scholarly journals An Improved Numerical Fit to the Peak Harmonic Gravitational Wave Frequency Emitted by an Eccentric Binary

2021 ◽  
Vol 5 (11) ◽  
pp. 275
Author(s):  
Adrian S. Hamers
Keyword(s):  
Binary System ◽  
Gravitational Wave ◽  
Wave Frequency ◽  
Population Synthesis ◽  
Newtonian Approximation ◽  
Numerical Fit

Abstract I present a numerical fit to the peak harmonic gravitational wave frequency emitted by an eccentric binary system in the post-Newtonian approximation. This fit significantly improves upon a previous commonly-used fit in population synthesis studies, in particular for eccentricities ≲0.8.

scholarly journals Weighing in on black hole binaries with bpass: LB-1 does not contain a 70 M⊙ black hole

2020 ◽  
Vol 495 (3) ◽  
pp. 2786-2795 ◽  
Author(s):  
J J Eldridge ◽  
E R Stanway ◽  
K Breivik ◽  
A R Casey ◽  
D T H Steeghs ◽  
...  
Keyword(s):  
Black Hole ◽  
Binary System ◽  
Current Understanding ◽  
Stellar Winds ◽  
Population Synthesis ◽  
Distance Determination ◽  
Black Hole Binaries ◽  
Binary Evolution

ABSTRACT The recent identification of a candidate very massive (70 M⊙) black hole (BH) is at odds with our current understanding of stellar winds and pair-instability supernovae. We investigate alternate explanations for this system by searching the bpass v2.2 stellar and population synthesis models for those that match the observed properties of the system. We find binary evolution models that match the LB-1 system, at the reported Gaia distance, with more moderate BH masses of 4–7 M⊙. We also examine the suggestion that the binary motion may have led to an incorrect distance determination by Gaia. We find that the Gaia distance is accurate and that the binary system is consistent with the observation at this distance. Consequently, it is highly improbable that the BH in this system has the extreme mass originally suggested. Instead, it is more likely to be representative of the typical BH binary population expected in our Galaxy.

scholarly journals Measuring the eccentricity of GW170817 and GW190425

2020 ◽  
Vol 497 (2) ◽  
pp. 1966-1971 ◽  
Author(s):  
Amber K Lenon ◽  
Alexander H Nitz ◽  
Duncan A Brown
Keyword(s):  
Parameter Estimation ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Matched Filter ◽  
Wave Frequency ◽  
Limited Information ◽  
Binary Neutron Star ◽  
Wave Emission

ABSTRACT Two binary neutron star mergers, GW170817 and GW190425, have been detected by Advanced LIGO and Virgo. These signals were detected by matched-filter searches that assume that the star’s orbit has circularized by the time their gravitational-wave emission is observable. This suggests that their eccentricity is low, but full parameter estimation of their eccentricity has not yet been performed. We use gravitational-wave observations to measure the eccentricity of GW170817 and GW190425. We find that the eccentricity at a gravitational-wave frequency of 10 Hz is e ≤ 0.024 and e ≤ 0.048 for GW170817 and GW190425, respectively (90 per cent confidence). This is consistent with the binaries being formed in the field, as such systems are expected to have circularized to e ≤ 10−4 by the time they reach the LIGO–Virgo band. Our constraint is a factor of 2 smaller that an estimate based on GW170817 being detected by searches that neglect eccentricity. However, we caution that we find significant prior dependence in our limits, suggesting that there is limited information in the signals. We note that other techniques used to constrain binary neutron star eccentricity without full parameter estimation may miss degeneracies in the waveform, and that for future signals, it will be important to perform full parameter estimation with accurate waveform templates.

scholarly journals Masses of double neutron star mergers

2020 ◽  
Vol 639 ◽  
pp. A123 ◽  
Author(s):  
Matthias U. Kruckow
Keyword(s):  
Neutron Star ◽  
Gravitational Wave ◽  
Milky Way ◽  
Radio Pulsar ◽  
Population Synthesis ◽  
Radio Pulsars ◽  
Wave Observation ◽  
Binary Evolution ◽  
Star Binary

Aims. I aim to explain the mass discrepancy between the observed double neutron-star binary population by radio pulsar observations and gravitational-wave observation. Methods. I performed binary population synthesis calculations and compared their results with the radio and the gravitational-wave observations simultaneously. Results. Simulations of binary evolution were used to link different observations of double neutron star binaries with each other. I investigated the progenitor of GW190425 in more detail. A distribution of masses and merger times of the possible progenitors is presented. Conclusions. A mass discrepancy between the radio pulsars in the Milky Way with another neutron star companion and the inferred masses from gravitational-wave observations of those kind of merging systems is naturally found in binary evolution.

scholarly journals Relativistic Equation Failure for LIGO Signals

2021 ◽  
Author(s):  
XD Dongfang
Keyword(s):  
Numerical Calculation ◽  
Gravitational Wave ◽  
Binary Stars ◽  
Frequency Equation ◽  
Wave Frequency ◽  
Signal Wave ◽  
Frequency Change ◽  
Wave Source ◽  
Change Rate ◽  
Equation Group

Signal waves of the monotone increasing frequency detected by LIGO are universally considered to be gravitational waves of spiral binary stars, and the general theory of relativity is thus universally considered to have been confirmed by the experiments. Here we present a universal method for signal wave spectrum analysis, introducing the true conclusions of numerical calculation and image analysis of GW150914 signal wave. Firstly, numerical calculation results of GW150914 signal wave frequency change rate obey the com quantization law which needs to be accurately described by integers, and there is an irreconcilable difference between the results and the generalized relativistic frequency equation of the gravitational wave. Secondly, the assignment of the frequency and frequency change rate of GW10914 signal wave to the generalized relativistic frequency equation of gravitational wave constructs a non-linear equation group about the mass of wave source, and the computer image solution shows that the equation group has no GW10914 signal wave solution. Thirdly, it is not unique to calculate the chirp mass of the wave source from the different frequencies and change rates of the numerical relativistic waveform of the GW150914 signal wave, and the numerical relativistic waveform of the GW150914 signal wave deviates too far from the original waveform actually. Other LIGO signal waveforms do not have obvious characteristics of gravitational frequency variation of spiral binary stars and lack precise data, so they cannot be used for numerical analysis and image solution. Therefore, LIGO signals represented by gw50914 signal do not support the relativistic gravitational wave frequency equation. However, whether gravitational wave signals from spiral binaries that may be detected in the future follow the same co quantization law? The answer is not clear at present.

scholarly journals Estimating the Chirp Mass of Eccentric Inspiraling Binary Systems from Time-Frequency Representations of their Gravitational Radiation

2021 ◽  
Vol 2081 (1) ◽  
pp. 012008
Author(s):  
Innocenzo M Pinto
Keyword(s):  
Binary System ◽  
Gravitational Wave ◽  
Gravitational Radiation ◽  
Binary Systems ◽  
Estimation Algorithm ◽  
Orbital Eccentricity ◽  
Reference Time ◽  
Time Frequency ◽  
Compact Binary ◽  
Non Gaussian

Abstract Using the simplest yet meaningful Peters-Mathews model describing the orbital damping of a compact binary system under the emission of gravitatonal radiation, we show that the chirp-mass of an eccentric inspiraling binary, and its (Keplerian) orbital eccentricity at some reference time, can be estimated from the time-frequency skeleton of its gravitational wave signal. The estimation algorithm is nicely simple, and is robust against the non-ideal (non Gaussian, non stationary) features of detector noise.

scholarly journals Contamination of RR Lyrae stars from Binary Evolution Pulsators

2015 ◽  
Vol 5 (1) ◽  
pp. 24-28
Author(s):  
P. Karczmarek
Keyword(s):  
Mass Transfer ◽  
Binary System ◽  
Synthesis Method ◽  
Population Synthesis ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Low Mass ◽  
Binary Evolution ◽  
Lyrae Stars ◽  
Range Of Values

A Binary Evolution Pulsator (BEP) is a low-mass (0.26 𝔐☉) member of a binary system, which pulsates as a result of a former mass transfer to its companion. The BEP mimics RR Lyrae-type pulsations, but has completely different internal structure and evolution history. Although there is only one known BEP (OGLE-BLG-RRLYR-02792), it has been estimated that approximately 0.2% of objects classified as RR Lyrae stars can be undetected Binary Evolution Pulsators. In the present work, this contamination value is re-evaluated using the population synthesis method. The output falls inside a range of values dependent on tuning the parameters in the StarTrack code, and varies from 0.06% to 0.43%.

scholarly journals Population synthesis of accreting neutron stars emitting gravitational waves

2019 ◽  
Vol 488 (1) ◽  
pp. 99-110 ◽  
Author(s):  
Fabian Gittins ◽  
Nils Andersson
Keyword(s):  
Neutron Stars ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Population Synthesis ◽  
Spin Distribution ◽  
Synthetic Populations ◽  
Low Mass ◽  
Wave Emission ◽  
X Ray Binaries ◽  
Production Mechanisms

ABSTRACT The fastest-spinning neutron stars in low-mass X-ray binaries, despite having undergone millions of years of accretion, have been observed to spin well below the Keplerian break-up frequency. We simulate the spin evolution of synthetic populations of accreting neutron stars in order to assess whether gravitational waves can explain this behaviour and provide the distribution of spins that is observed. We model both persistent and transient accretion and consider two gravitational-wave-production mechanisms that could be present in these systems: thermal mountains and unstable rmodes. We consider the case of no gravitational-wave emission and observe that this does not match well with observation. We find evidence for gravitational waves being able to provide the observed spin distribution; the most promising mechanisms being a permanent quadrupole, thermal mountains, and unstable r modes. However, based on the resultant distributions alone, it is difficult to distinguish between the competing mechanisms.

scholarly journals Origin of spin–orbit misalignments: the microblazar V4641 Sgr

2020 ◽  
Vol 495 (2) ◽  
pp. 2179-2204 ◽  
Author(s):  
Greg Salvesen ◽  
Supavit Pokawanvit
Keyword(s):  
Black Hole ◽  
Binary System ◽  
Compact Object ◽  
Alternative Interpretation ◽  
Spin Orbit ◽  
Population Synthesis ◽  
Common Envelope ◽  
Black Hole Spin ◽  
Relativistic Jet ◽  
Jet Axis

ABSTRACT Of the known microquasars, V4641 Sgr boasts the most severe lower limit (>52°) on the misalignment angle between the relativistic jet axis and the binary orbital angular momentum. Assuming the jet and black hole spin axes coincide, we attempt to explain the origin of this extreme spin–orbit misalignment with a natal kick model, whereby an aligned binary system becomes misaligned by a supernova kick imparted to the newborn black hole. The model inputs are the kick velocity distribution, which we measure customized to V4641 Sgr, and the immediate pre/post-supernova binary system parameters. Using a grid of binary stellar evolution models, we determine post-supernova configurations that evolve to become consistent with V4641 Sgr today and obtain the corresponding pre-supernova configurations by using standard prescriptions for common envelope evolution. Using each of these potential progenitor system parameter sets as inputs, we find that a natal kick struggles to explain the origin of the V4641 Sgr spin–orbit misalignment. Consequently, we conclude that evolutionary pathways involving a standard common envelope phase followed by a supernova kick are highly unlikely for V4641 Sgr. An alternative interpretation is that the jet axis does not reliably trace the black hole spin axis. Our results raise concerns about compact object merger statistics gleaned from binary population synthesis models, which rely on unverified prescriptions for common envelope evolution and natal kicks. We also challenge the spin–orbit alignment assumption routinely invoked to measure black hole spin magnitudes.

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