Radio Variability Studies of Gamma-Ray Blazars with the OVRO 40 m Telescope

TL;DR

This study monitors gamma-ray blazars at 15 GHz over several years, analyzing their radio variability and comparing different sub-populations, while also introducing a new receiver for enhanced measurements.

Contribution

The paper presents a large-scale radio variability analysis of gamma-ray blazars and introduces the KuPol receiver for improved polarization and intensity measurements.

Findings

Gamma-ray-loud blazars show higher variability than gamma-ray-quiet ones.

BL Lac objects exhibit different variability patterns compared to flat-spectrum radio quasars.

Variability amplitude trends with redshift are identified.

Abstract

Since late 2007, we have been monitoring a large sample of known and likely gamma-ray-loud blazars at 15 GHz twice per week with the Owens Valley Radio Observatory (OVRO) 40 m Telescope. Our initial sample included the 1158 sources above declination -20 degrees from the Candidate Gamma-Ray Blazar Survey (CGRaBS), and we have since added nearly 400 more sources, including all blazars associated with Fermi Large Area Telescope (LAT) detections in the First AGN Catalog (1LAC). Here, we describe the new sample and present results for 2008 through early 2011. Using statistical likelihood analyses, we compare the variability amplitude for various sub-populations within our sample. These include comparisons of gamma-ray-loud versus gamma-ray-quiet objects, BL Lac objects versus flat-spectrum radio quasars, and a study of the variability amplitude trend with redshift. We also describe KuPol, the new digital Ku-band receiver being constructed for the 40 m telescope. This new receiver will provide total intensity and linear polarization measurements over the 12-18 GHz band, with 16 MHz spectral resolution.