Multiwavelength Variability and Jet Properties of Low-synchrotron-peaked BL Lacertae Objects

Abstract Low-synchrotron-peaked BL Lac objects (LBLs) are promising candidates for masquerading BL Lacs, and the mechanism responsible for their high-energy γ -ray emission still requires further investigation. In this paper, we conduct detailed analyses of the variability and spectral properties of a sample of LBLs, utilizing 16 yr of multi-instrument observations spanning from 2008 October to 2024 September. To understand the physical properties of LBLs, we model their broadband, nearly simultaneous spectral energy distributions during different variability episodes using a one-zone leptonic scenario. The major outcomes can be outlined as follows. (1) The broadband spectra of LBLs can be reproduced within a leptonic model framework incorporating seed photons from both the broad-line region (BLR) and the dusty torus (DT). The γ -ray emission is inferred to be generated in the location beyond the BLR and within the DT. (2) For an e ± –p jet, the jet power of LBLs follows the relation P e ′ (the kinetic power carried in relativistic electrons) ∼ P p ′ (the kinetic power in cold protons) > P rad ′ (the radiation) > P B ′ ′ (Poynting flux). (3) The LBL radiation mechanism during multiwavelength simultaneous flares can be described by a one-zone leptonic model, while peculiar orphan X-ray flares are more plausibly explained by a stochastic dissipation scenario.