Evolutionary model and oscillation frequencies for α Ursae Majoris:: A comparison with observations

被引:17
作者
Guenther, DB [1 ]
Demarque, P
Buzasi, D
Catanzarite, J
Laher, R
Conrow, T
Kreidl, T
机构
[1] St Marys Univ, Dept Phys & Astron, Halifax, NS B3H 3C3, Canada
[2] Yale Univ, Dept Astron, Ctr Solar & Space Res, New Haven, CT 06520 USA
[3] Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA
[4] CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA
[5] No Arizona Univ, Dept Phys & Astron, Flagstaff, AZ 86011 USA
基金
加拿大自然科学与工程研究理事会;
关键词
stars : evolution; stars : individual (alpha Ursae Majoris A); stars : oscillations;
D O I
10.1086/312473
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Inspired by the observations of low-amplitude oscillations of alpha Ursae Majoris A by Buzasi et al. using the WIRE satellite, a,grid of stellar evolutionary tracks has been constructed to derive physically consistent interior models for the nearby red giant. The pulsation properties of these models were then calculated and compared with the observations. It is found that, by adopting the correct metallicity and for a normal helium abundance, only models in the mass range of 4.0-4.5 M. fall within the observational error box for alpha UMa A. This mass range is compatible, within the uncertainties, with the mass derived from the astrometric mass function. Analysis of the pulsation spectra of the models indicates that the observed alpha UMa oscillations can be most simply interpreted as radial (i.e., l = 0) p-mode oscillations of low radial order n. The lowest frequencies observed by Buzasi et al. are compatible, within the observational errors, with model frequencies of radial orders n = 0, 1, and 2 for models in the mass range of 4.0-4.5 M.. The higher frequencies observed can also be tentatively interpreted as higher n-valued radial p-modes, if we allow that some n-values are not presently observed. The theoretical l = 1, 2, and 3 modes in the observed frequency range are g-modes with a mixed mode character, that is, with p-mode-like characteristics near the surface and g-mode-like characteristics in the interior The calculated radial p-mode frequencies are nearly equally spaced, separated by 2-3 mu HZ. The nonradial modes are very densely packed throughout the observed frequency range and, even if excited to significant amplitudes at the surface, are unlikely to be resolved by the present observations.
引用
收藏
页码:L45 / L48
页数:4
相关论文
共 21 条