A Decade of Multiwavelength Observations of the TeV Blazar 1ES 1215+303: Extreme Shift of the Synchrotron Peak Frequency and Long-term Optical–Gamma-Ray Flux Increase

Abstract

Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and VERITAS, we present an extensive study of the long-term multiwavelength radio-to-gamma-ray flux-density variability, with the addition of a couple of short-time radio-structure and optical polarization observations of the blazar 1ES 1215+303 (z=0.130), with a focus on its gamma-ray emission from 100MeV to 30TeV. Multiple strong GeV gamma-ray flares, a long-term increase in the gamma-ray and optical flux baseline, and a linear correlation between these two bands are observed over the ten-year period. Typical HBL behaviors are identified in the radio morphology and broadband spectrum of the source. Three stationary features in the innermost jet are resolved by Very Long Baseline Array at 43.1, 22.2, and 15.3 GHz. We employ a two-component synchrotron self-Compton model to describe different flux states of the source, including the epoch during which an extreme shift in energy of the synchrotron peak frequency from infrared to soft X-rays is observed.

Variability Signatures of a Burst Process in Flaring Gamma-Ray Blazars

“…The longer the light curve, the more effectively the high-flux part of the flux distribution can be studied. Some previous studies that compared normal and lognormal distributions have excluded flaring intervals from the flux distribution so as not to overly favor the heavier-tailed lognormal distribution (e.g., Giebels & Degrange 2009;Valverde et al 2020). However, when only considering heavy-tailed distributions, these intervals should not be excluded.…”

“…These distributions are commonly modeled as a lognormal distribution, which can arise through the multiplicative combination of many independent events (Uttley et al 2005). Variability consistent with lognormality has been observed in many studies of blazars using data in multiple wave bands (e.g., Giebels & Degrange 2009;Kushwaha et al 2017;Valverde et al 2020;Acciari et al 2021;Bhatta 2021).…”

“…The autoregressive inverse gamma model may also be able to reproduce the less extreme variability associated with BL Lac objects. For example, an extensive analysis of the multiwavelength variability of the flaring high-synchrotronpeaked BL Lac object 1ES 1215+303 was performed by Valverde et al (2020), who found that its flux distribution was described better by a lognormal distribution than by a normal distribution. They obtained a lognormal distribution with a best-fit value of σ = 0.43 ± 0.02, which, using Equation (34), can be reproduced by an inverse gamma distribution with α ≈ 5.4.…”

A survey of active galaxies at TeV photon energies with the HAWC gamma-ray observatory

“…operations by Valverde et al (2020). We checked the dates of these four episodes and did not find evidence for them in the HAWC data.…”

Spin Tetrad Formalism Of Circular Polarization States In Relativistic Jets

“…Review AGN are quite possibly the largest, most luminous, extragalactic objects observed in the known universe. The FERMI-LAT collaboration has generated an extensive catalogue of AGN in the highenergy regime [1][2][3][4][5]. A number of probes and missions are dedicated to the multi-messenger aspects of observing these energetic objects with variable emission [6,7].…”