Poster abstract details
Spectral Analysis of the O(He)-type Central Stars of the Planetary Nebulae K1-27 and LoTr4
Abstract
The five known O(He)-type stars are post-AGB stars that exhibit almost pure
helium absorption-line spectra. Thus, their evolution deviates from the
hydrogen-deficient post-AGB evolutionary sequence of carbon-dominated stars
like e.g. PG 1159 stars. The origin of O(He) stars is still not explained.
They might be either post-early AGB stars or the progeny of R Coronae Borealis stars.
The central stars of the planetary nebulae K1-27 and LoTr4 belong to the
O(He) spectral type. Both have spectroscopic twins without a surrounding nebula,
namely HS,2209+8229 and HS,1522+6615, respectively.
We present preliminary results of an ongoing non-LTE spectral analysis of all
five O(He) stars, based on FUSE and HST/COS observations.
helium absorption-line spectra. Thus, their evolution deviates from the
hydrogen-deficient post-AGB evolutionary sequence of carbon-dominated stars
like e.g. PG 1159 stars. The origin of O(He) stars is still not explained.
They might be either post-early AGB stars or the progeny of R Coronae Borealis stars.
The central stars of the planetary nebulae K1-27 and LoTr4 belong to the
O(He) spectral type. Both have spectroscopic twins without a surrounding nebula,
namely HS,2209+8229 and HS,1522+6615, respectively.
We present preliminary results of an ongoing non-LTE spectral analysis of all
five O(He) stars, based on FUSE and HST/COS observations.