Letter to the Editor

Double-periodic blue variables in the Magellanic Clouds

¹ Universidad de Concepción, Departamento de Física, Casilla 160–C, Concepción, Chile e-mail: pietrzyn@hubble.cfm.udec.cl, wgieren@coma.cfm.udec.cl
² Warsaw University Observatory, Al. Ujazdowskie 4,00-478, Warsaw, Poland
³ Instituto Astronômico e Geofísico, Universidade de São Paulo, Brazil e-mail: marcos@astro.iag.usp.br

Corresponding author: R. E. Mennickent, rmennick@stars.cfm.udec.cl

Received: 26 November 2002
Accepted: 24 January 2003

Abstract

We report the discovery, based on an inspection of the OGLE-II database, of a group of blue variables in the Magellanic Clouds showing simultaneously two kinds of photometric variability: a short-term cyclic variability with typical amplitude  mag and period P₁ between 4 and 16 days and a sinusoidal, long-term cyclic oscillation with much larger amplitude  mag with period P₂ in the range of 150–1000 days. We find that both periods seems to be coupled through the relationship . In general, the short term variability is reminiscent of those shown by Algol-type binaries. We propose that the long-term oscillation could arise in the precession of a elliptical disc fed by a Roche-lobe filling companion in a low mass ratio Algol system.