Effects of Dust in Electron-Capture Supernovae: Difficulty in Explaining Intermediate Luminosity Red Transients

The progenitors of intermediate-luminosity red transients (ILRTs) spanning the luminosity gap between novae and supernovae are under debate, and electron-capture supernovae (ECSNe) have been proposed as a strong candidate. ECSNe from super asymptotic giant branch (super-AGB) stars have been theoretically predicted to be much brighter than ILRTs, but attenuation by dusty winds of their super-AGB progenitors may ease this tension. Here we construct a semi-analytical framework for calculating the light curves of ECSNe with dust attenuation and re-emission, by combining recent ECSN light curve predictions with a model for dust physics. Even by varying both the wind mass-loss rate and the ECSN model parameters, we find it challenging to simultaneously fit the light curve and color evolution of ILRTs. This poses a potential challenge to the standard models of ECSNe for explaining ILRTs. For explaining ILRTs, we propose either the existence of a population of ECSNe with much lower explosion energies ($\sim$10$^{48}$-$10^{49}$ erg) and dimmer plateaus, or alternative model(s) to ECSNe that realize such low explosion energies.