scholarly journals Testing the Strong Equivalence Principle in strong field regimes

1996 ◽  
Vol 160 ◽  
pp. 123-124
Author(s):  
Norbert Wex
Keyword(s):  
Neutron Star ◽  
White Dwarf ◽  
Equivalence Principle ◽  
Binary Systems ◽  
Strong Field ◽  
Functional Dependence ◽  
Binary Star ◽  
Inertial Mass ◽  
Small Eccentricity ◽  
Strong Equivalence Principle

A possible functional dependence of the ratio of ‘gravitational’ massmGand ‘inertial’ massmIon the gravitational self-energyEG,is called aviolation of the Strong Equivalence Principle (SEP).Weakly self-gravitating bodies are found in the solar system where lunarlaser-ranging data restrict the Nordtvedt parameter η to absolute values smaller than 0.001, (Dickey et al. 1994, Müller et al. 1995). To test higher order contributions one needs to consider strongly self-gravitating bodies such as neutron-stars.Small-eccentricity binary-star systems consisting of a neutron star (|EG|/mc2~ 0.15) and a white dwarf (|EG|/mc2~ 10−4) are excellent ‘laboratories’ to test the SEP in a strong-field regime. As shown by Damour and Schäfer (1991) a violation of the SEP would lead to a periodic change in the eccentricity of the orbit of the binary pulsar caused by the galactic acceleration. Thus the observation of old small-eccentricity long-orbital-period neutron-star white-dwarf binary systems put (with a certain confidence level) a limit on the violation of the SEP.

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 An improved test of the strong equivalence principle with the pulsar in a triple star system

2020 ◽  
Vol 638 ◽  
pp. A24 ◽  
Author(s):  
G. Voisin ◽  
I. Cognard ◽  
P. C. C. Freire ◽  
N. Wex ◽  
L. Guillemot ◽  
...  
Keyword(s):  
Equivalence Principle ◽  
Strong Field ◽  
Stellar System ◽  
Sampled Data ◽  
Theory Of Relativity ◽  
Data Set ◽  
Orbital Parameters ◽  
Timing Model ◽  
The Masses ◽  
Strong Equivalence Principle

Context. The gravitational strong equivalence principle (SEP) is a cornerstone of the general theory of relativity (GR). Hence, testing the validity of SEP is of great importance when confronting GR, or its alternatives, with experimental data. Pulsars that are orbited by white dwarf companions provide an excellent laboratory, where the extreme difference in binding energy between neutron stars and white dwarfs allows for precision tests of the SEP via the technique of radio pulsar timing. Aims. To date, the best limit on the validity of SEP under strong-field conditions was obtained with a unique pulsar in a triple stellar system, PSR J0337+1715. We report here on an improvement of this test using an independent data set acquired over a period of 6 years with the Nançay radio telescope. The improvements arise from a uniformly sampled data set, a theoretical analysis, and a treatment that fixes some short-comings in the previously published results, leading to better precision and reliability of the test. Methods. In contrast to the previously published test, we use a different long-term timing data set, developed a new timing model and an independent numerical integration of the motion of the system, and determined the masses and orbital parameters with a different methodology that treats the parameter Δ, describing a possible strong-field SEP violation, identically to all other parameters. Results. We obtain a violation parameter Δ = ( + 0.5 ± 1.8) × 10−6 at 95% confidence level, which is compatible with and improves upon the previous study by 30%. This result is statistics-limited and avoids limitation by systematics as previously encountered. We find evidence for red noise in the pulsar spin frequency, which is responsible for up to 10% of the reported uncertainty. We use the improved limit on SEP violation to place constraints on a class of well-studied scalar-tensor theories, in particular we find ωBD >  140 000 for the Brans-Dicke parameter. The conservative limits presented here fully take into account current uncertainties in the equation for state of neutron-star matter.

scholarly journals Collapse of White Dwarfs in Close Binary Systems

1979 ◽  
Vol 53 ◽  
pp. 52-55
Author(s):  
R. Canal ◽  
J. Isern
Keyword(s):  
Neutron Star ◽  
White Dwarf ◽  
Binary Systems ◽  
Critical Density ◽  
Close Binary ◽  
Type I ◽  
X Ray ◽  
Close Binary Systems ◽  
Chandrasekhar Limit ◽  
Thermonuclear Runaway

The presence of neutron stars in close binary systems, shown by the pulsating X-ray sources, poses the problem of their origin. In the case of the low-mass (M1 + M2 ≤ 5 M⊙) X-ray binaries, the neutron star might have originated from a massive white dwarf, driven over the Chandrasekhar limit by mass transfer (Schatzman 1974). A similar scenario had been put forward by Whelan and Iben (1973) for type I supernovae. To solve the problem of the very low eccentricities observed for the orbits, and to facilitate keeping the system bound after neutron star formation, Canal and Schatzman (1976) suggested a non explosive collapse of the white dwarf to a neutron star. The occurence of this kind of collapse depended on the possibility of avoiding thermonuclear ignition by means of neutronization. Since there is a density interval where the electron captures on carbon go faster than the pycnonuclear reactions, just above the critical density for the beginning of the collapse, there seemed also to be a chance of escape from thermonuclear runaway. A closer examination of this picture leads, however, to significant changes.

scholarly journals What binary systems are the most likely sources for periodically repeating FRBs?

2020 ◽  
Vol 498 (1) ◽  
pp. L1-L5
Author(s):  
Xianfei Zhang ◽  
He Gao
Keyword(s):  
Neutron Star ◽  
Birth Rate ◽  
Binary Systems ◽  
Binary Star ◽  
Synthesis Method ◽  
Strong Wind ◽  
Population Synthesis ◽  
Period Range ◽  
Companion Star ◽  
Rate Requirement

ABSTRACT The newly discovered 16.35-d period for repeating FRB 180916.J0158+65 provides an essential clue for understanding the sources and emission mechanism of repeating fast radio bursts (FRBs). Many models propose that the periodically repeating FRBs might be related to binary star systems that contain at least one neutron star (NSC-FRB system). It has been suggested that the neutron star ‘combed’ by the strong wind from a companion star might provide a solution. Following the binary comb model, we use the population synthesis method to study in detail the properties of the companion stars and the nature of NSC-FRB systems. Our main findings are as follows: (1) the companion star is most likely to be a B-type star; (2) the period of 16 d of FRB 180916 happens to fall in the most probable period range, which may explain why FRB 180916 was the first detected periodically repeating FRB, and we expect to observe more periodically repeating FRBs with periods around 10–30 d; and (3) the birth rate for the NSC-FRB system is large enough to fulfill the event rate requirement set by the observation of FRB 180916, which supports the proposal that the NSC-FRB can provide one significant channel for producing periodically repeating FRBs.

scholarly journals Simulation of Formation of Binary Compact Objects in Globular Cluster

2021 ◽  
Vol 2068 (1) ◽  
pp. 012049
Author(s):  
Yangyang Deng ◽  
Zhongmu Li ◽  
Wen Chen
Keyword(s):  
Neutron Star ◽  
Globular Cluster ◽  
White Dwarf ◽  
Binary Systems ◽  
Probability Of Detection ◽  
Compact Objects ◽  
Dynamic Interactions ◽  
Simulation Code ◽  
Wave Detection ◽  
Binary Evolution

Abstract Binary compact objects are the special binary systems, which were composed of compact objects (i.e., white dwarf, neutron star and black hole). They contribute a lot to the sources of gravitational waves. The study of binary compact objects in star clusters and galaxies can provide a theoretical guidance for gravitational wave detection and improve the probability of detection effectively. We simulate the formation and fraction of binary compact objects in a small globular cluster, via NBODY6++GPU, an efficient N-body simulation code. We obtain the fractions of white dwarf binaries and neutron star binaries at different ages. The results show that the dynamic interactions among stars can also result in some binary compact objects besides binary evolution.

scholarly journals Binary X-Ray Stars and Supernovae of Type I

1976 ◽  
Vol 73 ◽  
pp. 19-25
Author(s):  
H. Gursky
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
White Dwarf ◽  
Binary Systems ◽  
Close Binary ◽  
Type I ◽  
Mass Limit ◽  
X Ray ◽  
Close Binary Systems ◽  
Low Mass

Most of the strong galactic X-ray sources must be low mass, close binary systems, such as Her X-1 and Sco X-1. Two evolutionary scenarios are discussed, both involving type I supernovae that occur when mass-accreting white dwarfs are driven over their mass limit. In one, accepting the correctness of the idea that a neutron star or black hole is the seat of the X-ray emission, the SN occurs before the system is an X-ray source. Another possibility is that the white dwarf is the X-ray source, just prior to its collapse and the ensuing SN.

scholarly journals Interpreting binary neutron star mergers: describing the binary neutron star dynamics, modelling gravitational waveforms, and analyzing detections

2021 ◽  
Vol 53 (3) ◽  
Author(s):  
Tim Dietrich ◽  
Tanja Hinderer ◽  
Anuradha Samajdar
Keyword(s):  
Neutron Star ◽  
Gravitational Wave ◽  
Binary Systems ◽  
Strong Field ◽  
Fundamental Physics ◽  
Binary Neutron Star ◽  
Compact Binary ◽  
Dynamics Modelling ◽  
Numerical Approaches ◽  
Extract Information

AbstractGravitational waves emitted from the coalescence of neutron star binaries open a new window to probe matter and fundamental physics in unexplored, extreme regimes. To extract information about the supranuclear matter inside neutron stars and the properties of the compact binary systems, robust theoretical prescriptions are required. We give an overview about general features of the dynamics and the gravitational wave signal during the binary neutron star coalescence. We briefly describe existing analytical and numerical approaches to investigate the highly dynamical, strong-field region during the merger. We review existing waveform approximants and discuss properties and possible advantages and shortcomings of individual waveform models, and their application for real gravitational-wave data analysis.

scholarly journals A Machine Learning Approach For Classifying Low-mass X-ray Binaries Based On Their Compact Object Nature

2020 ◽  
Author(s):  
R Pattnaik ◽  
K Sharma ◽  
K Alabarta ◽  
D Altamirano ◽  
M Chakraborty ◽  
...  
Keyword(s):  
Machine Learning ◽  
Black Hole ◽  
Neutron Star ◽  
Binary Systems ◽  
Compact Object ◽  
X Ray ◽  
Average Accuracy ◽  
Machine Learning Approach ◽  
Low Mass ◽  
X Ray Binaries

Abstract Low Mass X-ray binaries (LMXBs) are binary systems where one of the components is either a black hole or a neutron star and the other is a less massive star. It is challenging to unambiguously determine whether a LMXB hosts a black hole or a neutron star. In the last few decades, multiple observational works have tried, with different levels of success, to address this problem. In this paper, we explore the use of machine learning to tackle this observational challenge. We train a random forest classifier to identify the type of compact object using the energy spectrum in the energy range 5-25 keV obtained from the Rossi X-ray Timing Explorer archive. We report an average accuracy of 87±13% in classifying the spectra of LMXB sources. We further use the trained model for predicting the classes for LMXB systems with unknown or ambiguous classification. With the ever-increasing volume of astronomical data in the X-ray domain from present and upcoming missions (e.g., SWIFT, XMM-Newton, XARM, ATHENA, NICER), such methods can be extremely useful for faster and robust classification of X-ray sources and can also be deployed as part of the data reduction pipeline.

Aspects of the Collapse of Compact Objects

1980 ◽  
Vol 4 (1) ◽  
pp. 49-50
Author(s):  
R. A. Gingold ◽  
J. J. Monaghan
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
White Dwarf ◽  
Compact Objects ◽  
Dwarf Star

Misner Thorne and Wheeler (1973), (page 629) suggested that a freshly formed White Dwarf star of several solar masses would, if slowly — rotating, collapse to form a neutron star pancake which would become unstable and eventually produce several, possibly colliding, neutron stars.

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