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Optical and infrared monitoring of BL Lac in 1999–2001

V. A. Hagen‐ThornAstronomical Institute, St. Petersburg State University, Universitetskii pr. 28, Petrodvorets, 198504, RussiaV. M. LarionovAstronomical Institute, St. Petersburg State University, Universitetskii pr. 28, Petrodvorets, 198504, RussiaЕ. Г. ЛарионоваAstronomical Institute, St. Petersburg State University, Universitetskii pr. 28, Petrodvorets, 198504, RussiaN. A. KudryavtsevaAstronomical Institute, St. Petersburg State University, Universitetskii pr. 28, Petrodvorets, 198504, RussiaА. В. ТихоновAstronomical Institute, St. Petersburg State University, Universitetskii pr. 28, Petrodvorets, 198504, RussiaA. V. Hagen-ThornAstronomical Institute, St. Petersburg State University, Universitetskii pr. 28, Petrodvorets, 198504, RussiaA. A. ArkharovPulkovo Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe shosse 65, St. Petersburg, 196140, RussiaA. Di PaolaINAF—Rome Astronomical Observatory, Via Frascati 33, Monteporzio Catone (Rome), I-00040, ItalyF. D’AlessioINAF—Rome Astronomical Observatory, Via Frascati 33, Monteporzio Catone (Rome), I-00040, Italy
2004en
ABI

Abstract

We present the results of our multicolor observations of BL Lac in the period 1999–2001. We show that the spectral energy distribution of the variable component in the range from K to B had remained unchanged for three years. The power-law spectrum is indicative of its synchrotron nature.

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