V379 Cephei: a quadruple system of two binaries ^*,**

¹ Astronomical Institute of the Charles University, Faculty of Mathematics and Physics, V Holešovičkách 2, 180 00 Praha 8, Czech Republic e-mail: Petr.Harmanec@mff.cuni.cz
² Astronomical Institute of the Academy of Sciences, 251 65 Ondřejov, Czech Republic
³ Department of Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
⁴ Hvar Observatory, Faculty of Geodesy, Zagreb University, 10000 Zagreb, Croatia
⁵ Departamento de Astronomia, Universidad de Guanajuato, Apartado 144, 36000 Guanajuato, GTO, Mexico
⁶ Department of Astronomy and Astrophysics, Villanova University, 800 Lancester Avenue, Villanova, PE 19085, USA
⁷ Physics & Astronomy Department, University of Victoria, PO Box 3055 STN CSC, Victoria, BC, V8W 3P6, Canada

Received: 29 September 2006
Accepted: 2 November 2006

Abstract

Context.Several binaries with masses anomalously small for their observed spectral types have been discussed in the astronomical literature and interpreted as the result of envelope ejection. V379 Cep is one of these objects.

Aims.We obtained new series of electronic spectra and  photometry of V379 Cep and analysed them in an effort to check whether the conclusion about its anomalous masses may not be premature.

Methods.Reduction of new spectra was carried out in the IRAF and SPEFO programs. New photometry was reduced and transformed to the standard system using the HEC22 program. Orbital elements were derived with the FOTEL program and via disentangling with the program KOREL. The final combined solution was obtained with the program PHOEBE. Some initial period searches were carried out using the phase dispersion minimalization technique.

Results.We found that the second system of spectral lines seen in the spectra of V379 Cep does not belong to the secondary but to the primary of another binary Ba + Bb (orbital period of 15871 ± 017), which constitutes a quadruple system with the narrow-lined 997638 ± 00006 eclipsing binary Aa + Ab (for which we report probable detection of the secondary and derive improved period and orbital elements). The mutual motion of the two binaries A + B around the common centre of gravity is also observable, and the probable orbital period is (7878 ± 77) days. Our result shows that the components Aa and Ba are somewhat evolved but removes the reported discrepancy of anomalously small masses.

Conclusions.We find that V379 Cep is an astrophysically interesting quadruple system for which a future combination of interferometry, spectroscopy, and photometry can provide individual masses of all four bodies.