HD 178892 - a cool Ap star with extremely strong magnetic field
T. Ryabchikova, O. Kochukhov, D. Kudryavtsev, I. Romanyuk, E. Semenko, S. Bagnulo, G. Lo Curto, P. North, M. Sachkov
Abstract
We report a discovery of the Zeeman resolved spectral lines, corresponding to the extremely large magnetic field modulus <Bs>=17.5 kG, in the cool Ap star HD 178892. The mean longitudinal field of this star reaches 7.5 kG, and its rotational modulation implies the strength of the dipolar magnetic component Bp>=23 kG. We have revised rotation period of the star using the All Sky Automated Survey photometry and determined P=8.2478 d. Rotation phases of the magnetic and photometric maxima of the star coincide with each other. We obtained Geneva photometric observation of HD 178892 and estimated Teff=7700+/-250 K using photometry and the hydrogen Balmer lines. Preliminary abundance analysis reveals abundance pattern typical of rapidly oscillating Ap stars.