Locating the γ-ray emission site in Fermi/LAT blazars – II. Multifrequency correlations
Abstract
In an attempt to constrain and understand the emission mechanism of γ-rays, we perform a cross-correlation analysis of 15 blazars using light curves in millimetre, optical and γ-rays. We use discrete correlation function and consider only correlations significant at the 99 per cent level. A strong correlation was found between 37 and 95 GHz with a near-zero time delay in most of the sources, and ∼1 month or longer in the rest. A similar result was obtained between the optical and γ-ray bands. Of the 15 sources, less than 50 per cent showed a strong correlation between the millimetre and γ-ray or millimetre and optical bands. The primary reason for the lack of statistically significant correlation is the absence of a major outburst in the millimetre bands of most of the sources during the 2.5 yr time period investigated in our study. This may indicate that only the long-term variations or large flares are correlated between these bands. The variability of the sources at every waveband was also inspected using fractional rms variability (F_(var)). The F_(var) displays an increase with frequency reaching its maximum in the γ-rays.
Additional Information
© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 November 9. Received 2015 November 2; in original form 2015 September 11. We thank the anonymous referee for valuable comments that improved the manuscript. VR acknowledges the support from the Finnish Graduate School in Astronomy and Space Physics. TH was supported by the Academy of Finland project number 267324. MB acknowledges support from the International Fulbright Science and Technology Award and the NASA Earth and Space Science Fellowship Program, grant NNX14AQ07H. We are grateful for the support from the Academy of Finland to the Metsähovi AGN monitoring project (numbers 212656, 210338, 121148 and others). Support for CARMA construction was derived from the states of California, Illinois and Maryland, the James S. McDonnell Foundation, the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the University of Chicago, the Associates of the California Institute of Technology and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement, and by the CARMA partner universities. Data from the Steward Observatory spectropolarimetric monitoring project were used. This programme is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G and NNX12AO93G. This paper has made use of up-to-date SMARTS optical/near-infrared light curves. We also acknowledge the computational resources provided by the Aalto Science-IT project. This research has made use of NASA's Astrophysics Data System.Attached Files
Published - MNRAS-2016-Ramakrishnan-171-80.pdf
Submitted - 1511.02654v1.pdf
Supplemental Material - online_figS1.pdf
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Additional details
- Alternative title
- Locating the gamma-ray emission site in Fermi/LAT blazars. II Multifrequency correlations
- Eprint ID
- 64243
- Resolver ID
- CaltechAUTHORS:20160204-143737290
- Finnish Graduate School in Astronomy and Space Physics
- 267324
- Academy of Finland
- Fulbright Commission
- NNX14AQ07H
- NASA Earth and Space Science Fellowship
- 212656
- Academy of Finland
- 210338
- Academy of Finland
- 121148
- Academy of Finland
- James S. McDonnell Foundation
- Gordon and Betty Moore Foundation
- Kenneth T. and Eileen L. Norris Foundation
- University of Chicago
- Caltech Associates
- NSF
- CARMA partner universities
- NNX08AW56G
- NASA
- NNX09AU10G
- NASA
- NNX12AO93G
- NASA
- Created
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2016-02-04Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field