J-GEM observations of an electromagnetic counterpart to the neutron star merger GW170817

Utsumi, Yousuke; Tanaka, Masaomi; Tominaga, Nozomu; Yoshida, Michitoshi; Barway, Sudhanshu; Nagayama, Takahiro; Zenko, Tetsuya; Aoki, Kentaro; Fujiyoshi, Takuya; Furusawa, Hisanori; Kawabata, Miho; Koshida, Shintaro; Lee, Chien‐Hsiu; Morokuma, Tomoki; Motohara, Kentaro; Nakata, Fumiaki; Ohsawa, Ryou; Ohta, Kouji; Okita, Hirofumi; Tajitsu, Akito; Tanaka, Ichi; Terai, Tsuyoshi; Yasuda, Naoki; Abe, F.; Asakura, Y.; Bond, I. A.; Miyazaki, Shota; Sumi, T.; Tristram, P. J.; Honda, Satoshi; Itoh, R.; Itoh, Yoichi; Morihana, K.; Nagashima, Hiroki; Nakaoka, Tatsuya; Ohshima, Tomohito; Takahashi, Jun; Takayama, Masaki; Aoki, Wako; Baar, Stefan; Doi, Mamoru; Finet, F.; Kanda, Nobuyuki; Kawai, N.; Kim, Ji Hoon; Kuroda, D.; Liu, Wei; Matsubayashi, Kazuya; Murata, Katsuhiro L.; Nagai, Hiroshi; Saito, Tomoki; Saito, Yoshihiko; Sako, Shigeyuki; Sekiguchi, Y.; Tamura, Motohide; Tanaka, Masayuki; Uemura, Makoto; Yamaguchi, Masaki

doi:10.1093/pasj/psx118

Cited by 198 publications

(115 citation statements)

References 36 publications

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“…Numerical relativity simulations' results, as in figure 8, show clearly that the dynamical ejecta is not spherical; the density in the equatorial region is higher than the density along the polar axis. We know from follow-up observations of GW170817 that the jet opening angle is small (θc ≈ 4 • ; Mooley et al 2018;Troja et al 2018;Ghirlanda et al 2019), this implies that the jet propagated in the polar region of the ejecta. Since the density in the equatorial region is not relevant to jet propagation, and since the scope of this study is limited to jet propagation, we do not include the excess in density in the equatorial region (relative to the polar region) in our calculation for GW170817's jet propagation.…”

Section: Angular Dependence and The Mass Of The Ejecta Mejmentioning

confidence: 99%

“…Late afterglow observations of GW170817 provided an estimation of the jet (and cocoon) energy and its final opening angle (Mooley et al 2018;Troja et al 2018;Ghirlanda et al 2019). Radio observations also determined the afterglow's peak time at ∼ 150 days, and the flux at this time.…”

Section: Afterglow Observations: Jet Energy and Opening Anglementioning

confidence: 99%

“…The observation of GW170817/sGRB 170817A (hereafter referred to as GW170817) was a major turning point for the multi-messenger astrophysics. As one of the best sGRB events observed ever, GW170817 is rich in new data; E-mail: hamidani.hamid@yukawa.kyoto-u.ac.jp such as, the mass of the BNS (∼ 2.7M ; Abbott et al 2017a), the viewing angle (∼ 20 • − 30 • ; Abbott et al 2017a;Troja et al 2018), and the delay between the GW and the EM signal (∼ 1.7s; Abbott et al 2017a;Abbott et al 2017c), all inferred for the first time. Superluminal motion in late radio afterglow observations (Mooley et al 2018), and macronova/kilonova (hereafter macronova) emission with a strong support for r-process nucleosynthesis (Arcavi et al 2017;Chornock et al 2017;Coulter et al 2017;Díaz et al 2017;Drout et al 2017;Kilpatrick et al 2017;Kasliwal et al 2017;Nicholl et al 2017;Pian et al 2017;Smartt et al 2017;Shappee et al 2017;Soares-Santos et al 2017;Tanaka et al 2017;Utsumi et al 2017;Valenti et al 2017) are also new revelations.…”

Section: Introductionmentioning

confidence: 99%

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Jet Propagation in Neutron Star Mergers and GW170817

Hamidani

Kiuchi

Ioka

2019

Monthly Notices of the Royal Astronomical Society

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The gravitational wave event from the binary neutron star (BNS) merger GW170817 and the following multi-messenger observations present strong evidence for i) merger ejecta expanding with substantial velocities and ii) a relativistic jet which had to propagate through the merger ejecta. The ejecta's expansion velocity is not negligible for the jet head motion, which is a fundamental difference from the other systems like collapsars and active galactic nuclei. Here we present an analytic model of the jet propagation in an expanding medium. In particular, we notice a new term in the expression of the breakout time and velocity. In parallel, we perform a series of over a hundred 2D numerical simulations of jet propagation. The BNS merger ejecta is prepared based on numerical relativity simulations of a BNS merger with the highestresolution to date. We show that our analytic results agree with numerical simulations over a wide parameter space. Then we apply our analytic model to GW170817, and obtain two solid constraints on: i) the central engine luminosity as L iso,0 ∼ 3 × 10 49 − 2.5 × 10 52 erg s −1 , and on ii) the delay time between the merger and engine activation t 0 − t m < 1.3 s. The engine power implies that the apparently-faint short gamma-ray burst (sGRB) sGRB 170817A is similar to typical sGRBs if observed on-axis.

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Section: Angular Dependence and The Mass Of The Ejecta Mejmentioning

confidence: 99%

Section: Afterglow Observations: Jet Energy and Opening Anglementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Jet Propagation in Neutron Star Mergers and GW170817

Hamidani

Kiuchi

Ioka

2019

Monthly Notices of the Royal Astronomical Society

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“…This multimessenger data provided convincing answers to many outstanding questions. For instance, the detection of a short gamma ray burst (GRB) 1.7 seconds after GW170817 [24][25][26], and subsequent kilonova [27][28][29][30][31][36][37][38][39][40][41][42][43][44], confirmed that BNS mergers are a progenitor of these events. Lanthanide signatures in the kilonova light curves also showed BNS mergers to be a major site for nucleosynthesis of elements heavier than iron [40,44,47,48].…”

Section: Introductionmentioning

confidence: 99%

Localization of binary neutron star mergers with second and third generation gravitational-wave detectors

Mills¹,

Tiwari²,

Fairhurst³

2018

Phys. Rev. D

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The observation of gravitational wave signals from binary black hole and binary neutron star mergers has established the field of gravitational wave astronomy. It is expected that future networks of gravitational wave detectors will possess great potential in probing various aspects of astronomy. An important consideration for successive improvement of current detectors or establishment on new sites is knowledge of the minimum number of detectors required to perform precision astronomy. We attempt to answer this question by assessing the ability of future detector networks to detect and localize binary neutron stars mergers on the sky. Good localization ability is crucial for many of the scientific goals of gravitational wave astronomy, such as electromagnetic follow-up, measuring the properties of compact binaries throughout cosmic history, and cosmology. We find that although two detectors at improved sensitivity are sufficient to get a substantial increase in the number of observed signals, at least three detectors of comparable sensitivity are required to localize majority of the signals, typically to within around 10 deg 2 -adequate for follow-up with most wide field of view optical telescopes.

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“…As a comparison, the mass of the dynamical ejecta of double NS mergers is typically ∼10 −4 -10 −2 M e (Rosswog 2007;Bauswein et al 2013;Hotokezaka et al 2013a). It also does not conflict with the estimation of M ej ∼10 −3 -10 −2 M e for the dynamical ejecta of GW170817 (Abbott et al 2017d;Utsumi et al 2017;Tanaka et al 2017;Matsumoto et al 2018). In a few recent studies, a more precise ejecta mass of M ej ∼0.05M e was estimated when modeling the GW170817 kilonova (Cowperthwaite et al 2017;Drout et al 2017;Kasliwal et al 2017;Kasen et al 2017;Villar et al 2017;Waxman et al 2017).…”

Section: Numerical Resultsmentioning

confidence: 83%

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

Huang

et al. 2018

ApJL

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The brightness of the multi-wavelength afterglow of GRB 170817A is increasing unexpectedly even ∼160 days after the associated gravitational burst. Here we suggest that the brightening can be caused by a late-time energy injection process. We use an empirical expression to mimic the evolution of the injection luminosity, which consists of a power-law rising phase and a power-law decreasing phase. It is found that the power-law indices of the two phases are 0.92 and −2.8, respectively, with the peak time of the injection being ∼110days. The energy injection could be due to some kind of accretion, with the total accreted mass being ∼0.006M e . However, normal fall-back accretion, which usually lasts for a much shorter period, cannot provide a natural explanation. Our best-fit decay index of −2.8 is also at odds with the expected value of −5/3 for normal fall-back accretion. Noting that the expansion velocities of the kilonova components associated with GW170817 are 0.1-0.3 c, we argue that there should also be some ejecta with correspondingly lower velocities during the coalescence of the double neutron star (NS) system. They are bound by the gravitational well of the remnant central compact object and might be accreted at a timescale of about 100 days, providing a reasonable explanation for the energy injection. Detailed studies on the long-lasting brightening of GRB 170817A thus may provide useful information on matter ejection during the merger process of binary neutron stars.

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J-GEM observations of an electromagnetic counterpart to the neutron star merger GW170817

Cited by 198 publications

References 36 publications

Jet Propagation in Neutron Star Mergers and GW170817

Jet Propagation in Neutron Star Mergers and GW170817

Localization of binary neutron star mergers with second and third generation gravitational-wave detectors

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

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