NDLI: Instability regions in the upper hr diagram

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Instability regions in the upper hr diagram

Content Provider	NASA Technical Reports Server (NTRS)
Author	deJager Sr., Cornelis Stothers, Richard Lobel, Alex Nieuwenhuijzen Sr., Hans
Copyright Year	2001
Description	The following instability regions for blueward evolving supergiants are outlined and compared: (1) Areas in the Hertzsprung-Russell(HR) diagram where stars are dynamically unstable. (2) Areas where the effective acceleration in the upper part of the photospheres is negative, hence directed outward. (3) Areas where the sonic points of the stellar wind (Where wind velocity = sound velocity) are situated inside the photospheres, at a level deeper than tau(sub Ross) = 0.01. We compare the results with the positions of actual stars in the HR diagram and we find evidence that the recent strong contraction of the yellow hypergiant HR8752 was initiated in a period during which (g(sub eff)) is less than 0, whereupon the star became dynamically unstable. The instability and extreme shells around IRC+10420 are suggested to be related to three factors: (g(sub eff)) is less than 0; the sonic point is situated inside the photosphere; and the star is dynamically unstable.
File Size	525331
Page Count	14
File Format	PDF
Alternate Webpage(s)	http://archive.org/details/NASA_NTRS_Archive_20010089283
Archival Resource Key	ark:/13960/t49p80m0p
Language	English
Publisher Date	2001-07-02
Access Restriction	Open
Subject Keyword	Astrophysics Stellar Winds Hertzsprung-russell Diagram Acoustic Velocity Wind Velocity Stellar Evolution Stellar Structure Photosphere Stellar Atmospheres Stellar Mass Dynamic Stability Supergiant Stars Stellar Interiors Stellar Physics Stellar Activity Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science
Content Type	Text
Resource Type	Article

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