Astronomy & Astrophysics

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Free access article

A&A 439, 1149-1158 (2005)
DOI: 10.1051/0004-6361:20052729

XMM-Newton spectroscopy of the metal depleted T Tauri star TWA 5

C. Argiroffi¹, A. Maggio², G. Peres¹, B. Stelzer^{1, 2} and R. Neuhäuser³

¹ Dipartimento di Scienze Fisiche ed Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
    e-mail: [argi;peres;stelzer]@astropa.unipa.it
² INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
    e-mail: maggio@astropa.unipa.it
³ Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergässchen 2-3, 07745 Jena, Germany
    e-mail: rne@astro.uni-jena.de

(Received 20 January 2005 / Accepted 28 April 2005 )

Abstract
We present results of X-ray spectroscopy for TWA 5 , a member of the young TW Hydrae association, observed with XMM-Newton. TWA 5 is a multiple system which shows H $\alpha$ emission, a signature typical of classical T Tauri stars, but no infrared excess. From this analysis of the RGS and EPIC spectra, we have derived the emission measure distribution vs. temperature of the X-ray emitting plasma, its abundances, and the electron density. The characteristic temperature and density of the plasma suggest a corona similar to that of weak-line T Tauri stars and active late-type main sequence stars. TWA 5 also shows low iron abundance (~0.1 times the solar photospheric one) and a pattern of increasing abundances for elements with increasing first ionization potential reminiscent of the inverse FIP effect observed in highly active stars. The especially high ratio ${\rm Ne/Fe}\sim10$ is similar to that of the classical T Tauri star TW Hya , where the accreting material has been held responsible for the X-ray emission. We discuss the possible role of an accretion process in this scenario. Since all T Tauri stars in the TW Hydrae association studied so far have very high ${\rm Ne/Fe}$ ratios, we also propose that environmental conditions may cause this effect.

Key words: X-rays: stars -- techniques: spectroscopic -- stars: activity -- stars: abundances -- stars: pre-main sequence -- stars: individual: TWA 5

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