Population synthesis of double neutron stars Osłowski, S.; Bulik, T.; Gondek-Rosińska, D. ...
Monthly Notices of the Royal Astronomical Society,
20/May , Letnik:
413, Številka:
1
Journal Article
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Using the StarTrack binary population synthesis code we model the population of double neutron stars in the Galaxy. We include a detailed treatment of the spin evolution of each pulsar due to ...processes such as spin-down and spin-up during accretion events as well as magnetic field decay. We also model the spatial distribution of double neutron stars by including their natal kicks and subsequent propagation in the Galactic gravitational potential. This synthetic pulsar population is compared to the observed sample of double neutron stars taking into account the selection effects of detection in the radio band, to determine the most likely evolutionary parameters. With these parameters we determine the properties of the double neutron star binaries detectable in gravitational waves by the high-frequency interferometers LIGO and VIRGO. In particular, we discuss the distributions of chirp masses and mass ratios in samples selected by their radio or gravitational wave emission.
We study the main astrophysical properties of differentially rotating neutron stars described as stationary and axisymmetric configurations of a moderately stiff Γ = 2 polytropic fluid. The high ...level of accuracy and of stability of our relativistic multidomain pseudo-spectral code enables us to explore the whole solution space for broad ranges of the degree of differential rotation, but also of the stellar density and oblateness. Staying within an astrophysically motivated range of rotation profiles, we investigate the characteristics of neutron stars with maximal mass for all types of families of differentially rotating relativistic objects identified in a previous article. We find that the maximum mass depends on both the degree of differential rotation and the type of solution. It turns out that the maximum allowed mass can be up to 4 times higher than what it is for nonrotating stars with the same equation of state. Such values are obtained for a modest degree of differential rotation but for one of the newly discovered types of solutions. Since such configurations of stars are not that extreme, this result may have important consequences for the gravitational wave signal expected from coalescing neutron star binaries or from some supernova events.
Summary of the long term data taking, related to one of the proposed next generation ground-based gravitational detector’s location is presented here. Results of seismic and infrasound noise, ...electromagnetic attenuation and cosmic muon radiation measurements are reported in the underground Matra Gravitational and Geophysical Laboratory near Gyöngyösoroszi, Hungary. The collected seismic data of more than two years is evaluated from the point of view of the Einstein Telescope, a proposed third generation underground gravitational wave observatory. Applying our results for the site selection will significantly improve the signal to noise ratio of the multi-messenger astrophysics era, especially at the low frequency regime.
Knowing the value of the maximum mass of a differentially rotating relativistic star is a key step towards the understanding of the signals to be expected from the merger of binary neutron stars, one ...of the most awaited alternative sources of gravitational waves after binary black holes. In this paper, we study the effects of differential rotation and of the equation of state on the maximum mass of rotating neutron stars modelled as relativistic polytropes with various adiabatic indices. Calculations are performed using a highly accurate numerical code, based on a multidomain spectral method. We thoroughly explore the parameter space and determine how the maximum mass depends on the stiffness, on the degree of differential rotation and on the maximal density, taking into account all the types of solutions that were proven to exist in a preceding paper. The highest increase with respect to the maximum mass for non-rotating stars with the same equation of state is reached for a moderate stiffness. With differential rotation, the maximum mass can even be 3-4 times higher than it is for static stars. This result may have important consequences for the gravitational wave signal from coalescing neutron star binaries or for some supernovae events.
We present analytical formulae for the orbital and epicyclic frequencies in orbits around Maclaurin spheroids in Newtonian gravity. The Laplace equation for the gravitational potential implies that ...the orbital frequency squared is the arithmetic mean of the squares of the epicyclic frequencies,
. The radial epicyclic frequency has a maximum at radius
for spheroid ellipticities
1/\sqrt{2}$>
, while for e = 0.834 583 18 it vanishes at the stellar equator (at r = a). For still larger ellipticities the innermost stable circular orbit (ISCO) is separated from the surface of the spheroid by a gap and has radius r
ms = 1.198 203 ae. The vertical epicyclic frequency is always larger than the orbital one, and always by a factor of
in the marginally stable orbit. The presence of periastron motion, nodal precession (whose sense is the same as in retrograde orbits in the Kerr metric) and of the ISCO makes the properties of orbital motion around Maclaurin spheroids analogous to those in the Kerr metric. We find that the condition for the existence of circular orbits in test-particle motion is
0$>
, equally for the Maclaurin spheroid and for the Kerr metric.
We study the viscosity driven bar mode (Jacobi-like) instability of rapidly rotating quark matter stars (strange stars) in general relativity. A triaxial, “bar shaped” compact star could be an ...efficient source of continuous wave gravitational radiation in the frequency range of the forthcoming interferometric detectors. We locate the secular instability point along several constant baryon mass sequences of uniformly rotating strange stars described by the MIT bag model. Contrary to neutron stars, strange stars with $T/|W|$ (the ratio of the rotational kinetic energy to the absolute value of the gravitational potential energy) much lower than the corresponding value for the mass-shed limit can be secularly unstable to bar mode formation if shear viscosity is high enough to damp out any deviation from uniform rotation. The instability develops for a broad range of gravitational masses and rotational frequencies of strange quark stars. It imposes strong constraints on the lower limit of the frequency at the innermost stable circular orbit around rapidly rotating strange stars. The above results are robust for all linear self-bound equations of state assuming the growth time of the instability is faster than the damping timescale. Whether the instability can grow or not depends on many different physical quantities (e.g. value of viscosities (rather uncertain)). We discuss astrophysical scenarios where triaxial instabilities (r-mode and viscosity driven instability) could be relevant (a new born star, an old star spinning up by accretion) in strange stars described by the standard MIT bag model of normal quark matter. The spin evolution of a strange star strongly depends on the strange quark mass. Taking into account actual values of viscosities in strange quark matter and neglecting the magnetic field we show that Jacobi-like instability cannot develop in any astrophysicaly relevant temperature windows. The main result is that strange quark stars described by the MIT bag model can be accelerated to very high frequency in Low Mass X-ray binaries if the strange quark mass is consistent with values based on particle data tables.
Context. The current gravitational wave detectors have reached their operational sensitivity and are nearing detection of compact object binaries. In the coming years, we expect that the Advanced ...LIGO/VIRGO will start taking data. At the same time, there are plans for third generation ground-based detectors such as the Einstein Telescope, and space detectors such as DECIGO. Aims. We discuss the eccentricity distribution of inspiral compact object binaries during they inspiral phase. We analyze the expected distributions of eccentricities at three frequencies that are characteristic of three future detectors: Advanced LIGO/VIRGO (30 Hz), Einstein Telescope (3 Hz), and DECIGO (0.3 Hz). Methods. We use the StarTrack binary population code to investigate the properties of the population of compact binaries in formation. We evolve their orbits until the point that they enter a given detector sensitivity window and analyze the eccentricity distribution at that time. Results. We find that the eccentricities of BH-BH and BH-NS binaries are quite small when entering the Advanced LIGO/VIRGO detector window for all considered models of binary evolution. Even in the case of the DECIGO detector, the typical eccentricities of BH-BH binaries are below 10-4, and the BH-NS eccentricities are smaller than 10-3. Some fraction of NS-NS binaries may have significant eccentricities. Within the range of considered models, we found that a fraction of between 0.2% and 2% NS-NS binaries will have an eccentricity above 0.01 for the Advanced LIGO/VIRGO detectors. For the ET detector, this fraction is between 0.4% and 4%, and for the DECIGO detector it lies between 2% and 27%.
The main biogenic amines in foods are histamine, tryptamin, cadaverin, putrescin, spermin, and spermidin. The samples of pork, beef, and poultry were extracted with 0.6 mol · l
−1
perchloric acid and ...extract was filtered. Histamine, cadaverine, putrescine, and tyramine were determined by reverse-phase HPLC using a C
18
stationary phase column. Acetate buffer with water (pH 4.5) and acetate buffer with acetonitrile (45/55 v/v) was used as a mobile phase, the flow-rate was 1 mL · min
−1
. The post column derivatization technique with OPT buffer (phthaldialdehyde buffer) as derivatization agent and the fluorescence detector at 330 nm and 465 nm as excitation and emission wavelengths was used. Limit of detection for biogenic amines was 0.2 mg · kg
−1
and limit of quantification was 0.5 mg · kg
−1
. The method was useful over a wide concentration range of biogenic amines. The concentrations from 0.5 to 1 000 mg · kg
−1
of histamine, tyramine, putrescine, and cadaverine in pork, beef, and poultry could be detected easily without any noticed disadvantage. Concentrations of biogenic amines were determined in pork, beef, and poultry and concentrations were increased depending on temperature and time. Concentrations of cadaverine and putrescine were highest for ground meat stored at 24°C after 10 days. Highest influence of temperature on production of biogenic amines was found in poultry samples. The concentrations of tyramine, putrescine and histamine were higher than 100 mg · kg
−1
and the concentration of cadaverine was more than 400 mg · kg
−1
.
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