X-ray emission from MP Muscae : an old classical T Tauri star

Aims. We study the properties of X-ray emitting plasma of MP Mus, an old classical T Tauri star. We aim at checking whether an accretion process produces the observed X-ray emission and at deriving the accretion parameters and the characteristi cs of the shockheated plasma. We compare the properties of MP Mus with those of younger classical T Tauri stars to test whether age is rela ted to the properties of the X-ray emission plasma. Methods. XMM-Newton X-ray spectra allows us to measure plasma temperatures, abundances, and electron density. In particular th e density of cool plasma probes whether X-ray emission is produced by plasma heated in the accretion process. Results. X-ray emission from MP Mus originates from high density cool plasma but a hot flaring component is also present, suggestin g that both coronal magnetic activity and accretion contribute to the observed X-ray emission. We find a Ne/O ratio similar to that observed in the much younger classical T Tauri star BP Tau. From the soft part of the X-ray emission, mostly produced by plasma heated in the accretion shock, we derive a mass accretion rate of 5× 10 −11 M⊙ yr −1 .