Bibcode
DOI
García-Alvarez, David; Drake, Jeremy J.; Ball, B.; Lin, LiWei; Kashyap, Vinay L.
Referencia bibliográfica
The Astrophysical Journal, Volume 638, Issue 2, pp. 1028-1040.
Fecha de publicación:
2
2006
Revista
Número de citas
13
Número de citas referidas
12
Descripción
The stars β Cet, 31 Com, and μ Vel represent the main stages
through which late-type giants evolve during their lifetime (the
Hertzsprung gap [31 Com], the rapid braking zone [μ Vel], and the
core helium burning ``clump'' phase [β Cet]). An analysis of their
high-resolution Chandra X-ray spectra reveals similar coronal
characteristics in terms of both temperature structure and element
abundances for the more evolved stars (μ Vel and β Cet), with
slight differences for the ``younger'' giant (31 Com). The coronal
temperature structure of 31 Com is significantly hotter, showing a clear
peak, while β Cet and μ Vel show a plateau. β Cet and μ
Vel show evidence for a FIP effect in which coronae are depleted in
high-FIP elements relative to their photospheres by a factor of ~2. In
contrast, 31 Com is characterized by a lack of FIP effect. In other
words, neither depletion nor enhancement relative to stellar
photospheric values is found. We conclude that the structural changes
during the evolution of late-type giants could be responsible for the
observed differences in coronal abundances and temperature structure. In
particular, the size of the convection zone coupled with the rotation
rate seem obvious choices for playing a key role in determining coronal
characteristics.