LSIV -12 degrees 111: A Candidate Halo Proto--Planetary Nebula

Abstract

We report on multiwavelength observations of LSIV -12 deg 111, which may be an emerging halo planetary nebula. This object was previously classified as a young emission-line B-type star, but a model atmosphere abundance analysis of high-resolution optical spectra has revealed it to be an evolved object, probably in the postasymptotic giant branch (AGB) evolutionary phase. The presence of an infrared excess and low-excitation nebular emission lines implies that the central star may just have started to photoionize the circumstellar material ejected during the AGB phase. In this paper we discuss the nebular and dust properties of LSIV -12 deg 111 and redetermine some metal abundances for the central star. These are used to constrain the evolutionary status of this unusual object.