Journal Article

The dense and asymmetric central star wind of the young PN He 2−138

R. K. Prinja, S. E. Hodges, M. A. Urbaneja and D. L. Massa

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 1, pages 641-649
Published in print February 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15928.x
The dense and asymmetric central star wind of the young PN He 2−138

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We present optical European Southern Observatory time series and UV archival (Far Ultraviolet Spectroscopic Explorer (FUSE), Hubble Space Telescope, International Ultraviolet Explorer) spectroscopy of the H-rich central star of He 2−138. Our study targets the central star wind in a very young planetary nebula, and explores physical conditions that may provide clues to the nature of the preceding post-asymptotic giant branch superwind phases of the star. We provide evidence for a dense, slowly accelerating outflow that is variable on time-scales of hours. Line-synthesis modelling (Sobolev with exact integration and cmfgen) of low- and high-ionization UV and optical lines is interpreted in terms of an asymmetric, two-component outflow, where high-speed high-ionization gas forms mostly in the polar region. Slower, low-ionization material is then confined primarily to a cooler equatorial component of the outflow. A dichotomy is also evident at photospheric levels. We also document temporal changes in the weak photospheric lines of He 2−138, with tentative evidence for a 0.36-day modulation in blue-to-red migrating features in the absorption lines. These structures may betray ‘wave leakage’ of prograde non-radial pulsations of the central star. These multiwaveband results on the aspherical outflow of He 2−138 are discussed in the context of current interest in understanding the origin of axi- and point-symmetric planetary nebulae.

Keywords: stars: evolution; stars: individual: He 2−138; stars: winds, outflows

Journal Article.  5560 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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