GRB 230817A

The Fermi GBM team reports the detection of a likely LONG GRB

At 12:02:56 UT on 17 Aug 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230817A (trigger 713966581.55559 / 230817502).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 325.9, Dec = 14.2 (J2000 degrees, equivalent to J2000 21h 43m, 14d 11'), with a statistical uncertainty of 3.3 degrees.

The angle from the Fermi LAT boresight is 93.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230817502/quicklook/glg_skymap_all_bn230817502.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/bn230817502/quicklook/glg_healpix_all_bn230817502.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230817502/quicklook/glg_lc_medres34_bn230817502.gif

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
713966581 at 12:02:56 on 17 Aug. 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) = 324.8+/-1.0 deg
Decl.(2000.0) = 17.0+/-0.9 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB230817502/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB230817502/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB230817502/json

                        

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-Tunka robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 230817A ( Fermi GBM team, GCN 34464
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 ) errorbox  5213 sec after notice time and 5246 sec after trigger time at 2023-08-17 13:30:22 UT, with upper limit up to  15.9 mag. Observations started at twilight.  The observations began at zenith distance = 59 deg. The sun  altitude  is -9.7 deg. 

The galactic latitude b = -29 deg., longitude l = 70 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2255349

We obtain a following upper limits.  

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

    5254 | 2023-08-17 13:30:22 |        MASTER-Tunka | (21h 48m 35.92s , +12d 10m 22.3s) |   C |    15 | 15.9 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

P. K. Navaneeth (IUCAA), B. Pari (IITB), 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 230817A which was also detected by Fermi (Fermi GBM Team, GCN Circ. 34464
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 ).

The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2023-08-17 12:03:31.50 UTC. The measured peak count rate associated with the burst is 470 (+48, -40) counts/s above the background in the combined data of all quadrants, with a total of 7321 (+420, -529) counts. The local mean background count rate was 418 (+2, -2) counts/s. Using cumulative rates, we measure a T90 of 48 (+6, -7) s. In the preliminary analysis, we find 537 Compton events associated with this event.

The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2023-08-17 12:03:31.31 UTC. The measured peak count rate associated with the burst is 361 (+80, -24) counts/s above the background in the combined data of all quadrants, with a total of 4084 (+1006, -1452) counts. The local mean background count rate was 1322 (+5, -4) counts/s. We measure a T90 of 33 (+9, -5) 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