Atoms

The field of matter wave interferometry is rapidly advancing on multiple frontiers [...]

We explore the parameter space of the pvCD-Bonn B potential within the relativistic Brueckner–Hartree–Fock framework under the constraints from the empirical saturation properties of symmetric nuclear matter. We first examined the effects of the scalar-meson and pion coupling constants. Changing the $\sigma$-meson couplings in the ${}^{1}S_0$ and ${}^{3}S_1$–${}^{3}D_1$ channels alone cannot reproduce the empirical saturation density and binding energy at the same time, whereas increasing $g_{\pi }$ moves the saturation point toward the empirical region. However, changing $g_{\pi }$ alone also affects the deuteron properties and tensor-sensitive observables. We therefore extended the parameter search by varying the $\rho$-meson tensor coupling $f_{\rho }/g_{\rho }$ and readjusting the effective $\sigma$-meson couplings in the ${}^{1}S_0$ and ${}^{3}P_0$ channels. Four representative parameter sets with –15.0 give deuteron properties close to the experimental values and maintain a reasonable description of the main neutron–proton phase shifts and differential cross sections at $E_{\mathrm{lab}}=50$ and 212 MeV. Their saturation densities lie in the range $0.159$–$0.161{\mathrm{fm}}^{-3}$, with saturation energies between $-15.00$ and $-15.38\mathrm{MeV}$. For the interactions obtained by varying $g_{\pi }$, the neutron-star mass–radius relations show only a weak dependence on the pion coupling, with maximum masses of about $2.24$–$2.28M_{\odot }$ and radii of about $12.3$–$12.6\mathrm{km}$ at $1.4M_{\odot }$. These results show that including the $\rho$-meson tensor coupling and partial-wave-dependent $\sigma$-meson couplings provides a better balance between free-space two-nucleon observables and nuclear-matter saturation properties than varying the pion coupling alone.

An empirical model of the TU Muscae binary star system has been developed by a study of 23 high resolution SWP spectrophotometric images that were obtained with the International Ultraviolet Explorer (IUE) satellite telescope including some that were downloaded from the NASA/MAST IUE Archive. The images are well distributed in Keplerian orbital phase thereby permitting a simultaneous fitting of the C IV wind-line profile by the SEI method and the light curve for the blanketed continuum (1450–1490 Å) bandpass by means of a program developed by the author. The result is a set of parameters characterizing the physical and geometric properties of the wind envelopes surrounding the stars. Surprisingly, there is no evidence for a P Cygni profile or strong, distinguishable shock front in the system, as has been found for similar investigations of EM Carinae and HD 159176. This is probably a result of the contact nature of the binary and the high-temperature environment of such a shock. That is, most of the carbon ions in the shock are more highly ionized. Based on the parameters for the SEI fit to the C IV profile, the value for the ionization fraction of C IV in the wind was calculated to be 10⁻⁴. With this value, the mass loss rate, Ṁ, calculated from two independent equations, was found to be about 10⁻⁶ solar masses per year (M_ʘ/yr). The UV line blanketing in the 1500 to 1600 Ångstrom bandpass was found to be erratically variable with orbital phase and time, indicating a variable amount of fast moving, dense clouds in the winds and/or a great amount of turbulence. The meaning of rotational velocities for the stars is problematic and depends on what point on the photospheres one is considering.