On the nature and environment of Omicron Scorpii

Omicron Scorpii (HR 6081) is a reddened A511 star situated in the direction of the Rho Ophiuchi dark cloud, and a probable member of the Sco OB2 association. A previous author included it in a recent study of bright B and A-type stars detected by IRAS, and deduced that the IRAS data are consistent with the presence of infrared excess radiation characteristic of hot circumstellar dust (Tsub(d) ≅ 400-3500 K). As the star has been used by various authors to investigate the interstellar extinction and polarization laws in the infrared, it is important to confirm the reality of any infrared excess. In this paper, ground-based broad-band photometry covering the wavelength range 0.36-10 μm is combined with the IRAS measurements to show that no significant infrared excess is, in fact, present: the star's spectral energy distribution is entirely consistent with that of an A511 star with the appropriate degree of reddening. (author)