New study reveals violent mass loss from supernova progenitor

A team of researchers led by Dr. Zhang Jujia from the Yunnan Observatories of the Chinese Academy of Sciences and Prof. Wang Xiaofeng from Tsinghua University has unveiled the dramatic expulsion of stellar mass from a dying star’s progenitor through their study of the once-in-a-decade supernova SN 2023ixf. This discovery sheds light on the critical processes that occur during the final stages of a massive star’s evolution.

Published on September 14 in Science Bulletin, this study delves into Type II supernovae (SNe II), which are the most common type of stellar explosions in the universe. However, understanding the exact path these hydrogen-rich, massive stars take in their evolution towards a core-collapse explosion has remained a mystery. The final stages of their evolution and the resulting environments around them give rise to a diverse array of these cosmic explosions.

To establish a connection between the explosion of SNe II and the late-stage evolution of massive stars, it’s crucial to capture the initial spectra of the supernova explosion, which occurs due to the ionization of the circumstellar material (CSM) and stellar wind by high-energy photons from the shock breakout cooling.

The recent occurrence of SN 2023ixf in the nearby galaxy Messier 101 presents a unique opportunity to address this longstanding scientific question. Timely, high-frequency flash spectra captured within one to five days of the explosion have allowed researchers to place strict constraints on the properties of the surrounding circumstellar material.

The research estimates that the progenitor of SN 2023ixf shed material at a rate of 6 × 10-4 solar masses per year during the two to three years leading up to the explosion. The nearby material, traveling at a velocity of 55 km/s, accumulated into a compact CSM shell within a radius of less than 7 × 1014 cm from the progenitor.

Considering the high rate of mass loss and relatively fast wind velocity, combined with observations made around two decades ago, it is plausible that the progenitor of SN 2023ixf was a short-lived yellow hypergiant that evolved from a red supergiant shortly before the explosion.

Dr. Zhang stated, “The observation and investigation of SN 2023ixf are ongoing, and a series of future studies on this supernova will mark a significant milestone in the history of SNe II. This, in turn, will contribute to our understanding of the fate of massive stars in the 10 to 20 solar mass range.”

Source: Chinese Academy of Sciences

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