TITLE:   GCN CIRCULAR
NUMBER:  33699
SUBJECT: [TEST] Super-Kamiokande finds a supernova in the Milky Way Galaxy
DATE:    26/04/28 01:50:23 GMT
FROM:    pronost@km.icrr.u-tokyo.ac.jp

        H. Sekiya, Kamioka Observatory, Institute for Cosmic Ray Research,
University of Tokyo, reports on behalf of the Super-Kamiokande collaboration:

Super-Kamiokande, a 50000 ton water Cherenkov imaging detector situated
1000 meters underground in the Kamioka mine, Gifu, Japan, has observed a
neutrino burst from a nearby supernova.  Within a fiducial volume of 22500
tons, preliminary results indicate 8302 neutrino-produced events have been
detected with energies greater than 6.0 MeV. An SN1987A-like explosion
would be expected to produce such a signal in Super-Kamiokande if the
progenitor star was located at a distance between 5.99 and 8.22 kpc from
Earth. These events were observed over an interval of 20.0 seconds, with
the first event arriving at 2026/Apr/28 01:13:00 122727 [us] UT. The estimated supernova
direction is R.A. = -81 (degrees) and Dec.= -3 (degrees), within
2.48, 3.66 and 4.17 degrees for, respectively, 68, 90 and 95%% C.L. error circles.
The probability to have the SN located within 2, 5, and 10 degrees of the
central position is 0.54, 0.99 and 1.00, respectively.