The Ultraviolet Brightest Type Ia Supernova 2011de

TL;DR

SN 2011de is the brightest UV Type Ia supernova observed, likely due to ejecta interaction with a red giant companion or intrinsic UV variation, highlighting diversity in supernova UV properties.

Contribution

This study presents detailed UV/optical light curves of SN 2011de, revealing it as the UV brightest Type Ia supernova, and discusses potential causes including ejecta-companion interaction.

Findings

SN 2011de is over ten times brighter in UV than normal SNe Ia.

Its light curves suggest possible ejecta interaction with a red giant companion.

It may represent either a new class of UV-bright SNe Ia or an extreme case of UV variation.

Abstract

We present and discuss the UV/optical photometric light curves and absolute magnitudes of the Type Ia supernova (SN) 2011de from the Swift Ultraviolet/Optical Telescope. We find it to be the UV brightest SN Ia yet observed--more than a factor of ten brighter than normal SNe Ia in the mid-ultraviolet. This object is an extreme example of the differences seen in the ultraviolet for objects which do not appear remarkable in the optical. We find that the UV/optical brightness and broad light curves are broadly consistent with additional flux from the shock of the ejecta hitting a red giant companion. SN~2011de is either the first external interaction of a SN Ia discovered in the UV or an extreme example of the intrinsic UV variations in SNe Ia.