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Title: SN 2018gjx reveals that some SNe Ibn are SNe IIb exploding in dense circumstellar material
ABSTRACT We present the data and analysis of SN 2018gjx, an unusual low-luminosity transient with three distinct spectroscopic phases. Phase I shows a hot blue spectrum with signatures of ionized circumstellar material (CSM), Phase II has the appearance of broad SN features, consistent with those seen in a Type IIb supernova at maximum light, and Phase III is that of a supernova interacting with helium-rich CSM, similar to a Type Ibn supernova. This event provides an apparently rare opportunity to view the inner workings of an interacting supernova. The observed properties can be explained by the explosion of a star in an aspherical CSM. The initial light is emitted from an extended CSM (∼4000 R⊙), which ionizes the exterior unshocked material. Some days after, the SN photosphere envelops this region, leading to the appearance of a SN IIb. Over time, the photosphere recedes in velocity space, revealing interaction between the supernova ejecta and the CSM that partially obscures the supernova nebular phase. Modelling of the initial spectrum reveals a surface composition consistent with compact H-deficient Wolf–Rayet and Luminous Blue Variable (LBV) stars. Such configurations may not be unusual, with SNe IIb being known to have signs of interaction so at least some more » SNe IIb and SNe Ibn may be the same phenomena viewed from different angles, or possibly with differing CSM configurations. « less
Authors:
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Award ID(s):
1636626 1813176 1911151 1911225
Publication Date:
NSF-PAR ID:
10203427
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
499
Issue:
1
Page Range or eLocation-ID:
1450 to 1467
ISSN:
0035-8711
Sponsoring Org:
National Science Foundation
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