Optically Visible Post-AGB Stars, Post-RGB Stars and Young Stellar
  Objects in the Large Magellanic Cloud
  We have carried out a search for optically visible post-Asymptotic Giant
Branch (post-AGB) stars in the Large Magellanic Cloud (LMC). First, we selected
candidates with a mid-IR excess and then obtained their optical spectra. We
disentangled contaminants with unique spectra such as M-stars, C-stars,
planetary nebulae, quasi-stellar objects and background galaxies. Subsequently,
we performed a detailed spectroscopic analysis of the remaining candidates to
estimate their stellar parameters such as effective temperature, surface
gravity (log g), metallicity ([Fe/H]), reddening and their luminosities. This
resulted in a sample of 35 likely post-AGB candidates with late-G to late-A
spectral types, low log g, and [Fe/H] < -0.5. Furthermore, our study confirmed
the existence of the dusty post-Red Giant Branch (post-RGB) stars, discovered
previously in our SMC survey, by revealing 119 such objects in the LMC. These
objects have mid-IR excesses and stellar parameters (Teff, log g, [Fe/H])
similar to those of post-AGB stars except that their luminosities (< 2500
Lsun), and hence masses and radii, are lower. These post-RGB stars are likely
to be products of binary interaction on the RGB. The post-AGB and post-RGB
objects show SED properties similar to the Galactic post-AGB stars, where some
have a surrounding circumstellar shell, while some others have a surrounding
stable disc similar to the Galactic post-AGB binaries. This study also resulted
in a new sample of 162 young stellar objects, identified based on a robust log
g criterion. Other interesting outcomes include objects with an UV continuum
and an emission line spectrum; luminous supergiants; hot main-sequence stars;
and 15 B[e] star candidates, 12 of which are newly discovered in this study.
