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GCN Circular 27585

Subject
IPN triangulation of GRB 200415A (possible Magnetar Giant Flare in Sculptor Galaxy?)
Date
2020-04-15T16:51:17Z (4 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, K. Hurley, and  D. Frederiks, 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. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team, and

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 short-duration, extremely bright GRB 200415A
(Fermi-GBM detection: The Fermi GBM Team, GCN Circ. 27579;
BALROG localization : Kunzweiler, et al., GCN Circ. 27580)
has been detected by Fermi (GBM trigger 608633290), Konus-Wind,
INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), and Swift (BAT),
so far, at about 31686 s UT (08:48:06).
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:
    11.960 (00h 47m 50s) -25.937 (-25d 56' 13")
  Corners:
    11.481 (00h 45m 55s) -23.109 (-23d 06' 33")
    11.740 (00h 46m 58s) -22.955 (-22d 57' 17")
    12.354 (00h 49m 25s) -28.885 (-28d 53' 07")
    12.073 (00h 48m 18s) -29.074 (-29d 04' 25")
  ---------------------------------------------
The error box area is 1.53 sq. deg, and its maximum
dimension is 6.126 deg (the minimum one is 15.4 arcmin).
The Sun distance was about 35 deg.

The IPN localization is consistent with, but reduces the area of,
the Fermi-GBM final position (GCN Circ. 27579) and
BALROG localization (GCN 27580).

The Fermi (GBM) light curve shows an extremely bright short pulse
with a duration of ~10 ms, followed, after a ~1 ms gap, by a decaying 
emission lasting for ~150 ms. The light curve shape is very similar to
the extragalactic soft gamma-repeater giant flare candidates:
GRB 051103 - Frederiks et al., AstL 33, 1, 19, 2007 (fig. 1 and 2) and
GRB 070201 - Mazets at al., ApJ 680, 1, 545, 2008 (fig. 1 and 2).
The IPN box contains a nearby Sculptor Galaxy (3.5 Mpc),
supporting the hypothesis of the magnetar Giant Flare nature
of the burst.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB200415_T31685/IPN/

Further localization improvements along with the burst time history and 
spectrum will be given in forthcoming GCN Circulars.

[GCN OPS NOTE(15apr20):  Per request of the author, the journal
in the Frederiks et al reference was changed from "ApJL" to "AstL".]
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