| 研究開始時の研究の概要 |
Gravitational waves (GW) detection is a new channel of observing black hole (BH) and neutron star (NS), which are difficult to detect by using traditional telescopes. Thus, GW provides a unique way to study BHs/NSs. In this research, a series of large N-body simulations of star clusters, where GW progenitors can efficiently form, will be carried out to study correlations between star formation, stellar dynamics and properties of GW progenitors. Using the result, we make predictions of the characteristics of GW events, such as the mass of the progenitors, event rate and more detailed features.
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| 研究実績の概要 |
We have developed a new N-body code, PeTar. Comparing the previous fastest code, the new code has several significant advantages: 1, For more than 100,000 stars, the performance of the code is much faster; 2. Using the slow-down algorithmic regularization method, it can handle 100 % binary fraction; 3. It has a well-designed user interface with rich data analysis tools; 4. It is modularized, and thus, including new functions from other codes.
By including updated stellar evolution code, BSE, we have investigated how the top-heavy IMF affects the event rate of GWs, we found that GCs with a top-heavy IMF is not efficient to produce GW mergers due to a low density after a strong expansion because of massive stellar wind mass loss. We also found the mass ratio distribution of BBHs is also different from that of GCs with the canonical IMF.
We have also carried out the first N-body models of intermediate massive star clusters with up to 100% binary fractions. We found that only massive primordial binaries can affect the long-term evolution of star clusters, but the effect is weak. This suggests that we can ignore low-mass binaries in the numerical modelling of GCs if we only care about the GW events.
By including PeTar in the hydrodynamical code, ASURA+BRIDGE, we studied how the OB binary affect the star formation of Orion nebular star clusters (ONC). We found the ejection of OB stars significantly affect the HII region in star-forming region, and thus, the binary dynamics affect the formation of multiple stellar population in ONC.
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