4,183 research outputs found
Stochastic gravitational-wave background from spin loss of black holes
Although spinning black holes are shown to be stable in vacuum in general
relativity, there exists exotic mechanisms that can convert the spin energy of
black holes into gravitational waves. Such waves may be very weak in amplitude,
since the spin-down could take a long time, and a direct search may not be
feasible. We propose to search for the stochastic background associated with
the spin-down, and we relate the level of this background to the formation rate
of spinning black holes from the merger of binary black holes, as well as the
energy spectrum of waves emitted by the spin-down process. We argue that
current LIGO-Virgo observations are not inconsistent with the existence of a
spin-down process, as long as it is slow enough. On the other hand, the
background may still exist as long as a moderate fraction of spin energy is
emitted within Hubble time. This stochastic background could be one interesting
target of next generation GW detector network, such as LIGO Voyager, and could
be extracted from total stochastic background
Determining the nature of white dwarfs from low-frequency gravitational waves
An extreme-mass-ratio system composed of a white dwarf (WD) and a massive
black hole can be observed by the low-frequency gravitational wave detectors,
such as the Laser Interferometer Space Antenna (LISA). When the mass of the
black hole is around , the WD will be disrupted by the
tidal interaction at the final inspiraling stage. The event position and time
of the tidal disruption of the WD can be accurately determined by the
gravitational wave signals. Such position and time depend upon the mass of the
black hole and especially on the density of the WD. We present the theory by
using LISA-like gravitational wave detectors, the mass-radius relation and then
the equations of state of WDs could be strictly constrained (accuracy up to
). We also point out that LISA can accurately predict the disruption
time of a WD, and forecast the electromagnetic follow-up of this tidal
disruption event.Comment: 7 pages, 2 figure
The wave nature of continuous gravitational waves from microlensing
Gravitational wave predicted by General Relativity is the transverse wave of
spatial strain. Several gravitational waveform signals from binary black holes
and from a binary neutron star system accompanied by electromagnetic
counterparts have been recorded by advanced LIGO and advanced Virgo. In analogy
to light, the spatial fringes of diffraction and interference should also exist
as the important features of gravitational waves. We propose that observational
detection of such fringes could be achieved through gravitational lensing of
continuous gravitational waves. The lenses would play the role of the
diffraction barriers. Considering peculiar motions of the observer, the lens
and the source, the spatial amplitude variation of diffraction or interference
fringes should be detectable as an amplitude modulation of monochromatic
gravitational signal.Comment: Accepted for publication in The Astrophysical Journa
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