Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The close T Tauri binary system V4046 Sgr: Rotationally modulated X-ray
  emission from accretion shocks   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.

17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th