1994A&A...291..295H

G 79.29+0.46 is a ring-like radio source with a diameter (at maximum brightness) of ∼3.2', discovered with the DRAO Synthesis Telescope. It has been observed at three frequencies with the Very Large Array. The flux density of the ring at 4.86GHz, where the angular resolution is ∼4.6", is (590±90)mJy, and the spectral index is β=-0.03±0.10 (S∝ν^β), implying that the ring is an ionized hydrogen shell. At its center is a point radio source whose radio spectrum, based on data from 1.49 to 394GHz, suggests that it is a mass-outflow object. For the point source, β varies from about +1.4 below 10GHz to a value of ~+0.6 at millimeter wavelengths. The central point source has been identified with a highly reddened star which has a strong Hα emission line, from which a wind velocity of ∼1400km/s is deduced. Infrared IRAS data imply a dust temperature of at least 125K in the stellar wind, and ∼65K in the ionized shell. DRAO H I line observations suggest that the shell is expanding at ∼70km/s into an ambient (or circumstellar) medium of density ∼25cm^–3. Comparison of the shape of the observed red continuum emission from the star (550-750nm) with models of the continuum emission from early-type stars yields an extinction of ∼16mag, giving an absolute visual magnitude of about -10. The suggested distance for the star is ∼2kpc, and it may be a "luminous blue variable". The wind from the star has swept up ∼15M_☉ of interstellar or circumstellar material, of which about half is now ionized by the star and the rest forms the H I shell. The age of the shell is estimated to be ∼10⁴yr. The star may be an outlying member of the Cyg OB2 association.