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Post Info TOPIC: RU Lupi
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RE: RU Lupi
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Title: X-rays from RU Lupi - Accretion and winds in CTTS
Authors: J. Robrade, J.H.M.M. Schmitt

Using three XMM-Newton observations we study the X-ray emission of RU Lup, a accreting and wind-driving CTTS. In comparison with other bright CTTS we study possible signatures of accretion and winds in their X-ray emission. Results: We find three levels of activity among the observations of RU Lup, clearly of magnetic origin due to the corresponding high plasma temperatures. Density analysis with the OVII triplet indicates high densities in the cool plasma, suggesting accretion shocks to be a significant contributor to the soft X-ray emission. No strong overall metal depletion is observed. Excess emission at 6.4 keV during the more active phase suggest the presence of iron fluorescence. In accreting stars we find an excess of cool plasma as evidenced by lower OVIII/OVII line ratios compared to main-sequence stars. High density plasma appears to be only present in low-mass CTTS, while accreting stars with intermediate masses (> 2 M_Sun) have lower densities.
Conclusions: In all investigated CTTS the characteristics of the cooler X-ray emitting plasma are influenced by the accretion process. We suspect different accretion rates and amount of funnelling, possibly linked to stellar mass and radius, to be mainly responsible for the different properties of their cool plasma component. The exceptional strong X-ray absorption in RU Lup and other CTTS is probably related to accretion flows and an optically transparent wind emanating from the star or the disk.

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Blobrana


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Posts: 131433
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Title: Periodic radial velocity variations in RU Lupi
Authors: H.C. Stempels, G.F. Gahm, P.P Petrov

Context. RU Lup is a Classical T Tauri star with unusually strong emission lines, which has been interpreted as manifestations of accretion. Recently, evidence has accumulated that this star might have a variable radial velocity.
Aims. We intended to investigate in more detail the possible variability in radial velocity using a set of 68 high-resolution spectra taken at the VLT (UVES), the AAT (UCLES) and the CTIO (echelle).
Methods. Using standard cross-correlation techniques, we determined the radial velocity of RU Lup. We analysed these results with Phasedispersion minimisation and the Lomb-Scargle periodogram and searched for possible periodicities in the obtained radial velocities. We also analysed changes in the absorption line shapes and the photometric variability of RU Lup.
Results. Our analysis indicated that RU Lup exhibits variations in radial velocity with a periodicity of 3.71 days and an amplitude of 2.17 km/s. These variations can be explained by the presence of large spots, or groups of spots, on the surface of RU Lup. We also considered a low-mass companion and stellar pulsations as alternative sources for these variations but found these to be unlikely.

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Position(2000): RA = 15 56 42.2 Dec = -37 49 16

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