(ORDO NEWS) — Astronomers have discovered a supernova showing an unprecedented increase in brightness in the millimeter wavelength range, which represents an intermediate case between two types of supernova: single stars and stars in close binary systems.
Many massive stars end their lives in a massive explosion known as a supernova (SN). The brightness of supernovae increases rapidly and then fades over several months.
Astronomers have long known that the presence or absence of a close binary companion can influence the evolution of a massive star.
In a close binary system, gravitational interaction with a binary companion deprives the ancestor SN of a large amount of material long before its final explosion.
In these cases, the progenitor will be “calm” up to the SN itself.
On the other hand, in the case of an SN precursor without a binary companion (or with a distant companion), the progenitor precursor will retain most of its initial mass until the moment of the SN explosion.
Astronomers wanted to know what happens when a binary is neither too close nor too far away.
The breakthrough came when an international research team used ALMA to observe the supernova known as SN 2018ivc as it dimmed for about 200 days after the initial explosion.
The results showed that SN 2018ivc was an unusual object, so the team decided to test it again, about 1,000 days after the explosion.
They found that the object is indeed overexposed – the first time this phenomenon has been observed in millimeter radiation.
Comparison with the results of numerical simulations suggests that the interaction with the binary companion at an intermediate distance about 1500 years before the SN explosion created a large hollow shell of the circumstellar medium.
200 days after SN, the ejecta released after the explosion had not yet reached the envelope. Then, between 200 and 1000 days, the ejecta collided with the circumstellar medium.
These results were published in a paper titled “Type IIL 2018ivc Supernova Resurrection: Implications for a Binary Evolution Sequence Connecting Hydrogen-rich and Hydrogen-poor Progenitors” in The Astrophysical Journal Letters on March 1, 2023.
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