CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI
We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ~30% of γ-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the opt...
| Main Authors: | , , , , , , , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
IOP Publishing
2015
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| Online Access: | http://hdl.handle.net/1721.1/95443 |
| _version_ | 1826203732067483648 |
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| author | Ruan, John J. Anderson, Scott F. MacLeod, Chelsea L. Becker, Andrew C. Burnett, T. H. Davenport, James R. A. Kochanek, Christopher S. Plotkin, Richard M. Sesar, Branimir Stuart, J. Scott Ivezic, Zeljko |
| author2 | Lincoln Laboratory |
| author_facet | Lincoln Laboratory Ruan, John J. Anderson, Scott F. MacLeod, Chelsea L. Becker, Andrew C. Burnett, T. H. Davenport, James R. A. Kochanek, Christopher S. Plotkin, Richard M. Sesar, Branimir Stuart, J. Scott Ivezic, Zeljko |
| author_sort | Ruan, John J. |
| collection | MIT |
| description | We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ~30% of γ-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the optical LINEAR asteroid survey, we characterize the optical variability of blazars by fitting a damped random walk model to individual light curves with two main model parameters, the characteristic timescales of variability τ, and driving amplitudes on short timescales [^ over σ]. Imposing cuts on minimum τ and [^ over σ] allows for blazar selection with high efficiency E and completeness C. To test the efficacy of this approach, we apply this method to optically variable LINEAR objects that fall within the several-arcminute error ellipses of γ-ray sources in the Fermi 2FGL catalog. Despite the extreme stellar contamination at the shallow depth of the LINEAR survey, we are able to recover previously associated optical counterparts to Fermi active galactic nuclei with E ≥ 88% and C = 88% in Fermi 95% confidence error ellipses having semimajor axis r < 8'. We find that the suggested radio counterpart to Fermi source 2FGL J1649.6+5238 has optical variability consistent with other γ-ray blazars and is likely to be the γ-ray source. Our results suggest that the variability of the non-thermal jet emission in blazars is stochastic in nature, with unique variability properties due to the effects of relativistic beaming. After correcting for beaming, we estimate that the characteristic timescale of blazar variability is ~3 years in the rest frame of the jet, in contrast with the ~320 day disk flux timescale observed in quasars. The variability-based selection method presented will be useful for blazar identification in time-domain optical surveys and is also a probe of jet physics. |
| first_indexed | 2024-09-23T12:42:28Z |
| format | Article |
| id | mit-1721.1/95443 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T12:42:28Z |
| publishDate | 2015 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/954432022-09-28T09:31:34Z CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI Ruan, John J. Anderson, Scott F. MacLeod, Chelsea L. Becker, Andrew C. Burnett, T. H. Davenport, James R. A. Kochanek, Christopher S. Plotkin, Richard M. Sesar, Branimir Stuart, J. Scott Ivezic, Zeljko Lincoln Laboratory Stuart, J. Scott We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ~30% of γ-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the optical LINEAR asteroid survey, we characterize the optical variability of blazars by fitting a damped random walk model to individual light curves with two main model parameters, the characteristic timescales of variability τ, and driving amplitudes on short timescales [^ over σ]. Imposing cuts on minimum τ and [^ over σ] allows for blazar selection with high efficiency E and completeness C. To test the efficacy of this approach, we apply this method to optically variable LINEAR objects that fall within the several-arcminute error ellipses of γ-ray sources in the Fermi 2FGL catalog. Despite the extreme stellar contamination at the shallow depth of the LINEAR survey, we are able to recover previously associated optical counterparts to Fermi active galactic nuclei with E ≥ 88% and C = 88% in Fermi 95% confidence error ellipses having semimajor axis r < 8'. We find that the suggested radio counterpart to Fermi source 2FGL J1649.6+5238 has optical variability consistent with other γ-ray blazars and is likely to be the γ-ray source. Our results suggest that the variability of the non-thermal jet emission in blazars is stochastic in nature, with unique variability properties due to the effects of relativistic beaming. After correcting for beaming, we estimate that the characteristic timescale of blazar variability is ~3 years in the rest frame of the jet, in contrast with the ~320 day disk flux timescale observed in quasars. The variability-based selection method presented will be useful for blazar identification in time-domain optical surveys and is also a probe of jet physics. 2015-02-20T16:16:15Z 2015-02-20T16:16:15Z 2012-11 2012-08 Article http://purl.org/eprint/type/JournalArticle 0004-637X 1538-4357 http://hdl.handle.net/1721.1/95443 Ruan, John J., Scott F. Anderson, Chelsea L. MacLeod, Andrew C. Becker, T. H. Burnett, James R. A. Davenport, Zeljko Ivezic, et al. “CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI.” The Astrophysical Journal 760, no. 1 (November 2, 2012): 51. © 2012 The American Astronomical Society en_US http://dx.doi.org/10.1088/0004-637x/760/1/51 The Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf IOP Publishing American Astronomical Society |
| spellingShingle | Ruan, John J. Anderson, Scott F. MacLeod, Chelsea L. Becker, Andrew C. Burnett, T. H. Davenport, James R. A. Kochanek, Christopher S. Plotkin, Richard M. Sesar, Branimir Stuart, J. Scott Ivezic, Zeljko CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI |
| title | CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI |
| title_full | CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI |
| title_fullStr | CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI |
| title_full_unstemmed | CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI |
| title_short | CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI |
| title_sort | characterizing the optical variability of bright blazars variability based selection of fermi active galactic nuclei |
| url | http://hdl.handle.net/1721.1/95443 |
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