Gamma-ray Burst 231018A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 18 Oct 23 12:30:40 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     719325015
GRB_RA:            4.350d {+00h 17m 24s} (J2000),
                   4.669d {+00h 18m 41s} (current),
                   3.684d {+00h 14m 44s} (1950)
GRB_DEC:         +53.100d {+53d 06' 00"} (J2000),
                 +53.232d {+53d 13' 55"} (current),
                 +52.822d {+52d 49' 20"} (1950)
GRB_ERROR:       16.73 [deg radius, statistical plus systematic]
GRB_INTEN:       140 [cnts/sec]
DATA_SIGNIF:     5.80 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        20235 TJD;   291 DOY;   23/10/18
GRB_TIME:        45010.66 SOD {12:30:10.66} UT
GRB_PHI:         144.00 [deg]
GRB_THETA:       130.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.71
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      93%  GRB
2nd_MOST_LIKELY:   2%  Cyg X-1
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 0,1,1, 0,0,
SUN_POSTN:       203.04d {+13h 32m 10s}   -9.63d {-09d 37' 44"}
SUN_DIST:        133.95 [deg]   Sun_angle= -10.8 [hr] (East of Sun)
MOON_POSTN:      247.03d {+16h 28m 08s}  -25.50d {-25d 30' 01"}
MOON_DIST:       126.55 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      117.76, -9.43 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       31.01, 45.69 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_lc_medres34_bn231018521.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 237.33,8.72 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 18 Oct 23 12:30:50 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     719325015
GRB_RA:          355.450d {+23h 41m 48s} (J2000),
                 355.743d {+23h 42m 58s} (current),
                 354.836d {+23h 39m 21s} (1950)
GRB_DEC:         +48.533d {+48d 31' 60"} (J2000),
                 +48.665d {+48d 39' 55"} (current),
                 +48.256d {+48d 15' 21"} (1950)
GRB_ERROR:       9.15 [deg radius, statistical plus systematic]
GRB_INTEN:       190 [cnts/sec]
DATA_SIGNIF:     10.50 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20235 TJD;   291 DOY;   23/10/18
GRB_TIME:        45010.66 SOD {12:30:10.66} UT
GRB_PHI:         151.00 [deg]
GRB_THETA:       135.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.77
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   2%  Cyg X-1
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 0,1,1, 0,0,
SUN_POSTN:       203.04d {+13h 32m 10s}   -9.63d {-09d 37' 44"}
SUN_DIST:        134.77 [deg]   Sun_angle= -10.2 [hr] (East of Sun)
MOON_POSTN:      247.04d {+16h 28m 09s}  -25.50d {-25d 30' 02"}
MOON_DIST:       120.96 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      111.21,-12.75 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       20.73, 45.11 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_lc_medres34_bn231018521.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 237.33,8.72 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 18 Oct 23 12:31:21 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      91
TRIGGER_NUM:     719325015
GRB_RA:          348.550d {+23h 14m 12s} (J2000),
                 348.824d {+23h 15m 18s} (current),
                 347.976d {+23h 11m 54s} (1950)
GRB_DEC:         +49.517d {+49d 31' 00"} (J2000),
                 +49.647d {+49d 38' 48"} (current),
                 +49.244d {+49d 14' 39"} (1950)
GRB_ERROR:       3.88 [deg radius, statistical plus systematic]
GRB_INTEN:       1657 [cnts/sec]
DATA_SIGNIF:     57.10 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        20235 TJD;   291 DOY;   23/10/18
GRB_TIME:        45010.66 SOD {12:30:10.66} UT
GRB_PHI:         149.00 [deg]
GRB_THETA:       140.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.78
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   2%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 0,1,1, 0,0,
SUN_POSTN:       203.04d {+13h 32m 10s}   -9.63d {-09d 37' 44"}
SUN_DIST:        130.95 [deg]   Sun_angle= -9.7 [hr] (East of Sun)
MOON_POSTN:      247.04d {+16h 28m 10s}  -25.50d {-25d 30' 06"}
MOON_DIST:       116.58 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      107.17,-10.36 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       16.15, 48.51 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_lc_medres34_bn231018521.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 237.33,8.72 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 18 Oct 23 12:30:59 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     719325015
GRB_RA:            2.380d {+00h 09m 31s} (J2000),
                   2.692d {+00h 10m 46s} (current),
                   1.727d {+00h 06m 54s} (1950)
GRB_DEC:         +51.690d {+51d 41' 24"} (J2000),
                 +51.822d {+51d 49' 20"} (current),
                 +51.412d {+51d 24' 42"} (1950)
GRB_ERROR:       4.00 [deg radius, statistical only]
DATA_SIGNIF:     12.40 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20235 TJD;   291 DOY;   23/10/18
GRB_TIME:        45010.66 SOD {12:30:10.66} UT
GRB_PHI:         146.00 [deg]
GRB_THETA:       131.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       203.04d {+13h 32m 10s}   -9.63d {-09d 37' 44"}
SUN_DIST:        134.66 [deg]   Sun_angle= -10.6 [hr] (East of Sun)
MOON_POSTN:      247.04d {+16h 28m 09s}  -25.50d {-25d 30' 03"}
MOON_DIST:       125.45 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      116.34,-10.64 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       28.46, 45.21 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_lc_medres34_bn231018521.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_719325015.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:     Wed 18 Oct 23 12:31:12 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      87
TRIGGER_NUM:     719325015
GRB_RA:            4.767d {+00h 19m 04s} (J2000),
                   5.086d {+00h 20m 21s} (current),
                   4.098d {+00h 16m 24s} (1950)
GRB_DEC:         +52.383d {+52d 22' 60"} (J2000),
                 +52.515d {+52d 30' 55"} (current),
                 +52.106d {+52d 06' 21"} (1950)
GRB_ERROR:       7.12 [deg radius, statistical plus systematic]
GRB_INTEN:       373 [cnts/sec]
DATA_SIGNIF:     15.80 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        20235 TJD;   291 DOY;   23/10/18
GRB_TIME:        45010.66 SOD {12:30:10.66} UT
GRB_PHI:         144.00 [deg]
GRB_THETA:       130.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      1.01
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      98%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 0,1,1, 0,0,
SUN_POSTN:       203.04d {+13h 32m 10s}   -9.63d {-09d 37' 44"}
SUN_DIST:        134.71 [deg]   Sun_angle= -10.8 [hr] (East of Sun)
MOON_POSTN:      247.04d {+16h 28m 09s}  -25.50d {-25d 30' 05"}
MOON_DIST:       126.86 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      117.92,-10.17 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       30.73, 44.96 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_lc_medres34_bn231018521.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 237.33,8.72 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 18 Oct 23 12:31:41 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      94
TRIGGER_NUM:     719325015
GRB_RA:          349.100d {+23h 16m 24s} (J2000),
                 349.376d {+23h 17m 30s} (current),
                 348.521d {+23h 14m 05s} (1950)
GRB_DEC:         +48.950d {+48d 57' 00"} (J2000),
                 +49.080d {+49d 04' 49"} (current),
                 +48.677d {+48d 40' 37"} (1950)
GRB_ERROR:       3.78 [deg radius, statistical plus systematic]
GRB_INTEN:       1979 [cnts/sec]
DATA_SIGNIF:     90.90 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20235 TJD;   291 DOY;   23/10/18
GRB_TIME:        45010.66 SOD {12:30:10.66} UT
GRB_PHI:         149.00 [deg]
GRB_THETA:       140.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.34
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, 0,1,1, 0,0,
SUN_POSTN:       203.04d {+13h 32m 10s}   -9.63d {-09d 37' 45"}
SUN_DIST:        131.60 [deg]   Sun_angle= -9.8 [hr] (East of Sun)
MOON_POSTN:      247.04d {+16h 28m 11s}  -25.50d {-25d 30' 08"}
MOON_DIST:       116.85 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      107.29,-11.01 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       16.09, 47.84 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_lc_medres34_bn231018521.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 237.33,8.72 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 18 Oct 23 12:39:30 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     719325015
GRB_RA:            3.050d {+00h 12m 12s} (J2000),
                   3.364d {+00h 13m 27s} (current),
                   2.393d {+00h 09m 34s} (1950)
GRB_DEC:         +50.700d {+50d 42' 00"} (J2000),
                 +50.832d {+50d 49' 56"} (current),
                 +50.422d {+50d 25' 19"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
GRB_DATE:        20235 TJD;   291 DOY;   23/10/18
GRB_TIME:        45010.66 SOD {12:30:10.66} UT
GRB_PHI:         146.00 [deg]
GRB_THETA:       131.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       203.05d {+13h 32m 11s}   -9.63d {-09d 37' 52"}
SUN_DIST:        135.73 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      247.12d {+16h 28m 29s}  -25.52d {-25d 31' 05"}
MOON_DIST:       125.88 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      116.61,-11.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       28.17, 44.15 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_lc_medres34_bn231018521.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_locplot_all_bn231018521.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(42.0<100sec) coincident with the CALET_GBM event (trignum=1381667434).

GCN Circular #34826
The Fermi GBM team reports the detection of a likely LONG GRB
At 12:30:10 UT on 18 Oct 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231018A (trigger 719325015.663762 / 231018521).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 3.0, Dec = 50.7 (J2000 degrees, equivalent to J2000 00h 12m, 50d 42'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 131.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_skymap_all_bn231018521.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/bn231018521/quicklook/glg_healpix_all_bn231018521.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231018521/quicklook/glg_lc_medres34_bn231018521.gif
GCN Circular #34827
T. Preis, B. Biltzinger, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger at 12:30:10 on 18 Oct. 2023 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
```
RA(2000.0) = 1.2+/-0.5 deg
Decl.(2000.0) = 51.5+/-0.2 deg
```
We estimate an additional systematic error of 1 deg.
Further details are available at: https://grb.mpe.mpg.de/grb/GRB231018521/
The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB231018521/healpix
The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB231018521/json
GCN Circular #34831
S. Lesage (UAH), E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 12:30:10 UT on 18 October 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231018A (trigger 719325015/231018521). The Fermi GBM Final Real-time Localization is reported in GCN 34826.
The angle from the Fermi LAT boresight is 131 degrees.
The GBM light curve consists of multiple multiple pulses with a duration (T90) of about 39.4 s (50-300 keV). The time-averaged spectrum from T0-4.6 to T0+92.7 s is best fit by a Band function with Epeak = 109 +/- 3 keV, alpha = -1.24 +/- 0.02, and beta = -2.56 +/- 0.05.
The event fluence (10-1000 keV) in this time interval is (1.192 +/- 0.009)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+57 s in the 10-1000 keV band is 75 +/- 1 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 #34839
R. Kumar, Y. Wagh, R. Sharma, A. Salgundi, V. Swain, D. Raman, T. Roychowdhury, V. Bhalerao (IIT Bombay), S. Barway, G. C. Anupama (IIA), K. Angail (IAO)
We observed the field of GRB 231018A detected by Fermi (Fermi GBM Team, GCN Circ. 34826; GCN Circ. 34831) with 0.7m GROWTH-India Telescope (GIT). GIT started observing the field at 2023-10-18 17:28:08.912 UT, i.e., 4.96 hours after the Fermi trigger. We obtained a series of 25 r' band images each of 300s exposure, covering 9.44 square degrees. This corresponds to 21.7% of the probability enclosed in the Fermi GBM Final Real-time Localisation (Fermi GBM Team, GCN Circ. 34826) and 20.17% of the probability enclosed in the BALROG localization (Preis et al., GCN Circ. 34827). Where available, PanSTARRS images (Chambers et al., 2016) were used as references for image subtraction. In other fields, we looked for new point sources absent in the GSC2.3 catalog. We did not find any suitable afterglow candidate, reaching a median limiting magnitude of 18.95 in the r' band. The detailed observing log is:
```
| Tile ID | RA (deg) | Dec (deg) | Lim Mag (AB) | Method |

| 54910 | 0.12 | 50.1 | 18.54 | Catalog     |
| 55565 | 1.25 | 51.5 | 18.93 | Subtraction |
| 55567 | 3.51 | 51.5 | 18.96 | Subtraction |
| 55883 | 0.13 | 51.5 | 18.82 | Catalog     |
| 54579 | 3.36 | 49.4 | 18.66 | Subtraction |
| 55238 | 0.12 | 50.1 | 18.25 | Catalog     |
| 54912 | 2.32 | 50.1 | 19.02 | Subtraction |
| 55241 | 2.35 | 50.8 | 19.01 | Subtraction |
| 55564 | 0.13 | 51.5 | 18.74 | Catalog     |
| 55242 | 3.46 | 50.8 | 18.96 | Subtraction |
| 55240 | 1.24 | 50.8 | 19.02 | Subtraction |
| 55243 | 4.57 | 50.8 | 18.98 | Subtraction |
| 54577 | 1.20 | 49.4 | 18.22 | Subtraction |
| 54914 | 4.51 | 50.1 | 17.48 | Subtraction |
| 54578 | 2.28 | 49.4 | 18.76 | Subtraction |
| 56201 | 2.45 | 52.9 | 15.70 | Subtraction |
| 55885 | 1.27 | 52.2 | 18.97 | Subtraction |
| 55887 | 3.56 | 52.2 | 19.03 | Subtraction |
| 55568 | 4.64 | 51.5 | 18.85 | Subtraction |
| 55886 | 2.42 | 52.2 | 18.97 | Subtraction |
| 54913 | 3.42 | 50.1 | 19.05 | Subtraction |
| 55563 | 0.13 | 50.8 | 18.64 | Catalog     |
| 54911 | 1.22 | 50.1 | 19.12 | Subtraction |
```
The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.
The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
GCN Circular #34845
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, report:
The bright, long-duration GRB 231018A (Fermi-GBM detection: The Fermi GBM team, GCN Circ. 34826; BALROG localization: Preis et al., GCN Circ. 34827) has been detected by Fermi (GBM trigger 719325015), CALET (GBM), GECAM-B, INTEGRAL (SPI-ACS), Konus-Wind, and Swift (BAT), so far, at about 45010 s UT (12:30:10). The burst was outside the coded field of view of the BAT.
We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:
```
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
    1.122 (00h 04m 29s) +47.410 (+47d 24' 36")
 Corners:
    6.422 (00h 25m 41s) +50.650 (+50d 39' 01")
  356.061 (23h 44m 15s) +43.842 (+43d 50' 31")
  357.865 (23h 51m 28s) +44.479 (+44d 28' 43")
   10.820 (00h 43m 17s) +51.565 (+51d 33' 55")
 ---------------------------------------------
```
The error box area is 6.6 sq. deg, and its maximum dimension is 12.54 deg (the minimum one is 38 arcmin). The Sun distance was 137 deg.
The IPN localization is consistent with, but reduces the area of, the final Fermi-GBM and the BALROG localizations.
This localization may be improved.
A triangulation map and HEALPix FITS files are posted at http://www.ioffe.ru/LEA/GRBs/GRB231018_T45043/IPN
The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
GCN Circular #34846
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, Yu. Temiraev, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The long, bright GRB 231018A (Fermi GBM detection: Lesage et al., GCN 34831= ; IPN triangulation: Svinkin et al., GCN 34845) triggered Konus-Wind (KW) at T0=3D45043.083 s UT (12:30:43.083).
The burst light curve shows a multi-peaked emission complex, which starts at ~T0-32 s, peaks at ~T0+28 s, and has a total duration of ~90 s. The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB231018_T45043/
As observed by Konus-Wind, the burst had a fluence of (1.17 =C2=B1 0.04)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 28.352 s, of (2.44 =C2=B1 0.10)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy = range).
The time-integrated spectrum (measured from T0 to T0+38.912 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha =3D -1.34 (-0.05,+0.05), the high energy photon index beta =3D -2.92 (-0.17,+0.12), the peak energy Ep =3D 114 (-4,+4) keV, chi2 =3D 90/96 dof.
The spectrum near the peak count rate (measured from T0+24.576 to T0+29.696= s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha =3D -1.19 (-0.05,+0.06), the high energy photon index beta =3D -3.15 (-0.37,+0.24), the peak energy Ep =3D 146 (-7,+8) keV, chi2 =3D 67/73 dof.
All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.
GCN Circular #34847
C.C. Cheung, M. Kerr, 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 231018A, which was also detected by = Fermi/GBM, Konus-Wind, CALET, GECAM-B, INTEGRAL/SPI-ACS, and Swift/BAT, res= ulting in an IPN localization (GCN 34826, 34845, 34846).
Using an adaptive window with a resolution of 32-ms, the burst onset is det= ermined to be 2023-10-18 12:30:07.824 with a duration of 87.6 s and a total= significance of about 159 sigma. The Glowbug light curve comprises multip= le peaks and is generally similar to the Konus-Wind light curve (GCN 34846)= .
Using a standard power-law function with an exponential high-energy cutoff = [3] to model the emission over this duration results in a photon index dN/d= E~E^x of x=3D1.0 and a cutoff energy ("Epeak") of 193 keV. The modeled 10-= 10000 keV fluence is 3.4e-05 erg/cm^2.
The analysis results presented here are preliminary and use a response func= tion that lacks a detailed characterization of the surrounding passive stru= cture of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost ga= mma-ray transient telescopes developed, built, and operated by the U.S. Nav= al 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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Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular #34849
P. S. Marrocchesi (U of Siena), A. Yoshida, T. Sakamoto, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), and the CALET collaboration:
The long GRB 231018A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 34826; BALROG localization: Preis et al., GCN Circ 34827; Fermi GBM Detection: Lesage et al., GCN Circ 34831; IPN triangulation: Svinkin et al., GCN Circ 34845; Konus-Wind detection: Frederiks et al., GCN Circ 34846; Glowbug gamma-ray detection: Cheung et al., GCN Circ 34847) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 12:30:52.87 UTC on 18 October 2023 (http://cgbm.calet.jp/cgbm_trigger/flight/1381667434/index.html). The burst signal was seen by only the SGM detector.
The burst light curve shows a multi-peaked structure that ends T+46 sec. Since CGBM was in the HV-on sequence, the whole episode was not observed by CGBM. The ground-processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1381667434/
The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University.
GCN Circular #34850
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 231018A (Fermi/GBM detection: GCN 34831; Konus/Wind d= etection: GCN 34846; Glowbug detection: GCN 34847; CALET/CGBM detection: GC= N 34849; INTEGRAL/SPI-ACS peak detection at 2023-10-18 ~12:31:08 UT) was ob= served by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; arXiv:230= 2.10048).
The detection was confirmed at the peak time 2023-10-18 12:31:08 UTC. The T= 90 duration measured by GRBAlpha is 32 s and the overall significance durin= g T90 reaches 91 sigma.
The light curve obtained by GRBAlpha is available here:=20 https://grbalpha.konkoly.hu/static/share/GRB231018A_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 #34865
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 231018A (Fermi/GBM detection: GCN 34831; Konus/Wind d= etection: GCN 34846; Glowbug detection: GCN 34847; CALET/CGBM detection: GC= N 34849; GRBAlpha detection: GCN 34850; INTEGRAL/SPI-ACS peak detection at = 2023-10-18 ~12:31:08 UT) was detected by the GRB detector on board of the V= ZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).
The data acquisition was performed by the GRB detector unit no. 1. The dete= ction was confirmed at the peak time 2023-10-18 12:31:10 UTC. The T90 durat= ion is 41 s and the significance during T90 reaches 25 sigma.
The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB231018A_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 #34873
Tyler Parsotan (NASA GSFC), Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), Samuele Ronchini (PSU), James DeLaunay (U Alabama), Jamie A. Kennea (PSU) report:
Swift/BAT did not localize GRB 231018A onboard (T0: 2023-10-18T12:30:10.66 UTC, Fermi trig 719325015-GCN#34826, CALET trigger 1381667434-GCN#34849)
The Fermi 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 90 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 BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 109.13 in a 16 s analysis time bin, starting at T0 - 12 s. The burst has a multi-peak structure with a duration of ~30 s in the BAT rates curve.
NITRATES results are consistent with a burst coming from outside the FOV, with DeltaLLHOut of -578.9.
See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/

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