GRB 220601A

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. Ridnaia, 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. Xiao, S.-L. Xiong, X.-Q. Li, X.-Y. Wen, L.-M. Song, S.-J. Zheng,
W.-X. Peng, and F. Zhang on behalf of the GECAM 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 220601A
was detected by Konus-Wind, INTEGRAL (SPI-ACS), GECAM-B,
and Mars-Odyssey (HEND) at about 22766 s UT (06:19:26).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   224.703 (14h 58m 49s) -47.978 (-47d 58' 41")
  Corners:
   221.059 (14h 44m 14s) -50.313 (-50d 18' 48")
   221.153 (14h 44m 37s) -50.501 (-50d 30' 02")
   227.990 (15h 11m 58s) -45.375 (-45d 22' 31")
   227.888 (15h 11m 33s) -45.177 (-45d 10' 37")
  ---------------------------------------------
The error box area is 1.2 sq. deg, and its maximum
dimension is 7.0 deg (the minimum one is 11 arcmin).
The Sun distance was 144 deg.

This box may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB220601_T22766/IPN/

The time history and spectrum will be given in forthcoming GCN Circulars.

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

The long-duration GRB 220601A
(IPN triangulation: Kozyrev et al., GCN Circ. 32163
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triggered Konus-Wind at T0=22766.297 s UT (06:19:26.297).

The burst light curve shows a multipeaked structure
which starts at ~T0-42.5 s and has a total duration of ~82.5 s.
The emission is seen up to ~3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220601_T22766/

As observed by Konus-Wind, the burst
had a fluence of 2.64(-0.16,+0.17)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+3.056s,
of 6.19(-1.55,+1.57)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+41.216 s)
is best fit in the 28 keV - 5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.79(-0.17,+0.18)
and Ep = 195(-17,+21) keV (chi2 = 58/71 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.6
(chi2 = 57/70 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 5 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.74(-0.16,+0.17),
the high energy photon index beta = -2.81(-2.84,+0.34),
the peak energy Ep = 220(-24,+31) keV
(chi2 = 62/70 dof).

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