81 day after trigger). In the co-added clear image (8 x 60 s), no optical afterglow is detected within the BAT error region or at the source 3 position later reported by the Swift-XRT (Evans et al., GCNC 30733; Gropp et al., GCNC 30734) down to 19.7 mag. This non-detection is consistent with the report by MASTER-Net (Lipunov et al., GCNC 30736).
We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for its excellent support.
GCN Circular #30743
A. A. Breeveld (UCL-MSSL) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the Swift/BAT-GUANO-detected burst GRB 210827A (DeLaunay et al., GCN Circ. 30732) 44720s after the Fermi-GBM trigger (Fermi GBM team, GCN Circ. 30724). No new optical source consistent with the candidate XRT positions (Gropp et al., GCN Circ. 30734) 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

white            44720        50434         1650         >21.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.0111 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #30745
P. D'Avanzo, M. G. Bernardini, A. Melandri, T. Sbarrato (INAF-OAB), P. A. Evans (U. Leicester) report on behalf of the Swift team:
Swift-XRT has performed further follow-up observations of the Swift/BAT-GUANO-detected burst GRB 210827A (James DeLaunay et al. GCN Circ. 30732), collecting a total of 12.2 ks of Photon Counting (PC) mode data between T0+44.4 ks and T0+257.2 ks. The uncatalogued candidate X-ray source (Source 3) reported in Gropp et al. (GCN Circ. 30734) faded to a count-rate of 3e-3 ct s^-1, thus suggesting it as the likely X-ray afterglow of GRB 210827A. The light curve can be described with a single power-law with a decay index alpha = 1.0 (+0.5, -0.4).
The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/00021461
This circular is an official product of the Swift-XRT team.

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Jochen Greiner, last update: 30-Aug-2021 [Disclaimer]