GRB 260211A

General information

GRB 260211A triggered SVOM/ECLAIRs at 2026-02-11 19:24:33 UTC with a 90% localization radius of 5.68 arcmin centered at RA=86.9994 deg, Dec=-0.4306 deg (J2000). Follow-up reported X-ray candidates (Einstein Probe) and an optical counterpart candidate (SVOM/VT) that fades and is proposed as the afterglow.

Wavelength coverage

• Gamma-ray / hard X-ray: SVOM/ECLAIRs and SVOM/GRM detected prompt emission; Fermi-GBM found a consistent transient via targeted search.
• X-ray: Einstein Probe EP-FXT detected two sources in the region, one proposed as the afterglow and one consistent with a known X-ray source.
• Optical/NIR: LAST, GOTO, LCO, SVOM/COLIBRÍ reported early non-detections; SVOM/VT reported two candidates and later fading/rebrightening behavior for Source1; NOT/ALFOSC detected the counterpart in i band and compared to archival DELVE.
• Radio: No radio observations mentioned.

Lightcurve and spectrum

• Prompt duration: ECLAIRs initial T90 ~15.15 s (5–120 keV) and refined T90 = 21.6 (+9.2/-2.8) s (4–120 keV); GRM T90 ~27.45 s (4–550 keV).
• Prompt temporal structure: refined ECLAIRs analysis describes a double-peaked pulse.
• Prompt spectrum (ECLAIRs, 5–120 keV, T0-7.54 s to T0+13.12 s): power law with photon index -1.71 (+0.06/-0.07); 4–120 keV fluence (1.08 ± 0.06)×10^-6 erg cm^-2.
• X-ray fluxes (EP-FXT, 0.5–10 keV): 1.243e-12 ± 2.24e-13 erg s^-1 cm^-2 for EPF_J054755.7-002705; 3.165e-13 ± 4.03e-14 erg s^-1 cm^-2 for EPF_J054802.6-002834 (noted consistent with 1eRASS J054803.1-002833).
• Optical evolution: SVOM/VT Source1 fades from VT_R = 22.5±0.3 (2.35 hr) to VT_R = 23.5±0.3 (2.79 d), with reported temporal slope ~-0.27; later VT_R = 22.91±0.25 (19.36 d) and 22.85±0.25 (21.31 d) reported as a rebrightening. NOT measured i = 22.5±0.2 at 23.1 d; subtraction vs archival DELVE gives i > 22.9 for any excess component.

Redshift

What’s special vs typical

Late-time VT photometry was interpreted as a rebrightening likely due to an associated supernova, but NOT i-band data plus subtraction against archival DELVE did not confirm an excess component, and the field has substantial extinction (A_V = 2.1 mag) that can introduce filter-dependent systematics.