Characterizing the optical nature of the blazar S5 1803+784 during its 2020 flare

Abstract

We report the results from our study of the blazar S5 1803+784 carried out using the quasi-simultaneous $B$, $V$, $R$, and $I$ observations from May 2020 to July 2021 on 122 nights. Our observing campaign detected the historically bright optical flare during MJD 59063.5$-$MJD 59120.5. We also found the source in its brightest ($R_{mag}$= 13.617) and faintest ($R_{mag}$= 15.888) states till date. On 13 nights, covering both flaring and non-flaring periods, we searched for the intraday variability using the power-enhanced $F-$test and the nested ANOVA test. We found significant variability in 2 out of these 13 nights. However, no such variability was detected during the flaring period. From the correlation analysis, we observed that the emission in all optical bands were strongly correlated with a time lag of $\sim$ 0 days. To get insights into its dominant emission mechanisms, we generated the optical spectral energy distributions of the source on 79 nights and estimated the spectral indices by fitting the simple power law. Spectral index varied from 1.392 to 1.911 and showed significant variations with time and $R-$band magnitude. We have detected a mild bluer-when-brighter trend (BWB) during the whole monitoring period while a much stronger BWB trend during the flare. We also carried out a periodicity search using four different methods and found no significant periodicity during our observation duration. Based on the analysis during the flaring state of the source one can say that the emissions most likely originate from the jet rather than the accretion disk.

17 pages, 8 figures, 7 tables, accepted for publication in The Astrophysical Journal (ApJ)

References in corpus (17)

• A massive binary black-hole system in OJ287 and a test of general relativity
• The Spectral Energy Distributions of Fermi Blazars
• Optical Intra-day Variability in Blazars
• Statistical analyses of long-term variability of AGN at high radio frequencies
• Intra-night Optical Variability of Luminous Radio Quiet QSOs
• Multi-band optical variability studies of BL Lacertae
• The Discovery of Timescale-Dependent Color Variability of Quasars
• X-ray Intraday Variability of Five TeV Blazars with NuSTAR
• Extremely violent optical microvariability in blazars: fact or fiction?
• Multiwavelength Variability Signatures of Relativistic Shocks in Blazar Jets
• On the reliability of microvariability tests in quasars
• Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and $\gamma$-ray activity in 2015$-$2016
• Optical Flux and Spectral Variability of the TeV blazar PG 1553+113
• Multi-band behaviour of the TeV blazar PG 1553+113 in optical range on diverse timescales
• Optical Variability of the TeV Blazar 1ES 0806+524 on Diverse Timescales
• Optical Variability of Three Extreme TeV Blazars
• Multi-wavelength flare observations of the blazar S5 1803+784

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