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arXiv 2005.05841astro-ph.EPastro-ph.SR
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用ALMA巡天星子带:在类日恒星HD 129590周围探测到气体

Survey of planetesimal belts with ALMA: gas detected around the Sun-like star HD 129590

Quentin Kral, Luca Matra, Grant Kennedy, Sebastian Marino, Mark Wyatt

摘要:

主序星周围的气体探测越来越普遍,大约有20个系统显示存在CO。然而,需要更多的探测,特别是在后来的光谱型恒星周围,以更好地了解这种气体的起源并改进我们的模型。要做到这一点,我们进行了调查的10颗恒星预测的二次CO检测的可能性高,使用ALMA在波段6。我们寻找毫米尘埃的连续排放以及气体排放(CO和CN转换)。在9/10系统中检测到连续辐射,我们推导出了圆盘的尘埃质量和几何特性,提供了HD 106906周围圆盘的第一个毫米波检测,HD 114082,117214,HD 15745,HD 191089的第一个毫米波半径以及HD 121191的第一个半径。我们的论文的一个重要发现是,我们首次在年轻的10-16百万年的G1 V恒星HD 129590周围检测到CO,类似于我们早期的太阳。气体似乎与它的微行星带共位,其总质量可能在$2-10 \times 10^{-5}$ M $_\oplus$之间。这是第一次在G型主序星周围探测到气体,这引发了一个问题,即太阳系是否也在年轻时释放了气体,这可能会影响行星形成。我们还在HD 121191周围检测到CO气体,S/N比以前更高,发现CO比系统中的星子更接近,这可能是以前怀疑的CO粘性扩散的证据,因为屏蔽阻止了它的光解。最后,我们作出估计的CO含量的星子和HCN/CO放气率(CN上限),我们发现在太阳系彗星在某些系统中看到的水平以下。

英文摘要:

Gas detection around main sequence stars is becoming more common with around 20 systems showing the presence of CO. However, more detections are needed, especially around later spectral type stars to better understand the origin of this gas and refine our models. To do so, we carried out a survey of 10 stars with predicted high likelihoods of secondary CO detection using ALMA in band 6. We looked for continuum emission of mm-dust as well as gas emission (CO and CN transitions). The continuum emission was detected in 9/10 systems for which we derived the discs' dust masses and geometrical properties, providing the first mm-wave detection of the disc around HD 106906, the first mm-wave radius for HD 114082, 117214, HD 15745, HD 191089 and the first radius at all for HD 121191. A crucial finding of our paper is that we detect CO for the first time around the young 10-16 Myr old G1V star HD 129590, similar to our early Sun. The gas seems colocated with its planetesimal belt and its total mass is likely between $2-10 \times 10^{-5}$ M$_\oplus$. This first gas detection around a G-type main-sequence star raises questions as to whether gas may have been released in the Solar System as well in its youth, which could potentially have affected planet formation. We also detected CO gas around HD 121191 at a higher S/N than previously and find that the CO lies much closer-in than the planetesimals in the system, which could be evidence for the previously suspected CO viscous spreading owing to shielding preventing its photodissociation. Finally, we make estimates for the CO content in planetesimals and the HCN/CO outgassing rate (from CN upper limits), which we find are below the level seen in Solar System comets in some systems.

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