VERITAS Detection of Very-High-Energy Gamma-Ray Flaring Activity from OP 313

ATel #16993; Amy Furniss (UC Santa Cruz) for the VERITAS Collaboration
on 25 Jan 2025; 16:12 UT
Credential Certification: Amy Furniss (afurniss@ucsc.edu)

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We report the VERITAS detection of very-high-energy (VHE; E> 100 GeV) flaring activity in the flat-spectrum radio quasar (FSRQ) OP 313 (z=0.997, R.A. = 197.61943 deg, Dec. = +32.34549 deg, J2000.0). Following the GeV gamma-ray activity observed by Fermi-LAT (reported in ATel #16970), approximately 1.7 hours of observations were collected by VERITAS on Jan 24, 2025 (UTC). A preliminary analysis of these data yields a detection with a statistical significance of 15 standard deviations and a flux of (7.8 +/- 1.0)e-7 m^-2 s^-1 above 150 GeV, which corresponds to (21 +/- 3)% of the Crab Nebula flux above the same threshold energy. OP 313 (also known as B2 1308+326 or RGB J1310+323) is undergoing a flare that has lasted for two weeks in gamma-ray and optical frequencies, as highlighted by recent ATels (#16951, #16964, #16970, #16972, #16977, #16979, #16991). VERITAS will continue to observe OP 313 as long as observations are feasible. Multi-wavelength observations are encouraged. 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).