BLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAM
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 15GHz r...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
2011
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| _version_ | 1797092794428293120 |
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| author | Richards, J Max-Moerbeck, W Pavlidou, V King, O Pearson, T Readhead, A Reeves, R Shepherd, M Stevenson, M Weintraub, L Fuhrmann, L Angelakis, E Zensus, J Healey, SE Romani, R Shaw, MS Grainge, K Birkinshaw, M Lancaster, K Worrall, D Taylor, G Cotter, G Bustos, R |
| author_facet | Richards, J Max-Moerbeck, W Pavlidou, V King, O Pearson, T Readhead, A Reeves, R Shepherd, M Stevenson, M Weintraub, L Fuhrmann, L Angelakis, E Zensus, J Healey, SE Romani, R Shaw, MS Grainge, K Birkinshaw, M Lancaster, K Worrall, D Taylor, G Cotter, G Bustos, R |
| author_sort | Richards, J |
| collection | OXFORD |
| description | 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 15GHz radio monitoring program with the 40 m telescope at the Owens Valley Radio Observatory. This program began with the 1158 northern (δ > -20°) sources from the Candidate Gamma-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4mJy (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 (6σ), 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 (3σ) 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 3σ significance. These findings represent an important step toward understanding why some blazars emit gamma-rays while others, with apparently similar properties, remain silent. © 2011. The American Astronomical Society. All rights reserved.. |
| first_indexed | 2024-03-07T03:51:07Z |
| format | Journal article |
| id | oxford-uuid:c148f8a6-4727-4ff6-892e-4b37ec620b42 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T03:51:07Z |
| publishDate | 2011 |
| record_format | dspace |
| spelling | oxford-uuid:c148f8a6-4727-4ff6-892e-4b37ec620b422022-03-27T06:00:34ZBLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAMJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:c148f8a6-4727-4ff6-892e-4b37ec620b42EnglishSymplectic Elements at Oxford2011Richards, JMax-Moerbeck, WPavlidou, VKing, OPearson, TReadhead, AReeves, RShepherd, MStevenson, MWeintraub, LFuhrmann, LAngelakis, EZensus, JHealey, SERomani, RShaw, MSGrainge, KBirkinshaw, MLancaster, KWorrall, DTaylor, GCotter, GBustos, RThe 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 15GHz radio monitoring program with the 40 m telescope at the Owens Valley Radio Observatory. This program began with the 1158 northern (δ > -20°) sources from the Candidate Gamma-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4mJy (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 (6σ), 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 (3σ) 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 3σ significance. These findings represent an important step toward understanding why some blazars emit gamma-rays while others, with apparently similar properties, remain silent. © 2011. The American Astronomical Society. All rights reserved.. |
| spellingShingle | Richards, J Max-Moerbeck, W Pavlidou, V King, O Pearson, T Readhead, A Reeves, R Shepherd, M Stevenson, M Weintraub, L Fuhrmann, L Angelakis, E Zensus, J Healey, SE Romani, R Shaw, MS Grainge, K Birkinshaw, M Lancaster, K Worrall, D Taylor, G Cotter, G Bustos, R BLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAM |
| title | BLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAM |
| title_full | BLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAM |
| title_fullStr | BLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAM |
| title_full_unstemmed | BLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAM |
| title_short | BLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAM |
| title_sort | blazars in the fermi era the ovro 40 m telescope monitoring program |
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