论文标题
原星云的变异性：ix。十年来进化的证据
Variability in Protoplanetary Nebulae: IX. Evidence for Evolution in a Decade
论文作者
论文摘要
我们进行了一项新的光度V，RC研究，对12个原星云，该研究是恒星进化的AGB和PN阶段短期过渡的物体。这些是使用1994 - 2007年的数据的早期研究的主题，发现所有12个周期性的差异都在约38至〜150天的范围内。它们都是富含碳的，具有F-G光谱类型的。我们将新的（2008-2018）数据与公共可用的ASAS-SN数据相结合，并确定了它们可变性的新时期。比较了较旧的和较新的时期值，以调查周期变化的证据，在某些情况下，有理论上的支持可以在一两年内检测到它。由于光曲线复杂，有多个时期，幅度变化和冲击证据，因此这种检测是具有挑战性的。尽管如此，我们发现了一种，可能是两种情况，这些情况与样品中较高的温度恒星有关（7250和8000 K）。这些结果与碳星质量范围的下端的恒星的演变（太阳）最一致。几个恒星显示出长期趋势的增加（六种情况）或降低（一个情况）亮度，我们认为这很可能是由于偶尔粉尘不透明度的变化所致。除较短的脉动外，还有一个可能的〜1.8年。这被解释为轨道伴侣的可能证据。
We have carried out a new photometric V,Rc study of 12 protoplanetary nebulae, objects in the short-lived transition between the AGB and PN phases of stellar evolution. These had been the subjects of an earlier study, using data from 1994-2007, that found that all 12 varied periodically, with pulsation periods in the range of ~38 to ~150 days. They are all carbon-rich, with F-G spectral types. We combined our new (2008-2018) data with publicly-available ASAS-SN data and determined new periods for their variability. The older and newer period values were compared to investigate evidence of period change, for which there is theoretical support that it might be detectable in a decade or two in some cases. Such a detection is challenging since the light curves are complicated, with multiple periods, changing amplitudes, and evidence of shocks. Nevertheless, we found one, and possibly two, such cases, which are associated with the higher temperature stars in the sample (7250 and 8000 K). These results are most consistent with the evolution of stars at the lower end of the mass range of carbon stars, ~1.5-2 M(sun). Several of the stars show longer-term trends of increasing (six cases) or decreasing (one case) brightness, which we think most likely due to changes in the circumstellar dust opacity. There is one case of a possible ~1.8 yr period in addition to the shorter pulsation. This is interpreted as possible evidence of an orbiting companion.
