再谈R Mon的情况：R<20 au时是否去除了CO？
Re-visiting the case of R Mon: Is CO removed at R<20 au?
摘要：
据我们所知，R Mon是唯一一颗被探测到气态开普勒盘的B 0恒星。然而，关于R Mon的光谱类型存在一些争议。一些作者认为它可能是一颗较晚的B8 e恒星，在那里盘状结构更为常见。我们已经重新评估了光谱类型的R Mon使用现有的连续数据和UVES发射线。我们使用了一个幂律盘模型来拟合以前的12个CO 1-0和2-1干涉观测和PACS CO数据来研究盘结构。利用IRAM的Plateau de Bure干涉仪（PdBI）对13条CO J=1-0、HCO+ 1-0和CN 1-0谱线进行了干涉检测。未检测到HCN 1-0线。我们的分析证实了R Mon是一颗B 0星。与12 CO 1-0和2-1干涉观测兼容的盘模型不能预测14<Ju<31 PACS线的观测通量;这与对这些线的一些贡献来自温暖的包层和/或UV照射的流出壁的情景一致。更有趣的是，Ju>31的CO谱线的通量上限表明，在原行星盘中R<20 au处存在一个没有CO的区域。HCO+和CN线的强烈发射显示了紫外光子对气体化学的强烈影响。在本文中收集的意见是一致的存在与周围的R Mon的过渡盘腔约20 AU。这一大小与光蒸发半径相似，支持了紫外光蒸发是大质量恒星主要的盘扩散机制的解释
英文摘要：
To our knowledge, R Mon is the only B0 star in which a gaseous Keplerian disk has been detected. However, there is some controversy about the spectral type of R Mon. Some authors propose that it could be a later B8e star, where disks are more common. We have re-evaluated the spectral type of R Mon using the available continuum data and UVES emission lines. We used a power-law disk model to fit previous 12 CO 1-0 and 2-1 interferometric observations and the PACS CO data to investigate the disk structure. Interferometric detections of 13 CO J=1-0, HCO+ 1-0, and CN 1-0 lines using the IRAM Plateau de Bure Interferometer (PdBI) are presented. The HCN 1-0 line was not detected. Our analysis confirms that R Mon is a B0 star. The disk model compatible with the 12 CO 1-0 and 2-1 interferometric observations falls short of predicting the observed fluxes of the 14<Ju<31 PACS lines; this is consistent with the scenario in which some contribution to these lines is coming from a warm envelope and/or UV-illuminated outflow walls. More interestingly, the upper limits to the fluxes of the Ju>31 CO lines suggest the existence of a region empty of CO at R<20 au in the proto-planetary disk. The intense emission of the HCO+ and CN lines shows the strong influence of UV photons on gas chemistry. The observations gathered in this paper are consistent with the presence around R Mon of a transition disk with a cavity about 20 au. This size is similar to the photoevaporation radius that supports the interpretation that UV photoevaporation is main disk dispersal mechanism in massive stars
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
