NitrogenV in the wind of the pre-main sequence Herbig Ae star ABAurigae

Recent GHRS observations of the Herbig Ae star AB Aur demonstrate the presence of N V in the wind of this star. This result reveals temperatures much higher than those previously considered for the wind of AB Aur. We show that homogeneous spherically symmetric models are unable to reproduce the available observations, including the C IV resonance lines in absorption and the absence of N IV emission. We then study models including hot (T≈140,000 K) clumps, and argue that the N V lines can be formed in such hot regions. The filling factor of the hot clumps can be as small as a few 10−3. This type of clumpy structure of the wind is expected in the framework of a model of the wind of AB Aur, in which fast and slow streams alternate, and produce shocks where fast streams overtake slow ones. The presence of shocks in the wind of AB Aur would also be consistent with its X-ray emission.