Mid-infrared JWST Spectra of Carbon Stars in the Large Magellanic Cloud
Journal article, 2026
Mid-infrared spectra from the Medium Resolution Spectrometer (MRS) on the James Webb Space Telescope have revealed the molecular chemistry of carbon stars in the Large Magellanic Cloud with better resolution and sensitivity than previously possible. Our sample spans a range of dust-production rates and includes three relatively dust-free semiregular variables and six dustier Mira variables. All were observed 15–20 yr earlier with the Infrared Spectrograph on the Spitzer Space Telescope at lower spectral resolution. The new spectra show that the C3 molecule is responsible for a strong absorption band centered at 5.2 μm. CS is clearly present in some of the sample, especially the stars with less dust. HCN also appears to be present. Some of the spectra have changed significantly between the Spitzer epoch and the MRS observations in 2023 and 2024, and in most cases these changes can be attributed to the stellar pulsation cycle. One exception is the disappearance of a dust emission feature at ∼18 μm in one of the Miras. The new spectra reveal a dip centered at ∼10 μm, which could arise either from an unknown carrier or from variable molecular emission to the red and blue. The presence of this spectral structure on the short-wavelength side of the SiC dust emission feature at ∼11.3 μm along with the broad C2H2 band centered at 14 μm raise the possibility that some previously reported detections of weak SiC dust emission in other carbon stars may not be real.
Circumstellar dust (236)
Long period variable stars (935)
Circumstellar gas (238)
Asymptotic giant branch stars (2100)
Carbon stars (199)
Author
G. C. Sloan
Space Telescope Science Institute (STScI)
The University of North Carolina System
B. Aringer
University of Vienna
Uppsala University
Kathleen E. Kraemer
Boston College
Jan Cami
Western University
K. Eriksson
Uppsala University
S. Höfner
Uppsala University
Kay Justtanont
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
E. Lagadec
Observatoire de la Cote d'Azur
P. Marigo
University of Padua
M. Matsuura
Cardiff University
I. McDonald
University of Manchester
E. J. Montiel
US Naval Observatory
National Aeronautics and Space Administration (NASA)
R. Sahai
California Institute of Technology (Caltech)
A. Zijlstra
University of Manchester
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 1002 2Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.3847/1538-4357/ae5a24