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Date and Time of the Query: 2019-08-18 T06:47:09 PDT
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For refcode 2011ApJS..194...29R:
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2011ApJS..194...29R Blazars in the Fermi Era: The OVRO 40 m Telescope Monitoring Program Richards, Joseph L.; Max-Moerbeck, Walter; Pavlidou, Vasiliki; King, Oliver G.; Pearson, Timothy J.; Readhead, Anthony C. S.; Reeves, Rodrigo; Shepherd, Martin C.; Stevenson, Matthew A.; Weintraub, Lawrence C.; Fuhrmann, Lars; Angelakis, Emmanouil; Zensus, J. Anton; Healey, Stephen E.; Romani, Roger W.; Shaw, Michael S.; Grainge, Keith; Birkinshaw, Mark; Lancaster, Katy; Worrall, Diana M.; Taylor, Gregory B.; Cotter, Garret; Bustos, Ricardo Abstract. The Large Area Telescope (LAT) aboard the Fermi GAMMA-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15 GHz radio monitoring program with the 40 m telescope at the Owens Valley Radio Observatory. This program began with the 1158 northern ({delta}> -20^degree^) sources from the Candidate GAMMA-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4 mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample. We demonstrate that, with high significance (6{sigma}), gamma-ray-loud blazars detected by the LAT during its first 11 months of operation vary with almost a factor of two greater amplitude than do the gamma-ray-quiet blazars in our sample. We also find a significant (3{sigma}) difference between variability amplitude in BL Lacertae objects and flat-spectrum radio quasars (FSRQs), with the former exhibiting larger variability amplitudes. Finally, low-redshift (z < 1) FSRQs are found to vary more strongly than high-redshift FSRQs, with 3{sigma} significance. These findings represent an important step toward understanding why some blazars emit gamma-rays while others, with apparently similar properties, remain silent. Key words: BL Lacertae objects: general, galaxies: active, methods: statistical, quasars: general, radio continuum: galaxies
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