TITLE:   GCN CIRCULAR
NUMBER:  31958
SUBJECT: IPN triangulation of GRB 220426A
DATE:    22/04/27 19:30:24 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

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,

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,

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 very bright, long-duration GRB 220426A
(BALROG localization: Biltzinger et al., GCN Circ. 31950;
Swift/BAT-GUANO detection: Tohuvavohu et al., GCN Circ. 31954;
Fermi-GBM detection: Malacaria and Meegan, GCN Circ. 31955)
has been detected by Fermi (GBM trigger 672648596), INTEGRAL (SPI-ACS),
Swift (BAT), Konus-Wind, and Mars-Odyssey (HEND), so far,
at about 24591 s UT (06:49:51).
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:
   338.692 (22h 34m 46s) -22.994 (-22d 59' 38")
  Corners:
   337.871 (22h 31m 29s) -22.760 (-22d 45' 38")
   337.994 (22h 31m 59s) -23.010 (-23d 00' 37")
   339.494 (22h 37m 59s) -23.176 (-23d 10' 35")
   339.374 (22h 37m 30s) -22.943 (-22d 56' 35")
  ---------------------------------------------
The error box area is 1131 sq. arcmin, and its maximum
dimension is 1.6 deg (the minimum one is 13.6 arcmin).
The Sun distance was 64 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi GBM Final Real-time position (GCN Circ. 31955) and BALROG
(GCN 31950) localizations.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB220426_T24589/IPN/

Swift ToO has been approved.

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