GRB 260604B
GCN Circular 45006
Subject
GRB 260604B: 239Alferov CubeSat detection
Date
2026-06-19T14:51:29Z (3 months ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
GRB 260604B: 239Alferov CubeSat detection
D. Svinkin (Ioffe), D. Frederiks (Ioffe), D. Kapshtan (Geoscan), M. Orlov (Geoscan),
V. Bazunova (Geoscan), E. Shchepin (Geoscan), E. Meltsov (Geoscan),
K. Starikov (Geoscan, SPbSU), A. Khogoev (Geoscan),
A. Razdobarin (SPbAU), and D. Dolmatov (SPbSU),
on behalf of the 239Alferov team, report:
The long-duration GRB 260604B
(Fermi-GBM detection: The Fermi GBM team, GCN 44818;
SVOM-GRM detection: Zhang et al., GCN 44850)
was detected by 239Alferov 3U CubeSat at about 31555 s (08:45:55) UT.
The burst was also detected by Konus-Wind in the waiting mode.
The burst light curve, as measured by 239Alferov detector,
shows a multi-peaked structure with a duration of ~8 s.
The emission is seen up to ~500 keV.
The light curve recorded by 239Alferov is available at:
http://www.ioffe.ru/LEA/239Alferov/260604B/
239Alferov GRB detections are listed at:
http://www.ioffe.ru/LEA/239Alferov/
239Alferov is an educational 3U CubeSat mission at SSO combining amateur radio
and space research objectives. The gamma-ray detector onboard 239Alferov contains
a 64x72x15 mm NaI(Tl) scintillator read out by a SiPM array and covers the energy range
from ~20 keV to ~1000 keV.
Currently, the instrument records count rates in five energy bands:
~20-50 keV, ~50-100 keV, ~100-500 keV, 500-1000 keV, and > 1000 keV, with 0.5 s temporal resolution.
The ground segment of the mission utilizes the SONIKS open ground station network.
GCN Circular 44850
Subject
GRB 260604B: SVOM/GRM detection
Date
2026-06-06T14:28:23Z (4 months ago)
From
zhangjinpeng@ihep.ac.cn
Via
Web form
SVOM/GRM team: Jin-Peng Zhang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Olivier GODET (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM detected GRB 260604B during the routine ground search at 2026-06-04T08:45:56.000 (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44818).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst mainly consists of multiple pulses with a T90 of 17 +9/-5 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb260604B.png
In addition, the position of this burst, according to Fermi/GBM localization (RA = 173.4, Dec = -19.9, Fermi GBM Team, GCN #44818), is located at about 82 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0-15 to T0+25 s is fitted by a power law function. The power law index is -1.67 +0.10/-0.11. The event fluence (10-1000 keV) in this time interval is (3.8 +0.8/-0.8)E-06 erg/cm^2.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng@ihep.ac.cn)
GCN Circular 44818
Subject
GRB 260604B: Fermi GBM Final Real-time Localization
Date
2026-06-04T08:58:18Z (4 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely SHORT GRB
At 08:45:55 UT on 4 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260604B (trigger 802255560.356374 / 260604365).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 173.4, Dec = -19.9 (J2000 degrees, equivalent to J2000 11h 33m, -19d 53'), with a statistical uncertainty of 10.8 degrees.
The angle from the Fermi LAT boresight is 60.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604365/quicklook/glg_skymap_all_bn260604365.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604365/quicklook/glg_healpix_all_bn260604365.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604365/quicklook/glg_lc_medres34_bn260604365.gif