Double-periodic blue variables in the Magellanic Clouds

Free access article

Issue		A&A Volume 399, Number 3, March I 2003


Page(s)		L47 - L50
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20030106

A&A 399, L47-L50 (2003)
DOI: 10.1051/0004-6361:20030106

Letter

Double-periodic blue variables in the Magellanic Clouds

R. E. Mennickent¹, G. Pietrzynski^{1, 2}, M. Diaz³ and W. Gieren¹

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

(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 $\Delta I \sim 0.05$ mag and period P₁ between 4 and 16 days and a sinusoidal, long-term cyclic oscillation with much larger amplitude $\Delta I \sim 0.2$ mag with period P₂ in the range of 150-1000 days. We find that both periods seems to be coupled through the relationship $P_{2} = 35.2 \pm 0.8~P_{1}$ . 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.

Key words: stars: binaries: eclipsing -- stars: binaries: close -- stars: variable: general -- stars: early-type

Offprint request: R. E. Mennickent, rmennick@stars.cfm.udec.cl

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