Volume 617, September 2018
|Number of page(s)||16|
|Section||Interstellar and circumstellar matter|
|Published online||12 September 2018|
Revisiting the case of R Monocerotis: Is CO removed at R < 20 au?★
Observatorio Astronómico Nacional (IGN),
Calle Alfonso XII 3,
e-mail: email@example.com, firstname.lastname@example.org
2 Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), 28049 Cantoblanco, Madrid, Spain
3 Departamento de Astrofísica, Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, Villanueva de la Cañada, 28692 Madrid, Spain
4 Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
Accepted: 20 May 2018
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 12CO 1 →0 and 2 →1 interferometric observations and the PACS CO data to investigate the disk structure. Interferometric detections of 13CO 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 12CO 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 protoplanetary 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 Rin ≳ 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
Key words: circumstellar matter / stars: emission-line, Be / stars: formation
The reduced PdBI datacubes are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/617/A31
© ESO 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.