Early interaction signatures and an extended plateau phase in Type II SN 2020aze

B. Ailawadhi; R. Dastidar; K. Misra; S. Valenti; D. J. Sand; J. E. Andrews; J. P. Anderson; K. A. Bostroem; P. J. Brown; R. Cartier; T. W. Chen; Y. Dong; N. Dukiya; E. Padilla Gonzalez; M. Gromadzki; J. Haislip; D. Hiramatsu; D. A. Howell; C. Inserra; D. Janzen; S. W. Jha; V. Kouprianov; C. McCully; T. E. Müller-Bravo; C. Pellegrino; G. Pignata; D. E. Reichart; J. Sollerman; D. R. Young; L. Yadav

arXiv · 2605.06313

Early interaction signatures and an extended plateau phase in Type II SN 2020aze

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Abstract

We present a photometric and spectroscopic analysis of the fast-declining Type II SN 2020aze, observed in optical bands from 2.2 to 137.4 days after explosion. The V-band light curve reaches a peak absolute magnitude of about minus 16.97$\pm$0.20 mag by 15 days, followed by a recombination phase with a decline rate of 2.04$\pm$0.13 mag per 100 days, lasting about 120 days. Early spectra (younger than 6 days) show a transient weak narrow emission line at 4687 Angstroms and a feature spanning 4400-4800 Angstroms, attributed to narrow and broad blue-shifted He II 4686, indicating interaction between the ejecta and dense circumstellar material. Comparison with spectral models suggests a red supergiant progenitor with a weak wind and a mass-loss rate of about 1e-3 solar masses per year. Semi-analytical light-curve modeling gives an initial radius of about 1100 solar radii, an ejecta mass of about 12 solar masses, an explosion energy of about 1.5e51 erg, and a progenitor mass of about 14 solar masses. These early interaction signatures, the steep decline, and the extended photospheric phase highlight the role of pre-supernova mass loss and circumstellar interaction in shaping the diversity of Type II supernovae.

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B. Ailawadhi, R. Dastidar, K. Misra, S. Valenti, D. J. Sand, J. E. Andrews, J. P. Anderson, K. A. Bostroem, P. J. Brown, R. Cartier, T. W. Chen, Y. Dong, N. Dukiya, E. Padilla Gonzalez, M. Gromadzki, J. Haislip, D. Hiramatsu, D. A. Howell, C. Inserra, D. Janzen, S. W. Jha, V. Kouprianov, C. McCully, T. E. Müller-Bravo, C. Pellegrino, G. Pignata, D. E. Reichart, J. Sollerman, D. R. Young, L. Yadav. 2026-05-07. Early interaction signatures and an extended plateau phase in Type II SN 2020aze. https://arxiv.org/abs/2605.06313

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