Multiband optical variability of the TeV blazar PG 1553 + 113 in 2019. Issue 2 (20th December 2022)

• Record Type: Journal Article
• Authors: Dhiman, Vinit; Gupta, Alok C; Kurtanidze, Sofia O; Eglitis, I; Strigachev, A; Damljanovic, G; Wiita, Paul J; Gu, Minfeng; Gaur, Haritma; Vince, Oliver; Bachev, R; Bisen, D P; Ibryamov, S; Ivanidze, R Z; Jovanovic, Miljana D; Kurtanidze, Omar M; Nikolashvili, M G; Semkov, E; Spassov, B; Stojanovic, M; Villarroel, Beatriz; Xu, Haiguang; Zhang, Zhongli
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 519:Issue 2(2023)
• Page Start: 2796
• Page End: 2811
• Publication Date: 2022-12-20
• Subjects: galaxies: active -- BL Lacertae objects: general -- BL Lacertae objects: individual: PG 1553 + 113 -- quasars: individual; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac3709
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We report the flux and spectral variability of PG 1553 + 113 on intra-night (IDV) to short-term time-scales using BVRI data collected over 91 nights from 28 February to 8 November 2019 employing 10 optical telescopes: three in Bulgaria, two each in India and Serbia, and one each in Greece, Georgia, and Latvia. We monitored the blazar quasi-simultaneously for 16 nights in the V and R bands and 8 nights in the V, R, I bands and examined the light curves (LCs) for intra-day flux and colour variations using two powerful tests: the power-enhanced F-test and the nested ANOVA test. The source was found to be significantly (>99 per cent) variable in 4 nights out of 27 in R-band, 1 out of 16 in V-band, and 1 out of 6 nights in I-band. No temporal variations in the colours were observed on IDV time-scale. During the course of these observations the total variation in R-band was 0.89 mag observed. We also investigated the spectral energy distribution (SED) using B-, V-, R-, and I-band data. We found optical spectral indices in the range of 0.878 ± 0.029 to 1.106 ± 0.065 by fitting a power law ( F ν ∝ν −α ) to these SEDs of PG 1553 + 113. We found that the source follows a bluer-when-brighter trend on IDV time-scales. We discuss possible physical causes of the observed spectral variability.