The Galactic Center Cloud G2—a Young Low-mass Star with a Stellar Wind

Abstract

We explore the possibility that the G2 gas cloud falling in toward SgrA^* is the mass-loss envelope of a young T Tauri star. As the star plunges to smaller radius at 1000-6000 km s^(–1), a strong bow shock forms where the stellar wind is impacted by the hot X-ray emitting gas in the vicinity of SgrA^*. For a stellar mass-loss rate of 4 × 10^(–8) M_☉ yr^(–1) and wind velocity 100 km s^(–1), the bow shock will have an emission measure (EM = n^2 vol) at a distance ~10^(16) cm, similar to that inferred from the IR emission lines. The ionization of the dense bow shock gas is potentially provided by collisional ionization at the shock front and cooling radiation (X-ray and UV) from the post shock gas. The former would predict a constant line flux as a function of distance from SgrA^*, while the latter will have increasing emission at lesser distances. In this model, the star and its mass-loss wind should survive pericenter passage since the wind is likely launched at 0.2 AU and this is much less than the Roche radius at pericenter (~3 AU for a stellar mass of 2 M_☉). In this model, the emission cloud will probably survive pericenter passage, discriminating this scenario from others.

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