ner_tags: O O O O O O O O O O O O O O B-ObservationalTechniques O O B-CelestialObject I-CelestialObject O O O O O O O O O B-CelestialObject B-ObservationalTechniques O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength B-Wavelength O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation O B-Citation O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O B-Citation I-Citation I-Citation I-Citation O O B-CelestialObject B-Citation I-Citation I-Citation I-Citation O B-CelestialObject B-Citation I-Citation I-Citation I-Citation O O O O O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-ObservationalTechniques O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O O
tokens: produce 2 mag of variation in peak luminosity between the polar and equatorial directions. Polarimetric observations of SN 1998bw were also consistent with asymmetry in the ejecta of 1998bw. Polarimetry studies suggest that CCSNe, particularly those with relatively small envelope masses, may exhibit significant asymmetry in their ejecta (see, e.g., Wang et al. 2001 ). If the ejecta of ASASSN-15nx were highly asymmetrical and viewed at a favorable angle, the actual amount of synthesized might be substantially reduced from the current estimate and produce its high peak luminosity. On the other hand, there is no strong evidence of asymmetry in the [O i ] ( 6300, 6364) nebular lines, as suggested by Taubenberger et al. ( 2009 , 2013 ). However, quantitative modeling is needed to investigate whether an asymmetric model could explain the prolonged linear light-curve and spectroscopic features of ASASSN-15nx. Synthesizing a large amount of radioactive normally should also lead to nebular-phase spectra rich with iron-group elements, as seen in Type Ia SNe, but this doesn’t appear to be the case with ASASSN-15nx. This could pose a serious challenge to the high mass scenario, and nebular-phase spectral modeling would be needed to examine it further. 7.2. CSM Interaction An alternative to the radioactive decay model is strong CSM interactions. In these models, the structure and distribution of the CSM can determine the shape of the light curves. As in SNe IIn (Schlegel 1990 ), which are characterized by narrow emission lines (FWHM ∼ few hundreds of ) in the spectra, strong interactions are thought to be responsible for powering their prolonged and often luminous light curves (e.g., Smith et al. 2008a ; Rest et al. 2011 ). Sometimes ejecta–CSM interactions can lead to steeply declining light curves, as has been proposed for SN 2009jp (jet–CSM interaction; Smith et al. 2012a ) and ASASSN-15no (Benetti et al. 2018 ). PTF10iam (Arcavi et al. 2016 ), which has early light curve features similar to ASASSN-15nx, may also be explained by interaction. The density profile of the CSM can be sculpted to produce the observed light curve of ASASSN-15nx. In ASASSN-15nx, we do not see narrow- or intermediate-width emission lines from the expanding shock driving photo-ionization of the remaining CSM. It is possible to miss such emission lines if those were only present before our spectroscopic observations began at 53.0 days. However, this seems unlikely, as the continuous and linear decline of the light curve indicates a single dominant powering source throughout the evolution, which should produce similar narrow emission lines at later phases if they were present earlier. On the other hand, sometimes CSM signatures may also remain hidden if there is asymmetry or the CSM has a velocity of several thousands of . Some of the spectral features in ASASSN-15nx can be attributed to indirect signatures of CSM interaction. The synow model could not reproduce the broad and