TITLE:   GCN CIRCULAR
NUMBER:  30110
SUBJECT: IPN triangulation of GRB 210531A
DATE:    21/06/01 17:29:39 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

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

K. Hurley, on behalf of the IPN,

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,
report:

The bright, long-duration GRB 210531A
(BALROG localization: Biltzinger et al., GCN Circ. 30105;
AGILE detection: Ursi et al., GCN Circ. 30106;
AstroSat-CZTI detection: Sawant et al., GCN Circ. 30108)
was detected by Fermi (GBM trigger 644155206), Konus-Wind,
INTEGRAL (SPI-ACS), AGILE (MCAL, SA, and AC),
and AstroSat (CZTI) at about 43201 s UT (12:00:01).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   140.592 (09h 22m 22s)  +8.281 ( +8d 16' 50")
  Corners:
   141.277 (09h 25m 06s) +11.425 (+11d 25' 30")
   142.066 (09h 28m 16s) +10.564 (+10d 33' 51")
   139.800 (09h 19m 12s)  +5.254 ( +5d 15' 16")
   139.052 (09h 16m 12s)  +6.081 ( +6d 04' 51")
  ---------------------------------------------
The error box area is 5.9 sq. deg, and its maximum
dimension is 6.3 deg (the minimum one is 1 deg).
The Sun distance was 70 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi final position and BALROG (GCN Circ. 30105) localizations.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210531_T43198/IPN/

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