Long-Term Optical and Spectral Variability of FSRQ 3C454.3

Abstract

3C454.3 is a widely studied and monitored flat spectrum radio quasar. We use the observations from the Small and Moderate Aperture Research Telescope System (SMARTS) to analyze the long-term optical and spectral variabilities of 3C454.3 at B, V, R, J, and K (BVRJK) bands. Based on the relation: Fν∝ν-α, we calculate the multiband spectral indices (α) and analyze the relations between α and Fν, where Fν is the flux density at ν band (ν=B, V, R, J, K). Main results are as follows. (1) The largest variations at BVRJK bands are ΔB = 3.37±0.08 mag, with the timescale ΔTB≈ 1015 days, at B band; ΔV = 3.31±0.07 mag, with the timescale ΔTV≈ 1014 days, at V band; ΔR = 3.62±0.12 mag, with the timescale ΔTR≈ 679 days, at R band; ΔJ = 4.08±0.01 mag, with the timescale ΔTJ≈ 763 days, at J band; and ΔK = 5.03±0.03 mag, with the timescale ΔTK≈ 2715 days, at K band. (2) We analyze the long-term BVRJK lightcurves and obtain the quasiperiodicities: P1=86.92±2.21 days, P2=204±8.1 days, and P3=1.24±0.19 years. (3) Multiband lightcurves show time delays: τVB = 0.15±0.12 days, τRB = 0.37±0.28 days, τJB = 0.58±0.40 days, and τKB = 1.02±0.47 days. (4) The relations between α and Fν show strong correlations, which are typical RWB behaviors; when the source turns to be brighter, the spectral indices turn to be redder.