The three dimensional morphology of the circumstellar ejecta of IRC +10420.

Abstract

This thesis explores the 3 dimensional behavior of the outer ejecta from the post-red supergiant IRC +10420. This star inhabits a region of the Hertzsprung- Russell diagram just below the Humphreys-Davidson instability limit. It also appears to be evolving from a cooler temperature to a hotter one, making it a very unique star. It is the only star of its type of have observed nebulosity. Images of this star show the nebulosity, or complex ejecta that is evidence of episodic mass loss. The transverse motions of the various features seen in the inner ejecta are explored. This information is obtained from two sets of images taken with the HST/WFPC2 in 1996 and 2008. Additional information from a previous paper also gives the radial velocity for several features, allowing the determination of the total motion for a number of the features. Combining the radial and transverse velocity information into a time since ejection, this gives a picture of the mass loss history, the time between ejection epochs and the outflow from the star. Additionally, the radial velocity measurements prove that these features are spatially distinct and that are expanding away from the star. The motion of these features is predominantly dominated by their transverse motion and they appear to be moving within a few degrees of the plane of the sky. The connection between this and the magnetic fields are discussed. This leads to the conclusion that IRC +10420 has approximate rotational symmetry and is viewed almost pole-on, with the equatorial plane nearly in the plane of the sky.