Spectroscopic and photometric variability of HD 51585 as a manifestation of stellar wind

Abstract

We present the results of our photoelectric observations of HD 51585 (OY Gem), a B[e] star with an infrared excess and a candidate for protoplanetary nebulae, obtained with a 60-cm telescope at the Crimean Station of the Sternberg Astronomical Institute in 1992–2005. The star exhibited rapid irregular brightness variations with amplitudes from $0^m .1$ in the V band to $0^m .2$ in U band within the observing season as well as slow systematic variations with amplitudes from $0^m .3$ in the V band to $0^m .65$ in the U band and with a quasi-period of ∼2800 days. The B-V color index varied within $0^m .1$ and did not follow the slow systematic brightness variations, while U-B correlated with the U brightness and varied between $- 0^m .7$ at maximum light and $- 0^m .35$ at minimum light. Our low-resolution spectroscopy performed in 1994–2005 has revealed significant variability of the Balmer and Paschen hydrogen emission lines as well as the He I and O I lines. Equivalent widths are given for the H I, He I, O I, and Fe II lines; a correlation has been found between the star’s photometric variability and the hydrogen line intensities. Our joint analysis of the photometric and spectroscopic data suggests that variations in a strong stellar wind are responsible for the variability of the star.