The optically bright post-AGB population of the LMC^⋆,⋆⋆

¹ Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D bus 2401, 3001 Leuven Belgium
e-mail: els.vanaarle@ster.kuleuven.be
² SUPA, School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, Scotland, UK
³ Department of Physics and Astronomy, University of Denver, 2112 E. Wesley, Denver, CO 80208, USA
⁴ Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611, Australia
⁵ Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA

Received: 29 September 2010
Accepted: 8 March 2011

Abstract

Context. The detected variety in chemistry and circumstellar shell morphology of the limited sample of Galactic post-asymptotic giant branch (AGB) stars is so large that there is no consensus yet on how the different objects are linked by evolutionary channels. The evaluation is complicated by the fact that their distances and hence luminosities remain largely unknown.

Aims. We construct a catalogue of the optically bright post-AGB stars in the Large Magellanic Cloud (LMC). The sample forms an ideal testbed for stellar evolution theory predictions of the final phase of low- and intermediate-mass stars, because the distance and hence luminosity and also the current and initial mass of these objects is well constrained.

Methods. Via cross-correlation of the Spitzer SAGE catalogue with optical catalogues we selected a sample of LMC post-AGB candidates based on their  [8]  −  [24]  colour index and estimated luminosity. We determined the fundamental properties of the central stars of 105 of these objects using low-resolution, optical spectra that we obtained at Siding Spring Observatory and SAAO.

Results. We constructed a catalogue of 70 high probability and 1337 candidate post-AGB stars that is available at the CDS. About half of the objects in our sample of post-AGB candidates show a spectral energy distribution (SED) that is indicative of a disc rather than an expanding and cooling AGB remnant. Like in the Galaxy, the disc sources are likely associated with binary evolution. Important side products of this research are catalogues of candidate young stellar objects, candidate supergiants with circumstellar dust, and discarded objects for which a spectrum was obtained. These too are available at the CDS.