Tomoya Kinugawa

We perform population synthesis simulations for Population III (Pop III) coalescing compact binary which merges within the age of the Universe. We found that the typical mass of Pop III binary black holes (BH-BHs) is 30 M so that the inspiral chirp signal of gravitational waves can be detected up to z = 0.28 by KAGRA, Adv. LIGO, Adv. Virgo and GEO network. Our simulations suggest that the detection rate of the coalescing Pop III BH-BHs is 140(68) events yr -1 (SFR p /(10 -2.5 M yr -1 Mpc -3 )) E

Using our population synthesis code, we found that the typical chirp mass defined by (<it>m</it><inf>1</inf><it>m</it><inf>2</inf>)3/5/(<it>m</it><inf>1</inf> + <it>m</it><inf>2</inf>)1/5 of Population III (Pop III) binary black holes (BH–BHs) is ∼30 M<inf>⊙</inf> with the total mass of ∼60 M<inf>⊙</inf> so that the inspiral chirp signal as well as quasi-norma

ABSTRACT In the case of zero-metal (Population III or Pop III) stars, we show that the total mass of binary black holes from binary Pop III star evolution can be ${\sim} 150 \, \mathrm{ M}_{\odot }$, which agrees with the mass of the binary black hole GW190521 recently discovered by LIGO/Virgo. The event rate of such binary black hole mergers is estimated as 0.13–0.66 (ρSFR/(6 × 105 M⊙ Mpc−3)) Errsys yr−1 Gpc−3, where ρSFR and Errsys are the cumulative comoving mass density of Pop III stars depe

ABSTRACT We performed Population III (Pop III) binary evolution using population synthesis simulations for seven different models. We found that Pop III binaries tend to be binary black holes (BBHs) with chirp mass Mchirp ∼ 30 M⊙ and they can merge in the present day, due to a long merger time. The merger rate densities of Pop III BBHs at z = 0 are in the range 3.34–21.2 $\rm yr^{-1}\,Gpc^{-3}$ which is consistent with the Advanced Laser Interferometer Gravitational Wave Observatory (aLIGO)/Adva

ABSTRACT We have devised fitting formulae for evolution tracks of massive stars with 8 ≲ M/M⊙ ≲ 160 under extreme metal-poor (EMP) environments for log (Z/Z⊙) = −2, −4, −5, −6, and −8, where M⊙ and Z⊙ are the solar mass and metallicity, respectively. Our fitting formulae are based on reference stellar models which we have newly obtained by simulating the time evolutions of EMP stars. Our fitting formulae take into account stars ending with blue supergiant (BSG) stars, and stars skipping Hertzspr

ABSTRACT The probability number distribution function of binary black hole mergers observed by LIGO/Virgo O3a has double peaks as a function of chirp mass Mchirp, total mass Mtotal, primary black hole mass M1, and secondary one M2, respectively. The larger chirp mass peak is at Mchirp≅ 30 M⊙. The distribution of M2 versus M1 follows the relation of M2≅ 0.7M1. For initial mass functions of Population III stars in the form of f(M) ∝ M−α, population synthesis numerical simulations with 0 ≤ α ≤ 1.5

Focusing on the remnant black holes after merging binary black holes, we show that ringdown gravitational waves of Population III binary black hole mergers can be detected at the rate of <f>5.9−500 events yr−1(SFRp/(10−2.5M⊙ yr−1 Mpc−3))⋅([fb/(1+fb)]/0.33)</f> for various parameters and functions. This rate is estimated for events with <f>SNR > 8</f> for second-generation gravitational wave detectors such as KAGRA. Here, <f>SFRp</f> and <f>fb

Abstract It is generally believed that Type Ia supernovae are thermonuclear explosions of carbon–oxygen white dwarfs (WDs). However, there is currently no consensus regarding the events leading to the explosion. A binary WD (WD–WD) merger is a possible progenitor of Type Ia supernovae. Space-based gravitational wave (GW) detectors with considerable sensitivity in the decihertz range such as the DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) can observe WD–WD mergers directly.

The existence of the ergoregion of the Kerr space-time has not been confirmed observationally yet. We show that the confirmation would be possible by observing the quasinormal mode in gravitational waves. As an example, using the recent population synthesis results of Pop III binary black holes, we find that the peak of the final merger mass ($M_f$) is about $50~\rm M_{\odot}$, while the fraction of the final spin $q_f = a_f/M_f > 0.7$ needed for the confirmation of a part of ergoregion is $\sim

ABSTRACT How massive stars end their lives depends on the core mass, core angular momentum, and hydrogen envelopes at death. However, these key physical facets of stellar evolution can be severely affected by binary interactions. In turn, the effectiveness of binary interactions itself varies greatly depending on the initial conditions of the binaries, making the situation much more complex. We investigate systematically how binary interactions influence core–collapse progenitors and their fates

Abstract We performed population synthesis simulations of Population III binary stars with Maxwellian kick velocity distribution when MGCOs (mass gap compact objects, with mass $2$–$5\,M_{\odot}$) are formed. We found that for eight kick velocity dispersion models of $\sigma_{\rm k}=0$–$500\>$km$\>$s$^{-1}$, the mean mass of black hole (BH)-MGCO binary is $\sim (30 \,M_\odot,\,2.6 \,M_\odot)$. In numerical data of our simulations, we found the existence of a BH-MGCO binary with mas

LIGO has detected gravitational waves from massive binary black hole mergers. In order to explain the origin of such massive stellar-mass black holes, extreme metal poor stars including first stars have been invoked. However, black holes do not carry information of the metallicity. In order to check the metallicity dependence of the black hole formation, we focus on galactic black hole-main sequence binaries (BH-MSs). Using a binary population synthesis method, we find that $\gaia$ can detect $\

It is generally believed that Type Ia supernovae are thermonuclear explosions of carbon-oxygen white dwarfs (WDs). However, there is currently no consensus regarding the events leading to the explosion. A binary WD (WD-WD) merger is a possible progenitor of Type Ia supernovae. Space-based gravitational wave (GW) detectors with considerable sensitivity in the deci-Hz range such as the DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) can observe WD-WD mergers directly. Therefore,

We performed population synthesis simulations of Population III binary stars\nwith Maxwellian kick velocity distribution when MGCOs (Mass Gap Compact Objects\nwith mass 2--5$\\,M_{\\odot}$) are formed. We found that for eight kick velocity\ndispersion models of $\\sigma_{\\rm k}=0$--$500$ km/s, the mean mass of black\nhole (BH)-MGCO binary is $\\sim (30 \\,M_\\odot,\\,2.6 \\,M_\\odot)$. In numerical\ndata of our simulations, we found the existence of BH-MGCO binary with mass\n$(22.9 \\,M_\\odot,

ABSTRACT Two neutron star (NS)-black hole (BH) binaries, GW200105 and GW200115 found in the LIGO/Virgo O3b run have smaller BH mass of 6–9 M⊙, which is consistent with Population I and II origin. Our population synthesis simulations using 106 Population I and II binaries with appropriate initial parameters show consistent binary mass, event rate, no detection of radio pulsar (PSR), and BH binaries in our Galaxy so far. Especially, we found possible progenitors of GW200105 and GW200115, which wer