TITLE:   GCN CIRCULAR
NUMBER:  32805
SUBJECT: Improved IPN localization for GRB 221009A (BepiColombo-MGNS light curve)
DATE:    22/10/19 16:43:28 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 MGNS/BepiColombo team,

J. Benkhoff on behalf of the BepiColombo 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,

and

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

The extremely bright, long-duration GRB 221009A
(GCNs 32632, 32635, 32636, 32637, 32641, 32642, 32650, 32657,
32658, 32668, 32685, 32751; ATels 15650, 15656, 15660)
was detected by the MGNS/BepiColombo interplanetary gamma-ray detector. 
The burst light curves in the energy range 280-460 keV exhibit a 
multi-peaked pulse structure with a total duration of ~6.6 min. The 
source of GRB 221009A was obscured for MGNS by spacecraft structure that 
have limited transparency in the specified above energy range.

The link below provides a plot of the time profile of the gamma-ray 
count rate. The GRB221009A.TXT file, also available at this link,
contains light curve data in three columns: time in UTC, accumulated 
count and accumulation time.

http://l503.iki.rssi.ru/owncloud/index.php/s/HZtqdQ1b9QW3ojv

Using the BepiColombo (MGNS) data we have triangulated GRB 221009A
to the 3 sigma error box whose coordinates are:
---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   287.761 (19h 11m 03s) +20.670 (+20d 40' 11")
  Corners:
   283.599 (18h 54m 24s) +27.415 (+27d 24' 54")
   283.634 (18h 54m 32s) +28.133 (+28d 08' 00")
   291.780 (19h 27m 07s) +12.770 (+12d 46' 14")
   291.767 (19h 27m 04s) +11.822 (+11d 49' 20")
  ---------------------------------------------
The error box area is 6.63 sq. deg, and its maximum
dimension is 18 deg (the minimum one is 23 arcmin).
The Sun distance was 92 deg.

This box may be further improved.

The Swift-XRT source (GCN 32632) is inside the box.
The distance between the source and
the Konus-MGNS annulus center line is 1.7 arcmin.

An updated triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB221009_T47819/IPN/