INVESTIGADORES
MAUAS Pablo Jacobo David
artículos
Título:
Modelling chromospheric line profiles as diagnostics of velocity fields in ω Centauri red giant stars
Autor/es:
VIEYTES, M. C.; MAUAS, P.J.D.; CACCIARI, C.; ORIGLIA, L.; PANCINO, E.
Revista:
ASTRONOMY AND ASTROPHYSICS
Editorial:
EDP SCIENCES S A
Referencias:
Año: 2011 vol. 526 p. 4 - 12
ISSN:
0004-6361
Resumen:
Context. Mass loss of ~0.1-0.3 Mȯ from Population II red
giant stars (RGB) is a requirement of stellar evolution theory in order
to account for several observational evidences in globular clusters. Aims: The aim of this study is to detect the presence of outward
velocity fields, which are indicative of mass outflow, in six luminous
red giant stars of the stellar cluster ω Cen. Methods: We
compare synthetic line profiles computed using relevant model
chromospheres to observed profiles of the Hα and Ca II K lines.
The spectra were taken with UVES (R = 45 000) and the stars were
selected so that three of them belong to the metal-rich population and
three to the metal-poor population, and sample as far down as 1 to 2.5
mag fainter than the respective RGB tips. Results: We do indeed
reveal the presence of low-velocity outward motions in four of our six
targets, without any apparent correlation with astrophysical parameters.
Conclusions: This provides direct evidence that outward velocity
fields and mass motions exist in RGB stars as much as 2.5 mag fainter
than the tip. On the assumption that the mass outflow may eventually
lead to mass loss from the star, we estimate mass-loss rates of some
10-9-10-10 Mȯ yr-1 that
are compatible with the stellar evolution requirements. These rates seem
to be correlated with luminosity rather than metallicity.