* Astronomy

Title: Central Stars of Planetary Nebulae
Author: David Jones

In this brief invited review, I will attempt to summarise some of the key areas of interest in the study of central stars of planetary nebulae which (probably) won't be covered by other speakers' proceedings. The main focus will, inevitably, be on the subject of multiplicity, with special emphasis on recent results regarding triple central star systems as well as wide binaries which avoid a common-envelope phase. Furthermore, in light of the upcoming release of Kepler's Campaign 11 data, I will discuss a few of the prospects from that data including the unique possibility to detect merger products.

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Title: A Survey for hot Central Stars of Planetary Nebulae I. Methods and First Results
Author: Graham C. Kanarek, Michael M. Shara, Jacqueline K. Faherty, David Zurek, Anthony F.J. Moffat

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.

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Title: On the distances of planetary nebulae 
Author: Haywood Smith Jr 

We reconsider calibration of statistical distance scales for planetary nebulae, examining precision and systematic error for various distance methods used as well as the scales themselves. A different calibration strategy, one based on precise trigonometric parallaxes by Harris et al. (2007), is presented. Most statistical scales have an overall scale error; in addition, all four tested show dependence of distance ratio [scale/actual] on nebular radius. Some methods used for calibration have systematic errors, and the extinction method is found to be mostly unreliable. Comparison of Hipparcos parallaxes for a few large planetaries with our "best estimate" distances for those confirms the overestimation of 2.5 found by Harris et al. for PHL 932. We suggest a possible connection with the smaller overestimation found by Melis et al. (2014) when testing Hipparcos parallaxes for some of the Pleiades. 

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Title: A New Grid of Synthetic Spectra for the Analysis of [WC]-type Central Stars of Planetary Nebulae
Authors: Graziela R. Keller, James E. Herald, Luciana Bianchi, Walter J. Maciel, Ralph C. Bohlin

We present a comprehensive grid of synthetic stellar-atmosphere spectra, suitable for the analysis of high resolution spectra of hydrogen-deficient post-Asymptotic Giant Branch (post-AGB) objects hotter than 50000 K, migrating along the constant luminosity branch of the Hertzsprung-Russell diagram (HRD). The grid was calculated with CMFGEN, a state-of-the-art stellar atmosphere code that properly treats the stellar winds, accounting for expanding atmospheres in non-LTE, line blanketing, soft X-rays, and wind clumping. We include many ionic species that have been previously neglected. Our uniform set of models fills a niche in an important parameter regime, i.e., high effective temperatures, high surface gravities, and a range of mass-loss values. The grid constitutes a general tool to facilitate determination of the stellar parameters and line identifications and to interpret morphological changes of the stellar spectrum as stars evolve through the central star of planetary nebula (CSPN) phase. We show the effect of major physical parameters on spectral lines in the far-UV, UV, and optical regimes. We analyse UV and far-UV spectra of the central star of NGC 6905 using the grid to constrain its physical parameters, and proceed to further explore other parameters not taken in consideration in the grid. This application shows that the grid can be used to constrain the main photospheric and wind parameters, as a first step towards a detailed analysis. The full grid of synthetic spectra, comprising far-UV, UV, optical, and IR spectral regions, is available on-line.

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