Discovery of an H I Counterpart to the Extended Tail of Mira

International audienceWe report the detection of an H I counterpart to the extended, far-ultraviolet-emitting tail associated with the asymptotic giant branch star Mira (o Ceti). Using the Nançay Radio Telescope (NRT), we have detected emission as far as 88' north of the star, confirming that the tail contains a significant atomic component (M<SUB>HI</SUB>~4×10<SUP>-3</SUP> M<SUB>solar</SUB>). The NRT spectra reveal a deceleration of the tail gas caused by interaction with the local interstellar medium. We estimate an age for the tail of ~1.2×10<SUP>5</SUP> yr, suggesting that the mass-loss history of Mira has been more prolonged than previous observational estimates. Using the Very Large Array we have also imaged the H I tail out to ~12' (0.4 pc) from the star. The detected emission shows a ``head-tail'' morphology, but with complex substructure. Regions with detected H I emission correlate with far-ultraviolet-luminous regions on large scales, but the two tracers are not closely correlated on smaller scales (<1'). We propose that detectable tails of H I are likely to be a common feature of red giants undergoing mass loss