A statistical spectropolarimetric study of Herbig Ae/Be stars
A statistical spectropolarimetric study of Herbig Ae/Be stars
复制标题
Herbig Ae/Be 星的统计光谱偏振研究
DOI：
10.1093/mnras/stx1891
复制
发表时间：
2017
影响因子：
4.8
通讯作者：
Ababakr K
中科院分区：
文献类型：
--
作者：
Ababakr K
我们给出了大样本HerBig Ae/Be星的H- α线偏振光谱测量结果。连同新获得的17个天体的数据，该样本包含56个天体，是迄今为止此类样本中最大的。在42个(每 α厘米75 )天体中探测到了H 线两端的线偏振变化，这证实了先前的发现，即这些恒星周围的小空间尺度上的星周环境具有不对称结构，这通常被识别为圆盘。这项研究的第二个结果是，我们证实了赫比格星和金牛座T星在表现出线偏振效应方面相似，而去极化在赫比格比星中更常见。这一发现之前曾被认为表明赫比格Ae星通过磁层吸积形成的方式与TTauri星相同。这两种不同的偏振线效应之间的转换似乎发生在B7-B8光谱类型附近。这不仅表明赫比格Ae恒星与低质量恒星以类似的方式共生，而且这种吸积机制也切换到赫比格Be恒星的另一种类型的吸积。我们报告了由靠近恒星的电子散射引起的线效应的大小不超过2 / cent。谱线效应的大小与H- α谱线的光谱类型或强度之间只有很弱的相关性。这表明线效应的检测仅依赖于线形成区的几何形状和散射电子的几何形状。
We present H α linear spectropolarimetry of a large sample of Herbig Ae/Be stars. Together with newly obtained data for 17 objects, the sample contains 56 objects, the largest such sample to date. A change in linear polarization across the H α line is detected in 42 (75 per cent) objects, which confirms the previous finding that the circumstellar environment around these stars on small spatial scales has an asymmetric structure, which is typically identified with a disc. A second outcome of this research is that we confirm that Herbig Ae stars are similar to T Tauri stars in displaying a line polarization effect, while depolarization is more common among Herbig Be stars. This finding had been suggested previously to indicate that Herbig Ae stars form in the same manner than T Tauri stars through magnetospheric accretion. It appears that the transition between these two differing polarization line effects occurs around the B7–B8 spectral type. This would in turn not only suggest that Herbig Ae stars accrete in a similar fashion as lower mass stars, but also that this accretion mechanism switches to a different type of accretion for Herbig Be stars. We report that the magnitude of the line effect caused by electron scattering close to the stars does not exceed 2 per cent. Only a very weak correlation is found between the magnitude of the line effect and the spectral type or the strength of the H α line. This indicates that the detection of a line effect only relies on the geometry of the line-forming region and the geometry of the scattering electrons.