Revisiting the case of R Monocerotis: Is CO removed at R < 20 au? ⋆ .

Autor: Alonso-Albi T; Observatorio Astronómico Nacional (IGN), Calle Alfonso XII, 3, 28014 Madrid, Spain., Riviere-Marichalar P; Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC). E-28049, Cantoblanco, Madrid, Spain., Fuente A; Observatorio Astronómico Nacional (IGN), Calle Alfonso XII, 3, 28014 Madrid, Spain., Pacheco-Vázquez S; Observatorio Astronómico Nacional (IGN), Calle Alfonso XII, 3, 28014 Madrid, Spain., Montesinos B; Departamento de Astrofísica, Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain., Bachiller R; Observatorio Astronómico Nacional (IGN), Calle Alfonso XII, 3, 28014 Madrid, Spain., Treviño-Morales SP; Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC). E-28049, Cantoblanco, Madrid, Spain.; Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden.
Jazyk: angličtina
Zdroj: Astronomy and astrophysics [Astron Astrophys] 2018 Sep 12; Vol. 617.
DOI: 10.1051/0004-6361/201731658
Abstrakt: Context: 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.
Aims: Our goal is to re-evaluate the R Mon spectral type and characterize its protoplanetary disk.
Methods: The spectral type of R Mon has been re-evaluated 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.
Results: 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 u <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 J u >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.
Conclusions: The observations gathered in this paper are consistent with the presence of a transition disk with a cavity of R in ≳20 au around R Mon. This size is similar to the photoevaporation radius that supports the interpretation that UV photoevaporation is main disk dispersal mechanism in massive stars.
Databáze: MEDLINE
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