2020-07-04

Do you remember Cassiopeia A supernova? Research shows that it is likely to have a black hole companion star

By ddzyx

Spectral analysis of the Astrophysics at the Japan Institute of Physics and Chemistry showed that the explosion formed a massive star of supernova Cassiopeia A, very There may be an undiscovered companion star, which will provide new impetus for astronomers’ efforts to find a companion star. Supernova explosions are one of the most violent events in the universe. When a massive star exhausts its fuel supply and its core collapses under the star’s gravitational force, they will explode. Although theory has been proposed to explain the processes involved, they have yet to be confirmed by observation.

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Toshiki Sato of Riken High Energy Astrophysics Laboratory Sato pointed out:The explosion mechanism of massive stars is a long-standing problem in astrophysics. We have theoretical assumptions, but we hope to confirm these assumptions through observation. An important parameter for studying the evolution of stars is the ratio of the heavier element to the lightest element hydrogen. This ratio is called metal abundance. Shortly after the Big Bang, there were only three elements:hydrogen, helium, and lithium; but with each generation of stars, heavier elements became more abundant.

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The star’s initial metal abundance is important in determining its fate Factors, the initial metal abundance will affect the way the star dies. Therefore, studying the initial metal abundance is very important for understanding how stars explode. Now, for the first time, researchers have measured the initial metal abundance of Cassiopeia A (Figure 1). By combining the data of 13 observations of the supernova in the past 18 years by the Chandra X-ray Observatory, the elements manganese and chromium at the time of the explosion were obtained. The ratio thus achieves this. Based on this ratio, the initial metal abundance of Cassiopeia A is estimated to be lower than that of the sun.

Black hole, neutron star or white dwarf companion star

Cassiopeia A is called a stripped cladding supernova because of its outer hydrogen Has been stripped. But the lower initial metal abundance means that the stellar wind is too weak to strip the hydrogen layer. The only explanation left is that it was sucked away by its companion star. This is a surprising discovery, because so far no signs of companion star have been found. The reason why this companion star is not observed may be because it is a dense, but very weak external radiation, such as a black hole, neutron star or white dwarf star. Therefore, this discovery provides a new direction for understanding the origin of Cassiopeia A.

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Researchers hope this companion star can understand the supernova explosion mechanism Significant progress has been made. The study detected the Mn-Kα spectrum in the SN-Ⅱb residue Cassiopeia Mn (55Mn after 55Co decay). The neutron-rich elements Cassiopeia A. Mn and Cr (52Cr after 52Fe decay) are mainly synthesized in nuclear collapsed supernova under the condition of supernova explosion and incomplete Si combustion. Therefore, the mass ratio of Mn/Cr and its neutron excess reflect the neutralization process of the corresponding combustion layer during the explosion. X-ray data of Cassiopeia A shows that the mass ratio of Mn/Cr of Cassiopeia A is very low:

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The value is between 0.4990.10-0.6 6. Compared with the one-dimensional Sn explosion model, this requires the electron fraction of incompletely burned silicon layer to be less than 0.5%. Suppose an explosion model with a typical explosion energy (1×10^51erg) solar metal abundance precursor cannot reproduce such a high electron fraction. If the deflagration Si extends to the O/Ne still water layer with higher Ye, the observed mass ratio of Mn/Cr can be satisfied, which will require the sub-solar metal abundance precursor of Cassiopeia A (Z less sim 0.5Z⊙) High energy (>2×1051erg) and/or asymmetric explosion. The low initial metal abundance can eliminate the possibility of single star precursors, leaving the possibility of double star precursors and dense companion stars.

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Bokeyuan|Research/From:Japan Institute of Physics and Chemistry

Reference periodical”Astrophysics”

DOI:10.3847/1538-4357/ab822a

Bo Science Park|Science, Science and Technology, Scientific Research, Popular Science

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