On steady shell formation in stellar atmospheres - I. Analytical 2-D calculations under an optically thin thermo-radiative mechanism

Kakouris, A; Moussas, X

dc.contributor.author	Kakouris, A	en
dc.contributor.author	Moussas, X	en
dc.date.accessioned	2014-03-01T01:47:40Z
dc.date.available	2014-03-01T01:47:40Z
dc.date.issued	1998	en
dc.identifier.issn	0004-6361	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/25285
dc.subject	hydrodynamics	en
dc.subject	methods : analytical	en
dc.subject	stars : atmospheres	en
dc.subject	supergiants	en
dc.subject	stars : mass-loss	en
dc.subject.classification	Astronomy & Astrophysics	en
dc.subject.other	HYPERGIANT P-CYGNI	en
dc.subject.other	ASTROPHYSICAL FLOWS	en
dc.subject.other	MASS-LOSS	en
dc.subject.other	STARS	en
dc.subject.other	WINDS	en
dc.subject.other	DRIVEN	en
dc.subject.other	VARIABILITY	en
dc.subject.other	OUTFLOWS	en
dc.subject.other	MODELS	en
dc.subject.other	LINES	en
dc.title	On steady shell formation in stellar atmospheres - I. Analytical 2-D calculations under an optically thin thermo-radiative mechanism	en
heal.type	journalArticle	en
heal.language	English	en
heal.publicationDate	1998	en
heal.abstract	In this work we study a possible physical mechanism which is able to create steady state shells around astrophysical objects. This mechanism is thermo - radiative and it is applied to optically thin stellar atmospheres. An outflow deceleration region separates the rest of the stellar envelope into inner and outer acceleration regions. The shell is formed in the supersonic region of the outflow. Studying the dynamic nature of the shells, it is found that the shell distance depends on the thin spectral line opacity and the number of thin lines. The shape of the shell depends on the differential rotation of the fluid. It is found that the mass concentration may look like a shell or a double blob over the poles of the central object. The present thermo - radiative mechanism is based on the analytical 2 - D, hydrodynamic solution of Kakouris & Moussas (1997) and the analysis of Chen & Marlborough (1994) for the thin radiative force as well as the work of Lamers (1986) for the acceleration mechanism in the envelope of P Cygni. The shell characteristics are deduced through applications to superluminous early type supergiants. Applications to late type supergiants as well as P Cygni are shown. It is found that superluminous supergiants are expected to form steady shells and an example for P Cygni illustrates such a shell at similar to 5 stellar radii. The present three - zone envelope for P Cygni resembles that of Nugis, Kolka & Luud (1979) but uses different driving outflow mechanisms. The parameters used in this article are in accordance with previous works and several observational data are reproduced successfully by the model.	en
heal.publisher	SPRINGER VERLAG	en
heal.journalName	ASTRONOMY & ASTROPHYSICS	en
dc.identifier.isi	ISI:000073806100045	en
dc.identifier.volume	333	en
dc.identifier.issue	2	en
dc.identifier.spage	678	en
dc.identifier.epage	686	en