The temporal changes of the pulsational periods of the pre-white dwarf PG 1159-035
The temporal changes of the pulsational periods of the pre-white dwarf PG 1159-035
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DOI：
10.1051/0004-6361:20079118
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发表时间：
2008-07
影响因子：
6.5
通讯作者：
J. E. Costa;S. O. Kepler
中科院分区：
文献类型：
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作者：
J. E. Costa;S. O. Kepler
上下文PG 1159-035是一颗Teff为140 000 K的前白矮星，是PG 1159光谱类和DOV脉动类的原型。脉动的前白矮星演化迅速：有效表面温度迅速降低，包层收缩，内部结构由于重力沉降而经历分层。星星的这些变化产生了振荡周期的变化。测量振荡周期的时间变化，使我们能够直接估计恒星演化的变化率，如冷却率和包络收缩率，提供了一种方法来测试和完善前白矮星脉动星的演化模型。目标。之前，仅测量了PG 1159-035最高振幅的两种脉动模式：516.0 s和539.3 s模式。我们测量了大量脉动模式的uP，增加了PG 1159-035进化研究的限制条件。我们试图利用多重态周期的长期变化来计算旋转周期的变化、包层收缩率和星星的冷却率。方法.周期变化直接从PG 1159-035观测数据中测量，并通过（O-C）方法进行了修正。结果我们测量了27个脉动模式周期变化。这些周期的变化率在1到100毫秒/年之间，有几个可以直接测量，相对标准不确定度低于10%。特别是对于振幅最大的516.0 s模，不仅可以直接测量uP值，相对标准不确定度为2%，而且还可以可靠地计算出二阶周期变化量-P。通过使用（O-C）方法，我们改进了uPs，并估计了其他六个脉动周期的-Ps。
Context. PG 1159-035, a pre-white dwarf with Teff � 140 000 K, is the prototype of the PG 1159 spectroscopic class and the DOV pulsating class. Pulsating pre-white dwarf stars evolve rapidly: the effective surface temperature decreases rapidly, the envelope contracts and the inner structure experiences stratification due to gravitational settling. These changes in the star generate variations in its oscillation periods. The measurement of temporal change in the oscillation periods, u P, allows us to estimate directly rates of stellar evolutionary changes, such as the cooling rate and the envelope contraction rate, providing a way to test and refine evolutionary models for pre-white dwarf pulsating stars. Aims. Previously, only two pulsation modes of the highest amplitudes for PG 1159-035 have had their u P measured: the 516.0 s and the 539.3 s modes. We measured the u P of a larger number of pulsation modes, increasing the number of constraints for evolutionary studies of PG 1159-035. We attempted to use the secular variations in the periods of multiplets to calculate the variation in the rotational period, the envelope contraction rate, and the cooling rate of the star. Methods. The period variations were measured directly from the PG 1159-035 observational data and refined by the (O–C) method. Results. We measured 27 pulsation mode period changes. The periods varied at rates of between 1 and 100 ms/yr, and several can be directly measured with a relative standard uncertainty below 10%. For the 516.0 s mode (the highest in amplitude) in particular, not only the value of u P can be measured directly with a relative standard uncertainty of 2%, but the second order period change, ¨ P, can also be calculated reliably. By using the (O–C) method, we refined the u Ps and estimated the ¨ Ps for six other pulsation periods.