Gamma-ray Burst 230826A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Aug 23 19:33:03 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1187463,   Seg_Num: 0
GRB_RA:           83.012d {+05h 32m 03s} (J2000),
                  83.610d {+05h 34m 26s} (current),
                  81.748d {+05h 27m 00s} (1950)
GRB_DEC:         +66.125d {+66d 07' 30"} (J2000),
                 +66.140d {+66d 08' 25"} (current),
                 +66.088d {+66d 05' 17"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4356 [cnts]    Image_Peak=470 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       16509 [cnts]
BKG_TIME:        70352.10 SOD {19:32:32.10} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20182 TJD;   238 DOY;   23/08/26
GRB_TIME:        70367.07 SOD {19:32:47.07} UT
GRB_PHI:          46.25 [deg]
GRB_THETA:        15.66 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     45.90 [sigma]
IMAGE_SIGNIF:    15.04 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +4  +0  +0 -28  +0 
SUN_POSTN:       155.24d {+10h 20m 58s}  +10.29d {+10d 17' 21"}
SUN_DIST:         73.22 [deg]   Sun_angle= 4.8 [hr] (West of Sun)
MOON_POSTN:      274.30d {+18h 17m 11s}  -28.16d {-28d 09' 52"}
MOON_DIST:       141.45 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      146.41, 17.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       86.15, 42.78 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 218.84,1.52 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(3.0<100sec) coincident with the FERMI_GBM event (trignum=714771169).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 26 Aug 23 19:33:13 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     714771169
GRB_RA:          297.500d {+19h 50m 00s} (J2000),
                 297.306d {+19h 49m 13s} (current),
                 297.900d {+19h 51m 36s} (1950)
GRB_DEC:         +76.733d {+76d 43' 60"} (J2000),
                 +76.794d {+76d 47' 38"} (current),
                 +76.604d {+76d 36' 14"} (1950)
GRB_ERROR:       16.98 [deg radius, statistical plus systematic]
GRB_INTEN:       122 [cnts/sec]
DATA_SIGNIF:     4.50 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20182 TJD;   238 DOY;   23/08/26
GRB_TIME:        70364.53 SOD {19:32:44.53} UT
GRB_PHI:          40.00 [deg]
GRB_THETA:       150.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.86
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      94%  GRB
2nd_MOST_LIKELY:   3%  Cyg X-1
DETECTORS:       0,0,1, 0,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       155.24d {+10h 20m 58s}  +10.29d {+10d 17' 21"}
SUN_DIST:         90.19 [deg]   Sun_angle= -9.5 [hr] (East of Sun)
MOON_POSTN:      274.30d {+18h 17m 12s}  -28.16d {-28d 09' 52"}
MOON_DIST:       105.91 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      108.96, 23.09 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       62.13, 76.90 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230826814/quicklook/glg_lc_medres34_bn230826814.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 177.65,5.62 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the SWIFT_BAT event (trignum=1187463).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 26 Aug 23 19:33:23 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     714771169
GRB_RA:           85.017d {+05h 40m 04s} (J2000),
                  85.605d {+05h 42m 25s} (current),
                  83.774d {+05h 35m 06s} (1950)
GRB_DEC:         +65.300d {+65d 17' 60"} (J2000),
                 +65.311d {+65d 18' 39"} (current),
                 +65.273d {+65d 16' 22"} (1950)
GRB_ERROR:       9.35 [deg radius, statistical plus systematic]
GRB_INTEN:       155 [cnts/sec]
DATA_SIGNIF:     8.90 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20182 TJD;   238 DOY;   23/08/26
GRB_TIME:        70364.53 SOD {19:32:44.53} UT
GRB_PHI:          55.00 [deg]
GRB_THETA:       115.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.12
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,1, 0,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       155.24d {+10h 20m 58s}  +10.29d {+10d 17' 21"}
SUN_DIST:         72.22 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      274.30d {+18h 17m 12s}  -28.16d {-28d 09' 52"}
MOON_DIST:       142.45 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      147.58, 17.48 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       87.20, 41.91 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230826814/quicklook/glg_lc_medres34_bn230826814.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 177.65,5.62 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the SWIFT_BAT event (trignum=1187463).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 26 Aug 23 19:33:32 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     714771169
GRB_RA:           88.110d {+05h 52m 26s} (J2000),
                  88.722d {+05h 54m 53s} (current),
                  86.816d {+05h 47m 16s} (1950)
GRB_DEC:         +66.940d {+66d 56' 24"} (J2000),
                 +66.944d {+66d 56' 37"} (current),
                 +66.928d {+66d 55' 40"} (1950)
GRB_ERROR:       4.07 [deg radius, statistical only]
DATA_SIGNIF:     18.90 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20182 TJD;   238 DOY;   23/08/26
GRB_TIME:        70364.53 SOD {19:32:44.53} UT
GRB_PHI:          53.00 [deg]
GRB_THETA:       116.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       155.24d {+10h 20m 58s}  +10.29d {+10d 17' 20"}
SUN_DIST:         71.47 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:      274.30d {+18h 17m 12s}  -28.16d {-28d 09' 52"}
MOON_DIST:       141.07 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      146.60, 19.32 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       88.98, 43.51 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230826814/quicklook/glg_lc_medres34_bn230826814.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_714771169.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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the SWIFT_BAT event (trignum=1187463).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 26 Aug 23 19:42:10 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     714771169
GRB_RA:           82.830d {+05h 31m 19s} (J2000),
                  83.443d {+05h 33m 46s} (current),
                  81.537d {+05h 26m 09s} (1950)
GRB_DEC:         +67.100d {+67d 05' 60"} (J2000),
                 +67.116d {+67d 06' 57"} (current),
                 +67.062d {+67d 03' 44"} (1950)
GRB_ERROR:       2.02 [deg radius, statistical only]
GRB_DATE:        20182 TJD;   238 DOY;   23/08/26
GRB_TIME:        70364.53 SOD {19:32:44.53} UT
GRB_PHI:          55.00 [deg]
GRB_THETA:       117.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       155.25d {+10h 20m 59s}  +10.29d {+10d 17' 13"}
SUN_DIST:         73.50 [deg]   Sun_angle= 4.8 [hr] (West of Sun)
MOON_POSTN:      274.40d {+18h 17m 36s}  -28.16d {-28d 09' 52"}
MOON_DIST:       140.48 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      145.48, 17.54 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       86.14, 43.76 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230826814/quicklook/glg_lc_medres34_bn230826814.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230826814/quicklook/glg_locplot_all_bn230826814.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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the SWIFT_BAT event (trignum=1187463).

GCN Circular 34563
V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin (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 (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)
MASTER-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB230826.81 (trigger No 1187463,05h 32m 02.88s , +66d 07m 30.0s, R=0.05) errorbox 23 sec after notice time and 45 sec after trigger time at 2023-08-26 19:33:32 UT, with upper limit up to 17.7 mag. The observations began at zenith distance = 66 deg. The sun altitude is -28.0 deg.
The galactic latitude b = 18 deg., longitude l = 147 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2260933
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

      50 |      MASTER-Tavrida |   C |    10 | 17.0 |        
      67 |      MASTER-Tavrida |   C |    10 | 16.9 |        
      89 |      MASTER-Tavrida |   C |    20 | 17.3 |        
     117 |      MASTER-Tavrida |   C |    20 | 17.3 |        
     149 |      MASTER-Tavrida |   C |    30 | 17.6 |        
     186 |      MASTER-Tavrida |   C |    30 | 17.5 |        
     229 |      MASTER-Tavrida |   C |    40 | 17.7 |        
     282 |      MASTER-Tavrida |   C |    50 | 17.7 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #34564
The Fermi GBM team reports the detection of a likely LONG GRB
At 19:32:44 UT on 26 Aug 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230826A (trigger 714771169.528076 / 230826814).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 82.8, Dec = 67.1 (J2000 degrees, equivalent to J2000 05h 31m, 67d 05'), with a statistical uncertainty of 2.0 degrees.
The angle from the Fermi LAT boresight is 117.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230826814/quicklook/glg_skymap_all_bn230826814.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230826814/quicklook/glg_healpix_all_bn230826814.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230826814/quicklook/glg_lc_medres34_bn230826814.gif
GCN Circular #34565
R. A. J. Eyles-Ferris (U Leicester), S. Dichiara (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU), D. M. Palmer (LANL), T. M. Parsotan (GSFC/UMBC/CRESSTII), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
At 19:32:47 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230826A (trigger=1187463). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 83.012, +66.125 which is
```
  RA(J2000) = 05h 32m 03s
  Dec(J2000) = +66d 07' 30"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Preliminary quicklook data suggests that the light curve is doubly peaked with a T90 of ~50 sec and background subtracted peak count rate of ~4000 counts/sec at T0+3 sec.
The XRT began observing the field at 19:34:03.7 UT, 76.7 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 83.05920, 66.12506 which is equivalent to:
```
   RA(J2000)  =  5h 32d 14.2s,
   Dec(J2000) = 66h 07d 30.2s
```
with an uncertainty of 10.0 arcseconds (radius, 90% containment). This location is 69 arcseconds from the BAT onboard position, within the BAT error circle.
Due to a telemetry gap, no further information is available at this time. However a simultaneous Fermi trigger (GCN #34564) confirms the GRB.
Burst Advocate for this burst is R. A. J. Eyles-Ferris (raje1 AT leicester.ac.uk). 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Aug 23 21:45:56 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1187463,   Seg_Num: 0
GRB_RA:           83.012d {+05h 32m 03s} (J2000),
                  83.610d {+05h 34m 26s} (current),
                  81.748d {+05h 27m 00s} (1950)
GRB_DEC:         +66.125d {+66d 07' 30"} (J2000),
                 +66.140d {+66d 08' 25"} (current),
                 +66.088d {+66d 05' 17"} (1950)
GRB_DATE:        20182 TJD;   238 DOY;   23/08/26
GRB_TIME:        70367.07 SOD {19:32:47.07} UT
TRIGGER_INDEX:   146
GRB_PHI:          46.25 [deg]
GRB_THETA:        15.66 [deg]
DELTA_TIME:      1799.00 [sec]
TRIGGER_DUR:      [sec],  copy from BAT_POS unavailable
SOLN_STATUS:     0x0
RATE_SIGNIF:     45.90 [sigma]
IMAGE_SIGNIF:    15.04 [sigma]
LC_URL:          sw01187463000msb.lc
SUN_POSTN:       155.33d {+10h 21m 18s}  +10.26d {+10d 15' 25"}
SUN_DIST:         73.28 [deg]   Sun_angle= 4.8 [hr] (West of Sun)
MOON_POSTN:      275.78d {+18h 23m 08s}  -28.16d {-28d 09' 27"}
MOON_DIST:       141.28 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      146.41, 17.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       86.15, 42.78 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        The 3rd packet (of 3) was missing in the lightcurve data stream.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Aug 23 21:45:41 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1187463,   Seg_Num: 0
GRB_RA:           83.0592d {+05h 32m 14.20s} (J2000),
                  83.6578d {+05h 34m 37.87s} (current),
                  81.7957d {+05h 27m 10.97s} (1950)
GRB_DEC:         +66.1250d {+66d 07' 30.0"} (J2000),
                 +66.1402d {+66d 08' 24.8"} (current),
                 +66.0883d {+66d 05' 17.9"} (1950)
GRB_ERROR:       5.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.52e-09 [erg/cm2/sec]
GRB_SIGNIF:      8.18 [sigma]
IMG_START_DATE:  20182 TJD;   238 DOY;   23/08/26
IMG_START_TIME:  70441.20 SOD {19:34:01.20} UT,   74.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.66 237.19 261.65 243.18
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       155.33d {+10h 21m 18s}  +10.26d {+10d 15' 25"}
SUN_DIST:         73.26 [deg]   Sun_angle= 4.8 [hr] (West of Sun)
MOON_POSTN:      275.78d {+18h 23m 08s}  -28.16d {-28d 09' 27"}
MOON_DIST:       141.28 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      146.42, 17.15 [deg] galactic lon,lat of the burst
ECL_COORDS:       86.18, 42.78 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.15 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Aug 23 21:49:07 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1187463,   Seg_Num: 0
GRB_RA:           83.0592d {+05h 32m 14.2s} (J2000),
                  83.6578d {+05h 34m 37.8s} (current),
                  81.7957d {+05h 27m 10.9s} (1950)
GRB_DEC:         +66.1250d {+66d 07' 30.0"} (J2000),
                 +66.1402d {+66d 08' 24.8"} (current),
                 +66.0883d {+66d 05' 17.9"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       67 [cnts]
IMG_START_DATE:  20182 TJD;   238 DOY;   23/08/26
IMG_START_TIME:  70441.20 SOD {19:34:01.20} UT,   74.1 [sec] since BAT Trigger Time
CENTROID_X:      288.03,  raw= 288  [pixels]
CENTROID_Y:      301.12,  raw= 301  [pixels]
ROLL:            102.20 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   7.12
GRB_POS_XRT_Z:   -45.64
IMAGE_URL:       sw01187463000msxps_rw.img
SUN_POSTN:       155.33d {+10h 21m 19s}  +10.26d {+10d 15' 22"}
SUN_DIST:         73.26 [deg]   Sun_angle= 4.8 [hr] (West of Sun)
MOON_POSTN:      275.82d {+18h 23m 17s}  -28.16d {-28d 09' 26"}
MOON_DIST:       141.28 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      146.42, 17.15 [deg] galactic lon,lat of the burst
ECL_COORDS:       86.18, 42.78 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN Circular #34567
N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI), S. Belkin (IKI) on behalf of GRB-IKI-FuN report.
We observed the field of GRB 230826A detected by Fermi GBM (Fermi GBM Team, GCN 34564) and Swift (Eyles-Ferris et al, 34565) with AZT-33IK telescope of Sayan observatory (Mondy). Observations started on 2023-08-26 220:06:00 (UT) (i.e. ~33 min since trigger). We obtained series of images in R-filter. We do not detect evident candidate within XRT error circle (Swift-XRT Position: +05h 32m 14.20s +66d 07' 30.0" 5.3 arcsec, radius) in a stacked image. Preliminary photometry is following:
```
Date       UT start   t-T0    Filter Exp.    OT   Err.  UL(3sigma)
                       (mid, days)    (s)

2023-08-26 20:06:00   0.038345  R     44*60  n/d  n/d   22.0
```
We note the presence of the object USNO-B1.0 1561-0095652 at 8.8 arces from the Swift-XRT Position. Measured brightness of the object is R = 18.1 +/- 0.01 what is brighter than USNO-B1.0 R2=18.22 magnitude.
All photometry is based on nearby USNO-B1.0 stars, R2 magnitudes
GCN Circular #34568
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), D.N. Burrows (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 8.3 ks of XRT data for GRB 230826A, from 65 s to 29.5 ks after the BAT trigger. The data comprise 56 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 83.0642, +66.1244 which is equivalent to:
```
RA (J2000): 05 32 15.41
Dec(J2000): +66 07 27.9
```
with an uncertainty of 3.5 arcsec (radius, 90% confidence).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.44 (+0.25, -0.24). At T+213 s the decay flattens to an alpha of -0.06 (+0.24, -0.26) before breaking again at T+1264 s to a final decay with index alpha=1.39 (+0.22, -0.14).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.93 (+0.32, -0.29). The best-fitting absorption column is 4.7 (+1.0, -0.9) x 10^21 cm^-2, in excess of the Galactic value of 1.5 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.15 (+0.22, -0.21) and a best-fitting absorption column of 4.4 (+1.1, -1.0) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (6.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     4.4 (+1.1, -1.0) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 4.8 sigma
Photon index:	     2.15 (+0.22, -0.21)
```
If the light curve continues to decay with a power-law decay index of 1.39, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x 10^-13 (1.8 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/01187463.
This circular is an official product of the Swift-XRT team.
GCN Circular #34569
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1910 s of XRT Photon Counting mode data and 5 UVOT images for GRB 230826A, 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 = 83.06410, +66.12384 which is equivalent to:
```
RA (J2000): 05h 32m 15.38s
Dec (J2000): +66d 07' 25.8"
```
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 #34571
O.J. Roberts (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 19:32:44.53 UT on 26 August 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230826A (trigger 714771169/230826814), which was also detected by Swift-BAT (R.A.J. Eyles-Ferris et al. 2023, GCN 34565). The Fermi GBM Final Real-time Localization (GCN 34564) is consistent with the Swift-BAT position.
The angle from the Fermi LAT boresight is 116 degrees.
The GBM light curve consists of a single FRED peak with a duration (T90) of about 37 s (50-300 keV). The time-averaged spectrum from T0-4.1 to T0+46.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.75 +/- 0.12 and the cutoff energy, parameterized as Epeak, is 87 +/- 5 keV.
The event fluence (10-1000 keV) in this time interval is (6.012 +/- 0.246)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.9 s in the 10-1000 keV band is 4.9 +/- 0.4 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 #34572
M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner= (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (= Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Kolar, J.-P. = Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. o= f Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, = M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U.= of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. = Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.= ), G. Dalya (Eotvos U.), yyT. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Fr= iss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya= U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Ob= servatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (U= niv of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso= , M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. = Michigan) -- the GRBAlpha collaboration.
The long-duration GRB 230826A (Fermi/GBM detection: GCN 34564; Swift/BAT de= tection: GCN 34565) was observed by the GRBAlpha 1U CubeSat (Pal et al. 202= 3; arXiv:2302.10048).
The detection was confirmed at the peak time 2023-08-26 19:32:45 UTC. The T= 90 duration measured by GRBAlpha is 18 s and the overall significance durin= g T90 reaches 8.3 sigma.
The light curve obtained by GRBAlpha is available here: https://grbalpha.ko= nkoly.hu/static/share/GRB230826A_GCN.pdf
All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/he= a/GRBAlpha/=20 GRBAlpha, launched on 2021 March 22, is a demonstration mission for a futur= e CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GR= BAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM ar= ray, covering the energy range from ~50 keV to ~1000 keV. To increase the d= uty cycle and the downlink rate, the upgrade of the on-board data acquisiti= on software stack is in progress. The ground segment is also supported by t= he radio amateur community and it takes advantage of the SatNOGS network fo= r increased data downlink volume.
GCN Circular #34582
A. A. Breeveld (UCL-MSSL) and R. A. J. Eyles-Ferris (U Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230826A 114 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 34565). No optical afterglow consistent with the enhanced XRT position (Osborne et al., GCN Circ. 34569) 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           114          263        147           >20.0
white              606         5452        312           >20.4
v                  657         1105         58           >17.8
b                  582         5339        255           >19.6
u                  327         5134        481           >19.5
uvw1               707         1320         71           >18.4
uvm2               682         1303         78           >18.4
uvw2               632         1254         78           >18.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.243 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #34586
M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werne= r (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Obs= ervatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. = Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rez= enov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Researc= h Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (= Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (= Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. = Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K= . Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gro= mes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration= .
The long duration GRB 230826A (Fermi/GBM detection: GCN 34564; Swift/BAT de= tection: GCN 34565; GRBAlpha detection: GCN 34572) was detected by the GRB = detectors on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/= ).
The data acquisition was performed by the GRB detector units no. 0 and no. = 1. The detection was confirmed at the peak time 2023-08-26 19:32:48 UTC. Th= e T90 duration is 17 s (18 s) and the significance during T90 reaches 11 si= gma (17 sigma) for detector unit no. 0 (no. 1).
The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB230826A_GCN_VZLUSAT2.pdf
All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/h= ea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future Cub= eSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLU= SAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range= from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.
GCN Circular #34592
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT team):
Using the data set from T-61 to T+1091 sec from the recent telemetry downlink, we report further analysis of BAT GRB 230826A (trigger #1187463) (Eyles-Ferris, et al., GCN Circ. 34565). The BAT ground-calculated position is RA, Dec = 83.048, 66.129 deg which is
```
RA(J2000) = 05h 32m 11.5s
Dec(J2000) = +66d 07' 43.9"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 87%.
The mask weighted light curve shows two main emission episodes where the first has enhanced structure. T90 (15-350 keV) is 41.07 +- 2.36 sec (estimated error including systematics).
The time-averaged spectrum from T-4.26 to T+56.79 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.20 +- 0.22, and Epeak of 122.3 +- 70.2 keV (chi squared 44.78 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.6 +- 0.1 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+2.44 sec in the 15-150 keV band is 3.0 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.55 +- 0.05 (chi squared 52.29 for 57 d.o.f.). 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/1187463/BA/
GCN Circular #34602
M. Kerr, C.C. Cheung, J. E. Grove, R. Woolf (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of GRB 230826A, which was also detected by Fermi/GBM, Swift/BAT, GRBAlpha, and VZLUSAT-2 (GCN 34564, 34565, 34572, 34586).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2023-08-26 19:32:44.336 with a duration of 12.3 s and a total significance of about 29.9 sigma. The light curve comprises a single peak.
Using a standard power-law function with an exponential high-energy cutoff [3] to model the emission over this duration results in a poorly constrained power-law index and a cutoff energy ("Epeak") of 138 keV. The modeled 10-10000 keV fluence is 1.5e-06 erg/cm^2.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program=E2=80=99s STP-H9 to the ISS. The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV.
```
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
```
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