16939979
Peak Luminosity-Spectral Lag Relation Caused by the Viewing Angle of the Collimated Gamma-Ray Bursts
We compute the kinematical dependence of the peak luminosity, the pulse width, and the spectral lag of the peak luminosity on the viewing angle θv of a jet. For appropriate model parameters we obtain a peak luminosity-spectral lag relation similar to the observed one including gamma-ray burst (GRB) 980425. A bright (dim) peak with short (long) spectral lag corresponds to a jet with small (large) viewing angle. This suggests that the viewing angle of the jet might cause various relations in GRBs such as the peak luminosity-variability relation and the luminosity-width relation. Our model also suggests that X-ray-rich GRBs (or X-ray flushes or fast X-ray transients) are typical GRBs observed from large θv with large spectral lag and low variability.
120122684
Overview of recent experimental works on high energy neutron shielding
Abstract Several experiments on high energy neutron shielding have recently been performed using medium to high energy accelerators of energies above 20 MeV. Below 100 MeV, the benchmark experiments have been done using 25 and 35 MeV p-Li quasi-monoenergetic neutrons at the Cyclotron and Radioisotope Center (CYRIC), Tohoku University, Japan, 43 and 68 MeV p-Li quasi-monoenergetic neutrons at the Azimuthally Varying Field (AVF) cyclotron facility, TIARA of Japan Atomic Energy Research Institute (JAERI). Above 100 MeV, the neutron shielding experiments have been done using 800 MeV protons at ISIS, Rutherford Appleton laboratory (RAL), England, 400 MeV/nucleon carbon ions at the heavy ion medical accelerator facility, HIMAC of National Institute of Radiological Sciences (NIBS), Japan, 500 MeV protons at the spallation neutron source facility, KEK spallation neutron source facility (KENS) of High Energy Accelerator Research Organization (KEK), Japan, 500 MeV protons at the accelerator facility, TRIUMF, Canada, 1.6 to 24 GeV protons at the Alternating Gradient Synchrotron (AGS), Brookhaven National Laboratory (BNL), U.S.A., 28.7 GeV electrons at the Stanford Linear Accelerator Center (SLAG), U.S.A., 800 MeV protons at the Los Alamos Neutron Science Center (LANSCE), Los Alamos National Laboratory (LANL), U.S.A., 120, 205 GeV/c protons and 160 GeV/nucleon lead ions at the European Organization for Nuclear Research (CERN), Switzerland, 230 MeV protons at the Loma Linda University Medical Center, U.S.A., 200 MeV protons at the Orsay Proton Therapy Center, France. In this review paper, the outlines of these deep penetration experiments are summarized together with the neutron detection techniques.
16735826
GRB 980425 in the Off‐Axis Jet Model of the Standard GRBs
Using a simple off‐axis jet model of GRBs, we can reproduce the observed unusual properties of the prompt emission of GRB 980425, such as the extremely low isotropic equivalent γ‐ray energy, the low peak energy, the high fluence ratio, and the long spectral lag when the jet with the standard energy of ∼ 1051 ergs and the opening half‐angle of 10°⩽Δθ⩽30° is seen from the off‐axis viewing angle θv ∼ Δθ + 10γ−1, where γ is a Lorentz factor of the jet. For our adopted fiducial parameters, if the jet that caused GRB 980425 is viewed from the on‐axis direction, the intrinsic peak energy Ep(1 + z) is ∼2.0–4.0 MeV, which corresponds to those of GRB 990123 and GRB 021004. Our model might be able to explain the other unusual properties of this event. We also discuss the connection of GRB 980425 in our model with the X‐ray flash, and the origin of a class of GRBs with small Eγ such as GRB 030329.
119096961
SOFT X-RAY EXTENDED EMISSIONS OF SHORT GAMMA-RAY BURSTS AS ELECTROMAGNETIC COUNTERPARTS OF COMPACT BINARY MERGERS; POSSIBLE ORIGIN AND DETECTABILITY
We investigate the possible origin of extended emissions (EE) of short gamma-ray bursts (SGRBs) with an isotropic energy of ∼ 10 50-51 erg and a duration of ∼ 100 s, based on the compact binary (neutron star (NS)-NS or NS-black hole (BH)) merger scenario. We analyze the evolution of magnetized neutrino-dominated accretion disks of mass ∼ 0.1 M⊙ around BHs formed after the mergers, and estimate the power of relativistic outflows via the Blandford-Znajek (BZ) process. We show that a rotation energy of the BH up to ∼ 10 53 erg can be extracted with a time scale of ∼ 100 s with a disk viscosity parameter of � ∼ 0.01. Such a BZ power dissipates by clashing with nonrelativistic pre-ejected matter of mass M ∼ 10 −(2-4) M⊙, and form a mildly relativistic fireball. We show that the dissipative photospheric emissions from such fireballs are likely in soft X-ray band (1-10 keV) for M ∼ 10 −2 M⊙ possibly in NS-NS mergers, and in the BAT band (15-150 keV) for M ∼ 10 −4 M⊙ possibly in NS-BH mergers. In the former case, such soft EEs can provide a good chance of ∼ 6 yr −1 (�softEE/4�) (RGW/40 yr −1 ) for simultaneous detections of the gravitational waves with a ∼ 0.1 ◦ angular resolution by soft X-ray survey facilities like Wide-Field MAXI. Here, �softEE is the beaming factor of the soft EEs and RGW is the NS-NS merger rate detectable by advanced LIGO, advanced Virgo, and KAGRA. While in the latter case, the observed EEs, which are associated with ∼ 25% of Swift SGRBs, can be well explained although the simultaneous detection rate with the GWs is expected to be very low . 10 −3 yr −1 . Subject headings: gamma rays: bursts — gamma rays: observations — gamma rays: theory
123083834
Can Current Detectors Detect Gravitational Radiation from Newborn Pulsars
120027595
Gravitational radiation from an extreme Kerr black hole
We analytically investigate gravitational radiation induced by a test particle falling into an extreme Kerr black hole. Assuming the radiation is dominated by the infinite sequence of quasi-normal modes which has the limiting frequencym/(2M), wherem is an azimuthal eigenvalue andM is the mass of the black hole. we find the radiated energy diverges logarithmically in time. Then we evaluate the back reaction to the black hole by appealing to the energy and angular momentum conservation laws. We find the radiation has a tendency to increase the ratio of the angular momentum to mass of the black hole, which is completely different from the non-extreme case, while the contribution of the test particle is to decrease it.
54195703
Rotating Unruh-DeWitt Detector in Minkowski Vacuum
Response of a circularly rotating Unruh-DeWitt detector to the Minkowski vacuum is investigated. What the detector observes depends on the surface (three volume) to define it by the Hamiltonian. Detectors in the past literature were defined on a surface of a constant Minkowski time, and this is the reason why rotating detectors investigated so far resister particles. No particle is detected by a detector defined by the Hamiltonian on a surface normal to the detector's orbit, in agreement with the global analysis of vacua. A detector with drift motion superposed on the linear acceleration is also examined, to find the same effect. c
55094258
Three Views of a Secret in Relativistic Thermodynamics
It has been shown three different views in relativistic thermodynamics can be derived from the basic formulation proposed by van Kampen and Israel. The way to decompose energy-momentum into work and heat is not uniquely determined; the different choices result in different views. Also the definition of three dimensional volume causes ambiguity of thermodynamical quantities. The present paper shows various theories are obtained depending on the choice of these two factors. Subject Index: 070
8249851
On Hawking/Unruh Process: Where does the Radiation Come from?
The energy source of the radiation in Unruh/Hawking process is investigated with emphasis on the particle number definition based on conservation laws. It has been shown that the particle radiation is not the result of pair creation by the gravitational force, but the result of difference in the conservation laws to define the particle number. The origin of the radiated energy in the distant future corresponds to the zero point oscillations with infinitely large wave numbers. This result implies the need of reconsideration on the scenario of black hole evaporation.
15093684
Lorentz transform of black-body radiation temperature
The Lorentz transform of black-body radiation has been investigated from the viewpoint of relativistic statistical mechanics. The result shows that the well-known expression with the directional temperature can be derived based on the inverse-temperature four-vector. The directional temperature in the past literature was the result of mathematical manipulation and its physical meaning is not clear. The inverse-temperature four-vector has, in contrast, clear meaning to understand relativistic thermodynamical processes.
15956163
Factor Two Discrepancy of Hawking Radiation Temperature
The possibility of an alternative way to formulate the Hawking radiation in a static Schwarzschild spacetime has been explored. To calculate the Hawking radiation, there can be two possible choices of the spacetime wedge pairs in the Krucal-Szekeres coordinates. One is the wedge pair consists of exterior spacetime of a black hole and the exterior spacetime of a white hole, and the other is that of exterior and interior spacetimes of one black hole. The radiation from the former is the Hawking's original one. Though the the latter has been often regarded as the same phenomena as the former, the result here suggests it is not; its radiation has a temperature twice as high as the Hawking temperature.