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Asteroid families are the remnants of catastrophic collisions, and their fundamental physical properties provide us the information of their parent bodies and thereafter dynamical evolutions. Especially, the orbit and spin characteristics can reveal the influences of the Yarkovsky effect and the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect on the evolution of the asteroid family, respectively. Based on the Asteroid Lightcurve Database (LCDB), the spin rate distribution of the Flora asteroid family is studied, and a tendency that the spin rates of the small Flora family members concentrate primarily in the range of 3–5 d−1 is found. The analysis on the spin states of the Flora family asteroids tells that most of these asteroid family members are in the prograde spinning state. However, for the Flora family members with an orbital semi-major axis smaller than 2.2 au, the ratio between the number of prograde spinning members and that of retrograde ones is close to that of the near-Earth asteroids, namely 1 : 3. Furthermore, for those prograde spinning Flora family asteroids with an orbital semi-major axis larger than 2.2 au, a portion of them exhibit the aggregation in the distribution of orbital semi-major axis against the absolute magnitude, and in which nine members show the features similar to the Slivan state. [ABSTRACT FROM AUTHOR]

Asteroid families are the remnants of catastrophic collisions, and their fundamental physical properties provide us the information of their parent bodies and thereafter dynamical evolutions. Especially, the orbit and spin characteristics can reveal the influences of the Yarkovsky effect and the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect on the evolution of the asteroid family, respectively. Based on the Asteroid Lightcurve Database (LCDB), the spin rate distribution of the Flora asteroid family is studied, and a tendency that the spin rates of the small Flora family members concentrate primarily in the range of 3–5 d−1 is found. The analysis on the spin states of the Flora family asteroids tells that most of these asteroid family members are in the prograde spinning state. However, for the Flora family members with an orbital semi-major axis smaller than 2.2 au, the ratio between the number of prograde spinning members and that of retrograde ones is close to that of the near-Earth asteroids, namely 1 : 3. Furthermore, for those prograde spinning Flora family asteroids with an orbital semi-major axis larger than 2.2 au, a portion of them exhibit the aggregation in the distribution of orbital semi-major axis against the absolute magnitude, and in which nine members show the features similar to the Slivan state. [ABSTRACT FROM AUTHOR]

Abstract: It is difficult to use the single-station satellite laser ranging (SLR) data for orbit determination, due to the singular geometrical distribution of the observations. The single-station data produced by performing the diffuse- reflection SLR on the earth-orbiting space debris are therefore ineffective for orbit improvement. To solve this problem, we propose an orbit determination method by using single-station SLR data in aid of the two-line element set (TLE). For verifying its feasibility, this method is implemented and applied to the orbit determination of the satellite Ajisai, using the single-station SLR data of five passes in one day and the corresponding TLE. And on this basis, the five-day orbit prediction is generated, the result indicates that the errors of predicted positions are less than 40 m. In addition, the potential application of this method in the orbit improvement of space debris is discussed. [Copyright &y& Elsevier]

In this paper, the gauge method for a special spinor field transformation Ψ(x) → Ψ′(x) = exp[(e/m)f(x)γa∂a]Ψ(x) is studied. We demonstrate that the Dirac equation involving electromagnetic interactions can be defined by the gauge method for the spinor field transformation, within the framework of gauge field theory. [ABSTRACT FROM AUTHOR]

In the relativistic mean field approximation, the relativistic energy losses of the nucleon direct Urca processes are studied in the degenerate baryon matter of neutron stars. We investigate the effects of hyperon degrees of freedom and the isovector scalar interaction which is considered by exchanging δ meson on the nucleon direct Urca processes in neutron star matter. The results indicate that the existence of hyperons decreases the abundance of protons and leptons and can sharply suppress the neutrino emissivity of the nucleon direct Urca processes, while it has only a little influence on the neutrino luminosity for a fixed neutron star whether δ mesons appear in a neutron star or not. However, the presence of δ mesons can result in obvious growth in the neutrino emissivity and luminosity which will speed up the cooling rate for the nonsuperfluid neutron star. [ABSTRACT FROM AUTHOR]

The properties of neutron and proton 1S0 superfluidity are studied within the relativistic mean field and the Bardeen-Cooper-Schrieffer theories by taking the effects of K- and K0 condensations into account in neutron star matter without the hyperon degrees of freedom. It is found that antikaon condensations change the Fermi momenta, the effective masses and the single particle energies of nucleons in neutron star matter. These changes lead to a strong suppression of the neutron 1S0 superfluidity and an obvious enhancement of the proton 1S0 superfluidity in neutron star matter, respectively. In particular, the neutron and proton 1S0 pairing gaps are gradually shrinking with the optical potential of antikaons from -80 to -130 MeV. And antikaon condensations have little influence on the neutron 1S0 superfluid range, however, they have been markedly downsized the proton 1S0 superfluid range as the deepening of the optical potential of antikaons in neutron star matter. We also found that the nucleon 1S0 superfluidity and K- condensations within the scope of above optical potential of antikaons can occur in the core of PSR J1614-2230 and PSR J0348+0432 at the same time. Whereas K0 condensations only occur in the two pulsars when the range of optical potential of antikaons is from -100 to -130 MeV. [ABSTRACT FROM AUTHOR]

The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree—Fock approximation. We particularly study the influences of the tensor couplings of vector mesons ω and ρ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons ω and ρ can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons ω and ρ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non-superfluid neutron star matter. However, when considering only the tensor coupling of vector meson ρ, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson ρ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star. [ABSTRACT FROM AUTHOR]

The nucleonic 1 S 0 superfluidity is investigated by solving the gap equation for the Reid soft-core potential as the nucleon–nucleon interaction in neutron star (NS) matter which is considered to be made up of n, p, e, μ and condensed antikaon matter. We mainly study the influence of the soft pion-induced potential on the nucleonic 1 S 0 pairing gaps in the above NS matter. It is found that the intensities of the nucleonic 1 S 0 pairing gaps including the soft pion-induced potential are smaller than those calculated in the case of not including the soft pion-induced potential. Furthermore, the nucleonic 1 S 0 pairing gaps with the soft pion-induced potential fall into decline with the deepening of the optical potential of antikaons in the above NS matter, whereas they increase with the parameter η for the fixed optical potential of antikaons. Due to the appearance of the soft pion-induced potential, the maximum values of nucleonic 1 S 0 pairing gaps at parameter η = 0.20, 0.55 are suppressed by 1.7%–6.8% with respect to the case without soft pion-induced potential in the above NS matter. [ABSTRACT FROM AUTHOR]