On the possibility of disk-fed formation in supergiant high-mass X-ray binaries

We consider the existence of a neutron star magnetic field by the detected cyclotron lines. We collected data on nine sources of high-mass X-ray binaries with supergiant companions as a test case for our model, to demonstrate their distribution and evolution. The wind velocity, spin period and magnetic field strength are studied under different mass loss rates. In our model, correlations between mass-loss rate and wind velocity are found and can be tested in further observations. We examine the parameter space where wind accretion is allowed, avoiding the barrier of rotating magnetic fields, with robust data on the magnetic field of neutron stars. Our model shows that most sources(six of nine systems) can be fed by the wind with relatively slow velocity, and this result is consistent with previous predictions. In a few sources,our model cannot fit the standard wind accretion scenario. In these peculiar cases, other scenarios(disk formation, partial Roche lobe overflow) should be considered. This would provide information about the evolutionary tracks of various types of binaries, and thus exhibit a clear dichotomy behavior in wind-fed X-ray binary systems.

Physical and geometrical parameters of CVBS XIV:the two nearby systems HIP 19206 and HIP 84425

Data release 2(DR2) from the Gaia mission was of great help in precise determination of fundamental parameters of Close Visual Binary and Multiple Systems(CVBMSs), especially masses of their components, which are crucial parameters in understanding formation and evolution of stars and galaxies. This article presents the complete set of fundamental parameters for two nearby close visual binary systems(CVBSs), which are HIP 19206 and HIP 84425. We utilised a combination of two methods;the first one is Tokovinin's dynamical method to solve the orbit of the system and to estimate orbital elements and the dynamical mass sum, and the second one is Al-Wardat's method for analysing CVBMSs to estimate the physical parameters of the individual components. The latest method employs grids of Kurucz lineblanketed plane parallel model atmospheres to build synthetic Spectral Energy Distributions(SEDs) of the individual components. Trigonometric parallax measurements given by Gaia DR2 and Hipparcos catalogues are used to analyse the two systems. The difference in these measurements yielded slight discrepancies in the fundamental parameters of the individual components, especially masses. So, a new dynamical parallax is suggested in this work based on the most convenient mass sum as given by each of the two methods. The new dynamical parallax for the system HIP 19205 of 22.97±0.95 mas coincides well with the trigonometric one reported recently(in December 2020) by Gaia EDR3 of 22.3689 ± 0.4056 mas. The positions of the components of the two systems on the evolutionary tracks and isochrones are plotted, which suggest that all components are solar-type main sequence stars. Their most probable formation and evolution scenarios are also discussed.