论文标题
预先序列恒星的Ca II红外三重排放线的测量
Measurements of the Ca II infrared triplet emission lines of pre-main-sequence stars
论文作者
论文摘要
我们研究了四个分子云和五个移动组的60个预序列（PMS）星的色球活性。据认为，强的色球活性是由恒星旋转产生的发电机过程驱动的。相比之下，一些研究人员指出，PMS恒星的色球球被其原行星磁盘的质量积聚激活。在这项研究中，使用中和高分辨率光谱研究了CA II红外三重发射线（IRT）发射线。观察结果是用Nayuta/Malls和Subaru/HDS进行的。此外，还使用了Keck/Hires，VLT/UVE和VLT/X-Shooter获得的存档数据。等效宽度的小比例表明，Ca II IRT发射线主要出现在密集的色层区域。七个PMS恒星显示宽阔的排放线。其中，与年轻的开放式簇中的低质量恒星相比，四个PMS恒星具有多个数量级的亮度发射线通量。四个PMS恒星的质量积聚率很高，这表明宽大而强大的质量积聚产生了较大的质量积聚。但是，大多数PMS星星都表现出狭窄的发射线。在发射线的积聚率和通量之间未发现显着相关。 Ca II IRT线的表面通量与具有窄发射线的PMS星的恒星辐射光度的比率与年轻开放式簇中低质量星的最大r'_IRT一样大。该结果表明，即使在经典的T Tauri恒星阶段，大多数PMS星的具有类似于零时代的主要序列恒星的色球活性。
We investigated the chromospheric activity of 60 pre-main-sequence (PMS) stars in four molecular clouds and five moving groups. It is considered that strong chromospheric activity is driven by the dynamo processes generated by the stellar rotation. In contrast, several researchers have pointed out that the chromospheres of PMS stars are activated by mass accretion from their protoplanetary disks. In this study, the Ca II infrared triplet (IRT) emission lines were investigated utilizing medium- and high-resolution spectroscopy. The observations were conducted with Nayuta/MALLS and Subaru/HDS. Additionally, archive data obtained by Keck/HIRES, VLT/UVES, and VLT/X-Shooter was used. The small ratios of the equivalent widths indicate that Ca II IRT emission lines arise primarily in dense chromospheric regions. Seven PMS stars show broad emission lines. Among them, four PMS stars have more than one order of magnitude brighter emission line fluxes compared to the low-mass stars in young open clusters. The four PMS stars have a high mass accretion rate, which indicates that the broad and strong emission results from a large mass accretion. However, most PMS stars exhibit narrow emission lines. No significant correlation was found between the accretion rate and flux of the emission line. The ratios of the surface flux of the Ca II IRT lines to the stellar bolometric luminosity, R'_IRT, of the PMS stars with narrow emission lines are as large as the largest R'_IRT of the low-mass stars in the young open clusters. This result indicates that most PMS stars, even in the classical T Tauri star stage, have chromospheric activity similar to zero-age main-sequence stars.
