Progenitor, environment, and modelling of the interacting transient, AT 2016jbu (Gaia16cfr)

TL;DR

This paper analyzes the progenitor and environment of the transient AT2016jbu, suggesting it originated from a massive yellow hypergiant in a binary system, with evidence of multiple outbursts and a low-energy explosion influenced by circumstellar material.

Contribution

It provides the first detailed analysis of AT2016jbu's progenitor, environment, and explosion modeling, highlighting the role of binary interactions and circumstellar material in its evolution.

Findings

Progenitor is a 22-25 M_sun yellow hypergiant with circumstellar dust.

Evidence of two successive outbursts with different velocities.

Lightcurve modeling suggests a low-energy explosion in a binary system.

Abstract

We present the bolometric lightcurve, identification and analysis of the progenitor candidate, and preliminary modelling of AT2016jbu (Gaia16cfr). We find a progenitor consistent with a $\sim$22--25~$M_{\odot}$ yellow hypergiant surrounded by a dusty circumstellar shell, in agreement with what has been previously reported. We see evidence for significant photometric variability in the progenitor, as well as strong H$\alpha$ emission consistent with pre-existing circumstellar material. The age of the environment as well as the resolved stellar population surrounding AT2016jbu, support a progenitor age of $>$10 Myr, consistent with a progenitor mass of $\sim$22~$M_{\odot}$. A joint analysis of the velocity evolution of AT2016jbu, and the photospheric radius inferred from the bolometric lightcurve shows the transient is consistent with two successive outbursts/explosions. The first outburst ejected material with velocity $\sim$650$kms^{-1}$, while the second, more energetic event, ejected material at $\sim$4500$kms^{-1}$. Whether the latter is the core-collapse of the progenitor remains uncertain. We place a limit on the ejected $^{56}$Ni mass of $<$0.016$M_{\odot}$. Using the BPASS code, we explore a wide range of possible progenitor systems, and find that the majority of these are in binaries, some of which are undergoing mass transfer or common envelope evolution immediately prior to explosion. Finally, we use the SNEC code to demonstrate that the low-energy explosion within some of these binary systems, together with sufficient CSM, can reproduce the overall morphology of the lightcurve of AT2016jbu.