Research Note

Mechanism of very high-energy radiation in BL Lacertae object 3C 66A

¹ National Astronomical Observatories, Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, PR China e-mail: yangjp@ynao.ac.cn
² Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, PR China
³ Yunnan Agricultural University, Kunming 650201, PR China

Received: 31 July 2009
Accepted: 16 November 2009

Abstract

Aims. Our goal is to understand the nature of blazars and the mechanisms for generating high-energy γ-rays, through investigation of the blazar 3C 66A.

Methods. We model the high-energy spectrum of 3C 66A, which was observed recently with the Fermi-LAT and VERITAS telescopes. The spectrum has a hard change from the energy range of 0.2–100 GeV to 200–500 GeV in recent almost contemporaneous observations of two telescopes.

Results. The de-absorbed VERITAS spectrum depends strongly on redshift, which is highly uncertain. If z = 0.444 is adopted, we are able to use the SSC model to produce the Fermi-LAT component and the EC model to the VERITAS component. However, if z = 0.1, the intrinsic VERITAS spectrum will be softer, and there will be a smooth link between the Fermi-LAT and VERITAS spectra that can be explained using an SSC model.