BV RI observations of the radio source S5 0716+71

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Photometric observations of the radio source S5 0716+714 were obtained in BV RI filters from January 20, 1998 to January 9, 2001 with Zeiss-600 and Zeiss-1000 telescopes of the Special Astrophysical Observatory of the Russian Academy of Sciences. The light curves in all the bands are synchronous, providing evidence for the real variability of the object in timescales, from hundreds of days to 5–10 min. No time shift between events in the adjacent filters was detected. The variability spectrum at frequencies of 0.003–100 d−1 (3.5 × 10−8–1.1 × 10−3 Hz) is close to that of a flicker noise. The optical spectral index α (S ∼ v α) varies from −1.59 at the minimum to −1.13 at the maximum brightness. Measurements of linear polarization in BV R carried out on April 12–13, 2000 confirmed a high degree of polarization and rapid fluctuations of the polarization in a timescale of 15–30 min, whose amplitude decreases at red wavelengths. All the optical properties of the source, its compactness, the absence of spectral lines, the high degree of polarization, and very rapid fluctuations of the brightness, polarization, and spectral index, suggest a synchrotron origin for optical radiation. It may be that we are observing the radiation from a group of very compact bodies (∼10−10 arcsec) at various stages of their evolution.