Violent material ejection process of a dying massive star observed

Such mass loss processes can provide essential information for understanding the final evolution of a massive star.

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Most stellar explosions in the universe are Type II supernovae. However, it is difficult to determine how these explosions evolved from their enormous, hydrogen-rich progenitors to a core-collapse state. The spectacular explosion of SN 2023ixf in the nearby galaxy Messier 101 offers a unique chance to investigate this enduring problem.

By observing the once-every-ten-years supernova SN 2023ixf, a research team led by Dr. ZHANG Jujia from the Yunnan Observatories of the Chinese Academy of Sciences and Prof. WANG Xiaofeng from Tsinghua University has discovered the star mass that was forcibly ejected from the progenitor at the end of its life. Such mass loss mechanisms can offer vital information for comprehending the huge star’s final evolution.

Capturing the first-light signals of the SN explosions, or the flashed spectra, caused by the ionization of the circumstellar material (CSM)/stellar wind by ultraviolet/high energy photons from shock breakout cooling, is necessary to establish a connection between the explosion of SNe II and the late-time evolution of massive stars.

The recent explosion of SN 2023ixf in the nearby galaxy Messier 101 offers a once-in-a-lifetime chance to address this persistent problem. The parameters of the circumstellar material around this supernova can be tightly constrained by timely, high-cadence flash spectra collected within 1–5 days following the explosion.

The progenitor of SN 2023ixf is thought to have shed material at a mass-loss rate of 6 10-4 M yr-1 in the final 2-3 years before the explosion. A compact CSM shell formed from surrounding material moving at a speed of 55 km s-1 and within a radius of less than 7 1014 cm of the progenitor.

The progenitor of SN 2023ixf may have been a short-lived yellow hypergiant that changed from a red supergiant just before the explosion, according to the high mass-loss rate, relatively high wind velocity, and pre-explosion data collected roughly 20 years ago.

Dr. Zhang said“The observation and investigation of SN 2023ixf is ongoing. A series of works on this SN will make it a milestone in the history of SNe II and will then help to reveal the fate of massive stars in the mass range from 10 to 20 M⊙.”

Journal Reference:

  1. Jujia Zhang, Han Lin, Xiaofeng Wang et al. Circumstellar material ejected violently by a massive star immediately before its death. Science Bulletin. DOI: 10.1016/j.scib.2023.09.015

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