GRB 230815B

B. Pari (IITB), P K. Navaneeth (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 230815B which was also detected by GECAM-B (TrigNum 211).

The source was clearly detected in the 20-200 keV energy range. The light curve peaks at 2023-08-15 16:08:28.5 UTC. The measured peak count rate associated with the burst is 271.4 (+40.4, -41.4) counts/s above the background in the combined data of all quadrants, with a total of 2148 (+375, -381) counts. The local mean background count rate was 335.7 (+2.4, -3.0) counts/s. Using cumulative rates, we measure a T90 of 33.2 (+8.9, -11.6) s. 

The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2023-08-15 16:08:27.3 UTC. The measured peak count rate associated with the burst is 725.5 (+75.8, -66.6) counts/s above the background in the combined data of all quadrants, with a total of 9598 (+1234, -1292) counts. The local mean background count rate was 1481.2 (+5.7, -6.9) counts/s. We measure a T90 of 43.5 (+8.7, -12.6) s from the cumulative Veto light curve.

CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.

CZTI GRB detections are reported regularly on the payload site at: 
http://astrosat.iucaa.in/czti/?q=grb

Shaolin Xiong, Yanqiu Zhang, Yue Huang report on behalf of the GECAM team:

GECAM-B and GECAM-C were triggered in-flight by a long burst, GRB 230815B,
at 2023-08-15T16:07:29.150 UTC and 2023-08-15T16:07:29.350 UTC, respetively,
which was also observed by INTEGRAL/SPI-ACS and Konus-Wind.

According to the realtime alert data of GECAM-B and GECAM-C, this burst
mainly consists of a bright short pulse followed by a broad pulse with
a total duration (T90) of about ~30 sec (15-1000 keV).

Using the automatic on-ground localization pipeline with the realtime alert data, 
GECAM-B localized this burst to the following position (J2000): 
RA: 325.9 deg 
DEC: 13.2 deg
Err: 5.1 deg (1-sigma, statistical only)
The systematic error of this location is estimated to be several degrees.

The time-averaged spectrum of GECAM-B realtime data shows that it could be
adequately fit by a Band function with a fluence about 1.6E-5 erg/cm^2 in 20-1000 keV. 

We note that these results are based on realtime alert data and thus very preliminary. 
Refined analysis will be reported later.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B)
launched in Dec. 2020. As the third member of GECAM constellation, 
GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. 
GECAM mission is funded by the Chinese Academy of Sciences (CAS).

A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the HEND/Mars Odyssey team,

A. Ridnaia, D. Frederiks, D. Svinkin, A. Lysenko,
and T. Cline on behalf of the Konus-Wind 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,

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:

The long-duration GRB 230815B
(AstroSat CZTI detection: Pari et al., GCN 34447
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 ;
GECAM-B and GECAM-C detection: Xiong et al., GCN 34448
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 )
has been detected by Konus-Wind, INTEGRAL (SPI-ACS),
Swift (BAT), AstroSat (CZTI), GECAM-B, GECAM-C,
and Mars-Odyssey (HEND), so far, at about 58049 s UT (16:07:29).
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:
  307.334 (20h 29m 20s)  +4.190 ( +4d 11' 24")
 Corners:
  307.122 (20h 28m 29s)  +2.976 ( +2d 58' 33")
  307.518 (20h 30m 04s)  +5.411 ( +5d 24' 38")
  307.571 (20h 30m 17s)  +5.398 ( +5d 23' 53")
  307.175 (20h 28m 42s)  +2.963 ( +2d 57' 47")
 ---------------------------------------------
The error box area is 487 sq. arcmin, and its maximum
dimension is 2.5 deg (the minimum one is 3 arcmin).
The Sun distance was 154 deg.

This localization may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB230815_T58054/IPN

The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.