Published Papers - Taniguchi Keisuke

Equilibriums of extremely magnetized compact stars with force-free magnetotunnels

Kōji Uryū, Shijun Yoshida, Eric Gourgoulhon, Charalampos Markakis, Kotaro Fujisawa, Antonios Tsokaros, Keisuke Taniguchi, Mina Zamani

Physical Review D ( Physical Review D )  107 ( 10 ) 103016-1 - 103016-14   2023.05 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Reducing orbital eccentricity in initial data of black hole-neutron star binaries in the puncture framework

Kyutoku Koutarou, Kawaguchi Kyohei, Kiuchi Kenta, Shibata Masaru, Taniguchi Keisuke

PHYSICAL REVIEW D ( Physical Review D )  103 ( 2 ) 023002-1 - 023002-15   2021.01 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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New code for equilibriums and quasiequilibrium initial data of compact objects. IV. Rotating relativistic stars with mixed poloidal and toroidal magnetic fields

Koji Uryu, Shijun Yoshida, Eric Gourgoulhon, Charalampos Markakis, Kotaro Fujisawa, Antonios Tsokaros, Keisuke Taniguchi, Yoshiharu Eriguchi

Physical Review D ( Physical Review D )  100 ( 12 ) 123019-1 - 123019-34   2019.12 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Revisiting the Lower Bound on Tidal Deformability Derived by AT 2017gfo

Kenta Kiuchi, Koutarou Kyutoku, Masaru Shibata, Keisuke Taniguchi

Astrophysical Journal Letters ( Astrophysical Journal Letters )  876 ( 2 ) L31-1 - L31-6   2019.05 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Frequency-domain gravitational waveform models for inspiraling binary neutron stars

Kyohei Kawaguchi, Kenta Kiuchi, Koutarou Kyutoku, Yuichiro Sekiguchi, Masaru Shibata, Keisuke Taniguchi

Physical Review D ( Physical Review D )  97 ( 4 ) 044044-1 - 044044-22   2018.02 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Neutrino transport in black hole-neutron star binaries: Neutrino emission and dynamical mass ejection

Koutarou Kyutoku, Kenta Kiuchi, Yuichiro Sekiguchi, Masaru Shibata, Keisuke Taniguchi

Physical Review D ( Physical Review D )  97 ( 2 ) 023009-1 - 023009-17   2018.01 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Modeling differential rotations of compact stars in equilibriums

Koji Uryū, Antonios Tsokaros, Luca Baiotti, Filippo Galeazzi, Keisuke Taniguchi, Shin'ichirou Yoshida

Physical Review D ( Physical Review D )  96 ( 10 ) 103011-1 - 103011-8   2017.11 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Sub-radian-accuracy gravitational waveforms of coalescing binary neutron stars in numerical relativity

Kenta Kiuchi, Kyohei Kawaguchi, Koutarou Kyutoku, Yuichiro Sekiguchi, Masaru Shibata, Keisuke Taniguchi

Physical Review D ( Physical Review D )  96 ( 8 ) 084060-1 - 084060-13   2017.10 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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The status of DECIGO

Shuichi Sato, Seiji Kawamura, Masaki Ando, Takashi Nakamura, Kimio Tsubono, Akito Araya, Ikkoh Funaki, Kunihito Ioka, Nobuyuki Kanda, Shigenori Moriwaki, Mitsuru Musha, Kazuhiro Nakazawa, Kenji Numata, Shin-ichiro Sakai, Naoki Seto, Takeshi Takashima, Takahiro Tanaka, Kazuhiro Agatsuma, Koh-suke Aoyanagi, Koji Arai, Hideki Asada, Yoichi Aso, Takeshi Chiba, Toshikazu Ebisuzaki, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa-Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Katsuhiko Ganzu, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Feng-Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Nobuki Kawashima, Fumiko Kawazoe, Naoko Kishimoto, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hideaki Kudoh, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Kei-ichi Maeda, Hideo Matsuhara, Yasushi Mino, Osamu Miyakawa, Shinji Miyoki, Mutsuko Y. Morimoto, Tomoko Morioka, Toshiyuki Morisawa, Shinji Mukohyama, Shigeo Nagano, Isao Naito, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Taiga Noumi, Yoshiyuki Obuchi, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Norio Okada, Kouji Onozato, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Masaaki Sakagami, Shihori Sakata, Misao Sasaki, Takashi Sato, Masaru Shibata, Hisaaki Shinkai, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Yudai Suwa, Rieko Suzuki, Hideyuki Tagoshi, Fuminobu Takahashi, Kakeru Takahashi, Keitaro Takahashi, Ryutaro Takahashi, Ryuichi Takahashi, Tadayuki Takahashi, Hirotaka Takahashi, Takamori Akiteru, Tadashi Takano, Keisuke Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Yasuo Torii, Morio Toyoshima, Shinji Tsujikawa, Yoshiki Tsunesada, Akitoshi Ueda, Ken-ichi Ueda, Masayoshi Utashima, Yaka Wakabayashi, Hiroshi Yamakawa, Kazuhiro Yamamoto, Toshitaka Yamazaki, Jun’ichi Yokoyama, Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino

Journal of Physics: Conference Series ( IOP Publishing )  840   012010 - 012010   2017.05 [ Peer Review Accepted ]

Type of publication: Research paper (international conference proceedings)

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Do triaxial supramassive compact stars exist?

Koji Uryu, Antonios Tsokaros, Luca Baiotti, Filippo Galeazzi, Noriyuki Sugiyama, Keisuke Taniguchi, Shin'ichirou Yoshida

Physical Review D ( Physical Review D )  94 ( 10 ) 101302-1 - 101302-6   2016.11 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Dynamical mass ejection from the merger of asymmetric binary neutron stars: Radiation-hydrodynamics study in general relativity

Yuichiro Sekiguchi, Kenta Kiuchi, Koutarou Kyutoku, Masaru Shibata, Keisuke Taniguchi

Physical Review D ( Physical Review D )  93 ( 12 ) 124046-1 - 124046-13   2016.06 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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New code for equilibriums and quasiequilibrium initial data of compact objects. III. Axisymmetric and triaxial rotating stars

Koji Uryu, Antonios Tsokaros, Filippo Galeazzi, Hideya Hotta, Misa Sugimura, Keisuke Taniguchi, Shin'ichirou Yoshida

Physical Review D ( Physical Review D )  93 ( 4 ) 044056-1 - 044056-18   2016.02 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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High resolution magnetohydrodynamic simulation of black hole-neutron star merger: Mass ejection and short gamma ray bursts

Kenta Kiuchi, Yuichiro Sekiguchi, Koutarou Kyutoku, Masaru Shibata, Keisuke Taniguchi, Tomohide Wada

Physical Review D - Particles, Fields, Gravitation and Cosmology ( Physical Review D - Particles, Fields, Gravitation and Cosmology )  92 ( 6 ) 064034-1 - 064034-8   2015.09 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Dynamical mass ejection from black hole-neutron star binaries

Koutarou Kyutoku, Kunihito Ioka, Hirotada Okawa, Masaru Shibata, Keisuke Taniguchi

Physical Review D - Particles, Fields, Gravitation and Cosmology ( Physical Review D - Particles, Fields, Gravitation and Cosmology )  92 ( 4 ) 044028-1 - 044028-37   2015.08 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Black hole-neutron star binary merger: Dependence on black hole spin orientation and equation of state

Kyohei Kawaguchi, Koutarou Kyutoku, Hiroyuki Nakano, Hirotada Okawa, Masaru Shibata, Keisuke Taniguchi

Physical Review D - Particles, Fields, Gravitation and Cosmology ( Physical Review D - Particles, Fields, Gravitation and Cosmology )  92 ( 2 ) 024014-1 - 024014-25   2015.07 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Quasiequilibrium sequences of binary neutron stars undergoing dynamical scalarization

Keisuke Taniguchi, Masaru Shibata, Alessandra Buonanno

Physical Review D   91   024033   2015.01 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Reducing orbital eccentricity in initial data of binary neutron stars

Kyutoku Koutarou, Shibata Masaru, Taniguchi Keisuke

PHYSICAL REVIEW D ( AMER PHYSICAL SOC )  90 ( 6 )   2014.09 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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We develop a method to compute low-eccentricity initial data of binary neutron stars required to perform realistic simulations in numerical relativity. The orbital eccentricity is controlled by adjusting the orbital angular velocity of a binary and incorporating an approaching relative velocity of the neutron stars. These modifications improve the solution primarily through the hydrostatic equilibrium equation for the binary initial data. The orbital angular velocity and approaching velocity of initial data are updated iteratively by performing time evolutions over similar to 3 orbits. We find that the eccentricity can be reduced by an order of magnitude compared to standard quasicircular initial data, specifically from similar to 0.01 to less than or similar to 0.001, by three successive iterations for equal-mass binaries leaving similar to 10 orbits before the merger.

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Coalescence of binary neutron stars in a scalar-tensor theory of gravity

Shibata Masaru, Taniguchi Keisuke, Okawa Hirotada, Buonanno Alessandra

PHYSICAL REVIEW D ( AMER PHYSICAL SOC )  89 ( 8 )   2014.04 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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We carry out numerical-relativity simulations of coalescing binary neutron stars in a scalar-tensor theory that admits spontaneous scalarization. We model neutron stars with realistic equations of state. We choose the free parameters of the theory taking into account the constraints imposed by the latest observations of neutron-star-white-dwarf binaries with pulsar timing. We show that even within those severe constraints, scalarization can still affect the evolution of the binary neutron stars, not only during the late inspiral but also during the merger stage. We also confirm that even when both neutron stars have quite small scalar charge at large separations, they can be strongly scalarized dynamically during the final stages of the inspiral. In particular, we identify the binary parameters for which scalarization occurs either during the late inspiral or only after the onset of the merger when a remnant, supramassive, or hypermassive neutron star is formed. We also discuss how those results can impact the extraction of physical information on gravitational waves once they are detected.

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Matter effects on binary neutron star waveforms

Read Jocelyn S., Baiotti Luca, Creighton Jolien D. E., Friedman John L., Giacomazzo Bruno, Kyutoku Koutarou, Markakis Charalampos, Rezzolla Luciano, Shibata Masaru, Taniguchi Keisuke

PHYSICAL REVIEW D ( AMER PHYSICAL SOC )  88 ( 4 )   2013.08 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Using an extended set of equations of state and a multiple-group multiple-code collaborative effort to generate waveforms, we improve numerical-relativity-based data-analysis estimates of the measurability of matter effects in neutron-star binaries. We vary two parameters of a parametrized piecewise-polytropic equation of state (EOS) to analyze the measurability of EOS properties, via a parameter Lambda that characterizes the quadrupole deformability of an isolated neutron star. We find that, to within the accuracy of the simulations, the departure of the waveform from point-particle (or spinless double black-hole binary) inspiral increases monotonically with Lambda and changes in the EOS that did not change Lambda are not measurable. We estimate with two methods the minimal and expected measurability of Lambda in second- and third-generation gravitational-wave detectors. The first estimate using numerical waveforms alone shows that two EOSs which vary in radius by 1.3 km are distinguishable in mergers at 100 Mpc. The second estimate relies on the construction of hybrid waveforms by matching to post-Newtonian inspiral and estimates that the same EOSs are distinguishable in mergers at 300 Mpc. We calculate systematic errors arising from numerical uncertainties and hybrid construction, and we estimate the frequency at which such effects would interfere with template-based searches.

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Remnant massive neutron stars of binary neutron star mergers: Evolution process and gravitational waveform

Hotokezaka Kenta, Kiuchi Kenta, Kyutoku Koutarou, Muranushi Takayuki, Sekiguchi Yu-ichiro, Shibata Masaru, Taniguchi Keisuke

PHYSICAL REVIEW D ( AMER PHYSICAL SOC )  88 ( 4 )   2013.08 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Massive (hypermassive and supramassive) neutron stars are likely to be often formed after the merger of binary neutron stars. We explore the evolution process of the remnant massive neutron stars and gravitational waves emitted by them, based on numerical-relativity simulations for binary neutron star mergers employing a variety of equations of state and choosing a plausible range of the neutron star mass of binaries. We show that the lifetime of remnant hypermassive neutron stars depends strongly on the total binary mass and also on the equations of state. Gravitational waves emitted by the remnant massive neutron stars universally have a quasiperiodic nature of an approximately constant frequency although the frequency varies with time. We also show that the frequency and time-variation feature of gravitational waves depend strongly on the equations of state. We derive a fitting formula for the quasiperiodic gravitational waveforms, which may be used for the data analysis of a gravitational-wave signal.

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