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arXiv 1611.03334astro-ph.SR
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脉动红巨星长次级周期的研究。II。低光度恒星

Studies of the Long Secondary Periods in Pulsating Red Giants. II. Lower-Luminosity Stars

John R. Percy, Henry Leung

摘要:

我们已经使用AAVSO视觉和光电V数据,和AAVSO时间序列包VSTAR和Lomb-Scargle时间序列算法来确定改进的脉动周期,“长二次周期”(LSP)。在AAVSO光电测光计划和AAVSO LPV(长周期变星)双目计划中,众所周知,在光谱类型大约为M0的红巨星中可以检测到径向脉动,周期大约为20天。我们发现,LSP现象也是第一次检测到约M0。脉动和LSP振幅在约100天的脉动周期处从接近零增加到约0.1。在较长的周期,脉动幅度继续增加,但LSP幅度一般平均在0.1和0.2之间。LSP与脉动周期的比率集中在5和10附近,大概取决于脉动周期是基本泛音还是第一泛音。脉动和LSP相位曲线通常接近正弦曲线,除了当振幅小时,在这种情况下,它们可能被观测散射或在LSP振幅的情况下,被脉动变化所扭曲。与较长周期的恒星一样,LSP的振幅在大约20个LSP的中位时间尺度上增加和减少了两倍或更多,原因不明。因此,LSP现象存在于所有周期的径向脉动红巨星中。其原因尚不清楚。

英文摘要:

We have used AAVSO visual and photoelectric V data, and the AAVSO time-series package VSTAR and the Lomb-Scargle time-series algorithm to determine improved pulsation periods, "long secondary periods" (LSPs). and their amplitudes in 51 shorter-period pulsating red giants in the AAVSO photoelectric photometry program, and the AAVSO LPV (long period variable) binocular program. As is well known, radial pulsation becomes detectable in red giants at about spectral type M0, with periods of about 20 days. We find that the LSP phenomenon is also first detectable at about M0. Pulsation and LSP amplitudes increase from near zero to about 0.1 at pulsation periods of about 100 days. At longer periods, the pulsation amplitudes continue to increase, but the LSP amplitudes are generally between 0.1 and 0.2 on average. The ratios of LSP to pulsation period cluster around 5 and 10, presumably depending on whether the pulsation period is the fundamental or first overtone. The pulsation and LSP phase curves are generally close to sinusoidal, except when the amplitude is small, in which case they may be distorted by observational scatter or, in the case of the LSP amplitude, by the pulsational variability. As with longer-period stars, the LSP amplitude increases and decreases by a factor of two or more, for unknown reasons, on a median time scale of about 20 LSPs. The LSP phenomenon is thus present and simiklar in radially pulsating red giants of all periods. Its cause remains unknown.

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