The Astrosphere of the Asymptotic Giant Branch Star Irc+10216

TL;DR

This paper reports the discovery of a large ultraviolet shock structure around the star IRC+10216, revealing its interaction with the interstellar medium and providing new insights into its envelope's age, mass, and movement.

Contribution

It presents the first detailed observation of the astrosphere of IRC+10216, identifying key structural features and deriving physical parameters from ultraviolet imaging.

Findings

Extended shock structure with 24 arcmin diameter identified

Envelope age estimated at 69,000 years

Star's velocity through ISM exceeds 91 km/s

Abstract

We have discovered a very extended shock structure (i.e., with a diameter of about 24 arcmin) surrounding the well-known carbon star IRC+10216 in ultraviolet images taken with the GALEX satellite. We conclude that this structure results from the interaction of IRC+10216's molecular wind with the interstellar medium (ISM), as it moves through the latter. All important structural features expected from theoretical models of such interactions are identified: the termination shock, the astrosheath, the astropause, the bowshock, and an astrotail (with vortices). The extent of the astropause provides new lower limits to the envelope age (69,000 years) and mass (1.4 solar masses, for a mass-loss rate of 2 x 10^(-5) solar masses/year). From the termination-shock standoff distance, we find that IRC+10216 is moving at a speed of about > 91 km/s [1 cm^(-3)/n_(ISM)]^1/2 through the local ISM.