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Temporal Correlations Between Optical and Gamma-ray Activity in Blazars

hal.structure.identifierDepartment of Astronomy [Berkeley]
hal.structure.identifierDepartment of Physics and Astronomy [UCLA, Los Angeles]
dc.contributor.authorCOHEN, D. P.
hal.structure.identifierPhysics Department [Stanford]
dc.contributor.authorROMANI, Roger W.
hal.structure.identifierDepartment of Astronomy [Berkeley]
dc.contributor.authorFILIPPENKO, Alexei V.
hal.structure.identifierNASA Goddard Space Flight Center [GSFC]
dc.contributor.authorCENKO, S. Bradley
hal.structure.identifierCentre d'Etudes Nucléaires de Bordeaux Gradignan [CENBG]
dc.contributor.authorLOTT, Benoit
hal.structure.identifierDepartment of Astronomy [Berkeley]
dc.contributor.authorZHENG, Weikang
hal.structure.identifierDepartment of Astronomy [Berkeley]
dc.contributor.authorLI, Weidong
dc.date.issued2014
dc.identifier.issn0004-637X
dc.description.abstractEnWe have been using the 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory to optically monitor a sample of 157 blazars that are bright in gamma rays, being detected with high significance (≥10σ) in one year by the Large Area Telescope (LAT) on the {\it Fermi Gamma-ray Space Telescope}. We attempt to observe each source on a 3-day cadence with KAIT, subject to weather and seasonal visibility. The gamma-ray coverage is essentially continuous. KAIT observations extend over much of the 5-year {\it Fermi} mission for several objects, and most have >100 optical measurements spanning the last three years. These blazars (flat-spectrum radio quasars and BL~Lac objects) exhibit a wide range of flaring behavior. Using the discrete correlation function (DCF), here we search for temporal relationships between optical and gamma-ray light curves in the 40 brightest sources in hopes of placing constraints on blazar acceleration and emission zones. We find strong optical--gamma-ray correlation in many of these sources at time delays of ∼1 to ∼10 days, ranging between −40 and +30 days. A stacked average DCF of the 40 sources verifies this correlation trend, with a peak above 99% significance indicating a characteristic time delay consistent with 0 days. These findings strongly support the widely accepted leptonic models of blazar emission. However, we also find examples of apparently uncorrelated flares (optical flares with no gamma-ray counterpart and gamma-ray flares with no optical counterpart) that challenge simple, one-zone models of blazar emission. Moreover, we find that flat-spectrum radio quasars tend to have gamma rays leading the optical, while intermediate and high synchrotron peak blazars with the most significant peaks have smaller lags/leads.
dc.language.isoen
dc.publisherAmerican Astronomical Society
dc.subject.engalaxies jets
dc.subject.enactive galactic nuclei blazars
dc.subject.enquasars general
dc.title.enTemporal Correlations Between Optical and Gamma-ray Activity in Blazars
dc.typeArticle de revue
dc.identifier.doi10.1088/0004-637X/797/2/137
dc.subject.halPhysique [physics]/Astrophysique [astro-ph]
dc.subject.halPhysique [physics]/Physique des Hautes Energies - Phénoménologie [hep-ph]
bordeaux.journalThe Astrophysical Journal
bordeaux.page137
bordeaux.volume797
bordeaux.peerReviewedoui
hal.identifierhal-01119034
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-01119034v1
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