The Close T Tauri Binary System V4046 Sgr: Rotationally Modulated X-Ray Emission from Accretion Shocks

TY - JOUR

T1 - The Close T Tauri Binary System V4046 Sgr: Rotationally Modulated X-Ray Emission from Accretion Shocks

AU - Argiroffi, C.

AU - Maggio, A.

AU - Montmerle, T.

AU - Huenemoerder, D. P.

AU - Alecian, E.

AU - Audard, M.

AU - Bouvier, J.

AU - Damiani, F.

AU - Donati, J. -F.

AU - Gregory, S. G.

AU - Güdel, M.

AU - Hussain, G. A. J.

AU - Kastner, J. H.

AU - Sacco, G. G.

PY - 2012/6

Y1 - 2012/6

N2 - 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~ 1011-1012 cm-3) 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.

AB - 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~ 1011-1012 cm-3) 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.

KW - : accretion, accretion disks

KW - stars: individual (V4046 Sgr)

KW - stars: magnetic field

KW - stars: pre-main sequence

KW - stars: variables: T Tauri, Herbig Ae/Be

KW - X-rays: stars

UR - https://ui.adsabs.harvard.edu/abs/2012ApJ...752..100A/abstract

U2 - 10.1088/0004-637X/752/2/100

DO - 10.1088/0004-637X/752/2/100

M3 - Article

SN - 0004-637X

VL - 752

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 100

ER -