PN fast winds: Temporal structure and stellar rotation

Abstract

To diagnose the time-variable structure in the fast winds of central stars of planetary nebulae (CSPN), we present an analysis of P Cygni line profiles in FUSE satellite far-UV spectroscopic data. Archival spectra are retrieved to form time-series datasets for the H-rich CSPN NGC 6826, IC 418, IC 2149, IC 4593 and NGC 6543. Despite limitations due to the fragmented sampling of the time-series, we demonstrate that in all 5 CSPN the UV resonance lines are variable primarily due to the occurrence of blueward migrating discrete absorption components (DACs). Empirical (SEI) line-synthesis modelling is used to determine the range of fluctuations in radial optical depth, which are assigned to the temporal changes in large-scale wind structures. We argue that DACs are common in CSPN winds, and their empirical properties are akin to those of similar structures seen in the absorption troughs of massive OB stars. Constraints on PN central star rotation velocities are derived from Fast-Fourier Transform analysis of photospheric lines for our target stars. Favouring the causal role of co-rotating interaction regions, we explore connections between normalised DAC accelerations and rotation rates of PN central stars and O stars. The comparative properties suggest that the same physical mechanism is acting to generate large-scale structure in the line-driven winds in the two different settings.

Accepted for publication in MNRAS; 10 pages, 5 figures

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• Weak magnetic fields in central stars of planetary nebulae?
• Discovery of Multiple Shells Around the Planetary Nebula IC 418
• Kepler photometry and optical spectroscopy of the ZZ Lep central star of the Planetary Nebula NGC 6826: rotational and wind variability
• Looking deep into the Cat's Eye: Structure and rotation in the fast wind of the PN central star of NGC6543
• Mass loss rates from mid-IR excesses in LMC and SMC O stars
• Long-Wavelength, Free-Free Spectral Energy Distributions from Porous Stellar Winds
• Analysis of absorption lines in the high resolution spectra of five hot post-AGB candidates
• Rummaging inside the Eskimo's parka: Variable asymmetric PN fast wind and a binary nucleus?