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Paper: Critically Rotating Post-Main Sequence Stars Hosting a Viscous Decretion Disk
Volume: 508, The B[e] Phenomenom: Forty Years of Studies
Page: 81
Authors: Granada, A.; Sigut, A.; Jones, C.; Georgy, C.; Ekström, S.; Meynet, G.
Abstract: Stellar evolution calculations of isolated, rotating, intermediate mass stars predict that only a handful of these objects reach the critical limit after the main sequence phase, during the helium burning phase, while describing a blue-loop in the HR diagram. During the red supergiant stage, angular momentum could be dredged-up to the surface so that when the star contracts describing the blue-loop, the surface velocities can reach larger values than those the star had when crossing the Hertzprung-Russell diagram for the first time. Even though these stars might indeed be rare objects, we explore the possibility of such stars undergoing mechanical mass loss and hence forming a viscous decretion disk. By taking into account the angular momentum loss rate from Geneva stellar evolution calculations for a star with 9 solar masses and large rotational rate at the ZAMS (Ω/Ωcrit=0.9), combined with the relations available in the literature we obtain the disk outer radius and disk mass loss rate for such an object. Using BEDISK/BERAY codes, we calculate observables (Hα and other hydrogen lines, forbidden lines, colors) generated in the gaseous component of the resulting star plus disk system and compare them with observations of evolved stars exhibiting the B[e] phenomenon.
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