Nebular observations and stellar coronae

Journal Article · Thu Jun 01 04:00:00 EDT 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156167· OSTI ID:6951073

Hartmann, L; Raymond, J C

We examine the ways in which nebular observations of He II lambda4686 can be used to infer the existence of coronae or hot winds of early-type stars. The O VI lambdalambda3811, 3834 doublet is seen in the spectra of some central stars of planetary nebulae, and several authors have considered this to be evidence of a coronal wind. Observations of NGC 6751 reinforce this view by showing that radiative equilibrium model atmospheres cannot sufficiently photoexcite the O VI transitions without producing too much nebular emission at lambda4686. The hot gas in the coronal model produces a significant amount of radiation at energies above 54 eV; therefore, the He II Zanstra temperatures can be affected. Discrepancies between the He II Zanstra temperatures and effective temperatures derived from other methods may indicate coronal emission from planetary nebula central stars.Observations of diffuse nebulae about Population I early-type stars may also prove useful in detecting hot winds. The Lamers and Morton model of the wind of the O4f star xi Pup predicts a small amount of He/sup +/ ionizing radiation. If NGC 7635 is associated with the Of star BD +60/sup 0/2522, then the observation of nebular emission at lambda4686 may indicate coronal emission.

• Research Organization: Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 6951073
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 222:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CRYOGENIC FLUIDS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY-LEVEL TRANSITIONS
EXCITATION
FLUIDS
IONIZATION
MASSLESS PARTICLES
MATHEMATICAL MODELS
NEBULAE
NONMETALS
OXYGEN
PHOTONS
PLANETARY NEBULAE
STAR MODELS
STARS
STELLAR ATMOSPHERES
STELLAR RADIATION
STELLAR WINDS
WOLF-RAYET STARS