Long-term optical and infrared variability characteristics of Fermi blazars

Title

Long-term optical and infrared variability characteristics of Fermi blazars

Creator

Safna P.Z.; Stalin C.S.; Rakshit S.; Mathew B.

Description

We present long-term optical and near-infrared flux variability analysis of 37 blazars detected in the ?-ray band by the Fermi Gamma-Ray Space Telescope. Among them, 30 are flat spectrum radio quasars (FSRQs) and 7 are BL Lac objects (BL Lacs). The photometric data in the optical (BVR) and infrared (JK) bands were from the Small and Moderate Aperture Research Telescope System acquired between 2008-2018. From cross-correlation analysis of the light curves at different wavelengths, we did not find significant time delays between variations at different wavelengths, except for three sources, namely PKS 1144-379, PKS B1424-418, and 3C 273. For the blazars with both B- and J-band data, we found that in a majority of FSRQs and BL Lacs, the amplitude of variability (?m) in the J band is larger than that in B band, consistent with the dominance of the non-thermal jet over the thermal accretion disc component. Considering FSRQs and BL Lacs as a sample, there are indications of ?m to increase gradually towards longer wavelengths in both, however, found to be statistically significant only between B and J bands in FSRQs. In the B-J v/s J-colour magnitude diagram, we noticed complicated spectral variability patterns. Most of the objects showed a redder when brighter (RWB) behaviour. Few objects showed a bluer when brighter (BWB) trend, while in some objects both BWB and RWB behaviours were noticed. These results on flux and colour characteristics indicate that the jet emission of FSRQs and BL Lacs is indistinguishable. 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.

Source

Monthly Notices of the Royal Astronomical Society, Vol-498, No. 3, pp. 3578-3591.

Date

2020-01-01

Publisher

Oxford University Press

Subject

BL Lacertae objects: general; galaxies: active; galaxies: jets; galaxies: nuclei

Coverage

Safna P.Z., Department of Physics and Electronics, CHRIST (Deemed to Be University), Hosur Road, Bangalore, 560029, India; Stalin C.S., Indian Institute of Astrophysics, Department of Science and Technology, Block II, Koramangala, Bangalore, 560034, India; Rakshit S., Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Vesilinnantie 5, Quantum, FI-20014, Finland; Mathew B., Department of Physics and Electronics, CHRIST (Deemed to Be University), Hosur Road, Bangalore, 560029, India

Rights

All Open Access; Green Open Access

Relation

ISSN: 358711; CODEN: MNRAA

Format

Online

Language

English

Type

Article

Identifier

https://doi.org/10.1093/mnras/staa2622

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096858185&doi=10.1093%2fmnras%2fstaa2622&partnerID=40&md5=ed7dfb1362310af3e4be9549adbed8f4