Submillimeter Variability and the Gamma-ray Connection in Fermi Blazars

TL;DR

This study investigates the relationship between gamma-ray emissions and submillimeter variability in a large sample of blazars, revealing that their variability characteristics are consistent across subclasses and may indicate class transitions during flares.

Contribution

It provides the first comprehensive analysis of submillimeter variability and gamma-ray connection in a large blazar sample, using multi-epoch SMA observations and autoregressive modeling.

Findings

No variability differences between subclasses or luminosities.

Blazar light curves are consistent with a single variability process.

Evidence suggests blazars may transition between classes during flaring episodes.

Abstract

We present multi-epoch observations from the Submillimeter Array (SMA) for a sample of 171 bright blazars, 43 of which were detected by Fermi during the first three months of observations. We explore the correlation between their gamma-ray properties and submillimeter observations of their parsec-scale jets, with a special emphasis on spectral index in both bands and the variability of the synchrotron component. Subclass is determined using a combination of Fermi designation and the Candidate Gamma-Ray Blazar Survey (CGRaBS), resulting in 35 BL Lac objects and 136 flat-spectrum radio quasars (FSRQs) in our total sample. We calculate submillimeter energy spectral indices using contemporaneous observations in the 1 mm and 850 micron bands during the months August-October 2008. The submillimeter light curves are modeled as first-order continuous autoregressive processes, from which we derive characteristic timescales. Our blazar sample exhibits no differences in submillimeter variability amplitude or characteristic timescale as a function of subclass or luminosity. All of the the light curves are consistent with being produced by a single process that accounts for both low and high states, and there is additional evidence that objects may be transitioning between blazar class during flaring epochs.