GRB 241021A

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

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

E. Burns on behalf of the IPN,

E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB 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 241021A was detected by
Konus-Wind, INTEGRAL (SPI-ACS), and Mars-Odyssey (HEND)
at about 53930 s UT (14:58:50).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
  267.026 (17h 48m 06s) +29.592 (+29d 35' 31")
 Corners:
  265.186 (17h 40m 45s) +28.733 (+28d 43' 57")
  268.672 (17h 54m 41s) +30.598 (+30d 35' 53")
  268.925 (17h 55m 42s) +30.399 (+30d 23' 57")
  265.442 (17h 41m 46s) +28.544 (+28d 32' 37")
 ---------------------------------------------
The error box area is 3597 sq. arcmin, and its maximum
dimension is 3.6 deg (the minimum one is 16 arcmin).
The Sun distance was 69 deg.

This localization may be improved.

A triangulation map and a HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB241021_T53930/IPN
The HEALPix triangulation map is the multi-order HEALPix in units of
probability density.

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

V. Panteleeva, D. Frederiks, A. Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 241021A
(IPN triangulation: Kozyrev et al., GCN 37847
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triggered Konus-Wind at T0=53930.240 s UT (14:58:50.240).

The burst light curve shows a multipeaked structure
which starts at ~T0-25 s and has a total duration of ~236 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/GRB241021_T53930/

As observed by Konus-Wind, the burst
had a fluence of 2.62(-0.21,+0.23)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+15.616 s,
of 6.42(-1.49,+1.50)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+224 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 = -1.09(-0.04,+0.04),
the high energy photon index beta = -2.76(-0.60,+0.29),
the peak energy Ep = 359(-25,+26) keV
(chi2 = 103/97 dof).

The spectrum near the maximum count rate
(measured from T0+15.360 to T0+21.504 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 = -1.05(-0.07,+0.07),
the high energy photon index beta = -2.54(-0.58,+0.26),
the peak energy Ep = 474(-60,+71) keV
(chi2 = 102/97 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.