Panchromatic JWST Observations and Models of the Dim Type Iax Supernova 2024vjm at 200 days
Abstract
We report JWST spectra and photometry of the underluminous Type Iax supernova (SN Iax) 2024vjm obtained 202.8 rest-frame days postexplosion. The spectrum exhibits a rich set of forbidden lines from low-ionization, intermediate-mass, and iron-group elements, notably the [Ni ii ] 6.64 μ m resonance line, which is a direct indicator of stable nickel. Strong CO and SiO emission is detected alongside a warm dust continuum; the spectral properties are consistent with preexisting rather than newly formed dust. Synthetic spectra were computed with the generalized stellar atmospheres code PHOENIX using simplified ejecta models. The models reproduce the overall spectral energy distribution and the molecular emission features reasonably well, but substantially underestimate the strength of the mid-infrared atomic forbidden lines, leaving the synthetic spectrum dominated by molecular emission. Experiments in which the molecular opacity is suppressed do not recover the forbidden lines; instead, the emission peak migrates to Co and Fe transitions near 2 μ m. We attribute this discrepancy to poorly constrained collisional rates and possibly to an excess of iron group material in the current ejecta models. A prominent feature at 12.8 μ m is not well accounted for by the [Ne ii ] 12.81 μ m line, indicating that the 12.8 μ m feature may be largely due to [Fe iii ]. The presence of CO, SiO, and stable nickel together with the nondetection of neon places tight constraints on the total ejecta mass and the nucleosynthetic yields of SN Iax progenitor systems.
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BibTeX
@article{baron2026panchromatic,
title = {{Panchromatic JWST Observations and Models of the Dim Type Iax Supernova 2024vjm at 200 days}},
author = {E Baron and J.M Derkacy and C Ashall and M Shahbandeh and Peter H Hauschildt and T Barman and J.P Aufdenberg and C.R Burns and N Morrell and M.D Stritzinger and P Hoeflich and K Medler and E Fereidouni and C.M Pfeffer and T Mera and W.B Hoogendam and S Shiber and P.J Brown and Divya Mishra and Inma Dominguez and L Galbany and Paolo Mazzali and E.Y Hsiao and Huangfei Xiao and T de Jaeger and S Kumar},
journal = {Astrophys.J.Lett.},
year = {2026},
month = sep,
doi = {10.3847/2041-8213/ae99c9},
eprint = {2608.15040},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05736218v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Panchromatic JWST Observations and Models of the Dim Type Iax Supernova 2024vjm at 200 days
AU - E Baron
AU - J.M Derkacy
AU - C Ashall
AU - M Shahbandeh
AU - Peter H Hauschildt
AU - T Barman
AU - J.P Aufdenberg
AU - C.R Burns
AU - N Morrell
AU - M.D Stritzinger
AU - P Hoeflich
AU - K Medler
AU - E Fereidouni
AU - C.M Pfeffer
AU - T Mera
AU - W.B Hoogendam
AU - S Shiber
AU - P.J Brown
AU - Divya Mishra
AU - Inma Dominguez
AU - L Galbany
AU - Paolo Mazzali
AU - E.Y Hsiao
AU - Huangfei Xiao
AU - T de Jaeger
AU - S Kumar
PY - 2026
DA - 2026/09/02
JO - Astrophys.J.Lett.
DO - 10.3847/2041-8213/ae99c9
UR - https://hal.science/hal-05736218v1
AB - We report JWST spectra and photometry of the underluminous Type Iax supernova (SN Iax) 2024vjm obtained 202.8 rest-frame days postexplosion. The spectrum exhibits a rich set of forbidden lines from low-ionization, intermediate-mass, and iron-group elements, notably the [Ni ii ] 6.64 μ m resonance line, which is a direct indicator of stable nickel. Strong CO and SiO emission is detected alongside a warm dust continuum; the spectral properties are consistent with preexisting rather than newly formed dust. Synthetic spectra were computed with the generalized stellar atmospheres code PHOENIX using simplified ejecta models. The models reproduce the overall spectral energy distribution and the molecular emission features reasonably well, but substantially underestimate the strength of the mid-infrared atomic forbidden lines, leaving the synthetic spectrum dominated by molecular emission. Experiments in which the molecular opacity is suppressed do not recover the forbidden lines; instead, the emission peak migrates to Co and Fe transitions near 2 μ m. We attribute this discrepancy to poorly constrained collisional rates and possibly to an excess of iron group material in the current ejecta models. A prominent feature at 12.8 μ m is not well accounted for by the [Ne ii ] 12.81 μ m line, indicating that the 12.8 μ m feature may be largely due to [Fe iii ]. The presence of CO, SiO, and stable nickel together with the nondetection of neon places tight constraints on the total ejecta mass and the nucleosynthetic yields of SN Iax progenitor systems.
ER -