THE NEAR INFRARED AND OPTICAL PHOTOMETRIC ACTIVITY OF V517 Cyg

A near infrared and optical photometric study of Herbig star V517 Cyg has been carried out. Infrared data were obtained in 2003–2017 at the Campo Imperatory Observatory (Italy) with the Pulkovo telescope AZT-24 in Johnson’s $JHK$ bands. Optical light curves in Johnson $UBVR$ bands were obtained at the Maidanak observatory. Additional optical photometry from different sources (ASSAS, WISE, and AAVSO) was also used. It was shown that the behavior of V517 Cyg in the near infrared is typical for UX Ori stars. A considerable contribution to the near infrared variability is due to variable extinction along the line of sight, but the disk radiation becomes strong in the $H$ and $K$ bands: there is a significant correlation of $V$ and $J$ magnitudes ($r\sim 0.84$), while $H$ and $K$ bands correlates poorly with $V$ band. The amplitude of variability in $J$ is quite large ($\sim {1.8}^m$). The deepest minimum ($\mathrm{\Delta }V\sim {3.6}^m$) in the $V$ band demonstrates quasi-periodic variations with an amplitude of $\sim {0.8}^m$ and a period of $\sim 19$ days, the origin of which is still unclear. It is possible that these quasi-periodic variations are related to rotation period of a second companion, a cold T Tauri star. The spectrum V517 Cyg reveals typical for UX Ori stars the double-peaked emission line H_α. The NaI D doublet has inverse P Cyg profiles, indicating intense accretion of gas onto the star. The accretion rate from an equivalent width of the H_α line is ${\dot{M}}_{acc}=3.6\times {10}^{-8}{M}_{\odot }$ per year.