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arXiv · 1204.0964

The close T Tauri binary system V4046 Sgr: Rotationally modulated X-ray emission from accretion shocks

C. Argiroffi·A. Maggio·T. Montmerle·D. P. Huenemoerder·E. Alecian·M. Audard·J. Bouvier·F. Damiani·J. -F. Donati·S. G. Gregory·M. Güdel·G. A. J. Hussain·J. H. Kastner·G. G. Sacco
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Abstract

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 (n_e ~ 10^(11-12) cm^(-3)) plasma at temperatures of 3-4 MK. Our multiwavelength 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.

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C. Argiroffi, A. Maggio, T. Montmerle, D. P. Huenemoerder, E. Alecian, M. Audard, J. Bouvier, F. Damiani, J. -F. Donati, S. G. Gregory, M. Güdel, G. A. J. Hussain, J. H. Kastner, G. G. Sacco. 2012-04-04. The close T Tauri binary system V4046 Sgr: Rotationally modulated X-ray emission from accretion shocks. https://doi.org/10.1088/0004-637x%2F752%2F2%2F100

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