1,153 research outputs found

### A Resonance Model of Quasi-Periodic Oscillations of Low-Mass X-Ray Binaries

We try to understand the quasi-periodic oscillations (QPOs) in low-mass
neutron-star and black-hole X-ray binaries by a resonance model in warped disks
with precession. Our main concern is high-frequency QPOs, hectohertz QPOs, and
horizontal-branch QPOs in the z sources and the atoll sources, and the
correponding QPOs in black-hole X-ray binaries. Our resonance model can
qualitatively, but systematically, explain these QPOs by regarding hectohertz
QPOs as a precession of warp.Comment: 4 pages, to be published in PASJ Vol.57, No.

### 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 which non-linearly and
resonantly interact with a warp. The warp is assumed to be a low-frequency
global pattern on the disk. This identification suggests that the relevant
mass, $M$, and spin, $a$, of GRS 1915+105 are, $M=13\sim 14 M_\odot$ and
$a=0\sim 0.15$Comment: 4 pages, 5 figures, accepted in PASJ Vol.56(2004) No.5, The English
was improved on September

### An Attempt to Describe Frequency-Correlations among kHz QPOs and HBOs by Two-Armed Vertical p-mode Oscillations: Case of No Magnetic Field

Trapping of two-armed ($m=2$) vertical p-mode oscillations in relativistic
disks are 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 have been 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 ($n_{\rm r}=0$) and the
other the first overtone ($n_{\rm r}=1$)] 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 ($n_{\rm
r}=0$) 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
normal and horizontal branches.Comment: 17 pages, 8 figures, to be published in PASJ Vol. 65, No. 1 (2013

### Resonant Excitation of Disk Oscillations in Two-Armed-Deformed Disks and Application to High-Frequency QPOs

In previous papers we showed that in a one-armed deformed disks, p-mode and
g-mode oscillations are resonantly excited by horizontal resonance, and applied
it to high frequency QPOs observed in low mass X-ray binaries. In that model,
the observed time variation of kHz QPOs is regarded as a result of a
time-dependent precession of the deformation. In this paper we consider another
possible cause of time variation of kHz QPOs. That is, we demonstrate that in a
two-armed deformed disks, p-mode and g-mode oscillations are excited by {\it
vertical resonance}, not by horizontal resonance(horizontal resonance dampens
them). Furthermore, we show that in the case of vertical resonance, the
frequencies of disk oscillations excited can vary with time if vertical disk
structure changes with time. A brief application of these results to the time
variation of observed kHz QPOs is made.Comment: 19 pages, 5 figures. To be published in PASJ 61, No.6 (2009

### Resonant Excitation of Disk Oscillations in Deformed Disks V: Effects of Dissipative Process

It is suggested that a set of positive- and negative-energy oscillations can
be resonantly excited in the inner region of deformed (warped or eccentric)
relativistic disks. In this paper we examine how a dissipative process affects
on this wave excitation process. The results show that when the resonant
condition in frequency is roughly satisfied and thus the oscillations are
excited, introduction of a dissipative process works so as to decrease the
growth rate of the oscillations. When the frequency difference of the two
oscillations deviates more than a certain amount from that required by resonant
condition, however, the oscillations are excited by introduction of dissipative
process. This excitation by dissipative process can be understood as a special
example of the double-diffusive instability.Comment: 14 pages, 2 figures, to be published in PASJ 63, No 2 (2011

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