Gamma-ray Burst 210626A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 26 Jun 21 08:16:40 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     646388180
GRB_RA:          222.667d {+14h 50m 40s} (J2000),
                 222.925d {+14h 51m 42s} (current),
                 222.067d {+14h 48m 16s} (1950)
GRB_DEC:         +12.100d {+12d 05' 60"} (J2000),
                 +12.012d {+12d 00' 44"} (current),
                 +12.306d {+12d 18' 21"} (1950)
GRB_ERROR:       17.13 [deg radius, statistical plus systematic]
GRB_INTEN:       79 [cnts/sec]
DATA_SIGNIF:     7.00 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19391 TJD;   177 DOY;   21/06/26
GRB_TIME:        29775.99 SOD {08:16:15.99} UT
GRB_PHI:         134.00 [deg]
GRB_THETA:        60.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.38
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,1,0, 0,0,
SUN_POSTN:        95.41d {+06h 21m 37s}  +23.34d {+23d 20' 34"}
SUN_DIST:        117.68 [deg]   Sun_angle= -8.5 [hr] (East of Sun)
MOON_POSTN:      299.33d {+19h 57m 19s}  -24.52d {-24d 31' 19"}
MOON_DIST:        82.95 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:       10.53, 58.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      216.12, 27.12 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210626345/quicklook/glg_lc_medres34_bn210626345.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 147.90,23.87 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 26 Jun 21 08:16:57 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     646388180
GRB_RA:          216.910d {+14h 27m 38s} (J2000),
                 217.189d {+14h 28m 45s} (current),
                 216.260d {+14h 25m 03s} (1950)
GRB_DEC:          -3.220d {-03d 13' 11"} (J2000),
                  -3.315d {-03d 18' 55"} (current),
                  -2.996d {-02d 59' 46"} (1950)
GRB_ERROR:       5.42 [deg radius, statistical only]
DATA_SIGNIF:     10.70 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        19391 TJD;   177 DOY;   21/06/26
GRB_TIME:        29775.99 SOD {08:16:15.99} UT
GRB_PHI:         127.00 [deg]
GRB_THETA:        75.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        95.41d {+06h 21m 37s}  +23.34d {+23d 20' 34"}
SUN_DIST:        120.38 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      299.33d {+19h 57m 20s}  -24.52d {-24d 31' 18"}
MOON_DIST:        81.48 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      344.08, 51.80 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      215.64, 10.78 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210626345/quicklook/glg_lc_medres34_bn210626345.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_646388180.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:     Sat 26 Jun 21 08:17:43 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      1
TRIGGER_NUM:     646388180
GRB_RA:          218.660d {+14h 34m 38s} (J2000),
                 218.933d {+14h 35m 44s} (current),
                 218.025d {+14h 32m 06s} (1950)
GRB_DEC:          +1.850d {+01d 51' 00"} (J2000),
                  +1.757d {+01d 45' 24"} (current),
                  +2.068d {+02d 04' 06"} (1950)
GRB_ERROR:       5.36 [deg radius, statistical only]
DATA_SIGNIF:     14.40 [sigma]
DATA_INTERVAL:   14.336 [sec]
GRB_DATE:        19391 TJD;   177 DOY;   21/06/26
GRB_TIME:        29775.99 SOD {08:16:15.99} UT
GRB_PHI:         129.00 [deg]
GRB_THETA:        70.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        95.41d {+06h 21m 38s}  +23.34d {+23d 20' 34"}
SUN_DIST:        119.65 [deg]   Sun_angle= -8.2 [hr] (East of Sun)
MOON_POSTN:      299.34d {+19h 57m 22s}  -24.52d {-24d 31' 14"}
MOON_DIST:        82.02 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      351.68, 54.64 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      215.66, 16.14 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210626345/quicklook/glg_lc_medres34_bn210626345.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_646388180.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
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:     Sat 26 Jun 21 08:18:08 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     646388180
GRB_RA:          216.860d {+14h 27m 26s} (J2000),
                 217.136d {+14h 28m 33s} (current),
                 216.219d {+14h 24m 53s} (1950)
GRB_DEC:          -0.280d {-00d 16' 47"} (J2000),
                  -0.376d {-00d 22' 31"} (current),
                  -0.056d {-00d 03' 22"} (1950)
GRB_ERROR:       3.98 [deg radius, statistical only]
DATA_SIGNIF:     15.50 [sigma]
DATA_INTERVAL:   20.480 [sec]
GRB_DATE:        19391 TJD;   177 DOY;   21/06/26
GRB_TIME:        29775.99 SOD {08:16:15.99} UT
GRB_PHI:         127.00 [deg]
GRB_THETA:        72.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        95.41d {+06h 21m 38s}  +23.34d {+23d 20' 34"}
SUN_DIST:        119.04 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      299.34d {+19h 57m 23s}  -24.52d {-24d 31' 12"}
MOON_DIST:        82.76 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      346.95, 54.17 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      214.62, 13.54 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210626345/quicklook/glg_lc_medres34_bn210626345.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_646388180.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
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:     Sat 26 Jun 21 08:25:36 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     646388180
GRB_RA:          215.970d {+14h 23m 53s} (J2000),
                 216.251d {+14h 25m 00s} (current),
                 215.318d {+14h 21m 16s} (1950)
GRB_DEC:          -4.240d {-04d 14' 23"} (J2000),
                  -4.337d {-04d 20' 11"} (current),
                  -4.014d {-04d 00' 49"} (1950)
GRB_ERROR:       3.87 [deg radius, statistical only]
GRB_DATE:        19391 TJD;   177 DOY;   21/06/26
GRB_TIME:        29775.99 SOD {08:16:15.99} UT
GRB_PHI:         126.00 [deg]
GRB_THETA:        76.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        95.41d {+06h 21m 39s}  +23.34d {+23d 20' 33"}
SUN_DIST:        119.95 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      299.43d {+19h 57m 42s}  -24.51d {-24d 30' 36"}
MOON_DIST:        82.00 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      341.89, 51.50 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      215.08,  9.51 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210626345/quicklook/glg_lc_medres34_bn210626345.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210626345/quicklook/glg_locplot_all_bn210626345.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:        This is likely a Long GRB.

GCN Circular #30323
The Fermi GBM team reports the detection of a likely LONG GRB
At 08:16:15 UT on 26 Jun 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210626A (trigger 646388180.992174 / 210626345).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 216.0, Dec = -4.2 (J2000 degrees, equivalent to J2000 14h 24m, -4d 12'), with a statistical uncertainty of 3.9 degrees.
The angle from the Fermi LAT boresight is 76.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210626345/quicklook/glg_skymap_all_bn210626345.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/bn210626345/quicklook/glg_healpix_all_bn210626345.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210626345/quicklook/glg_lc_medres34_bn210626345.gif
GCN Circular #30325
Aaron Tohuvavohu (U Toronto), James DeLaunay (PSU), Jamie A. Kennea (PSU), Gayathri Raman (PSU) report:
Swift/BAT did not trigger on GRB 210626A (T0: 2021-06-26 08:16:15.9 UTC, Fermi/GBM GCN 30323).
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 greater than 20 seconds. The burst occurred during a Swift slew. Using the normal BAT imaging technique, we find the location for the GRB with an SNR of 7.6.
The BAT position is RA, Dec = 221.6199, -1.1512 deg which is
```
   RA(J2000)  = 14h 46m 28.78s
   Dec(J2000) =  -1d 09′ 4.3″
```
with an estimated uncertainty of 5 arcmin.
This position is consistent with the Ferm/GBM localization (GCN 30323).
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 #30326
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Swift/BAT-GUANO GRB 210626A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021453
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 #30327
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-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210626A ( Fermi GBM team, GCN 30323) errorbox 45371 sec after notice time and 45494 sec after trigger time at 2021-06-26 20:54:30 UT, with upper limit up to 18.5 mag. Observations started at twilight. The observations began at zenith distance = 33 deg. The sun altitude is -10.6 deg.
The galactic latitude b = 51 deg., longitude l = 343 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1645256
We obtain a following upper limits.

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

   45524 | 2021-06-26 20:54:30 |          MASTER-IAC | (14h 31m 35.31s , -04d 23m 21.9s) |   C |    60 | 17.3 |        
   45524 | 2021-06-26 20:54:30 |          MASTER-IAC | (14h 23m 30.29s , -04d 17m 54.2s) |   C |    60 | 16.8 |        
   45604 | 2021-06-26 20:55:49 |          MASTER-IAC | (14h 29m 54.51s , -02d 30m 25.6s) |   C |    60 | 17.3 |        
   45604 | 2021-06-26 20:55:49 |          MASTER-IAC | (14h 21m 50.29s , -02d 24m 57.4s) |   C |    60 | 17.1 |        
   45684 | 2021-06-26 20:57:09 |          MASTER-IAC | (14h 19m 03.53s , -06d 19m 19.7s) |   C |    60 | 17.5 |        
   45684 | 2021-06-26 20:57:09 |          MASTER-IAC | (14h 10m 57.01s , -06d 13m 53.3s) |   C |    60 | 17.3 |        
   45763 | 2021-06-26 20:58:29 |          MASTER-IAC | (14h 16m 27.27s , -04d 25m 15.0s) |   C |    60 | 17.6 |        
   45763 | 2021-06-26 20:58:29 |          MASTER-IAC | (14h 08m 22.21s , -04d 19m 48.0s) |   C |    60 | 17.5 |        
   45843 | 2021-06-26 20:59:49 |          MASTER-IAC | (14h 34m 23.49s , -06d 17m 53.6s) |   C |    60 | 17.7 |        
   45843 | 2021-06-26 20:59:49 |          MASTER-IAC | (14h 26m 16.98s , -06d 12m 26.1s) |   C |    60 | 17.5 |        
   45924 | 2021-06-26 21:01:09 |          MASTER-IAC | (14h 29m 01.44s , -00d 37m 28.8s) |   C |    60 | 18.1 |        
   45924 | 2021-06-26 21:01:09 |          MASTER-IAC | (14h 20m 57.52s , -00d 32m 00.3s) |   C |    60 | 17.9 |        
   46004 | 2021-06-26 21:02:30 |          MASTER-IAC | (14h 14m 40.67s , -02d 29m 37.6s) |   C |    60 | 18.1 |        
   46004 | 2021-06-26 21:02:30 |          MASTER-IAC | (14h 06m 36.35s , -02d 24m 10.3s) |   C |    60 | 17.5 |        
   46084 | 2021-06-26 21:03:50 |          MASTER-IAC | (14h 22m 43.90s , -08d 12m 29.4s) |   C |    60 | 17.9 |        
   46084 | 2021-06-26 21:03:50 |          MASTER-IAC | (14h 14m 35.23s , -08d 07m 03.1s) |   C |    60 | 17.7 |        
   46164 | 2021-06-26 21:05:10 |          MASTER-IAC | (14h 13m 45.82s , -00d 35m 27.8s) |   C |    60 | 18.5 |

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

GCN Circular #30329
M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (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-GUANO-detected burst GRB 210626A (Aaron Tohuvavohu et al. GCN Circ. 30325), collecting 1.4 ks of Photon Counting (PC) mode data between T0+29.7 ks and T0+31.1 ks.
An uncatalogued X-ray source is detected and is above the 2SXPS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 1180 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 221.52429, -1.15625 which is equivalent to:
```
RA (J2000): 14h 46m 05.83s
Dec(J2000): -01d 09' 22.5"
```
with an uncertainty of 5.7 arcsec (radius, 90% confidence). This position is 5.7 arcmin from the Swift/BAT-GUANO position. We cannot determine at the present time whether the source is fading.
The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021453/Source1.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021453.
This circular is an official product of the Swift-XRT team.
GCN Circular #30336
H. Kumar(IITB), J. Stanzin (IAO), V. Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the GIT team:
We observed GRB 210626A detected by Fermi GBM (GCN #30323) with 0.7 m GROWTH-India Telescope (GIT). The GRB was also detected by Swift/BAT-GUANO (GCN #30325) and later on, Swift-XRT detected X-ray afterglow candidate (GCN #30329). We obtained exposures in the r' filter. We did not detect any new source in our stacked image within the 5.7 arcsec circle, around RA: 14:46:05.83, Dec: -01:09:22.5 (GCN #30329). Further, we did not find any new source within the 5 arcmin region identified by BAT localisation (GCN #30325). The obtained upper limit follow as:
-------------------------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Exposure (sec) | Filter | Lim_mag (5-sigma) |
-------------------------------------------------------------------------
2459392.2353 | 9.37 | 2 x 300 (stacked) | r' | > 20.5 |
-------------------------------------------------------------------------
The magnitudes are calibrated against PanSTARRS (Flewelling et al., 2018) and not corrected for Galactic extinction.
The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA).
GCN Circular #30337
Martin Jelinek, Jan Strobl, Rene Hudec and Cyril Polasek (ASU CAS Ondrejov, CZ), report:
We observed the Swift-improved localization (Tohuvavohu et al. GCN 30325, Perri et al. GCN 30329) of the GBM-detected GRB 210626A (Fermi GBM Team, GCN 30323) with the 50 cm robotic telescope (D50) of Ondrejov observatory in Czech Republic. We obtained a set of 120 s Sloan-i' exposures starting at 21:10 UT, i.e. 0.5386 d after the initial trigger.
The magnitude limit of our 34 x 120 s image with a mean time T-T0 0.5626 d post burst is i' > 21.2 (AB). The XRT (Perri et al. GCN 30329) error box does not appear completely clean in the image, there is a noise fluctuation or possibly a candidate at the level of i' = 21.3 +/- 0.4. While we mention this, we also note that this is in a light halo of a nearby bright star, so artefacts of this kind may not be excluded.
GCN Circular #30339
Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, M. D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), A. Fernandez and I. Hermelo (CAHA) on behalf of a larger collaboration, report:
Following the detection of GRB 210626A by both Swift (Tohuvavohu et al. GCNC 30325) and Fermi (Fermi/GBM team GCNC 30323), we triggered the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain), gathering images starting on June 27, 20:37 UT (i.e. 1.5 day post trigger). On the co-added image (i-band, 3x180s), no optical transient down to 22.4 mag is detected at the X-ray afterglow candidate position reported by Swift/XRT (Evans et al. GCNC 30326, Perri et al. GCNC 30329).
We thank the staff at Calar Alto observatory for their excellent support.
GCN Circular #30340
A. von Kienlin (MPE) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 08:16:15.99 UT on 26 June 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210626A (trigger 646388180 / 210626345), which was also detected by the Swift/BAT-GUANO (Tohuvavohu et al. 2021, GCN 30325). The Fermi GBM Final Real-time Localization is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 73 degrees.
The GBM light curve shows a singel pulse with a duration (T90) of about 34 s (50-300 keV). The time-averaged spectrum from T0-5.632 s to T0+29.184 s is best fit by a Band function with Epeak= 86 +/- 18 keV, alpha = -1.21 +/- 0.16 and beta = -2.25 +/- 0.24
The event fluence (10-1000 keV) in this time interval is (5.1 +/- 0.4)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+5.696 s in the 10-1000 keV band is 3.40 +/- 0.24 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 #30341
Antonino D'A� (INAF-IASFPA) & Aaron Tohuvavohu (Uni. Toronto) report on behalf of the Swift-XRT team:
Swift-XRT has performed further follow-up observations of the Fermi/GBM (von Kienlin GCN 30340) and Swift/BAT-GUANO detected burst GRB 210626A (Tohuvavohu et al., GCN Circ. 30325), collecting 7.9 ks of Photon Counting (PC) mode data between T0+29.7 ks and T0+143 ks.
The X-ray source detected in the first 1.4 ks of data as possible GRB afterglow candidate (Perri et al. GCN 30329) has faded more than 3 sigma in the latest observation, and it is thus confirmed as the X-ray afterglow of the burst.
The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/xrt_curves/00021453/.
This circular is an official product of the Swift-XRT team.

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Jochen Greiner, last update: 28-Jun-2021 [Disclaimer]