Photometric and spectroscopic evolution of the interacting transient AT 2016jbu (Gaia16cfr)

TL;DR

This paper presents detailed multi-wavelength observations of the interacting transient AT 2016jbu, revealing complex circumstellar material, variable lightcurve behavior, and spectral features that inform its nature and relation to similar transients like SN 2009ip.

Contribution

It provides high-cadence, extended coverage of AT 2016jbu's evolution, offering new insights into its circumstellar environment and spectral characteristics compared to prior studies.

Findings

AT 2016jbu experienced two luminous events with significant variability.

Spectra show narrow emission lines and asymmetric hydrogen profiles indicating complex CSM.

Late-time spectra lack forbidden lines, suggesting it is not a typical core-collapse supernova.

Abstract

We present the results from a high cadence, multi-wavelength observation campaign of AT 2016jbu (aka Gaia16cfr), an interacting transient. This dataset complements the current literature by adding higher cadence as well as extended coverage of the lightcurve evolution and late-time spectroscopic evolution. Photometric coverage reveals that AT 2016jbu underwent significant photometric variability followed by two luminous events, the latter of which reached an absolute magnitude of M$_V\sim$-18.5 mag. This is similar to the transient SN 2009ip whose nature is still debated. Spectra are dominated by narrow emission lines and show a blue continuum during the peak of the second event. AT 2016jbu shows signatures of a complex, non-homogeneous circumstellar material (CSM). We see slowly evolving asymmetric hydrogen line profiles, with velocities of 500km$s^{-1}$ seen in narrow emission features from a slow moving CSM, and up to 10,000km$s^{-1}$ seen in broad absorption from some high velocity material. Late-time spectra ($\sim$+1 year) show a lack of forbidden emission lines expected from a core-collapse supernova and are dominated by strong emission from H, He i and Ca ii. Strong asymmetric emission features, a bumpy lightcurve, and continually evolving spectra suggest an inhibit nebular phase. We compare the evolution of H$\alpha$ among SN 2009ip-like transients and find possible evidence for orientation angle effects. The light-curve evolution of AT 2016jbu suggests similar, but not identical, circumstellar environments to other SN 2009ip-like transients.