Long term variability and correlation study of the blazar 3C 454.3 in radio, NIR and optical wavebands

TL;DR

This study analyzes over 8 years of multiwavelength data from blazar 3C 454.3, revealing correlated emission regions, spectral behaviors, and jet dynamics through variability and lag analysis.

Contribution

It provides a detailed long-term multiwavelength variability and correlation analysis, introducing a curved jet model with variable Doppler factors to explain observed lag changes.

Findings

Optical and IR bands are co-spatial with near-zero lag.

Radio and optical/IR emissions show 10-100 day lags, indicating different regions.

Variable Doppler factors explain lag variations and emission timescales.

Abstract

We performed a long-term optical (B, V, R bands), infra-red (J and K bands) and radio band (15, 22, 37 GHz band) study on the flat spectrum radio quasar, 3C 454.3, using the data collected over a period of more than 8 years (MJD 54500--57500). The temporal variability, spectral properties and inter-waveband correlations were studied by dividing the available data into smaller segments with more regular sampling. This helped us constrain the size and the relative locations of the emission regions for different wavebands. Spectral analysis of the source revealed the interplay between the accretion disk and jet emission. The source predominantly showed a redder-when-brighter trend, though we observed a bluer-when-brighter trend at high flux levels which could be signatures of particle acceleration and radiative cooling. Significant correlations with near-zero lag were seen between various optical/infra-red bands, indicating that these emission regions are co-spatial. Correlations with a time lag of about 10--100 days are seen between optical/infra-red and radio bands indicating these emissions arise from different regions. We also observe the DCF peak lag change from year to year. We try to explain these differences using a curved jet model where the different emission regions have different viewing angles resulting in a frequency dependent Doppler factor. This variable Doppler factor model explains the variability timescales and the variation in DCF peak lag between the radio and optical emissions in different segments. Lags of 6-180 days are seen between emissions in various radio bands, indicating a core-shift effect