TITLE:   GCN CIRCULAR
NUMBER:  36393
SUBJECT: IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
DATE:    24/05/05 00:09:50 GMT
FROM:    Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>

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

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

E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

G. Waratkar (IITB), J.Joshi (IUCAA), A. Vibhute (IUCAA),
V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA),
A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL)
on behalf of the Astrosat-CZTI team,

and

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

The long-duration GRB 240501B
(AstroSat CZTI detection: Waratkar et al., GCN 36360;
GRBAlpha detection: Dafcikova et al., GCN 36374)
was detected by INTEGRAL (SPI-ACS), Konus-Wind,
AstroSat (CZTI), GRBAlpha, and Mars-Odyssey (HEND)
at about 38616 s UT (10:43:36).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
  265.232 (17h 40m 56s) +27.954 (+27d 57' 15")
 Corners:
  265.021 (17h 40m 05s) +32.390 (+32d 23' 24")
  265.108 (17h 40m 26s) +32.347 (+32d 20' 48")
  265.394 (17h 41m 34s) +23.414 (+23d 24' 51")
  265.314 (17h 41m 15s) +23.466 (+23d 27' 56")
 ---------------------------------------------
The error box area is 2315 sq. arcmin, and its maximum
dimension is 9.0 deg (the minimum one is 4 arcmin).
The Sun distance was 115 deg.

This localization is consistent with the 
GBM-HEND annulus (180.767 1.045 84.864 0.509)
and the Fermi-GBM final localization (The Fermi GBM Team, GCN 36359)
reported for the GRB 240501A (occurred ~660 s after GRB 240501B),
indicating that GRB 240501B and GRB 240501A are likely distinct 
emission episodes of the same ultra-long GRB.

This localization may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB240501_T38616/IPN/

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