A pair of possible supernovae Refsdal in the Pantheon+ sample

TL;DR

This paper investigates potential gravitational lensing of supernovae in the Pantheon+ sample, identifying pairs that may be images of the same event caused by compact objects like ultra massive white dwarfs.

Contribution

It proposes that certain supernova pairs are gravitationally lensed images, providing new insights into lensing objects and their distances, especially in the context of the Pantheon+ sample.

Findings

Identified supernova pairs with similar light curves suggesting lensing.

Estimated lens distances, one near the Milky Way's halo and another near Andromeda.

Inferred lens masses indicating ultra massive white dwarfs.

Abstract

On December 1980, supernova 1980N was discovered in NGC 1316, a galaxy of the Fornax cluster. Three months later, supernova 1981D was observed in the same galaxy. The light curves of these two supernovae Ia were found to be virtually identical, suggesting that they are images of the same event, the delay between them being due to strong gravitational lensing. If so, as anticipated by Sjur Refsdal, the distance to the lens can be determined accurately, namely, 90 $\pm$ 1 kpc, meaning that it belongs to the outer halo of the Milky Way. Interestingly, there is another pair of possible images in the Pantheon+ sample, namely, supernovae 2013aa and 2017cbv, the distance to the lens being 702 $\pm$ 1 kpc, that is, nearly the same as the distance to the Andromeda galaxy. In both cases, given the relatively large angle of deviation of the supernova light by the lens, namely, 271" and 325", respectively, the lens has to be a compact object, with a mass to radius ratio over 150 M$_\odot$ R$_\odot^{-1}$. It is likely to be an ultra massive white dwarf.