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Abstract We present analysis of the plateau and late-time phase properties of a sample of 39 Type II supernovae (SNe II) that show narrow, transient, high-ionization emission lines (i.e., “IIn-like”) in their early-time spectra from interaction with confined, dense circumstellar material (CSM). Originally presented by W. V. Jacobson-Galán et al., this sample also includes multicolor light curves and spectra extending to late-time phases of 35 SNe with no evidence for IIn-like features at <2 days after first light. We measure photospheric phase light-curve properties for the distance-corrected sample and find that SNe II with IIn-like features have significantly higher luminosities and decline rates at +50 days than the comparison sample, which could be connected to inflated progenitor radii, lower ejecta mass, and/or persistent CSM interaction. However, we find no statistical evidence that the measured plateau durations and56Ni masses of SNe II with and without IIn-like features arise from different distributions. We estimate progenitor zero-age main-sequence (ZAMS) masses for all SNe with nebular spectroscopy through spectral model comparisons and find that most objects, both with and without IIn-like features, are consistent with progenitor masses ≤12.5M⊙. Combining progenitor ZAMS masses with CSM densities inferred from early-time spectra suggests multiple channels for enhanced mass loss in the final years before core collapse, such as a convection-driven chromosphere or binary interaction. Finally, we find spectroscopic evidence for ongoing ejecta-CSM interaction at radii >1016cm, consistent with substantial progenitor mass-loss rates of ∼10−4–10−5M⊙yr−1(vw < 50 km s−1) in the final centuries to millennia before explosion.
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This content will become publicly available on June 23, 2026
Unveiling the Diversity of Type IIn Supernovae via Systematic Light-curve Modeling
Abstract Type IIn supernovae (SNe IIn) are a highly heterogeneous subclass of core-collapse supernovae, spectroscopically characterized by signatures of interaction with a dense circumstellar medium (CSM). Here, we systematically model the light curves of 142 archival SNe IIn using the Modular Open Source Fitter for Transients. We find that the observed and inferred properties of SN IIn are diverse, but there are some trends. The typical supernova CSM is dense (∼10−12g cm−3) with highly diverse CSM geometry, with a median CSM mass of ∼1M⊙. The ejecta are typically massive (≳10M⊙), suggesting massive progenitor systems. We find positive correlations between the CSM mass and the rise and fall times of SNe IIn. Furthermore, there are positive correlations between the rise time and fall times and ther-band luminosity. We estimate the mass-loss rates of our sample (where spectroscopy is available) and find a high median mass-loss rate of ∼10−2M⊙yr−1, with a range between 10−3and 1M⊙yr−1. These mass-loss rates are most similar to the mass loss from great eruptions of luminous blue variables, consistent with the direct progenitor detections in the literature. We also discuss the role that binary interactions may play, concluding that at least some of our SNe IIn may be from massive binary systems. Finally, we estimate a detection rate of 1.6 × 105yr−1in the upcoming Legacy Survey of Space and Time at the Vera C. Rubin Observatory.
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- PAR ID:
- 10648138
- Publisher / Repository:
- AAS
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 987
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 13
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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