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Galaxies 2018, 6(1), 2;

Microvariability in BL Lacertae: “Zooming” into the Innermost Blazar Regions

Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland
Department of Physics, Florida International University, Miami, FL 33199, USA
Southeastern Association for Research in Astronomy (SARA).
Author to whom correspondence should be addressed.
Received: 23 November 2017 / Revised: 18 December 2017 / Accepted: 22 December 2017 / Published: 3 January 2018
(This article belongs to the Special Issue Microvariability of Blazars)
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In this work, we present the results of our multi-band microvariability study of the famous blazar BL Lac. We performed microvariablity observations of the source in the optical VRI bands for four nights in 2016. We studied the intranight flux and spectral variability of the source in detail with an objective to characterize microvariability in the blazars, a frequently observed phenomenon in blazars. The results show that the source often displays a fast flux variability with an amplitude as large as ~0.2 magnitude within a few hours, and that the color variability in the similar time scales can be characterized as “bluer-when-brighter” trend. We also observed markedly curved optical spectrum during one of the nights. Furthermore, the correlation between multi-band emission shows that in general the emission in all the bands are highly correlated; and in one of the nights V band emission was found to lead the I band emission by ~13 min. The search for characteristic timescale using z-transformed auto-correlation function and the structure function analyses reveals characteristic timescale of ~50 min in one of the R band observations. We try to explain the observed results in the context of the passage of shock waves through the relativistic outflows in blazars. View Full-Text
Keywords: particles acceleration; non-thermal radiation; AGN; BL Lacertae objects; individual; BL Lac; galaxies; jets particles acceleration; non-thermal radiation; AGN; BL Lacertae objects; individual; BL Lac; galaxies; jets

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Bhatta, G.; Webb, J.R. Microvariability in BL Lacertae: “Zooming” into the Innermost Blazar Regions. Galaxies 2018, 6, 2.

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