Abstract Title:
Blazar Optical Variability: 20 Years of Observations at Belogradchik Observatory

Authors:
Rumen Bachev

Institution: *
Institute of Astronomy with NAO, BAS

Oral

Abstract Text:
Blazars are powerful, jet-dominated active galactic nuclei, whose jets happen to be pointed
almost directly towards the observer. A large variety of physical processes and phenomena take
place along the jet, most of which are not fully understood. This special orientation of the blazar
jets offers a unique perspective into the hearts of these cosmic ultra-high energy accelerators,
powered by supermassive black holes. One ways to probe the blazar central engine is through
its continuum variability, and in particular – through its optical variability. Blazars are known to
vary rapidly on diverse time scales – from minutes to years. Studying variability in detail,
especially when combine optical with radio, X- and gamma-ray observations can be of crucial
significance to constrain the models, measure parameters and better understand the physics of
the relativistic jets. Blazar observations in the optical have been performed at Belogradchik
Observatory for more than 20 years. Most of these observations were a part of large
international campaigns to monitor blazar variability. Such a cooperation among many
observatories, even with modest capabilities some of them, proved to be very successful and
extremely fruitful. In this talk I give some examples of the most interesting blazar variability
results obtained at (or with the participation of) Belogradchik Observatory and discuss what can
be learned from them.