Astrophys. J., 752, 100 (2012/June-3)
The close T Tauri binary system V4046 Sgr: rotationally modulated X-ray emission from accretion shocks.
ARGIROFFI C., MAGGIO A., MONTMERLE T., HUENEMOERDER D.P., ALECIAN E., AUDARD M., BOUVIER J., DAMIANI F., DONATI J.-F., GREGORY S.G., GUDEL M., HUSSAIN G.A.J., KASTNER J.H. and SACCO G.G.
Abstract (from CDS):
We report initial results from a quasi-simultaneous X-ray/optical observing campaign targeting V4046 Sgr, a close, synchronous-rotating classical T Tauri star (CTTS) binary in which both components are actively accreting. V4046 Sgr is a strong X-ray source, with the X-rays mainly arising from high-density (ne∼ 1011-1012/cm3) plasma at temperatures of 3-4 MK. Our multi-wavelength campaign aims to simultaneously constrain the properties of this X-ray-emitting plasma, the large-scale magnetic field, and the accretion geometry. In this paper, we present key results obtained via time-resolved X-ray-grating spectra, gathered in a 360 ks XMM-Newton observation that covered 2.2 system rotations. We find that the emission lines produced by this high-density plasma display periodic flux variations with a measured period, 1.22±0.01 d, that is precisely half that of the binary star system (2.42 d). The observed rotational modulation can be explained assuming that the high-density plasma occupies small portions of the stellar surfaces, corotating with the stars, and that the high-density plasma is not azimuthally symmetrically distributed with respect to the rotational axis of each star. These results strongly support models in which high-density, X-ray-emitting CTTS plasma is material heated in accretion shocks, located at the base of accretion flows tied to the system by magnetic field lines.
accretion, accretion disks - stars: individual: V4046 Sgr - stars: magnetic field - stars: pre-main sequence - stars: variables: T Tauri, Herbig Ae/Be - X-rays: stars
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