González, J.F. ; Briquet, M. ; Przybilla, N. ; Nieva, M.-F. ; De Cat, P. ; Saesen, S. ; Hubrig, S. ; Thoul, A. ; Pápics, P.I. ; Palaversa, L. ; Naef, D. ; Neveu-Van Malle, M. ; Järvinen, S. ; Pollard, K.R. ; Kilmartin, P. ; Mowlavi, N. ; Butler, K.

published in Astronomy & Astrophysics, 626 issue A94, pp. 1-15

Abstract: Aims: HD 96446 is a magnetic B2p He-strong star that has been reported to be a β Cep pulsator. We present a detailed spectroscopic analysis of this object based on an intensive observational data set obtained in a multisite campaign with the spectrographs Coralie, Feros, and Harps (La Silla), Uves (Paranal), Hercules (Mt. John Observatory), and Giraffe (SAAO). Methods: Radial velocities were measured by cross-correlations and analyzed to detect periodic variations. On the other hand, the mean spectrum was fitted with spectral synthesis to derive atmospheric parameters and chemical abundances. Results: From the analysis of radial velocities HD 96446 was discovered to be a spectroscopic binary with a period of 799 days. The stellar companion, that contributes only ∼5% of the total flux, is an A0-type star. A frequency analysis of the radial velocities allows to detect two pulsational modes with periods 2.23 h and 2.66 h. The main mode is most probably a low-inclination, dipole mode (l, m) = (1,0) and the second pulsation mode corresponds to (l, m) = (2,2) or to a pole-on (l, m) = (3,2) configuration. Besides radial velocities, the main pulsation mode is evidenced through small variations of the spectral morphology (temperature variations) and the light flux. The rotation period, of 23.4 d, was detected through the variation of line intensities. Chemical abundances are unevenly distributed over the stellar surface, with helium concentrated on the negative magnetic pole and most metals strengthened at lower latitudes. The mean chemical abundance of helium is strongly abnormal reaching 0.60 by number.

Keyword(s): binaries: spectroscopic ; stars: chemically peculiar ; stars: early-type ; stars: magnetic field ; stars: oscillations (including pulsations) ; stars: individual: HD 96446
DOI: 10.1051/0004-6361/201935177