UV spectra of T Tauri stars from the HST and IUE satellites: BP Tau

Ultraviolet spectra of BP Tau observed with HST/GHRS and IUE satellites were analysed. We found that BP Tau activity can be explained in the frame of a disk accretion model if we assume that the stellar magnetic axis is strongly inclined to the disk plane. The following set of accretion process parameters were derived: relative surface area of the accretion zone $f \simeq 0.25,$ accretion rate $\dot M_\mathrm{ac} \simeq 3.6\times 10^{-8}$ $M_\odot$ yr-1, accretion energy flux ${\cal F}=2.3\times 10^{10}$ erg s-1 cm-2 and accretion luminosity $L_\mathrm{ac} \simeq 0.37$ $L_\odot$. The relevance of these parameters is discussed. We argue that the Calvet & Gullbring ([CITE]) accretion shock model is too crude to believe that the accretion spot surface area is indeed proportional to the square of the accretion rate, as Ardila & Basri ([CITE]) found through this model. A strong flare in the Fei