Abstract
The main goal of this work is to characterize the mass accretion and ejection processes of the classical T Tauri star V354 Mon, a member of the young stellar cluster NGC 2264. In March 2008, photometric and spectroscopic observations of V354 Mon were obtained simultaneously with the CoRoT satellite, the 60 cm telescope at the Observat\'orio Pico dos Dias (LNA - Brazil) equipped with a CCD camera and Johnson/Cousins BVRI filters, and the SOPHIE \'echelle spectrograph at the Observatoire de Haute-Provence (CNRS - France). The light curve of V354 Mon shows periodical minima (P = 5.26 +/- 0.50 days) that vary in depth and width at each rotational cycle. From the analysis of the photometric and spectroscopic data, it is possible to identify correlations between the emission line variability and the light-curve modulation of the young system, such as the occurrence of pronounced redshifted absorption in the H_alpha line at the epoch of minimum flux. This is evidence that during photometric minima we see the accretion funnel projected onto the stellar photosphere in our line of sight, implying that the hot spot coincides with the light-curve minima. We applied models of cold and hot spots and a model of occultation by circumstellar material to investigate the source of the observed photometric variations. We conclude that nonuniformly distributed material in the inner part of the circumstellar disk is the main cause of the photometric modulation, which does not exclude the presence of hot and cold spots at the stellar surface. It is believed that the distortion in the inner part of the disk is created by the dynamical interaction between the stellar magnetosphere, inclined with respect to the rotation axis, and the circumstellar disk, as also observed in the classical T Tauri star AA Tau and predicted by magnetohydrodynamical numerical simulations.
Highlights
The study of young stellar objects is important for understanding the phenomena that occur in star and planet formation, including our solar system
The light curve of V354 Mon shows periodical minima (P = 5.26 ± 0.50 days) that vary in depth and width at each rotational cycle
The broadband, white-light curve of V354 Mon obtained with CoRoT (Fig. 1, top panel) displays a typical CTTS behavior, 1 This problem was first investigated by selecting only nebular emission lines and calculating the ratio between the highest intensity of these lines in the sky and stellar spectra
Summary
The study of young stellar objects is important for understanding the phenomena that occur in star and planet formation, including our solar system. T Tauri stars are young (∼106 years), low-mass stars (M ≤ 2 M ) in the pre-main sequence (PMS) phase, which are of great interest as prototypes of young solar-type stars. They emit X-rays and have strong magnetic fields (∼2 kG, Johns-Krull et al 2001). Based on their Hα emission strength, they are classified as classical (CTTSs) or weak-line T Tauri stars (WTTSs). The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA’s RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain
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