HSC16aayt: A Slowly Evolving Interacting Transient Rising for More than 100 Days

Abstract

We report our observations of HSC16aayt (SN 2016jiu), which was discovered by the Subaru/Hyper Suprime-Cam (HSC) transient survey conducted as part of the Subaru Strategic Program. It shows very slow photometric evolution and its rise time is more than 100 days. The optical magnitude change in 400 days remains within 0.6 mag. Spectra of HSC16aayt show a strong narrow emission line and we classify it as a Type IIn supernova. The redshift of HSC16aayt is 0.6814 ± 0.0002 from the spectra. Its host galaxy center is at 5 kpc from the supernova location and HSC16aayt might be another example of isolated Type IIn supernovae, although the possible existence of underlying star-forming activity of the host galaxy at the supernova location is not excluded.

An extremely energetic supernova from a very massive star in a dense medium

“…At this redshift, observed i-band was closest to rest-frame r, and observed g to rest-frame u. The comparison data [5,6,14,13,58,59,37,60,61,62,63,64] in the figure were obtained from the Open Supernova Catalog [33] if possible, or otherwise directly from these papers.…”

Supernovae and transients with circumstellar interaction

“…Unfortunately SN 2010jl was first discovered when it was emerging from behind the Sun, and so there are only lower limits to the rise time to peak luminosity. However, a number of other long-lived and energetic Type IIn SNe (for example, PTF12glz [51] and HSC16aayt [52]) have shown a very slow and long rise time. This could be interpreted as being indicative of a long diffusion time for photons to escape from a massive optically thick CSM.…”

Properties of Thorne-Zytkow object explosions

“…6, we compare our TŻO light curve models with some long-lasting SNe. HSC16aayt (Moriya et al 2019) and SN 2008iy (Miller et al 2010 are Type IIn SNe showing narrow emission lines that are interpreted to originate from the interaction between dense circumstellar media and SN ejecta. The photospheric velocities of the TŻO explosions are predicted to be lower than those of SNe and so relatively narrow spectral features may actually originate from small photospheric velocities.…”

“…In such cases, the jets may lead to gamma-ray bursts with a very long duration as proposed for Swift 1644+57 (Quataert & Kasen 2012), although several different progenitors may lead to such gamma-ray bursts with a very long duration (e.g., Soker 2021). (Moriya et al 2019), SN 2008iy (Miller et al 2010, and iPTF14hls (Arcavi et al 2017;Sollerman et al 2019). Time is arbitrary shifted to match the observations and models.…”