118484674
Trapped, Two-Armed, Nearly Vertical Oscillations in Disks with Toroidal Magnetic Fields
We have examined the trapping of two-armed (m = 2) nearly vertical oscillations (vertical p-mode) in vertically isothermal (cs = const.) relativistic disks with toroidal magnetic fields. The magnetic fields are stratified so that the Alfven speed, cA, is constant in the vertical direction. The ratio c 2 A =c 2 in the vertical direction is taken to be a parameter that examines the effects of magnetic fields on wave trapping. We find that the two-armed nearly vertical oscillations are trapped in the inner region of the disks, and their frequencies decrease with an increase of c 2 A =c 2 s . The trapped regions of the fundamental (n = 1) and the first-overtone (n = 2) are narrow (less than the length of the Schwarzschild radius, rg), and their frequencies are relatively high (on the order of the angular frequency of disk rotation in the inner region). In contrast to this, the second overtone (n = 3) is trapped in a wide region (a few times rg), and the frequencies are low and tend to zero in the limit of c 2 A =c 2 s = 2.0.
14220941
Frequency Correlations of QPOs Based on a Disk Oscillation Model in Warped Disks
In previous papers, we proposed a model that high-frequency quasi-periodic oscillations (QPOs) observed in black-hole and neutron-star X-ray binaries are disk oscillations (inertial-acoustic and/or g-mode oscillations) resonantly excited on warped disks. In this paper we examine whether time variations of the QPOs and their frequenc yc orrelations observed in neutron-star X-ray binaries can be accounted for by this disk-oscillation model. By assuming that a warp has a time-dependent precession, we can well describe the observed frequency correlations among kHz QPOs and low-frequency QPOs over a wide range of frequencies.
118396687
Tidal Instability and Superhump by a Wave-Wave Resonant Model
On a disk deformed to a non-axisymmetric form, a set of oscillations can be excited by their resonant interaction through the disk deformation (Kato et al. 2011). This resonant instability process has been proposed to suggest a possible cause of the high-frequency quasi-periodic oscillations (HF QPOs) observed in black-hole lowmass X-ray binaries. In the present paper, we examine whether the above-mentioned wave-wave resonant process can describe the tidal instability and superhump in dwarf novae. The results show that the process seems to well describe the observations. If this process is really the cause of the tidal instability and superhump, a two-armed oscillation with high frequency roughly on the magnitude of three times the orbital frequency is present on disks, although its expected amplitude may be small.
17631509
Quasi-Periodic Oscillations Resonantly Induced on Spin-Induced Deformed-Disks of Neutron Stars
We consider the situation where a spin-induced wavy perturbation is present on disks of neutron-star low-mass X-ray binaries. By non-linearly coupling with the perturbation, some modes of disk oscillations resonantly interact with the disks. We examine the resonant conditions under the assumption that the disks are vertically isothermal. The results show that when the spin frequency has some particular values, resonant coupling occurs at some radii. The modes and frequencies of these resonant oscillations are summarized. Some of these resonant oscillations seem to explain the frequencies of the observed kHz QPOs in objects of which the spin frequency is known.
118539083
Simultaneous resonant excitation of low-frequency eccentric wave and tilt wave on tidally deformed disks
Simultaneous excitation of low-frequency eccentric precessing mode (one-armed p-mode) and tilt mode on tidally deformed disks is considered. If the orbit of the secondary star is eccentric and its orbital plane is misaligned with the disk plane of the primary, the above-mentioned two low-frequency oscillation modes are simultaneously excited on the primary disk, the former having prograte precession and the latter having retrograde precession. This excitation of disk oscillations is due to a wave–wave resonant excitation process considered by Kato (2013, PASJ, 65, 75). If parameter values relevant to Be/X-ray binary systems are adopted, the periods of these excited oscillations are around 10 times the orbital period of the secondary, which may be comparable with the timescale of giant outbursts observed in Be/X-ray systems.
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
15439880
Lattice analysis of the KEKB colliding rings
A low beta lattice with /spl beta/x*//spl beta/y*=100/1 cm has been realized in the KEKB colliding rings. The basic optical parameters have been measured and compared with the model.
120413457
Coherent bremsstrahlung from the internal target of the 1.3 GeV electron synchrotron
Abstract A Si single crystal has been mounted on the conventional internal target holder of the 1.3 GeV electron synchrotron at the Institute for Nuclear Study, Tokyo. The energy spectrum measured with the pair spectrometer has a clear enhancement due to the coherent bremsstrahlung process. The linear polarization of the photon beam thus obtained is estimated to be 27% and 10% at the photon energy of 200 and 540 MeV, respectively.
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.
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.
119906527
MEASUREMENT OF THE POLARIZATION PARAMETER IN BACKWARD $pi$$sup +$p ELASTIC SCATTERING AT 1.60, 1.80, 2.11, AND 2.31 GeV/c.