A Survey for hot Central Stars of Planetary Nebulae I. Methods and First Results

TL;DR

This paper reports initial spectroscopic follow-up of faint NIR emission-line candidates in the Galactic plane, revealing potential massive central stars of planetary nebulae with Wolf-Rayet characteristics, expanding the known candidate population.

Contribution

It introduces a new survey method for identifying faint central stars of planetary nebulae using NIR spectroscopy and presents first results from this approach.

Findings

Seven stars show Wolf-Rayet-like emission lines.

Candidates have NIR colors inconsistent with classical WR stars.

Survey has identified thousands of potential central star candidates.

Abstract

We present the results of initial spectrographic followup with the Very Large Telescope (UT3, Melipal) for $K_s \ge 14$ Galactic plane CIV emission-line candidates in the near-infrared (NIR). These 7 faint stars all display prominent HeI and CIV emission lines characteristic of a carbon-rich Wolf-Rayet star. They have NIR colours which are much too blue to be those of distant, classical WR stars. The magnitudes and colours are compatible with those expected for central stars of planetary nebulae, and are likely to come from massive progenitor populations, and themselves be more massive than any sample of planetary nebulae known. Our survey has identified thousands of such candidates.