High-cadence, High-resolution Spectroscopic Observations of Herbig Stars HD 98922 and V1295 Aquila
High-cadence, High-resolution Spectroscopic Observations of Herbig Stars HD 98922 and V1295 Aquila
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DOI：
10.3847/1538-4357/aa8997
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发表时间：
2017-10
期刊：
影响因子：
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通讯作者：
A. Aarnio;J. Monnier;T. Harries;S. Kraus;N. Calvet;D. Acreman;X. Che
中科院分区：
文献类型：
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作者：
A. Aarnio;J. Monnier;T. Harries;S. Kraus;N. Calvet;D. Acreman;X. Che
最近的观测工作表明，Herbig Ae/Be 星盘系统中的吸积和流出机制可能与磁层吸积（MA）不同，因为它被认为发生在金牛座 T 星盘系统中。在这项工作中，我们评估了 Herbig Ae/Be 系统中探测吸积和质量损失的谱线的时间演化，并测试与 MA 范式的一致性。对于两颗 Herbig Ae/Be 星 HD 98922 (B9e) 和 V1295 Aql (A2e)，我们收集了多历元（~年）和高节奏（~分钟）高分辨率光谱来探测广泛的运动过程。采用此处介绍的线等效宽度进化相关性度量，我们通过新颖的可视化来识别物种共同进化（表明共同的线起源）。我们通过干涉测量来约束经常出现问题的简并参数、倾角和内盘半径，使我们能够专注于辐射传输模型中的风、磁层和内部气盘的结构。在所有采样的时间尺度上，最强的变化发生在巴尔默系列线的蓝移吸收分量内；变异性的强度随着观察的节奏而增加。最后，高分辨率光谱使我们能够探测巴尔默系列蓝移吸收成分内的子结构：我们观察静态、低速特征和较高速度下的时间演化特征。总的来说，我们发现观察到的线形态和变异性与放大的 T Tauri MA 场景不一致。我们认为，随着从金牛座 T 星到赫比格 Ae/Be 星的恒星质量的增加，磁场结构和强度会发生巨大变化，吸积和流出过程也会发生巨大变化。
Recent observational work has indicated that mechanisms for accretion and outflow in Herbig Ae/Be star–disk systems may differ from magnetospheric accretion (MA) as it is thought to occur in T Tauri star–disk systems. In this work, we assess the temporal evolution of spectral lines probing accretion and mass loss in Herbig Ae/Be systems and test for consistency with the MA paradigm. For two Herbig Ae/Be stars, HD 98922 (B9e) and V1295 Aql (A2e), we have gathered multi-epoch (∼years) and high-cadence (∼minutes) high-resolution optical spectra to probe a wide range of kinematic processes. Employing a line equivalent width evolution correlation metric introduced here, we identify species co-evolving (indicative of common line origin) via novel visualization. We interferometrically constrain often problematically degenerate parameters, inclination and inner-disk radius, allowing us to focus on the structure of the wind, magnetosphere, and inner gaseous disk in radiative transfer models. Over all timescales sampled, the strongest variability occurs within the blueshifted absorption components of the Balmer series lines; the strength of variability increases with the cadence of the observations. Finally, high-resolution spectra allow us to probe substructure within the Balmer series’ blueshifted absorption components: we observe static, low-velocity features and time-evolving features at higher velocities. Overall, we find the observed line morphologies and variability are inconsistent with a scaled-up T Tauri MA scenario. We suggest that as magnetic field structure and strength change dramatically with increasing stellar mass from T Tauri to Herbig Ae/Be stars, so too may accretion and outflow processes.