Outbursts and stellar properties of the classical Be star HD 6226
Outbursts and stellar properties of the classical Be star HD 6226
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DOI：
10.1093/mnras/stab2759
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发表时间：
2021-09
影响因子：
4.8
通讯作者：
N. Richardson;O. Thizy;J. Bjorkman;A. Carciofi;A. Rubio;Joshua D Thomas;K. Bjorkman;J. Labadie-Bartz-J
中科院分区：
文献类型：
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作者：
N. Richardson;O. Thizy;J. Bjorkman;A. Carciofi;A. Rubio;Joshua D Thomas;K. Bjorkman;J. Labadie-Bartz-J
明亮而未被充分研究的经典Be星HD 6226在过去几年中多次爆发，在此期间恒星形成了一个粘性的圆盘。我们分析了从2017年到2020年收集的该系统的659个光谱，以及哈勃太空望远镜的紫外光谱，以及凌日系外行星巡天卫星（TESS）和千度极小望远镜（KELT）巡天的高节奏光度测定。我们发现这颗恒星的光谱类型为B2.5IIIe，自转速率为临界值的74%。这颗恒星接近极向，倾角为13${_{.}^{\circ}}$4。我们证实了先前报道的光谱脉动特性，并报道了KELT光度法的三个光度振荡。用H α和H β的等效宽度测量研究了爆发行为，两者的变化可以通过傅里叶分析用两个频率定量解释。发射爆发的其中一个频率等于两个光度振荡之间的差，将这些脉动模式与某些爆发的质量抛射机制联系起来。在2019年10月7日至2019年11月2日的TESS观测期间，这颗恒星正在形成一个圆盘。利用大量的H α和H β光谱数据集，我们能够确定这两条线的耗散时间尺度，类似于过去用光学光度法对Be星所做的工作。鉴于其明显的周期性，HD 6226是研究Be盘演化的理想目标，允许将来使用其他设施进行有针对性的观测。
The bright and understudied classical Be star HD 6226 has exhibited multiple outbursts in the last several years during which the star grew a viscous decretion disc. We analyse 659 optical spectra of the system collected from 2017 to 2020, along with a ultraviolet spectrum from the Hubble Space Telescope and high cadence photometry from both Transiting Exoplanet Survey Satellite (TESS) and the Kilodegree Extremely Little Telescope (KELT) survey. We find that the star has a spectral type of B2.5IIIe, with a rotation rate of 74 per cent of critical. The star is nearly pole-on with an inclination of 13${_{.}^{\circ}}$4. We confirm the spectroscopic pulsational properties previously reported, and report on three photometric oscillations from KELT photometry. The outbursting behaviour is studied with equivalent width measurements of H α and H β, and the variations in both of these can be quantitatively explained with two frequencies through a Fourier analysis. One of the frequencies for the emission outbursts is equal to the difference between two photometric oscillations, linking these pulsation modes to the mass ejection mechanism for some outbursts. During the TESS observation time period of 2019 October 7 to 2019 November 2, the star was building a disc. With a large data set of H α and H β spectroscopy, we are able to determine the time-scales of dissipation in both of these lines, similar to past work on Be stars that has been done with optical photometry. HD 6226 is an ideal target with which to study the Be disc-evolution given its apparent periodic nature, allowing for targeted observations with other facilities in the future.