Recently, Zhang Jujia, an associate researcher at Yunnan Astronomical Observatory of Chinese Academy of Sciences, and his collaborators published their research results on the origin of type II supernova diversity in the Journal of the Royal Astronomical Society. In this paper, the interaction model is used to explain the origin of type II supernova diversity, which is an important part of studying the explosion mechanism of type II supernova and cosmological application.
type ii supernova is another high-quality cosmological ranging tool after type Ia supernova, which is expected to extend the range of supernova ranging to the earlier universe, thus revealing the evolution history of the universe. According to the profile of light curve, type II supernovae are traditionally divided into IIP type with platform characteristics and IIL type with linear decline of light curve on magnitude scale. However, the origins of these two type II supernovae are still controversial. It is generally believed that the hydrogen-rich shell ionization compound model can explain the luminosity platform and luminosity cliff-fall of IIP supernovae, but it can not explain the relatively higher luminosity of IIL supernovae and the same possible luminosity cliff-fall.
through the monitoring of supernova SN 218zd, Zhang jujia et al. found that the supernova had a severe process of star wind loss before its explosion, thus a shock wave with a total mass of about .18 solar energy was formed at a distance of 2, solar radii from the center of the star, and the projectile interacted with circumstellar matter, resulting in higher luminosity. Based on the spectral and photometric evolution characteristics of the supernova, the researchers suggest that IIL supernovae come from IIP supernovae with strong and short-lived interaction in the early stage. This can explain the higher peak luminosity, faster luminosity decline rate and luminosity cliff-like fall similar to IIP of IIL supernovae.
This work thinks that the interaction exists generally in the very early stage of type II supernova explosion, and its strength and duration are the main factors leading to the diversity of type II supernova observation. It is further pointed out that the early interaction is the main source of the dispersion of luminosity-velocity relationship of type II supernovae, and the direction to improve the cosmological ranging accuracy of type II supernovae is pointed out.
Because the observation is not timely enough, the key information of the initial time of explosion is often not captured before, which leads to misunderstanding of the classification of type II supernovae. Thanks to the flexible and efficient time allocation strategy of Lijiang 2.4-meter telescope (LJT), spectral and photometric observations can be carried out within a few hours after the discovery of SN 218zd, thus capturing early key information. Through LJT's excellent dark field detection ability, scientists obtained the 456-day evolution trajectory of the supernova, combined with global joint measurement, revealed the explosion The Secret Behind and decoded the diversity origin of type II supernova.
this work uses the Lijiang 2.4m telescope, Xinglong 2.16m telescope, Tsinghua-Guotai 8cm telescope, Konkoly 1m telescope, Apache Point 3.5 telescope and Keck-I 1 telescope, and is supported by the National Natural Science Foundation of China, the Youth Innovation Promotion Association of Chinese Academy of Sciences, Yunnan Ten Thousand Talents Program "Top-notch Youth" talent project and the national key basic research development planning project.
three-color imaging of sn 218zd and its host galaxy NGC 2146 UBV (data from Lijiang 2.4m telescope).