973744
Wave Effects in the Gravitational Lensing of Gravitational Waves from Chirping Binaries
In the gravitational lensing of gravitational waves, wave optics should be used instead of geometrical optics when the wavelength λ of the gravitational waves is longer than the Schwarzschild radius of the lens mass ML. For gravitational lensing of chirp signals from the coalescence of supermassive black holes at redshift zS ~ 1 relative to the Laser Interferometer Space Antenna, the wave effects become important for a lens mass smaller than ~108 M☉. For such cases, we compute how accurately we can extract the mass of the lens and the source position from the lensed signal. We consider two simple lens models: the point-mass lens and the SIS (singular isothermal sphere). We find that the lens mass and the source position can be determined to within ~0.1% of [(S/N)/103]-1 for a lens mass larger than 108 M☉ and 10% of [(S/N)/103]-1 for a lens mass smaller than 107 M☉ because of the diffraction effect, where S/N is the signal-to-noise ratio of the unlensed chirp signals. For the SIS model, if the source position is outside the Einstein radius, only a single image exists in the geometrical optics approximation, so that the lens parameters cannot be determined, while in the wave optics cases we find that the lens mass can be determined even for ML < 108 M☉. For the point-mass lens, one can extract the lens parameters even if the source position is far outside the Einstein radius. As a result, the lensing cross section is an order of magnitude larger than that for the usual strong lensing of light.
177071162
Evolution of magnetized dense clouds.
11224492
The Decihertz Laser Interferometer Can Determine the Position of the Coalescing Binary Neutron Stars within an Arcminute a Week before the Final Merging Event to the Black Hole
It may be possible to construct a laser interferometer gravitational wave antenna in space with hrms ~ 10-23 at f ~ 0.1 Hz in ~2020. This decihertz antenna may be called the Decihertz Interferometer Gravitational Wave Observatory and Big Bang Observer (DECIGO/BBO). The analysis of 1-10 yr of observational data of the coalescing binary neutron stars or black holes at the distance of ~300 Mpc will give us the spatial position within approximately an arcminute and the time of the coalescence within ~0.1 s beforehand. With the knowledge of the accurate position and the time of the final merging event, the follow-up simultaneous observation using high-frequency (f ~ 100 Hz) gravitational wave antennae as well as electromagnetic wave antennae from the radio frequency to the ultra-high-energy gamma ray will reveal the physics in the enigmatic event of the coalescence and the formation of the black hole.
15501366
Determination of the Equation of State of the Universe Using ∼0.1 Hz Gravitational Wave Detectors
We show that a ten year operation of the ultimate DECIGO (DECihertz Interferometer Gravitational wave Observatory) could determine the cosmic equation of state with 0.06%, 0.08% and 0.06% accuracies for Ω m , Ω w and w, respectively, while a one year operation could do so with 3%, 4% and 3% accuracies. In the more realistic case of a practical DECIGO or BBO (Big Bang Observer), w should be determined within ∼ 10% by a ten year observation assuming the flat universe model. Hence, a DECIGO or BBO should give an independent determination of the cosmic equation of state.
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.
96043155
Measurements of Activation Cross Sections on Spallation Reactions for 59Co and natCu at Incident Neutron Energies of 40 to 120 MeV
In our previous work, we have measured the neutron spallation cross sections of 12C and 209Bi in the 20-to 150-MeV energy range. Here in this succeeding study, the neutron activation cross sections on spallation reactions for 59Co and natCu have been measured in the quasi-monoenergetic p-7Li neutron fields in the 40-to 120-MeV energy range which have been established at two cyclotron facilities of Takasaki Research Establishment of Japan Atomic Energy Research institute (TIARA) and the Institute of Physical and Chemical Research (RIKEN). The neutron spectrum has been measured with the TOF (Time of Flight) method using an organic liquid scintillator, and the absolute value of peak neutron fluence has been determined from the proton recoil counter telescope at TIARA and the activation method of lithium target at RIKEN. In this study, the following seventeen neutron activation cross section data are reported which produce 56Mn, 54Mn, 52Mn, 58Co, 57Co, 56Co, 55Co, 59Fe from 59Co reactions and 56Mn, 59Fe, 60Co...
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.