VHE Analyses of Long-Term Low-Flux-State Observations by VERITAS of Intermediate-Frequency-Peaked BL Lacertae Sources: 3C 66A and W Comae

TL;DR

This paper reports on long-term VHE gamma-ray observations of two IBL blazars, 3C 66A and W Comae, during their low-flux states, revealing significant detections and contributing to understanding blazar emission mechanisms.

Contribution

It presents the first detailed VHE analyses of IBLs during low-flux states, expanding knowledge of blazar behavior outside high-activity episodes.

Findings

12σ detection of 3C 66A in low-flux state

6σ detection of W Comae in low-flux state

Multiwavelength data supports blazar emission models

Abstract

Intermediate-frequency-peaked BL Lacertae objects (IBLs) are a class of blazars characterized by a spectral energy distribution (SED) with a lower-energy synchrotron peak than the majority of extragalactic sources detected by ground-based imaging atmospheric Cherenkov telescopes (IACTs). Consequently, the peak gamma-ray flux falls outside the very-high-energy regime (VHE, >100 GeV) covered by IACTs such as VERITAS, making IBLs difficult to detect except during infrequent episodes of elevated flux. However, the study of these sources in a low-flux state is essential for developing a complete understanding of the blazar paradigm. We present the results of VHE analyses of long-term low-flux-state observations completed for two IBL sources: 3C 66A and W Comae. For both sources, data from VERITAS were analyzed for the VHE regime. The study of 3C 66A extends from 2007 to 2015, resulting in a 12 standard deviation ($\sigma$) detection from $\sim$61 observing hours. Analysis of W Comae from 2010 to 2014, totaling $\sim$39 hours, resulted in a 6$\sigma$ low-flux-state detection. We report on the results from these VHE analyses and describe contemporaneous multiwavelength data to be used in further analyses. We comment on how these low-flux-state IBL detections fit within the context of the blazar paradigm.