General information
GRB 260705A was detected by SVOM/ECLAIRs at 2026-07-05T13:06:46 UTC and also by SVOM/GRM, with Fermi-GBM Targeted Search reporting a spatially consistent sub-threshold transient. The SVOM/ECLAIRs localization was R.A. 58.2851 deg, Dec. -31.6391 deg with a 90% confidence radius of 7.06 arcmin.
Wavelength coverage
- Gamma-ray: SVOM/ECLAIRs triggered with best image SNR 11.38, SVOM/GRM detected the burst with significance 10.40, and Fermi-GBM Targeted Search found a spatially consistent sub-threshold transient.
- Optical/NIR: LCO obtained r and z imaging at about 14.8-15.1 hr after trigger with non-detections to r > 20.9 AB and z > 19.9 AB; SOAR and Gemini-South later reported a candidate optical counterpart with r = 21.48 ± 0.08 AB and i = 21.44 ± 0.04 AB.
- Radio: ATCA observed at 4-12 GHz about 6.3 days post-burst and did not detect a radio source at the candidate optical counterpart position; the 8 GHz rms was 8 microJy/beam.
- X-ray: SVOM/MXT could not observe the burst at the time of the initial SVOM report due to constraints.
No observations are mentioned in UV, neutrino, or gravitational-wave bands.
Lightcurve and spectrum
- SVOM/ECLAIRs initially reported a broad peak structure with T90 about 18.387 s, while SVOM/GRM reported a broad peak with T90 about 33.216 s.
- Refined SVOM/ECLAIRs analysis reported a single broad peak with T90 = 35.55 -9.04/+6.05 s in 4-80 keV.
- The ECLAIRs time-averaged spectrum from T0-5.49 s to T0+29.72 s was best fit by a power law with index -1.68 ± 0.09.
- The refined 4-120 keV fluence was (1.053 ± 0.087)e-6 erg/cm² and the 4-120 keV photon flux was 1.002 ± 0.059 ph/cm²/s.
- The Fermi-GBM Targeted Search event was most significant on a 32 s timescale and was found with highest significance using a normal GRB Band spectrum with Epeak = 230 keV, alpha = -1.0, beta = -2.3.
Redshift
A photometric redshift z = 0.178 ± 0.009 was reported from Legacy Survey DR10 for WISEA J035312.50-313908.7, the catalogued galaxy in which the candidate optical counterpart is embedded.
What’s special vs typical
The optical candidate is reported to be consistent with a nuclear origin, with an offset of about 0.4 arcsec from the host center, and the authors note that the extended gamma-ray duration and nuclear location are reminiscent of jetted TDEs. A possible association with GRB 260705B was suggested, but later ATCA reporting states that the GRB 260705A and GRB 260705B positions are not statistically consistent.