Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992a%26a...256..231b&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 256, no. 1, p. 231-234.
Astronomy and Astrophysics
Astrophysics
20
H Alpha Line, Hydrogen Recombinations, Planetary Nebulae, Radio Spectra, Millimeter Waves, Stellar Mass Ejection
Scientific paper
We report observations of the millimeter recombination lines H30-alpha, H35-alpha, and H41-alpha in the compact planetary nebula BD +30 deg 3639. The line emission at millimeter wavelengths arises in an optically thin, expanding HII region with an LTE electron temperature of 8800 +/- 1500 K. By fitting the observed line profiles with a radiative transfer model of the ionized shell, we find that the expansion velocity of the ionized gas is less than about 20 km/s. Our observations confirm that the expansion velocity of the ionized gas is considerably smaller than the expansion velocity of the molecular envelope detected in the CO J = 2 - 1 and J = 1 - 0 lines by Bachiller et al. (1991). We briefly rediscuss the CO observations in the light of the radio recombination line data, paying special attention to the blending of the CO J = 1 - 0 line and H38-alpha. We find that H38-alpha contributes about 60 percent of the blend in BD +30 deg 3639 and completely changes the appearance of the CO J = 1 - 0 line profile. In other nebulae with little or no molecular gas, H38-alpha could be mistaken for the CO J = 1 - 0 line without careful checks.
Bachiller Rafael
Cox Pierre
Huggins Patrick J.
Martín-Pintado Jesús
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