论文标题
进化星的Sio Maser发射的非常快的变化
Very fast variations of SiO maser emission in evolved stars
论文作者
论文摘要
语境。渐近巨型分支（AGB）上的恒星是长周期变量，在包括SIO Maser系列在内的几乎所有波长处都具有强烈的通量变化。这些变化的周期为Mira型恒星中的300-500天，半规则变量的时期较短。已经研究了SIO线在短时标准上的可变性，但数据尚无定论。目标。我们的目标是研究在短时间内MIRA型和半规则变量中SIO MASER系的时间演变。我们还讨论了观察到的快速变化的起源。方法。我们使用40 m Yebes天线和30 m IRAM望远镜分别观察到7 mm（28SIO V = 1,2 j = 1-0）和3 mm（28sio v = 1 J = 2-1）的Sio Maser系。我们研究了半规则变量RX BOO和RT VIR，以及Mira型变量，您，r lmi，r leo和$χ$ cyg。我们对不同时间尺度的变化进行了详细的统计分析。结果。 RX BOO在7 mm和3 mm处的不同光谱特征的强度表现出强烈而快速的变化。在一天的时间尺度上，我们发现25％的病例中的变化> 10％。当观测值分开2或3天时，通常会发现大于$ \ sim $ 50％的变化。对于RT VIR，发现SIO系的SIO线的变化速率相似，但是该物体的观察结果较少。相反，Mira型变量中Sio Maser线强度的变化是中等的，典型的变化速率在7天内<10％。这种现象可以通过半规则变量中特别小的maser发射团块的存在来解释，这将导致强度对由于冲击的传递而对密度变化的强度依赖。
Context. Stars on the asymptotic giant branch (AGB) are long-period variables that present strong flux variations at almost all wavelengths, including the SiO maser lines. The periods of these variations are of 300-500 days in Mira-type stars and somewhat shorter in semi-regular variables. The variability of the SiO lines on short timescales has been investigated, but the data are inconclusive. Aims. We aim to study the time evolution of the SiO maser lines in Mira-type and semi-regular variables at short timescales. We also discuss the origin of the observed fast variations. Methods. We observed the SiO maser lines at 7 mm (28SiO v=1,2 J=1-0) and 3 mm (28SiO v=1 J=2-1) using the 40 m Yebes antenna and the 30 m IRAM telescope, respectively, with a minimum spacing of 1 day. We studied the semi-regular variables RX Boo and RT Vir and the Mira-type variables U Her, R LMi, R Leo, and $χ$ Cyg. We performed a detailed statistical analysis of the variations on different timescales. Results. RX Boo shows strong and fast variations in the intensity of the different spectral features of the SiO lines at 7 mm and 3 mm. On a timescale of one day, we find variations of >10% in 25% of the cases. Variations of greater than $\sim$50% are often found when the observations are separated by 2 or 3 days. A similar variation rate of the SiO lines at 7 mm is found for RT Vir, but the observations of this object are less complete. On the contrary, the variations of the SiO maser line intensity in the Mira-type variables are moderate, with typical variation rates around <10% in 7 days. This phenomenon can be explained by the presence of particularly small maser-emitting clumps in semi-regular variables, which would lead to a strong dependence of the intensity on the density variations due to the passage of shocks.
