SST-1M detection of increased very-high-energy gamma-ray activity of Mrk 421
ATel #17597; Srija Reddy Muthyala (FZU), for the SST-1M Collaboration
on 14 Jan 2026; 20:32 UT
Credential Certification: Thomas Tavernier (tavernier@fzu.cz)
Subjects: Gamma Ray, TeV, VHE, AGN, Blazar
We report the detection of enhanced activity from the nearby blazar Mrk 421 (z = 0.031) on 12 January 2026. Observation was conducted through stereoscopic observations between 01:27 and 04:37 UTC using the two SST-1M Cherenkov telescopes currently operating at the Ondrejov Observatory in the Czech Republic. This detection is part of our ongoing monitoring program of Mrk 421 and is consistent with the flare reported by VERITAS (ATel #17594).
A preliminary analysis of data corresponding to a total live time of 3.07 hours indicates a strong gamma-ray signal with a statistical significance of 9.65 sigma and 53 excess counts. The observed energy spectrum of the source, fitted with a simple power-law model, yields a spectral index of 3.3 +/- 0.23 (stat) above 2 TeV. The integrated photon flux above 2 TeV is measured to be (4.0 +/- 0.7 stat)e-12 ph/cm2/s, corresponding to approximately 0.65 +/- 0.1 (stat) Crab units.
Mrk 421 appears to be in an active state. Future observations are scheduled, and multi-wavelength follow-up observations are strongly encouraged.
The SST-1M instrument consists of a pair of small-sized Cherenkov telescopes designed to detect gamma rays in the energy range from 1 to 300 TeV [1, 2]. The project is the result of a collaboration among institutions in Poland, Switzerland, and the Czech Republic.
[1] 2025JCAP...02..047A
[2] 2025A&A...699A.255A
