Supernova Observations Reveal How Massive Stars Shed Skin Before Explosion
Astronomers analyzing a nearby supernova discovered unexpected signs that the star ejected dense material into space years before detonating—a finding that reshapes models of stellar death and could improve predictions of future explosions. Understanding these pre-explosion processes matters for gravitational wave detection and for refining astrophysics simulations used across research institutions.
Originaltitel: Early interaction signatures and an extended plateau phase in Type II SN 2020aze
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 post-explosion. The V-band light curve reaches a peak absolute magnitude of −16.97 ±0.20 mag by 15 days, followed by a recombination phase with a decline rate of 2.04 ± 0.13 mag (100 day)−1, lasting ~120 days. Early spectra (<6.0 day) exhibits a transient weak narrow emission line at 4687 Å and a bump or ledge feature spanning 4400-4800 Å, attributed to narrow and broad blue-shifted He ii λ4686, indicating interaction between the rapidly expanding ejecta and dense circumstellar material (CSM). Spectral comparison with literature models suggests a red supergiant progenitor with a weak wind and a mass-loss rate of ~10−3 M⊙ yr−1. Semi-analytical light curve modelling yields an initial radius of 1100 R⊙, an ejecta mass of 12 M⊙, a total explosion energy of 1.5× 1051 erg, and a progenitor mass of approximately 14 M⊙. The combination of a steep luminosity decline, early interaction signatures, and an unusually extended photospheric phase highlights the complex interplay between pre-SN mass loss, CSM interaction, and progenitor properties, positioning SN 2020aze as an important case for understanding the diversity of Type II SNe.