The accretion rates and mechanisms of Herbig Ae/Be stars
The accretion rates and mechanisms of Herbig Ae/Be stars
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DOI：
10.1093/mnras/staa169
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发表时间：
2020-01
影响因子：
4.8
通讯作者：
C. Wichittanakom;C. Wichittanakom;R. D. Oudmaijer;J. Fairlamb;I. Mendigut'ia;M. Vioque;K. Ababakr-K.-Ababa
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文献类型：
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作者：
C. Wichittanakom;C. Wichittanakom;R. D. Oudmaijer;J. Fairlamb;I. Mendigut'ia;M. Vioque;K. Ababakr-K.-Ababa
本文介绍了163颗Herbig Ae/Be星的光谱研究。其中，我们提出了30个对象的新数据。恒星的参数，如温度，红化，质量，光度和年龄是均匀确定的。质量吸积率确定从$\rm H\alpha$发射线测量。我们的数据与以前研究中的X-Shooter样本进行了补充，我们使用Gaia DR 2天体更新了结果，共获得了78个具有均匀确定的恒星参数和质量吸积率的物体。此外，质量吸积率的另外85 HAeBes的测定。我们证实了以前的研究结果，质量吸积率增加作为恒星质量的函数，并存在一个不同的斜率为较低和较高质量的恒星，分别。斜率变化处的质量为3.98 ^{+1.37}_{-0.94}\rm M_{\odot }$。我们讨论这种突破的背景下，不同的模式的光盘吸积低，高质量的恒星。由于它们与金牛T星的相似性，我们确定了晚型赫比格星的吸积机制与磁层吸积。早期型恒星的可能性仍然是开放的，我们建议边界层吸积模型可能是一个可行的选择。最后，我们还研究了物质增积与年龄的关系。即使使用基于上级盖亚的数据，也很难选择足够大的子样本来消除这种关系中的质量依赖性。然而，从基本的理论考虑来看，质量吸积确实会随着年龄的增长而下降。
This work presents a spectroscopic study of 163 Herbig Ae/Be stars. Amongst these, we present new data for 30 objects. Stellar parameters such as temperature, reddening, mass, luminosity, and age are homogeneously determined. Mass accretion rates are determined from $\rm H\alpha$ emission line measurements. Our data is complemented with the X-Shooter sample from previous studies and we update results using Gaia DR2 parallaxes giving a total of 78 objects with homogeneously determined stellar parameters and mass accretion rates. In addition, mass accretion rates of an additional 85 HAeBes are determined. We confirm previous findings that the mass accretion rate increases as a function of stellar mass, and the existence of a different slope for lower and higher mass stars, respectively. The mass where the slope changes is determined tobe $3.98^{+1.37}_{-0.94}\, \rm M_{\odot }$. We discuss this break in the context of different modes of disc accretion for low- and high-mass stars. Because of their similarities with T Tauri stars, we identify the accretion mechanism for the late-type Herbig stars with the Magnetospheric Accretion. The possibilities for the earlier-type stars are still open, we suggest the Boundary Layer accretion model may be a viable alternative. Finally, we investigated themass accretion–age relationship. Even using the superior Gaia based data, it proved hard to select a large enough sub-sample to remove the mass dependence in this relationship. Yet, it would appear that the mass accretion does decline with age as expected from basic theoretical considerations.