The atypical emission-line star Hen 3-209

We analyse observations, spanning 15 yr, dedicated to the extreme emission-line object Hen 3-209. Our photometric data indicate that the luminosity of the star undergoes marked variations with a peak-to-peak amplitude of 0.65 mag. These variations are recurrent, with a period of 16.093 +/- 0.005 d. The spectrum of Hen 3-209 is peculiar with many different lines (H I, He I, Fe II,. showing P Cygni profiles. The line profiles are apparently changing in harmony with the photometry. The spectrum also contains [O III] lines that display a saddle profile topped by three peaks, with a maximum separation of about 600 km s(-1). Hen 3-209 is most likely an evolved luminous object suffering from mass ejection events and maybe belonging to a binary system.