The First VHE Activity of OJ 287 and the Extragalactic Background Light
Abstract
The BL Lacertae (BL Lac) object OJ 287 underwent an intense X-ray activity phase, exhibiting its brightest recorded X-ray flare in 2016–2017, characterized by much softer X-ray spectra and, concurrently, its first-ever recorded very-high-energy (VHE) emission (100–560 GeV), reported by the VERITAS observatory. Broadband spectral energy distribution reveals a new jet emission component similar to high-synchrotron-peaked BL Lac objects, thereby implying the soft X-ray spectrum for the synchrotron emission. Using the advantage of simultaneous X-ray and VHE spectral information, as well as the source being a low-synchrotron-peaked BL Lac object, we systematically explored the extragalactic background light (EBL) spectrum by demanding that the VHE spectrum cannot be harder than the X-ray spectrum. We used three different phenomenological forms of the EBL spectral shape (power-law, parabola, and polynomial) motivated by current constraints on the EBL with the Bayesian Monte Carlo approach to infer the credible EBL range. Our study favors an almost flat power-law spectral shape and is consistent with previous studies. The other spectral forms capable of capturing curvature though result in a better statistics value; the improvement is statistically insignificant given the additional parameters.
- Publication:
-
Galaxies
- Pub Date:
- June 2024
- DOI:
- 10.3390/galaxies12040034
- arXiv:
- arXiv:2407.07047
- Bibcode:
- 2024Galax..12...34Y
- Keywords:
-
- OJ 287;
- EBL;
- BL Lacertae objects;
- Bayesian statistics;
- VHE gamma-rays;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 13 pages, 4 figures, 2 tables