A high-speed bi-polar outflow from the archetypical pulsating star Mira A

TL;DR

This study reveals a high-speed bipolar outflow from Mira A, with detailed imaging and spectral analysis showing a tilted, 160 km/s outflow approximately 1000 years old, indicating dynamic mass ejection in this pulsating star.

Contribution

First detailed imaging and spectral analysis of Mira A's bipolar outflow, revealing its velocity, tilt, and age, advancing understanding of mass loss in pulsating AGB stars.

Findings

Bipolar outflow with velocities of ±150 km/s

Outflow tilted at 69 degrees to the sky plane

Outflow age estimated at approximately 1000 years

Abstract

Optical images and high-dispersion spectra have been obtained of the ejected material surrounding the pulsating AGB star Mira A. The two streams of knots on either side of the star, found in far ultra-viollet (FUV) GALEX images, have now been imaged clearly in the light of Halpha. Spatially resolved profiles of the same line reveal that the bulk of these knots form a bi-polar outflow with radial velocity extremes of +- 150 km/s with respect to the central star. The South stream is approaching and the North stream receding from the observer. A displacement away from Mira A between the position of one of the South stream knots in the new Halpha image and its position in the previous Palomar Observatory Sky Survey (POSS I) red plate has been noted. If interpreted as a consequence of expansion proper motions the bipolar outflow is tilted at 69deg +- 2deg to the plane of the sky, has an outflow velocity of 160 +- 10 km/s and is ~1000 y old.