Nebular Spectra of the Extremely Metal-Poor SN II 2023ufx Over a Year After Explosion: A Massive Progenitor and Unique Circumstellar Environment
Abstract
We present new observations of the metal-poor (< 0.1 Z⊙) Type II supernova 2023ufx and its host galaxy. The deep nebular spectrum, obtained roughly a year after explosion, has a triple-peaked [O I] emission profile suggesting an asymmetric explosion. Comparison to nebular spectra models suggests a zero-age main sequence mass of $ M_{\rm ZAMS} \sim 25-35$ M⊙, which is supported by the low [Ca II]/[O I] emission-line ratio of ≈0.4. The diminishing, broad, boxy Hα emission and flattening of the light curve in the late (∼2 yr) photometry suggest a complex mass-loss history in the centuries to millennia before explosion. New optical and near-infrared imaging of the host galaxy confirms that it is a dwarf, with a stellar mass of 106.6±0.1 M⊙ and a SFR of 10−2.5±0.1 M⊙/yr. Results from both SED fitting and galaxy stellar mass-metallicity scaling relations all lead to an environmental metallicity estimate of $0.02-0.07$ Z⊙. Taken together, these observations confirm that SN 2023ufx is the explosion of a very metal-poor, heavily stripped red supergiant.
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BibTeX
@misc{jennerjahn2026nebular,
title = {{Nebular Spectra of the Extremely Metal-Poor SN II 2023ufx Over a Year After Explosion: A Massive Progenitor and Unique Circumstellar Environment}},
author = {Evan Jennerjahn and Michael A. Tucker and Christopher S. Kochanek and Luc Dessart and Willem B. Hoogendam and Benjamin J. Shappee},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.04307},
eprint = {2609.04307},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.04307},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Nebular Spectra of the Extremely Metal-Poor SN II 2023ufx Over a Year After Explosion: A Massive Progenitor and Unique Circumstellar Environment
AU - Evan Jennerjahn
AU - Michael A. Tucker
AU - Christopher S. Kochanek
AU - Luc Dessart
AU - Willem B. Hoogendam
AU - Benjamin J. Shappee
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.04307
UR - https://arxiv.org/abs/2609.04307
AB - We present new observations of the metal-poor (< 0.1 Z_⊙) Type II supernova 2023ufx and its host galaxy. The deep nebular spectrum, obtained roughly a year after explosion, has a triple-peaked [O I] emission profile suggesting an asymmetric explosion. Comparison to nebular spectra models suggests a zero-age main sequence mass of $ M_{\rm ZAMS} \sim 25-35$ M_⊙, which is supported by the low [Ca II]/[O I] emission-line ratio of ≈0.4. The diminishing, broad, boxy Hα emission and flattening of the light curve in the late (∼2 yr) photometry suggest a complex mass-loss history in the centuries to millennia before explosion. New optical and near-infrared imaging of the host galaxy confirms that it is a dwarf, with a stellar mass of 10^6.6±0.1 M_⊙ and a SFR of 10^−2.5±0.1 M_⊙/yr. Results from both SED fitting and galaxy stellar mass-metallicity scaling relations all lead to an environmental metallicity estimate of $0.02-0.07$ Z_⊙. Taken together, these observations confirm that SN 2023ufx is the explosion of a very metal-poor, heavily stripped red supergiant.
ER -