Temporal Changes in the Infrared Spectra of Magellanic Carbon Stars

TL;DR

This study compares mid-infrared spectra of Magellanic carbon stars taken over 16-19 years, revealing significant spectral variability likely linked to pulsation or stellar evolution.

Contribution

First long-term comparison of infrared spectra of Magellanic carbon stars, highlighting spectral variability over nearly two decades.

Findings

Significant spectral changes observed in two stars over 16-19 years.

Variations in molecular absorption bands linked to stellar pulsation or evolution.

Long-period Mira shows cycle-consistent changes; short-period Mira exhibits dramatic spectral shifts.

Abstract

The Medium-Resolution Spectrometer on the Mid-Infrared Instrument on JWST obtained spectra of three carbon stars in the Large Magellanic Cloud. Two of the spectra differ significantly from spectra obtained ~16-19 years earlier with the Infrared Spectrograph on the Spitzer Space Telescope. The one semi-regular variable among the three has changed little. The long-period Mira variable in the sample shows changes consistent with its pulsation cycle. The short-period Mira shows dramatic changes in the strength of its molecular absorption bands, with some bands growing weaker and some stronger. Whether these variations result from its pulsation cycle or its evolution is not clear.