A Robust Light-Curve Diagnostic for Electron-Capture Supernovae and Low-Mass Fe-Core-Collapse Supernovae
arxiv(2024)
摘要
Core-collapse supernovae (CCSNe) are the terminal explosions of massive
stars. While most massive stars explode as iron-core-collapse supernovae
(FeCCSNe), slightly less massive stars explode as electron-capture supernovae
(ECSNe), shaping the low-mass end of CCSNe. ECSNe was proposed ∼ 40 years
ago and first-principles simulations also predict their successful explosions.
Observational identification and investigation of ECSNe are important for the
completion of stellar evolution theory. To date, only one promising candidate
has been proposed, SN 2018zd, other than the historical progenitor of the Crab
Nebula, SN 1054. We present representative synthetic light curves of low-mass
FeCCSNe and ECSNe exploding with energies in circumstellar media (CSM)
estimated with theoretically or observationally plausible methods. The plateaus
of the ECSNe are shorter, brighter, and bluer than those of the FeCCSNe. To
investigate the robustness of their intrinsic differences, we adopted various
explosion energies and CSM. Although they may have similar bolometric
light-curve plateaus, ECSNe are bluer than FeCCSNe in the absence of strong CSM
interaction, illustrating that multicolor observations are essential to
identify ECSNe. This provides a robust indicator of ECSNe because the bluer
plateaus stem from the low-density envelopes of their
super-asymptotic-giant-branch progenitors. Furthermore, we propose a
distance-independent method to identify ECSNe: (g-r)_t_ PT/2 < 0.008
× t_ PT - 0.4, i.e., blue g-r at the middle of the plateau
(g-r)_t_ PT/2, where t_ PT is the transition epoch from plateau
to tail. Using this method, we identified SN 2018zd as an ECSN, which we
believe to be the first ECSN identified with modern observing techniques.
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