Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989a%26a...218..273b&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 218, no. 1-2, July 1989, p. 273-276.
Astronomy and Astrophysics
Astrophysics
10
Astronomical Spectroscopy, H Alpha Line, Planetary Nebulae, Stellar Envelopes, Emission Spectra, Halos, Line Spectra, Red Giant Stars, Stellar Winds
Scientific paper
The 2.2m ESO telescope with a medium resolution spectrograph and a CCD-detector was used to look for emission from extended halos around planetary nebulae. In most cases the search was successful. The ratio R(halo)/R(neb) ranges from two to six. Assuming that the halos have been produced by the winds of the red giant progenitor stars, M-dot/V(AGB) is determined for the progenitors, using the measured H-alpha fluxes. These values vary in a relatively narrow range around 2-8 x 10 to the -7th (solar mass/y)(km/s). In some objects emission line fluxes were measured at two or more halo positions. The derived values are in good agreement with the expected n proportional to 1/r-squared density law. By extrapolating the halo density inwards, the density enhancement factor n(neb)/n(halo can be determined). In most cases this turns out to be bigger than four, which suggests that the compression of the gas was caused by an isothermal shock.
Baessgen Martin
Grewing Michael
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