TITLE:   GCN CIRCULAR
NUMBER:  30053
SUBJECT: IPN triangulation of GRB 210518A
DATE:    21/05/19 19:18:30 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

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

A. Ridnaia, S. Golenetskii, D. Frederiks, D. Svinkin,
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,

and

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

The long-duration GRB 210518A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 30045)
was detected by Fermi (GBM trigger 643035854), Konus-Wind,
and Mars-Odyssey (HEND) at about 47050 s UT (13:04:10).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
  271.081 (18h 04m 19s) +50.035 (+50d 02' 07")
 Corners:
  288.400 (19h 13m 36s) +51.036 (+51d 02' 11")
  287.357 (19h 09m 26s) +51.489 (+51d 29' 21")
  255.561 (17h 02m 15s) +46.119 (+46d 07' 07")
  256.707 (17h 06m 50s) +46.052 (+46d 03' 09")
 ---------------------------------------------
The error box area is 9.4 sq. deg, and its maximum
dimension is 22.0 deg (the minimum one is 26 arcmin).
The Sun distance was 96 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210518_T47051/IPN

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