Search for systemic mass loss in Algols with bow shocks

¹ University of ViennaDepartment of Astrophysics, Sternwartestraße 77, 1180 Wien, Austria
e-mail: a.mayer@univie.ac.at
² Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles, CP 226, Av. F. Roosevelt 50, 1050 Brussels, Belgium
³ European Southern Observatory, Alonso de Cordova 3107, 19001 Casilla, Santiago, Chile

Received: 28 May 2015
Accepted: 24 December 2015

Abstract

Aims. Various studies indicate that interacting binary stars of Algol type evolve non-conservatively. However, direct detections of systemic mass loss in Algols have been scarce so far. We study the systemic mass loss in Algols by looking for the presence of infrared excesses originating from the thermal emission of dust grains, which is linked to the presence of a stellar wind.

Methods. In contrast to previous studies, we make use of the fact that stellar and interstellar material is piled up at the edge of the astrosphere where the stellar wind interacts with the interstellar medium. We analyse WISE W3 12 μm and WISE W4 22 μm data of Algol-type binary Be and B[e] stars and the properties of their bow shocks. From the stand-off distance of the bow shock we are able to determine the mass-loss rate of the binary system.

Results. Although the velocities of the stars with respect to the interstellar medium are quite low, we find bow shocks present in two systems, namely π Aqr, and ϕ Per; a third system, CX Dra, shows a more irregular circumstellar environment morphology which might somehow be related to systemic mass loss. The properties of the two bow shocks point to mass-loss rates and wind velocities typical of single B stars, which do not support an enhanced systemic mass loss.