GCN 44896: EP260610a: SVOM/VT optical upper limits
2026-06-10T14:40:01.361Z | rev 0
H. L. Li, L. P. Xin, C. Wu, Y. L. Qiu, J. R. Xu,, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team.
SVOM/VT performed a ToO observation of the field of EP260610a triggered by Einstein Probe (Wu et al., GCN 44889). The observation started at 2026-06-10T05:47:51 UTC, i.e., about 1.18 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
No uncatalogued optical source was detected at the FXT source position (Wu et al., GCN 44889) in our stacked images, compared to the Legacy Survey. The 3-sigma upper limits are:
Mid_time Band Exposure Time Magnitude (AB)
2.27 h VT_B 83*50 s > 23.8 mag
2.27 h VT_R 84*50 s > 23.4 mag
The magnitudes are in the AB system and are not corrected for Galactic extinction.
Our non-detection is consistent with the observation from COLIBRÍ (Postigo et al., GCN 44890).
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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN 44892: GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
2026-06-10T10:19:57.670Z | rev 3
GCN Circular 44892 is a duplicate of GCN Circular 44891.
GCN 44892: GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
2026-06-10T10:19:57.670Z | rev 3
GCN Circular 44892 is a duplicate of GCN Circular 44891.
GCN 44891: GRB 260610A: Fermi GBM Final Real-time Localization
2026-06-10T10:18:35.100Z | rev 2
The Fermi GBM team reports the detection of a likely LONG GRB
At 10:07:46 UT on 10 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260610b (trigger 802778871.805202 / 260610422).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 354.7, Dec = 8.4 (J2000 degrees, equivalent to J2000 23h 38m, 8d 24'), with a statistical uncertainty of 10.5 degrees.
The angle from the Fermi LAT boresight is 102.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610422/quicklook/glg_skymap_all_bn260610422.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/bn260610422/quicklook/glg_healpix_all_bn260610422.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610422/quicklook/glg_lc_medres34_bn260610422.gif
GCN 44890: EP260610a: COLIBRÍ optical upper limits
2026-06-10T10:12:50.907Z | rev 2
Antonio de Ugarte Postigo (LAM), Diego López-Cámara (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) report:
We imaged the field of EP260610a (Wu et al., GCN Circ. 44889) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-10 08:23:40 to 09:56:22 UTC (from 3.78 to 5.32 hours after the trigger) and obtained 69 minutes of simultaneous exposure in the r and z filters.
The data were reduced and coadded and analysed with the ASU COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
In the stacked image, we do not detect any new source at the FXT source position (Wu et al., GCN Circ. 44889) down to the following 5-sigma limits:
r > 24.0 mag
z > 22.6 mag
We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.