다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

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The Observation of Gravitational Waves from a Binary Black Hole Merger

日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

Gamma-ray bursts (GRB's), short and intense pulses of low-energy $\ensuremath{\gamma}$ rays, have fascinated astronomers and astrophysicists since their unexpected discovery in the late sixties. During the last decade, several space missions---BATSE (Burst and Transient Source Experiment) on the Compton Gamma-Ray Observatory, BeppoSAX and now HETE II (High-Energy Transient Explorer)---together with ground-based optical, infrared, and radio observatories have revolutionized our understanding of GRB's, showing that they are cosmological, that they are accompanied by long-lasting afterglows, and that they are associated with core-collapse supernovae. At the same time a theoretical understanding has emerged in the form of the fireball internal-external shocks model. According to this model GRB's are produced when the kinetic energy of an ultrarelativistic flow is dissipated in internal collisions. The afterglow arises when the flow is slowed down by shocks with the surrounding circumburst matter. This model has had numerous successful predictions, like the predictions of the afterglow itself, of jet breaks in the afterglow light curve, and of the optical flash that accompanies the GRB's. This review focuses on the current theoretical understanding of the physical processes believed to take place in GRB's.

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The physics of gamma-ray bursts

EDDINGTON'S “Internal Constitution of the Stars” was published in 1926 and gives what now ranks as a classical account of his own researches and of the general state of the theory at that time. Since then, a tremendous amount of work has appeared. Much of it has to do with the construction of stellar models with different equations of state applying in different zones. Other parts deal with the effects of varying chemical composition, with pulsation and tidal and rotational distortion of stars, and with the precise relations between the interior and the atmosphere of a star. The striking feature of all this work is that so much can be done without assuming any particular mechanism of stellar energy-generation. Only such very comprehensive assumptions are made about the distribution and behaviour of the energy sources that we may expect future knowledge of their mechanism to lead mainly to more detailed results within the framework of the existing general theory. An Introduction to the Study of Stellar Structure By S. Chandrasekhar. (Astrophysical Monographs sponsored by The Astrophysical Journal.) Pp. ix+509. (Chicago: University of Chicago Press; London: Cambridge University Press, 1939.) 50s. net.

An Introduction to the Study of Stellar Structure

Whether gamma-ray bursts are highly beamed or not is a very difficult but important problem that we are confronted with. Some theorists suggest that beaming effect usually leads to a sharp break in the afterglow light curve during the ultrarelativistic phase, with the breaking point determined by γ = 1/θ0, where γ is the Lorentz factor of the blast wave and θ0 is the initial half-opening angle of the ejecta, but numerical studies tend to reject the suggestion. We note that previous studies are uniformly based on dynamics that is not proper for nonrelativistic blast waves. Here we investigate the problem in more detail, paying special attention to the transition from the ultrarelativistic phase to the nonrelativistic phase. Due to some crucial refinements in the dynamics, we can follow the overall evolution of a realistic jet until its velocity is as small as βc ~ 10-3c. We find no obvious break in the optical light curve during the relativistic phase itself. However, an obvious break does appear at the transition from the relativistic phase to the Newtonian phase if the physical parameters involved are properly assumed. Generally speaking, the Newtonian phase is characterized by a sharp decay of optical afterglows, with the power-law timing index α ~ 1.8-2.1. This is due to the quick lateral expansion at this stage. The quick decay of optical afterglows from GRB 970228, 980326, and 980519 and the breaks in the optical light curves of GRB 990123 and 990510 may indicate the presence of highly collimated gamma-ray burst ejecta.

https://iopscience.iop.org/article/10.1086/317076/pdf

Overall Evolution of Jetted Gamma-ray Burst Ejecta

The conventional generic model is deemed to explain the dynamics of $\gamma$-ray burst remnants very well, no matter whether they are adiabatic or highly radiative. However, we find that for adiabatic expansion, the model could not reproduce the Sedov solution in the non-relativistic phase, thus the model needs to be revised. In the present paper, a new differential equation is derived. The generic model based on this equation has been shown to be correct for both radiative and adiabatic fireballs, and in both ultra-relativistic and non-relativistic phase.

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A generic dynamical model of gamma-ray burst remnants

Very recently, Spitler et al. and Scholz et al. reported their detections of 16 additional bright bursts in the direction of the fast radio burst (FRB) 121102. This repeating FRB is inconsistent with all of the catastrophic event models put forward previously for hypothetically non-repeating FRBs. Here, we propose a different model, in which highly magnetized pulsars travel through the asteroid belts of other stars. We show that a repeating FRB could originate from such a pulsar encountering a large number of asteroids in the belt. During each pulsar-asteroid impact, an electric field induced outside of the asteroid has such a large component parallel to the stellar magnetic field that electrons are torn off the asteroidal surface and accelerated to ultra-relativistic energies instantaneously. The subsequent movement of these electrons along magnetic field lines will cause coherent curvature radiation, which can account for all of the properties of an FRB. In addition, this model can self-consistently explain the typical duration, luminosity, and repetitive rate of the 17 bursts of FRB 121102. The predicted occurrence rate of repeating FRB sources may imply that our model would be testable in the next few years.

https://iopscience.iop.org/article/10.3847/0004-637X/829/1/27/pdf

Repeating fast radio bursts from highly magnetized pulsars traveling through asteroid belts

Very recently Spitler et al. (2016) and Scholz et al. (2016) reported their detections of sixteen additional bright bursts from the direction of the fast radio burst (FRB) 121102. This repeating FRB is inconsistent with all the catastrophic event models put forward previously for hypothetically non-repeating FRBs. Here we propose a different model, in which highly magnetized pulsars travel through asteroid belts of other stars. We show that a repeating FRB could originate from such a pulsar encountering lots of asteroids in the belt. During each pulsar-asteroid impact, an electric field induced outside the asteroid has such a large component parallel to the stellar magnetic field that electrons are torn off the asteroidal surface and accelerated to ultra-relativistic energies instantaneously. Subsequent movement of these electrons along magnetic field lines will cause coherent curvature radiation, which can account for all the properties of an FRB. In addition, this model can self-consistently explain the typical duration, luminosity, and repetitive rate of the seventeen bursts of FRB 121102. The predicted occurrence rate of repeating FRB sources may imply that our model would be testable in the next few years.

Repeating Fast Radio Bursts from Highly Magnetized Pulsars Travelling through Asteroid Belts

It is believed that orphan afterglow searches can help to measure the beaming angle in gamma-ray bursts (GRBs). Great expectations have been put on this method. We point out that the method is in fact not as simple as we originally expected. As a result of the baryon-rich environment that is common to almost all popular progenitor models, there should be many failed gamma-ray bursts, i.e. fireballs with Lorentz factor much less than 100-1000, but still much larger than unity. In fact, the number of failed gamma-ray bursts may even be much larger than that of successful bursts. Owing to the existence of these failed gamma-ray bursts, there should be many orphan afterglows even if GRBs are due to isotropic fireballs, then the simple discovery of orphan afterglows never means that GRBs are collimated. Unfortunately, to distinguish between a failed-GRB orphan and a jetted but off-axis GRB orphan is not an easy task. The major problem is that the trigger time is unknown. Some possible solutions to the problem are suggested.

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Yong-Feng Huang

Papers

Overall Evolution of Jetted Gamma-ray Burst Ejecta

A generic dynamical model of gamma-ray burst remnants

Repeating fast radio bursts from highly magnetized pulsars traveling through asteroid belts

Repeating Fast Radio Bursts from Highly Magnetized Pulsars Travelling through Asteroid Belts

Failed gamma-ray bursts and orphan afterglows