![]() ![]() When the initiall solar mass stars form oxygen-rich cores, the stars undergo dynamical pulsation because the temperature in the stellar interior becomes high enough for photons to be converted into electron-positron pairs. In close binary systems, initially 80 to 130 solar mass stars lose their hydrogen-rich envelope and become helium stars of 40 to 65 solar masses. Pulsational pair-instability supernova evolutionary process. To answer this question, a research team at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) consisting of Project Researcher Shing-Chi Leung (currently at the California Institute of Technology), Senior Scientist Ken'ichi Nomoto, and Visiting Senior Scientist Sergei Blinnikov (professor at the Institute for Theoretical and Experimental Physics in Mosow) have investigated the final stage of the evolution of very massive stars, in particular 80 to 130 solar mass stars in close binary systems. But it is not clear which stars can form such a massive black hole, or what the maximum size of black holes observed by the gravitational wave detectors is. In one such event, GW170729, the observed mass of a black hole before merging is actually as large as about 50 solar masses. The masses of the observed black holes before merging have been measured and turned out to have a much larger than previously expected mass of about 10 times the mass of the Sun (solar mass). The exciting detection of gravitational waves with LIGO (laser interferometer gravitational-wave observatory) and VIRGO (Virgo interferometric gravitational-wave antenna) have shown the presence of merging black holes in close binary systems. Through simulations of a dying star, a team of theoretical physics researchers have found the evolutionary origin and the maximum mass of black holes which are discovered by the detection of gravitational waves. Credit: Shing-Chi Leung et al./Kavli IPMU These two paths could explain the origin of the detected binary black hole masses of the gravitational wave event GW170729. After that, the star continues to evolve and forms a massive iron core, which collapses in a fashion similar to the ordinary core-collapse supernova, but with a higher final black hole mass between 38 - 52 solar masses. ![]() The ejected materials form the circumstellar matter surrounding the star. This excites strong pulsation and partial ejection of the stellar materials. After the star forms a massive carbon-oxygen core, the core experiences catastrophic electron-positron pair-creation. A star between 80 and 140 solar masses evolves and develops into a pulsational pair-instability supernova. After the star forms a massive iron core, it collapses by its own gravity and forms a black hole with a mass below 38 solar masses. The star does not experience pair-instability, so there is no significant mass ejection by pulsation. A star below 80 solar masses evolves and develops into a core-collapse supernova. Schematic diagram of the binary black hole formation path for GW170729. ![]()
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