An Exceptional Very-High-Energy Gamma-Ray Flare From Mrk 421 Observed with VERITAS
ATel #17594; Amy Furniss (UC Santa Cruz) for the VERITAS Collaboration
on 14 Jan 2026; 01:33 UT
Credential Certification: Amy Furniss (afurniss@ucsc.edu)
Subjects: TeV, VHE, Blazar
We report the VERITAS detection of a very-high-energy flare of the famous blazar Mrk 421.
A preliminary analysis, considering an energy threshold of 500 GeV, shows a flux above 250% Crab on January 10, 2026 (UTC), a peak up to ~400% Crab (2.5 +/- 0.3)e-6 m^-2 s^-1 on January 11, and a flux decrease down to ~170% Crab in our latest observations on January 13.
The long-term VERITAS lightcurve suggests a once-per-decade event. As Mrk 421 is still in an active state, we strongly encourage multiwavelength follow-up on this exceptional flare. VERITAS will continue to perform daily observations of Mrk 421 as long as feasible.
Questions regarding the VERITAS observations should be directed to Amy Furniss (afurniss@ucsc.edu). VERITAS (Very Energetic Radiation Imaging Telescope Array System) is located at the Fred Lawrence Whipple Observatory in southern Arizona, USA, and is most sensitive to gamma rays between 85 GeV and 30 TeV (http://veritas.sao.arizona.edu).
