A New Peculiar Emission-Line Object

Spectrographic and spectrophometric observations indicate that the object M1-2, formerly identified as a high-density planetary nebula, is actually more complex. The underlying continuous radiation is that of a cool continuum with the absorption spectrum of a G2 supergiant. The emission lines are formed in a region optically thick to the lower members of the Balmer series and have a radial velocity 12 km/sec more negative than the absorption lines. There are no large variations in the radial velocities. The low radial velocity and the position in the Galaxy argues against the system being as luminous as a real G supergiant while the absolute luminosity in HP is similar to that of known very young planetary nebulae. Two models for the system are examined, the first being a binary star system with a G supergiant and a hot-star companion, the second of a single hot star surrounded by a very extensive outer shell that is only ionized in the innermost regions. Under the second model the emission lines arise from the inner, ionized region and the absorption spectrum is formed as the continuous nebular radiation and the stellar continuum pass through the un-ionized outer gas. It is not possible to positively identify either model for the system with the object, although the single-star model seems more consistent with all of the observations.