The pre-cataclysmic variable, LTT 560

¹ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica, Vicuña Mackenna 4860, 782-0436 Macul, Chile e-mail: ctappert@astro.puc.cl
² Department of Physics, University of Warwick, Coventry CV4 7AL, UK e-mail: [Boris.Gaensicke;a.aungwerojwit]@warwick.ac.uk
³ European Southern Observatory, Casilla 19001, Santiago 19, Chile e-mail: lschmidt@eso.org
⁴ Department of Physics, Faculty of Science, Naresuan University, Phitsanulok 65000, Thailand
⁵ Departamento de Física, Universidad de Concepción, Casilla 160-C, Concepción, Chile e-mail: rmennick@astro-udec.cl
⁶ Institut für Theoretische Physik und Astrophysik, University of Kiel, 24098 Kiel, Germany e-mail: koester@astrophysik.uni-kiel.de

Received: 16 February 2007
Accepted: 11 August 2007

Abstract

Aims. System parameters of the object LTT 560 are determined in order to clarify its nature and evolutionary status.

Methods. We apply time-series photometry to reveal orbital modulations of the light curve, time-series spectroscopy to measure radial velocities of features from both the primary and the secondary star, and flux-calibrated spectroscopy to derive temperatures of both components.

Results. We find that LTT 560 is composed of a low temperature (T ~ 7500 K) DA white dwarf as the primary and an M5.5±1 main-sequence star as the secondary component. The current orbital period is P_orb = 3.54(07) h. We derive a mass ratio  = 0.36(03) and estimate the distance to d = 25–40 pc. Long-term variation of the orbital light curve and an additional Hα emission component on the white dwarf indicate activity in the system, probably in the form of flaring and/or accretion events.