Radio recombination lines and expansion velocity of the planetary nebula NGC 7027.
Abstract
Observations of the H56-alpha radio recombination line of the planetary nebula NGC 7027 are reported. Analysis of the data shows that the observed radial velocity of NGC 7027 is dependent on the principal quantum number, or frequency. This makes it possible to obtain an expansion velocity for the nebula. A dynamical model is proposed in which the envelope expands at 21 + or - 2 km/s. It is suggested that this value should be used for distance determination toward NGC 7027. The radial velocity of the nebula derived from this model is 26.1 + or - 0.3 km/s, in good agreement with the radial velocity of the surrounding molecular gas.
- Publication:
-
Pisma v Astronomicheskii Zhurnal
- Pub Date:
- May 1989
- Bibcode:
- 1989PAZh...15..413E
- Keywords:
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- Planetary Nebulae;
- Radial Velocity;
- Radiative Recombination;
- Radio Spectra;
- Astronomical Models;
- H Alpha Line;
- Molecular Clouds;
- Quantum Numbers;
- Astrophysics