The Morphology of IRC +10420's Circumstellar Ejecta

TL;DR

This study analyzes the complex, episodic mass loss in IRC +10420 by measuring the motions of ejecta features, revealing multiple ejection events from different star regions and suggesting a pole-on viewing angle.

Contribution

It provides the first detailed kinematic analysis of IRC +10420's ejecta, highlighting episodic, multi-directional mass loss and the influence of surface activity and magnetic fields.

Findings

Ejecta features have distinct motions indicating multiple ejection events.

The star is viewed nearly pole-on, with ejecta moving close to the plane of the sky.

Episodic mass loss is linked to surface activity and magnetic fields.

Abstract

Images of the circumstellar ejecta associated with the post-red supergiant IRC +10420 show a complex ejecta with visual evidence for episodic mass loss. In this paper we describe the transverse motions of numerous knots, arcs and condensations in the inner ejecta measured from second epoch {\it HST/WFPC2} images. When combined with the radial motions for several of the features, the total space motion and direction of the outflows show that they were ejected at different times, in different directions, and presumably from separate regions on the surface of the star. These discrete structures in the ejecta are kinematically distinct from the general expansion of the nebula and their motions are dominated by their transverse velocities. They are apparently all moving within a few degrees of the plane of the sky. We are thus viewing IRC +10420 nearly pole-on and looking nearly directly down onto its equatorial plane. We also discuss the role of surface activity and magnetic fields on IRC +10420's recent mass loss history.