Present observational status of the intermediate mass stars:: δ Sct stars, γ Dor stars and roAp stars

被引:6
|
作者
Kurtz, DW [1 ]
机构
[1] Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England
[2] Observ Midi Pyrenees, Lab Astrophys OMP, CNRS, UMR 5572, F-31400 Toulouse, France
关键词
stars : variable : delta Sct; gamma Dor; roAp;
D O I
10.1023/A:1023268108380
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The present observational status of the delta Sct stars, gamma Dor stars and roAp stars is discussed. The d Sct stars are the most intensively observed of the three groups, but it has become clear that there are severe problems in extracting asteroseismic information from them. Dozens of frequencies are observed, but hundreds of frequencies are predicted from the models; unique matches of observation and theory still elude us. The delta Sct stars are observationally complex - some recent 'best case' campaigns are discussed. It is possible that substantial observational advances for delta Sct stars may need to await upcoming satellite missions. New gamma Dor stars are being discovered frequently, and new behaviour is being found for them. They constitute an observationally young field. Their pulsational frequency range is being expanded, their position in the HR diagram is becoming better known ( but is yet to be fully constrained), and the possibility exists of hybrid gamma Dor - delta Sct stars that have great asteroseismic promise, although it is clear such stars are rare, if they do exist. It has been observationally challenging to extract more than a few frequencies for any gamma Dor star so far. Exciting spectroscopic discoveries of new behaviour in roAp stars promise unprecedented information about the structure of the peculiar atmospheres of those stars - pulsation amplitude and phase in 3D, magnetic field structure in 3D, abundance stratification in 3D, realistic T-tau for the most peculiar stars - as well as entirely new information about the interaction of pulsation, rotation and magnetic fields. Recent theoretical work has led to new understanding of the previously inexplicable frequency spacing of HR 1217 with new Whole Earth Telescope observations supporting this theory. An 'improved oblique pulsator model' has been developed in which the pulsation axis is not the magnetic axis; this model has passed several observational tests and new ones are being devised to examine it further.
引用
收藏
页码:29 / 35
页数:7
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