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arXiv · 1807.01893

Re-visiting the case of R Mon: Is CO removed at R<20 au?

T. Alonso-Albi·P. Riviere-Marichalar·A. Fuente·S. Pacheco-Vázquez·B. Montesinos·R. Bachiller·S. P. Treviño-Morales
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Abstract

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 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

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T. Alonso-Albi, P. Riviere-Marichalar, A. Fuente, S. Pacheco-Vázquez, B. Montesinos, R. Bachiller, S. P. Treviño-Morales. 2018-07-05. Re-visiting the case of R Mon: Is CO removed at R<20 au?. https://doi.org/10.1051/0004-6361%2F201731658

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