GCN 45227: EP260723a: SVOM/ECLAIRs Upper Limit
2026-07-27T13:44:17.526Z | rev 0
H. Yang, M. Brunet, O. Godet, S. Guillot (IRAP)
report on behalf of the SVOM team:
We performed a targeted search of the X-ray transient EP260723a, detected by EP-WXT at 2026-07-23T18:56:01 UTC (T0) with a duration of about 100 s (EP team, GCN 45201), using the SVOM/ECLAIRs event-by-event data downloaded through the X-band ground station.
At T0, the transient position was within the ECLAIRs field of view. No statistically significant signal was identified in the [T0 - 500 s, T0 + 3000 s] interval by the ECLAIRs image trigger performed on multiple timescales and energy bands.
For the interval from T0 to T0 + 100 s, we derive a 3-sigma upper limit of 2.4e-9 erg/cm^2/s in the 4-120 keV energy band, assuming a power-law spectrum with a photon index of 1.4, as measured by EP-WXT (GCN 45201). Alternatively, assuming a “soft” spectral template (a Band function with Epeak = 25 keV, alpha = -1.5, beta = -3.0), we derive a 3-sigma upper limit of 1.5e-9 erg/cm^2/s.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP.
The SVOM/ECLAIRs point of contact for this event is : Hui Yang (hui.yang@cnrs.fr)
GCN 45205: EP260723a: SVOM/VT optical observation
2026-07-24T12:08:26.042Z | rev 0
Y. N. Ma, L. P. Xin, H. L. Li, Y. L. Qiu, C. Wu, Z. H. Yao, J. R. Xu, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team.
SVOM/VT performed a Target of Opportunity observation of EP260723a detected by EP/WXT (Zhang et al., GCN 45201). SVOM/VT began observing the field at 2026-07-24T05:35:28 UTC, 10.658 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With X-band data available, the optical counterpart (Eyles-Ferris et al., GCN 45202; He et al., GCN 45203; Basa et al., GCN 45204) was detected in both VT_B and VT_R bands. The AB magnitudes are:
mid time (h) | exposure time (s) | band | mag (AB)
-------------|-------------------|------|---------------
10.98 | 37*50 | VT_B | 22.1+-0.1
10.96 | 29*50 | VT_R | 21.9+-0.2
Our photometry was not corrected for Galactic extinction.
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 45200: GRB 260723A: Fermi GBM Final Localization
2026-07-23T21:06:26.267Z | rev 0
The Fermi GBM team reports the detection of a likely LONG GRB.
"At 13:54:48.40 UT on 23 July 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260723A (trigger 806507693/260723580).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 284.5, Dec = 7.7 (J2000 degrees, equivalent to J2000 18h 57m, +7d 42'), with a statistical uncertainty of 9.5 degrees.
The angle from the Fermi LAT boresight is 87 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260723580/quicklook/glg_skymap_all_bn260723580.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/bn260723580/quicklook/glg_healpix_all_bn260723580.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260723580/quicklook/glg_lc_medres34_bn260723580.gif"