Multi-epoch monitoring of the AA Tauri-like star V 354 Mon

Disk warps around classical T Tauri stars (CTTSs) can periodically obscure the central star for some viewing geometries. For these so- called AA Tau-like variables, the obscuring material is located in the inner disk and absorption spectroscopy allows one to characterize its dust and gas content. Si...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2018-06, Vol.614
Main Authors: Schneider, P. C., Manara, C. F., Facchini, S., Günther, H. M., Herczeg, G. J., Fedele, D., Teixeira, P. S.
Format: Article
Language:English
Subjects:
Absorption
Absorption spectroscopy
accretion
Accretion disks
Broadband
circumstellar matter
Dust
Emission spectra
Extinction
Gas absorption
Herbig Ae/Be
Photosphere
protoplanetary disks
Spectrum analysis
stars: individual: v354 Mon
stars: variables: T Tauri
Stellar evolution
T Tauri stars
Variability
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Description
Summary:Disk warps around classical T Tauri stars (CTTSs) can periodically obscure the central star for some viewing geometries. For these so- called AA Tau-like variables, the obscuring material is located in the inner disk and absorption spectroscopy allows one to characterize its dust and gas content. Since the observed emission from CTTSs consists of several components (photospheric, accretion, jet, and disk emission), which can all vary with time, it is generally challenging to disentangling disk features from emission variability. Multi- epoch, flux-calibrated, broadband spectra provide us with the necessary information to cleanly separate absorption from emission variability. We applied this method to three epochs of VLT/X-shooter spectra of the CTTS V 354 Mon (CSI Mon-660) located in NGC 2264 and find that: (a) the accretion emission remains virtually unchanged between the three epochs; (b) the broadband flux evolution is best described by disk material obscuring part of the star, and (c) the Na and K gas absorption lines show only a minor increase in equivalent width during phases of high dust extinction. The limits on the absorbing gas column densities indicate a low gas-to-dust ratio in the inner disk, less than a tenth of the ISM value. We speculate that the evolutionary state of V 354 Mon, rather old with a low accretion rate, is responsible for the dust excess through an evolution toward a dust dominated disk or through the fragmentation of larger bodies that drifted inward from larger radii in a still gas dominated disk.
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361/201731959