Modeling the bow-shock of Ophiuchi

Abstract

Runaway masive stars are O- and B-type stars with large peculiar veloci- ties. Runaway OB stars can produce stellar bowshocks in the surrounding interstellar medium. Bowshocks develop as arc-shaped structures while the star moves superson- ically through the ambient gas. The shocked material is expected to emit thermal and non-thermal radiation in a wide range of energies. Recently, non-thermal radio emis- sion has been detected in the bow-shock region produced by a very massive runaway star, BD+43 3654, indicating the presence of relativistic particles.The star ¢ Ophiuchi (HD 149757) is one of the brightest massive stars in the northern hemisphere and has been intensively studied. This star has spectral type O9.5V and is a well-known run- away. A bowshock has been detected at far-infrared wavelengths. ¢ Oph is rapidly rotating with almost break-up velocity.We model the shape of the bowshock and the non-thermal radiation produced in the interaction between the strong wind of ¢ Oph and the interstellar medium. We consider a non-axisymmetric bowshock. We assume thal the asymmetry arises as a result of the fast rotation of the star (the stellar wind are has symmetry with respect to the equatorial plane). Spectral energy distributions calculated for the whole electromagnetic spectrum.