Multi-epoch monitoring of the AA Tauri-like star V354 Mon. Indications for a low gas-to-dust ratio in the inner disk warp

P. C. Schneider*, C. F. Manara, S. Facchini, H. M. Guenther, G. J. Herczeg, D. Fedele, P. S. Teixeira

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


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. Multiepoch, 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.

Original languageEnglish
Article numberA108
Number of pages9
JournalAstronomy & Astrophysics
Publication statusPublished - 28 Jun 2018


  • Stars: variables: T Tauri, Herbig Ae/Be
  • Stars: individual: v354 Mon
  • Circumstellar matter
  • Accretion, accretion disks
  • Protoplanetary disks


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