Gaia DR2 study of Herbig Ae/Be stars
Gaia DR2 study of Herbig Ae/Be stars
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DOI：
10.1051/0004-6361/201832870
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发表时间：
2018-08
影响因子：
6.5
通讯作者：
M. Vioque;R. Oudmaijer;D. Baines;I. Mendigut'ia;R. P'erez-Mart'inez
中科院分区：
文献类型：
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作者：
M. Vioque;R. Oudmaijer;D. Baines;I. Mendigut'ia;R. P'erez-Mart'inez
目标。我们使用Gaia数据发布2 （DR2）将252颗赫比格Ae/Be恒星放置在赫茨普龙-罗素图中，并研究了它们的特征和性质。方法。对于盖亚DR2中所有已知的具有视差的赫比格Ae/Be恒星，我们从文献中收集了它们的大气参数、光度和消光值。在此基础上加入近红外和中红外光度法，采集了Hα发射谱线的等效宽度、谱线轮廓及其二值状态。此外，我们根据盖亚的DR2信息开发了一个光度变异性指标。结果。我们提供质量，年龄，光度，距离，光度变化和红外过量均匀导出的最完整的赫比格Ae/Be星的样本。我们发现，与质量较低的恒星相比，大质量恒星的红外过剩量要小得多，光学变异性也要低得多，在7 M⊙左右出现断裂。Hα发射通常与红外过量相关，在最靠近恒星的热尘埃的波长处的红外发射相关性更强。我们开发的变异性指标表明，所有赫比格Ae/Be恒星中有25%是强变异性的。我们观察到，强变化的物体显示出双峰的Hα线轮廓，表明一个边缘上的圆盘。结论。强变星赫比格Ae的比例接近于a型UX Ori恒星的比例。曾有人提出，这种变化在大多数情况下是由于不对称的尘埃盘结构所造成的。这里的观察结果有力地支持了这一假设。最后，尘埃性质的差异发生在7 M⊙处，而在较低质量的3 M⊙处，紫外/光学波长追踪到的各种性质不同。后者与不同的吸积机制有关，而不同的红外特性和光度变化则与不同或不同作用的（尘埃）盘分散机制有关。
Aims. We use Gaia Data Release 2 (DR2) to place 252 Herbig Ae/Be stars in the Hertzsprung–Russell diagram and investigate their characteristics and properties. Methods. For all known Herbig Ae/Be stars with parallaxes in Gaia DR2, we collected their atmospheric parameters and photometric and extinction values from the literature. To these data we added near-infrared and mid-infrared photometry, and collected Hα emission line properties such as equivalent widths and line profiles, and their binarity status. In addition, we developed a photometric variability indicator from Gaia’s DR2 information. Results. We provide masses, ages, luminosities, distances, photometric variabilities and IR excesses homogeneously derived for the most complete sample of Herbig Ae/Be stars to date. We find that high-mass stars have a much smaller IR excess and have much lower optical variabilities compared to lower-mass stars, with the break at around 7 M⊙. Hα emission is generally correlated with IR excess, with the correlation being stronger for IR emission at wavelengths tracing the hot dust closest to the star. The variability indicator as developed by us shows that ∼25% of all Herbig Ae/Be stars are strongly variable. We observe that the strongly variable objects display doubly peaked Hα line profiles, indicating an edge-on disk. Conclusions. The fraction of strongly variable Herbig Ae stars is close to that found for A-type UX Ori stars. It had been suggested that this variability is in most cases due to asymmetric dusty disk structures seen edge-on. The observation here is in strong support of this hypothesis. Finally, the difference in dust properties occurs at 7 M⊙, while various properties traced at UV/optical wavelengths differ at a lower mass, 3 M⊙. The latter has been linked to different accretion mechanisms at work, whereas the differing IR properties and photometric variabilities are related to different or differently acting (dust-)disk-dispersal mechanisms.