Gamma-ray Burst 220910A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #32540
A. Ursi, E. Menegoni (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, Y. Evangelista, L. Foffano, G. Piano (INAF/IAPS), A. Bulgarelli, A. Di Piano, V. Fioretti, G. Panebianco, N. Parmiggiani (INAF/OAS-Bologna), F. Lucarelli, C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), M. Romani (INAF/OA-Brera), M. Marisaldi (INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), F. Longo (Univ. Trieste and INFN Trieste), and P. Tempesta (TeleSpazio), report on behalf of the AGILE Team:
The AGILE satellite detected the GRB 220910A at T0 = 2022-09-10 05:48:26 s (UTC). The burst is clearly visible in the AGILE scientific ratemeters of the MiniCALorimeter (MCAL; 0.4-100 MeV) and AntiCoincidence (AC; 50-200 keV) detectors. The event lasted about 3 s and it released a total number of 8416 counts in the MCAL detector (above a background rate of 1310 Hz) and 25992 counts in the AC detector (above a background rate of 4830 Hz). The AGILE ratemeters light curves can be found at http://www.agilescienceapp.it/notices/GRB220910A_AGILE_RM.png .
Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.
GCN Circular #32541
R. Gopalakrishnan (IUCAA), V. Prasad (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 bright long GRB 220910A which was also detected by AGILE (Ursi et al., GCN 32540) and reported in an IPN_RAW notice (by Konus-Wind).
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 2022-09-10 05:48:29.0 UTC. The measured peak count rate associated with the burst is 4111 (+341, -343) counts/s above the background in the combined data of all quadrants, with a total of 5809 (+205, -203) counts. The local mean background count rate was 503 (+6, -11) counts/s. Using cumulative rates, we measure a T90 of 2.6 (+0.4, -0.3) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2022-09-10 05:48:27.0 UTC. The measured peak count rate is 6301 (+143, -155) counts/s above the background in the combined Veto data of all quadrants, with a total of 14603 (+414, -431) counts. The local mean background count rate was 1477 (+7, -8) counts/s. We measure a T90 of 3.7 (+0.5, -0.6) s from the cumulative Veto light curve.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. 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.
GCN Circular #32550
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, and C. Wilson-Hodge on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, report:
The very bright, long-duration GRB 220910A (AGILE detection: Ursi et al., GCN Circ. 32540; AstroSat-CZTI detection: Gopalakrishnan et al., GCN Circ. 32541) was detected by AGILE (MCAL, AC), AstroSat (CZTI), Konus-Wind, Fermi (GBM trigger 684481706), and INTEGRAL (SPI-ACS), at about 20910 s UT (05:48:30).
We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:
```
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
     8.124 (00h 32m 30s)  -0.115 ( +0d 06' 55")
  Corners:
     9.094 (00h 36m 23s)  -2.392 ( -2d 23' 30")
     7.404 (00h 29m 37s)  +2.183 ( +2d 11' 01")
     7.046 (00h 28m 11s)  +2.146 ( +2d 08' 44")
     8.743 (00h 34m 58s)  -2.426 ( -2d 25' 32")
  ---------------------------------------------
```
The error box area is 1.68 sq. deg, and its maximum dimension is 4.98 deg (the minimum one is 20.6 arcmin). The Sun distance was 160 deg.
This box may be improved.
The IPN localization is consistent with, but reduces the area of, the Fermi-GBM final localization (glg_healpix_all_bn220910242_v00).
A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB220910_T20910/IPN/
The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
GCN Circular #32551
C. Malacaria (ISSI) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 05:48:21.55 UT on 10 September 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220910A (trigger 684481706 / 220910242), which was also detected by AGILE (Ursi et al. 2022, GCN 32540) and AstroSAT/CZTI (Gopalakrishnan et al. 2022, GCN 32541). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 9.1, Dec = -1.1 (J2000 degrees, equivalent to J2000 00h 32m, -01d 06'), with a statistical uncertainty of 1.0 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error [Connaughton et al. 2015, ApJS, 216, 32].
The angle from the Fermi LAT boresight at the GBM trigger time is 89 degrees.
The GBM light curve shows a precursor and a main, subsequent peak with a duration (T90) of about 4 s (50-300 keV). The time-averaged spectrum from T0-4.5 s to T0+10.6 s is best fit by a Band function with Epeak = 357 +/- 8 keV, alpha = -0.69 +/- 0.01, and beta = -2.51 +/- 0.06
The event fluence (10-1000 keV) in this time interval is (4.69 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.85 s in the 10-1000 keV band is 76.9 +/- 0.6 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 #32555
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report:
The very bright, long-duration GRB 220910A (AGILE detection: Ursi et al., GCN Circ. 32540; AstroSat-CZTI detection: Gopalakrishnan et al., GCN Circ. 32541; IPN triangulaton: Svinkin et al., GCN Circ. 32550; Fermi-GBM observation: Malacaria and Meegan, GCN Circ. 32551) triggered Konus-Wind at T0=20910.521 s UT (05:48:30.521).
The burst light curve shows a multipeaked structure which starts at ~T0-5.7 s and has a total duration of ~13.4 s. The emission is seen up to ~16 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB220910_T20910/
As observed by Konus-Wind, the burst had a fluence of 5.23(-0.50,+0.53)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+2.112 s, of 3.93(-0.47,+0.49)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+10.496 s) is best fit in the 20 keV - 16 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.53(-0.14,+0.17), the high energy photon index beta = -2.46(-0.29,+0.19), the peak energy Ep = 310(-37,+39) keV (chi2 = 110/97 dof).
The spectrum near the maximum count rate (measured from T0+1.280 to T0+2.304 s) is best fit in the 20 keV - 16 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.21(-0.19,+0.25), the high energy photon index beta = -2.61(-0.27,+0.19), the peak energy Ep = 254(-29,+30) keV (chi2 = 72/59 dof).
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN Circular #32559
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the MGNS/BepiColombo team,
J. Benkhoff on behalf of the BepiColombo team,
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, and C. Wilson-Hodge on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, report:
Using the BepiColombo (MGNS) data we have triangulated GRB 220910A (GCNs 32540, 32541, 32550, 32551, 32555) to an improved 3 sigma error box whose coordinates are:
```
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
     8.734 (00h 34m 56s)  -1.848 ( -1d 50' 54")
  Corners:
     8.884 (00h 35m 32s)  -1.753 ( -1d 45' 11")
     9.042 (00h 36m 10s)  -2.231 ( -2d 13' 53")
     8.584 (00h 34m 20s)  -1.943 ( -1d 56' 35")
     8.411 (00h 33m 39s)  -1.432 ( -1d 25' 53")
  ---------------------------------------------
```
The error box area is 646 sq. arcmin, and its maximum dimension is 1.019 deg (the minimum one is 19.44 arcmin). The Sun distance was 159 deg.
This box may be further improved.
An updated triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB220910_T20910/IPN/

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Jochen Greiner, last update: 15-Sep-2022 [Disclaimer]