The period and amplitude changes in the coolest GW Virginis variable star (PG 1159-type) PG 0122+200
The period and amplitude changes in the coolest GW Virginis variable star (PG 1159-type) PG 0122+200
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最冷GW Virginis变星（PG 1159型）PG 0122 200的周期和振幅变化
DOI：
10.1051/0004-6361/201014457
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发表时间：
2011-04
影响因子：
6.5
通讯作者：
Vauclair, G.
中科院分区：
文献类型：
--
作者：
Dolez, N.;Fu, J.N.;Kim, S.L.;Solheim, J.-E.;Vauclair, G.
上下文PG 1159前白矮星实验快速冷却阶段的时间尺度为几个10 - 6年。理论模型预测，在其核心产生的中微子应该在冷却中发挥主导作用，主要是在PG 1159序列的冷端。测量最冷的PG 1159恒星的演化时间尺度可以提供一个独特的机会来经验性地限制中微子发射率。目标。PG 1159的一个子群是非径向变星，即GW Vir型变星。它们表现出周期为几百秒的g模式脉动。随着恒星冷却，脉动频率根据其内部结构的变化而演变。人们预计，测量它们的变化率将直接确定演化的时间尺度，从而限制中微子的发射率。由于PG 0122+200（BB Psc）定义了GW Vir不稳定带的红色边缘，因此它是这种测量的良好候选者。方法.从1986年到2008年的22年间，通过快速测光技术观测到PG 0122+200的脉动。我们用这些数据来测量它的频率和振幅的变化率。结果在识别出的24个l = 1模中，获得了7个最大振幅模的频率和振幅变化。我们发现它们的频率变化的幅度更大，时间尺度更短，比理论模型，假设冷却占主导地位的频率变化所预测的。在2497 μHz（400 s）的最大振幅模式的情况下，它的变化是最好的拟合由两个项的组合：一个长期的时间尺度为5.4 × 104年，这是显着短于预测的演化时间尺度的8 × 106年;和一个额外的周期项的周期为261或211天。冷却之外的一些其他机制必须对这种变化负责。我们认为星星旋转引起的三重态共振耦合可能是这样一种机制。因此，只要没有正确理解主导机制，目前就无法推导出对中微子发射率的有用约束。结论.在PG 0122+200中观察到的脉动频率的时间变化不能简单地归因于星星的冷却，不管中微子损失的贡献。我们的研究结果表明，由旋转引起的共振耦合起着主导作用，必须进一步研究。
Context. The PG 1159 pre-white dwarf stars experiment a rapidly cooling phase with a time scale of a few 10 6 years. Theoretical models predict that the neutrinos produced in their core should play a dominant role in the cooling, mainly at the cool end of the PG 1159 sequence. Measuring the evolutionary time scale of the coolest PG 1159 stars could offer a unique opportunity to empirically constrain the neutrino emission rate. Aims. A subgroup of the PG 1159 stars are nonradial pulsators, the GW Vir type of variable stars. They exhibit g-mode pulsations with periods of a few hundred seconds. As the stars cool, the pulsation frequencies evolve according to the change in their internal structure. It was anticipated that the measurement of their rate of change would directly determine the evolution time scale and so constrain the neutrino emission rates. As PG 0122+200 (BB Psc) defines the red edge of the GW Vir instability strip, it is a good candidate for such a measurement. Methods. The pulsations of PG 0122+200 have been observed during 22 years from 1986 to 2008, through the fast photometry technique. We used those data to measure the rate of change of its frequencies and amplitudes. Results. Among the 24 identified l = 1 modes, the frequency and amplitude variations have been obtained for the seven largest amplitude ones. We find changes of their frequency of much larger amplitudes and shorter time scales than the one predicted by theoretical models that assume that the cooling dominates the frequency variations. In the case of the largest amplitude mode at 2497 μHz (400 s), its variations are best fitted by a combination of two terms: one long term with a time scale of 5.4 x 10 4 years, which is significantly shorter than the predicted evolutionary time scale of 8 x 10 6 years; and one additional periodic term with a period of either 261 or 211 days. Some other mechanism(s) than the cooling must be responsible for such variations. We suggest that the resonant coupling induced within triplets by the star rotation could be such a mechanism. As a consequence, no useful constraints on the neutrino emission rate can presently be derived as long as the dominant mechanism is not properly understood. Conclusions. The temporal variations in the pulsation frequencies observed in PG 0122+200 cannot be simply attributed to the cooling of the star, regardless of the contribution of the neutrino losses. Our results suggest that the resonant coupling induced by the rotation plays a dominant role which must be further investigated.
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DOI：
10.1086/309216
发表时间：
2000-03
期刊：
The Astrophysical Journal
影响因子：
--
作者：
M. O'Brien;S. Kawaler
通讯作者：
M. O'Brien;S. Kawaler
DOI：
10.1086/169196
发表时间：
1990-09
期刊：
The Astrophysical Journal
影响因子：
--
作者：
R. Nather;D. Winget;J. Clemens;C. Hansen;B. Hine
通讯作者：
R. Nather;D. Winget;J. Clemens;C. Hansen;B. Hine
影响因子：
6.5
作者：
A. C'orsico;L. Althaus
通讯作者：
A. C'orsico;L. Althaus
DOI：
10.1553/cia146s53
发表时间：
2005-06
期刊：
Third Coast
影响因子：
--
作者：
P. Lenz;M. Breger
通讯作者：
P. Lenz;M. Breger
影响因子：
6.5
作者：
J. E. Costa;S. O. Kepler
通讯作者：
J. E. Costa;S. O. Kepler