Pulsational properties of 1.8 M$_{\odot}$ stellar models covering the lateststages of contraction toward the main sequence up to early hydrogen burningphases are investigated by means of linear nonadiabatic analyses. Resultsconfirm that pre-main sequence stars (pms) which cross the classicalinstability strip on their way toward the main sequence are pulsationallyunstable with respect to the classical opacity mechanisms. For both pms andmain sequence types of models in the lower part of the instability strip, theunstable frequency range is found to be roughly the same. Some non-radialunstable modes are very sensitive to the deep internal structure of the star.It is shown that discrimination between pms and main sequence stages ispossible using differences in their oscillation frequency distributions in thelow frequency range.
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机译：通过线性非绝热分析研究了1.8 M $ _ {\ odot} $恒星模型的脉动特性，涵盖了向主序列收缩的最新阶段，直至早期的氢燃烧阶段。结果证实，相对于经典的不透明机制，在穿越经典不稳定性带的过程中穿过主经典序列的恒星（pms）在脉冲上不稳定。对于不稳定带下部的模型的pms和主要序列类型，发现不稳定频率范围大致相同。一些非径向不稳定模式对恒星的深层内部结构非常敏感。研究表明，利用低频率范围内它们的振荡频率分布差异，可以区分pms和主序级。
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