scholarly journals Extended reduced-order surrogate models for scalar-tensor gravity in the strong field and applications to binary pulsars and gravitational waves

2021 ◽  
Vol 104 (10) ◽  
Author(s):  
Minghao Guo ◽  
Junjie Zhao ◽  
Lijing Shao
Keyword(s):  
Gravitational Waves ◽  
Strong Field ◽  
Surrogate Models ◽  
Reduced Order ◽  
Binary Pulsars

Gravitational waves: Some less discussed intriguing issues

2015 ◽  
Vol 24 (12) ◽  
pp. 1544023 ◽  
Author(s):  
C. Sivaram
Keyword(s):  
Gravitational Waves ◽  
Strong Field ◽  
Direct Detection ◽  
Recent Observation ◽  
High Redshift ◽  
Nonlinear Effects ◽  
Resonant Absorption ◽  
Compact Objects ◽  
The Waves ◽  
Very High

Attempts to detect gravitational waves is actively in progress with sophisticated devices like LIGO setup across continents. Despite being predicted almost 100 years ago, there has so far been no direct detection of these waves. In this work, we draw attention to some of the less discussed but subtle aspects arising, for example, from high orbital eccentricities, where emission near periastron could be millions of times more than that in the distant parts of the orbit. The strong field nonlinear effects close to the compact objects can substantially slow down and deflect the waves in the last (few) orbit(s) where much of the intensity is expected. Spin–orbit and other forces could be significant. There would also be plasma like resonant absorption (of kilohertz radiation) during the collapse. Recent observation of supermassive black holes at high redshift implies cluster collapse, where the gravitational wave intensity depends on very high powers of the mass. Any unambiguous claim of detection should perhaps consider several of these effects.

Binary pulsars as probes of relativistic gravity

1992 ◽  
Vol 341 (1660) ◽  
pp. 135-149 ◽  
Keyword(s):  
Binary Systems ◽  
Strong Field ◽  
Field Tests ◽  
Weak Field ◽  
Multidimensional Space ◽  
Alternative Theory ◽  
Theory Approach ◽  
Binary Pulsars ◽  
Weak Field Limit ◽  
Self Gravity

Until now, most experiments have succeeded in testing relativistic gravity only in its extreme weak-field limit. Because of the strong self-gravity of neutron stars, observations of pulsars in binary systems provide a unique opportunity for probing the strong-field régime of relativistic gravity. The two basic approaches to using binary pulsar measurements as probes of relativistic gravity are reviewed: the phenomenological (‘parametrized post-keplerian’ formalism) and the alternative-theory approach (multidimensional space of possible theories). The experimental constraints recently derived from the actual timing observations of three binary pulsars are summarized. General relativity passes these new, strong-field tests with complete success.

HETERODYNE DETECTION OF GRAVITATIONAL WAVES EMITTED FROM BINARY PULSARS

1999 ◽  
Vol 14 (25) ◽  
pp. 1733-1738 ◽  
Author(s):  
G. BRAUTTI
Keyword(s):  
Gravitational Waves ◽  
Heterodyne Detection ◽  
Spectral Filtering ◽  
Rotating Platform ◽  
Binary Pulsars ◽  
Weber Type ◽  
Long Term Observation

The gravitational waves (GWs) emitted by binary pulsars have very long periods, and are buried within the terrestrial noise. We propose to shift their signals to higher frequency by modulating the amplitude, using a resonant of the Weber type on a rotating platform, and using phase locked detection. We evaluate orders of magnitude of the expected sensitivity and noise. The results show that the signals from PSRB1913 + 16 can be detected by long term observation and digital spectral filtering with a small, rather inexpensive antenna.

Pulsar timing and relativistic gravity

1992 ◽  
Vol 341 (1660) ◽  
pp. 117-134 ◽  
Keyword(s):  
Gravitational Waves ◽  
Binary Systems ◽  
Strong Field ◽  
Low Frequency ◽  
Rate Of Change ◽  
Pulsar Timing ◽  
Basic Physics ◽  
Time Standards ◽  
The Universe

In addition to being fascinating objects to study in their own right, pulsars are exquisite tools for probing a variety of issues in basic physics. Recycled pulsars, thought to have been spun up in previous episodes of mass accretion from orbiting companion stars, are especially well suited for such applications. They are extraordinarily stable clocks, approaching and perhaps exceeding the long-term stabilities of the best terrestrial time standards. Most of them are found in binary systems, with orbital velocities as large as 10 -3 c. They provide unique opportunities for measuring neutron star masses, thereby yielding fundamental astrophysical data difficult to acquire by any other means. And they open the way for high precision tests of the nature of gravity under conditions much more ‘relativistic ’ than found anywhere within the Solar System. Among other results, pulsar timing observations have convincingly established the existence of quadrupolar gravitational waves propagating at the speed of light. They have also placed interesting limits on possible departures of the strong-field nature of gravity from general relativity, on the rate of change of Newton’s constant, G , and on the energy density of low-frequency gravitational waves in the universe.

scholarly journals Binary pulsars and tests of general relativity

2009 ◽  
Vol 5 (S261) ◽  
pp. 218-227 ◽  
Author(s):  
I. H. Stairs
Keyword(s):  
General Relativity ◽  
Neutron Star ◽  
White Dwarf ◽  
Strong Field ◽  
Binding Energies ◽  
Tests Of General Relativity ◽  
Binary Pulsars ◽  
The Difference

AbstractBinary pulsars are a valuable laboratory for gravitational experiments. Double-neutron-star systems such as the double pulsar provide the most stringent tests of strong-field gravity available to date, while pulsars with white-dwarf companions constrain departures from general relativity based on the difference in gravitational binding energies in the two stars. Future observations may open up entirely new tests of the predictions of general relativity.

scholarly journals Relativistic effect of gravitational deflection of light in binary pulsars

1996 ◽  
Vol 160 ◽  
pp. 131
Author(s):  
Oleg V. Doroshenko ◽  
Sergei M. Kopeikin
Keyword(s):  
Gravitational Field ◽  
Strong Field ◽  
Alternative Theories Of Gravity ◽  
Estimation Of Parameters ◽  
Orbital Inclination ◽  
Binary Pulsars ◽  
Deflection Of Light ◽  
Shapiro Effect ◽  
Gravitational Deflection Of Light ◽  
Gravitational Deflection

Timing formula for data processing of observations of binary pulsars that accounts for the relativistic deflection of light in the gravitational field of the pulsar’s companion is presented, and the measurability of this effect along with its variance estimates is discussed. The deflection of the pulsar’s pulse trajectory in the gravitational field of its companion leads to variation in the pulsar’s rotational phase. This variation appears as a narrow sharp growth of the magnitude of the post-fit residuals in the vicinity of the moment of the superior conjunction of the pulsar with its companion. In contrast to the relativistic Shapiro effect, the amplitude of the effect of gravitational deflection of the pulsar radio beam has two peaks with opposite signs, which become sharper as the inclinationiof the pulsar’s orbit approaches to the right angle. The effect under consideration influences the estimation of parameters of the relativistic Shapiro effect in the binary pulsars with nearly edgewise orbits. Its inclusion in the fitting procedure provides a more careful measurement of the sine of the orbital inclinationi, as well as the masses of the pulsar and its companion. This permits an improved testing of alternative theories of gravity in the strong field regime. The effect of the gravitational deflection of light has been numerically investigated for binary pulsars with nearly edgewise orbits. It is shown that the effect is observed in general only when cosi is less than 0.003. This estimate becomes less restrictive as the pulsar’s spin axis approaches the line of sight.

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