VERITAS detection of VHE emission from the optically bright quasar OJ 287

TL;DR

The paper reports the first detection of very-high-energy gamma-ray emission from the quasar OJ 287 by VERITAS, supporting models involving a binary black hole or helical jet, and includes multiwavelength observational data.

Contribution

First VHE gamma-ray detection of OJ 287, providing new insights into its emission mechanisms and supporting binary black hole or jet models.

Findings

Detection of VHE gamma rays at >5 sigma significance

Triggered by elevated Swift-XRT count rates

Multiwavelength observations conducted after detection

Abstract

We report on the VERITAS detection of very-high-energy (VHE, $E > 100~\mathrm{GeV}$) $\gamma$-ray emission from the optically bright quasar OJ 287 which is located at a redshift of z = 0.306. OJ 287 has been observed to display regular optical outbursts with a period of approximately 12 years, with the last major optical outburst having occurred in 2015. To explain this periodicity, models involving a binary supermassive black hole system at the core of OJ 287, or a helical jet, have been developed. Motivated by elevated Swift-XRT count rates, VERITAS observed OJ 287 in February 2017, and detected the object at >5 standard deviations above background. This detection prompted further VERITAS, Swift-XRT and multiwavelength observations of the object. The results of the VERITAS observational campaign are presented.