16806997
Spin of Stellar-Mass Black Holes Estimated by a Model of Quasi-Periodic Oscillations
We have proposed in previous papers that the high-frequency pair of quasi-periodic oscillations observed in black-hole binaries with a frequency ratio of 3 : 2 are inertial-acoustic oscillations (nearly horizontal oscillations with no node in the vertical direction) or g-mode oscillations, which are resonantly excited on warped relativistic disks. The resonance occurs through horizontal motions. In this model, the dimensionless spin parameter, a∗ ,o f the central sources can be estimated when their masses are known from other observations. This estimate is done for
19434452
Resonant excitation of disk oscillations in deformed disks. VII. Stability criterion in MHD systems
In a disk with an oscillatory deformation from an axisymmetric state with frequency ωD and azimuthal wavenumber mD, two normal mode oscillations with a set of frequency and azimuthal wavenumber being (ω1, m1) and (ω2, m2) are resonantly coupled to each other through the disk deformation when the resonant conditions (ω1 + ω2 + ωD = 0 and m1 + m2 + mD = 0) are satisfied. In the case of hydrodynamical disks, the resonance amplifies the set of the oscillations if (E1/ω1)(E2/ω2) > 0 (Kato 2013b, PASJ, 65, 75), where E1 and E2 are wave energies of the two oscillations with ω1 and ω2, respectively. In this paper we show that this instability criterion is still valid even when the oscillations are ideal MHD ones in magnetized disks, if the displacements associated with the oscillations vanish on the boundary of the system.
118590299
Trapped, Two-Armed, Nearly Vertical Oscillations in Disks with Toroidal Magnetic Fields II: Effects of Finite Thickness
We examine the radial trapping of two-armed (m = 2) vertical p-mode oscillations in geometrically thin relativistic disks that are vertically isothermal, but terminated at a certain height by the presence of hot and low-density corona. The disks are assumed to be subject to toroidalmagneticfields. The oscillationsare classified by n, anumber related to the node number of oscillations in the vertical direction, and starting from n = 1. In modes with n = 1, the frequencies of trapped oscillations depend little on the height of termination, but in modes with n = 2, 3, ��� the frequencies decrease and the radial extentions of the trapped region become wide, as the termination height decreases. This study is a preparation to examine whether these oscillations can describe kilo-hertz quasi-periodic oscillations (kHz QPOs), horizontal branch oscillations (HBOs), and their correlations.
119286608
Resonant excitation of tilt mode in tidally deformed disks
In a previous paper (Kato 2013b), we have shown that in deformed disks a pair of trapped oscillation modes can be resonantly excited through couplings with disk deformation. In this paper we examine in what cases tilts are excited on tidally deformed disks by the above-mentioned wave-wave resonant process. The results show that tilts can be excited in various evolutional stages of tidally deformed disks, although the wave mode which becomes the pair to the tilt and the mode of tidal waves contributing to the resonance change by change of disk stages.
14113517
Mass and Spin of GRS 1915+105 Based on a Resonance Model of QPOs
We demonstrate that the four high-frequency QPOs observed in GRS 1915+105 can be interpreted as the oscillation modes on disks that non-linearly and resonantly interact with a warp. The warp is assumed to be a lowfrequency global pattern on the disk. This identification suggests that the relevant mass, M, and spin parameter, a,
118632115
An Attempt to Describe Frequency-Correlations among kHz QPOs and HBOs by Two-Armed Vertical p-Mode Oscillations: Case of No Magnetic Field
The trapping of two-armed (m = 2) vertical p-mode oscillations in relativistic disks is examined. The disks are assumed to be isothermal in the vertical direction, but are truncated at a certain height by the presence of corona. The same issues were examined in a previous paper (Kato 2012a). In this paper, unlike the previous paper, however, we do not use the approximation that the oscillations are nearly vertical, but limit to a simpler case of no magnetic field. As in the previous paper, the results suggest that the two basic oscillation modes [both are the fundamental (n = 1) in the vertical direction, but in the horizontal direction one is the fundamental (nr = 0) and the other the first overtone (nr = 1)] correspond to the twin kHz QPOs. Second, the oscillation mode, which is the first overtone (n = 2) in the vertical direction and the fundamental in the horizontal direction (nr = 0), will correspond to the horizontal branch oscillation (HBO) of Z-sources. The latter suggests that the horizontal branch of Z-sources is a sequence of temperature change in disks whose vertical thickness is strongly terminated. The temperature increases leftward along the sequence from the apex between the normal and horizontal branches.
126057573
Study of vertical beam blowup in KEKB low energy ring
Vertical beam blowup has been observed in the KEKB low energy positron ring (LER) since early operation. The main characteristics of the blowup are explained by single-beam head-tail instability caused by an electron cloud. About 4600 solenoids were installed in the LER in order to remove the electrons. This paper describes the experimental study of the vertical beam blowup emphasizing the effect of the solenoids.
122245696
Optical field ionization effects on the generation of wakefields with short pulse lasers
Abstract In recent experiments involving high intensity short pulse lasers, large wakefields have been observed to occur even when the pulse is much longer than the length necessary to generate wakefields. It was observed in the experiments that the plasma wave starts near the position of the ionization front. The whole process of wake amplification from optical field ionization to Raman scattering is investigated by using a one-dimensional particle-in-cell simulation code which includes the effect of optical field ionization.
122941128
Differential cross sections for proton compton scattering at incident photon energies between 900 MeV and 1150 MeV
Abstract Differential cross sections of proton Compton scattering have been measured in the angular range between 50° and 130° at incident photon energies from 900 MeV to 1150 MeV. A sharp dip in the angular distribution found by a Bonn group at 110° in the photon energy region around 900 MeV is not observed in the present measurement. A new dip-bump structure is found at photon energies above 1050 MeV, which is similar to that for pion-nucleon scattering.
7967891
Beam-beam effect observed in the KEKB
This report summarizes observed phenomena related to the beam-beam effects in the KEKB collider. A general performance of the beam-beam effect is described. An em- phasis is put on the reduction of the specific luminosity with shorter bunch spacing. ible with the present maximum beam current. The scrub- bing effect of the chamber wall also possibly contributed to suppress the blowup. The present beam current limitation comes from a heating problem in the IR region. Another feature of the KEKB is that working points are very close to the half integer resonance particularly in the horizontal direction as is seen in the table. These horizon- tal tunes make the horizontal emittance large and the hori- zonal beta functions small to a large extent. This large emit- tance compensates the large bunch currents and contributes to stabilize the beams against the beam-beam effect. As is seen in the table, both of the horizontal and vertical tunes of the both rings are located above the half integer resonance, while the vertical tunes are above the integer resonance in the design. In the early days of the KEKB, the vertical tunes were above the integer resonance. In February 2001, the vertical tunes moved to above the half integer based on results of new beam-beam simulations. This change of the tunes brought some increase of the luminosity.
55477539
An idea of dynamical cooling of electron beam in SR ring
A beam cooling method which uses a stimulated emission of radiation by relativistic electrons in a magnetic field, is proposed to apply to an electron beam in synchrotron radiation rings. The simulation is produced by a traveling RF electric field in a transmission line against the beam. Averaging the emission power over electron energy distributions, the net emission from the beam is taken place in a certain frequency region. Some conditions for the energy emission are discussed. The emission power is shown to be enough large to decrease the horizontal emittance of the beam to a very small value in typical synchrotron radiation rings.<<ETX>>