Circumstellar Interaction Powers the Light Curves of Luminous Rapidly Evolving Optical Transients
Abstract

Rapidly evolving transients, or objects that rise and fade in brightness on timescales two to three times shorter than those of typical Type Ia or Type II supernovae (SNe), have uncertain progenitor systems and powering mechanisms. Recent studies have noted similarities between rapidly evolving transients and Type Ibn SNe, which are powered by ejecta interacting with He-rich circumstellar material (CSM). In this work we present multiband photometric and spectroscopic observations from Las Cumbres Observatory and Swift of four fast-evolving Type Ibn SNe. We compare these observations with those of rapidly evolving transients identified in the literature. We discuss several common characteristics between these two samples, including their light curve and color evolution as well as their spectral features. To investigate a common powering mechanism we construct a grid of analytical model light curves with luminosity inputs from CSM interaction as well as56Ni radioactive decay. We find that models with ejecta masses of ≈1–3M, CSM masses of ≈0.2–1M, and CSM radii of ≈20–65 au can explain the diversity of peak luminosities, rise times, and decline rates observed in Type Ibn SNe and rapidly evolving transients. This suggests that a common progenitor system—the core collapse of a high-mass star within a more »

Authors:
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Award ID(s):
Publication Date:
NSF-PAR ID:
10362974
Journal Name:
The Astrophysical Journal
Volume:
926
Issue:
2
Page Range or eLocation-ID:
Article No. 125
ISSN:
0004-637X
Publisher:
DOI PREFIX: 10.3847
National Science Foundation
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1. Abstract

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2. Context. Supernovae (SNe) Type Ibn are rapidly evolving and bright ( M R, peak  ∼ −19) transients interacting with He-rich circumstellar material (CSM). SN 2018bcc, detected by the ZTF shortly after explosion, provides the best constraints on the shape of the rising light curve (LC) of a fast Type Ibn. Aims. We used the high-quality data set of SN 2018bcc to study observational signatures of the class. Additionally, the powering mechanism of SN 2018bcc offers insights into the debated progenitor connection of Type Ibn SNe. Methods. We compared well-constrained LC properties obtained from empirical models with the literature. We fit the pseudo-bolometric LC with semi-analytical models powered by radioactive decay and CSM interaction. Finally, we modeled the line profiles and emissivity of the prominent He  I lines, in order to study the formation of P-Cygni profiles and to estimate CSM properties. Results. SN 2018bcc had a rise time to peak of the LC of 5.6 −0.1 +0.2 days in the restframe with a rising shape power-law index close to 2, and seems to be a typical rapidly evolving Type Ibn SN. The spectrum lacked signatures of SN-like ejecta and was dominated by over 15 He emission features at 20 days past peak,more »
3. Abstract We present a high-cadence short term photometric and spectroscopic monitoring campaign of a type Ibn SN 2019wep, which is one of the rare SN Ibn after SNe 2010al and 2019uo to display signatures of flash ionization (He ii , C iii , N iii ). We compare the decline rates and rise time of SN 2019wep with other SNe Ibn and fast transients. The post-peak decline in all bands (0.1 mag day −1 ) are consistent with SNe Ibn but less than the fast transients. On the other hand, the Δ m 15 values are slightly lower than the average values for SNe Ibn but consistent with the fast transients. The rise time is typically shorter than SNe Ibn but longer than fast transients. SN 2019wep lies at the fainter end of SNe Ibn but possesses an average luminosity among the fast transients sample. The peculiar color evolution places it between SNe Ib and the most extreme SNe Ibn. The bolometric light-curve modeling shows resemblance with SN 2019uo with ejecta masses consistent with SNe Ib. SN 2019wep belongs to the P cygni subclass of SNe Ibn and shows faster evolution in line velocities as compared to the emission subclass.more »
4. Abstract

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5. Abstract

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