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GCN Circular 33659

Subject
IPN triangulation of GRB 230418A (short)
Date
2023-04-20T14:30:46Z (a year ago)
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, C. Wilson-Hodge,
and E. Burns 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 short-duration GRB 230418A
(Fermi-GBM detection: Roberts et al., GCN Circ. 33652;
Swift/BAT-GUANO detection: Ronchini et al., GCN Circ. 33653;
AGILE detection: Panebianco et al., GCN Circ. 33656;
AstroSat-CZTI detection: Navaneeth et al., GCN Circ. 33657)
was detected by Fermi (GBM trigger 703545098), Swift (BAT),
Konus-Wind, INTEGRAL (SPI-ACS), AGILE (MCAL, AC), AstroSat (CZTI),
and Mars-Odyssey (HEND) at about 76293 s UT (21:11:33).
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:
   43.442 (02h 53m 46s) -20.343 (-20d 20' 36")
 Corners:
   43.565 (02h 54m 16s) -20.460 (-20d 27' 37")
   43.510 (02h 54m 02s) -20.481 (-20d 28' 53")
   43.320 (02h 53m 17s) -20.226 (-20d 13' 34")
   43.375 (02h 53m 30s) -20.205 (-20d 12' 19")
 ---------------------------------------------
The error box area is 61 sq. arcmin, and its maximum
dimension is 20 arcmin (the minimum one is 3.2 arcmin).
The Sun distance was 35 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of,
the Fermi-GBM final localization (GCN 33652).

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB230418_T76289/IPN

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

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