ABELL 43 a second pulsating "hybrid PG 1159 star"

Abstract

We report observations of the planetary nebula nucleus Abell 43, obtained at the 2.5m Nordic Optical Telescope, which shows that it is a pulsator. Abell 43, a "hybrid-PG 1159" type star, is the second pulsator of this class, after HS 2324+3944. From the limited data set aquired, we find that Abell 43 exhibits at least two periods of 2600s and 3035s, the longest ones observed up to now in PG 1159 and "hybrid-PG 1159" pulsators. This strongly suggests that the variations are due to non-radial g-mode pulsations and cannot be a consequence of binarity. This discovery raises puzzling questions regarding the exitation mechanism in this H rich, C and O poor "hybrid-PG 1159" since the C and O abundances are too low to trigger the instability through the $\kappa$-mechanism invoked to explain the instability in the PG 1159 stars and in the previously known "hybrid-PG 1159" pulsator HS 2324+3944.

6 pages, 4 figures Accepted for publication in Astronomy and Astrophysics

References in corpus (1)

• A Hubble Space Telescope Survey for Resolved Companions of Planetary-Nebula Nuclei

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• New evolutionary calculations for the Born Again scenario
• The Nature of the Driving Mechanism in the Pulsating Hybrid PG 1159 Star Abell 43
• Astrophysics in 2005
• Abell 43: Longest period Planetary Nebula Nucleus variable