TITLE:   GCN CIRCULAR
NUMBER:  25250
SUBJECT: IPN Triangulation of GRB 190731A
DATE:    19/08/01 20:42:05 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin,
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,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team,

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long-duration, bright GRB 190731A
(Fermi LAT detection: Ohno et al., GCN 25244;
CALET GBM detection: Asaoka et al., GCN 25246;
Fermi GBM detection: Roberts & Meegan, GCN 25248)
has been detected by FERMI (GBM trigger 586305505), INTEGRAL (SPI-ACS),
Mars-Odyssey (HEND), Konus-Wind, CALET (GBM), and Swift (BAT),
so far, at about 81500 s UT (22:38:20).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a GBM-HEND annulus centered at
RA(2000)=321.552 deg (21h 26m 13s)  Dec(2000)=-16.302 deg (-16d 18' 08"),
whose radius is 61.012 +/- 0.062 deg (3 sigma).

The LAT position reported by Ohno et al. (GCN Circ. 25244)
is consistent with the annulus. The annulus combined with
the LAT (90 % containment, statistical-only) error circle
gives the following error box:
--------------------------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ------------------------------------------------------------
  Center:
   339.864 (22h 39m 27s) -76.572 (-76d 34' 19")
  Corners:
   338.734 (22h 34m 56s) -76.599 (-76d 35' 57")
   338.813 (22h 35m 15s) -76.724 (-76d 43' 27")
   341.083 (22h 44m 20s) -76.530 (-76d 31' 50")
   340.796 (22h 43m 11s) -76.424 (-76d 25' 25")
  -------------------------------------------------------------
The error box area is 244 sq. arcmin (a factor of 4
smaller than that of the LAT error circle), and its maximum
dimension is 33.6 arcmin (the minimum one is 7.4 arcmin).
The Sun distance was ~121 deg.

Both Swift XRT sourses found so far (www.swift.ac.uk/ToO_GRBs/00020914/)
are consistent with the box.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB190731_T81500/IPN/

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