The Mystery of Photometric Twins DES17X1boj and DES16E2bjy

TL;DR

This paper analyzes two peculiar transients with nearly identical double-peaked light curves but different luminosities, exploring their properties, environments, and possible explosive origins, while noting the challenges in identifying their progenitors.

Contribution

It provides the first detailed analysis of DES17X1boj and DES16E2bjy, highlighting their unusual light curves and environments, and discusses potential explosive origins despite uncertain progenitor identification.

Findings

Both transients have double-peaked light curves with different peak luminosities.

Spectroscopic data suggest explosive or eruptive origins, with possible supernova classification for DES17X1boj.

The transients are located in different host galaxy environments, indicating diverse progenitor scenarios.

Abstract

We present an analysis of DES17X1boj and DES16E2bjy, two peculiar transients discovered by the Dark Energy Survey (DES). They exhibit nearly identical double-peaked light curves which reach very different maximum luminosities (M$_\mathrm{r}$ = -15.4 and M$_\mathrm{r}$ = -17.9, respectively). The light curve evolution of these events is highly atypical and has not been reported before. The transients are found in different host environments: DES17X1boj was found near the nucleus of a spiral galaxy, while DES16E2bjy is located in the outskirts of a passive red galaxy. Early photometric data is well fitted with a blackbody and the resulting moderate photospheric expansion velocities (1800 km/s for DES17X1boj and 4800 km/s for DES16E2bjy) suggest an explosive or eruptive origin. Additionally, a feature identified as high-velocity CaII absorption (v $\approx$ 9400km/s) in the near-peak spectrum of DES17X1boj may imply that it is a supernova. While similar light curve evolution suggests a similar physical origin for these two transients, we are not able to identify or characterise the progenitors.