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تسجيل مستخدم جديدSN 2018gjx reveals that some SNe Ibn are SNe IIb exploding in dense circumstellar material
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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 ionised 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 Rsun), which ionises 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 LBV stars. Such configurations may not be unusual, with SNe IIb being known to have signs of interaction so at least some SNe IIb and SNe Ibn may be the same phenomena viewed from different angles or, possibly with differing CSM configurations.
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Type Ibn supernovae (SNe Ibn) are intriguing stellar explosions whose spectra exhibit narrow helium lines with little hydrogen. They trace the presence of circumstellar material (CSM) formed via pre-SN eruptions of their stripped-envelope progenitors
. Early work has generally assumed that SNe Ibn come from massive Wolf-Rayet (WR) stars via single star evolution. In this paper, we report ultraviolet (UV) and optical observations of two nearby Type Ibn SNe 2006jc and 2015G conducted with the Hubble Space Telescope (HST) at late times. A point source is detected at the position of SN 2006jc, and we confirm the conclusion of Maund et al. that it is the progenitors binary companion. Its position on the Hertzsprung-Russell (HR) diagram corresponds to a star that has evolved off the main sequence (MS); further analysis implies a low initial mass for the companion star ($M_2$ $le$ 11.9$^{+1.2}_{-0.8}$ $M_odot$) and a secondary-to-primary initial mass ratio very close to unity ($q$ = $M_2/M_1$ $sim$ 1); the SN progenitors hydrogen envelope had been stripped through binary interaction. We do not detect the binary companion of SN 2015G. For both SNe, the surrounding stellar populations have relatively old ages and argue against any massive WR stars as their progenitors. These results suggest that SNe Ibn may have lower-mass origins in interacting binaries. As a result, they also provide evidence that the giant eruptions commonly seen in massive luminous blue variables (LBVs) can also occur in much lower-mass, stripped-envelope stars just before core collapse.
In this study, we present observations of a type Iax supernova, PS1-12bwh, discovered during the Pan-STARRS1 3$pi$-survey. Our analysis was driven by previously unseen pre-maximum, spectroscopic heterogeneity. While the light curve and post-maximum s
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