The mass of the compact object in the X-ray binary her X-1/HZ her

We have obtained the first estimates of the masses of the components of the Her X-1/HZ Her X-ray binary system taking into account non-LTE effects in the formation of the H _γ absorption line: m _x = 1.8 M _⊙ and m _v = 2.5 M _⊙. These mass estimates were made in a Roche model based on the observed radial-velocity curve of the optical star, HZ Her. The masses for the X-ray pulsar and optical star obtained for an LTE model lie are m _x = 0.85 ± 0.15 M _⊙ and m _v = 1.87 ± 0.13 M _⊙. These mass estimates for the components of Her X-1/HZ Her derived from the radial-velocity curve should be considered tentative. Further mass estimates from high-precision observations of the orbital variability of the absorption profiles in a non-LTE model for the atmosphere of the optical component should be made.     

Influence of Digital Noise on Interpretation of a Transit Light Curve

Astronomy Reports - The algorithms often used for the interpretation of light curves, such as the frequently applied JKTEBOP algorithm, have limited accuracy, which causes rounding errors, and...     

Error estimates for parameters in inverse parametrical problems. Light-curve analysis for classical eclipsing binaries

Parameters and their error intervals numerically estimated for the observed light curve of the binary eclipsing system YZ Cas as well as for one-, two-, three-, and four-parameter functions, and the associated parameters and their error intervals numerically estimated. The error intervals are calculated using differential corrections method, Monte-Carlo simulations, and confidence areas. We study the error intervals and the reliability of the techniques used.     

The mass of the compact object in the X-ray binary 4U 1700-37

The results of a systematic analysis of master radial-velocity curves for the X-ray binary 4U 1700-37 are presented. The dependence of the mass of the X-ray component on the mass of the optical component is derived in a Roche model based on a fit of the master radial-velocity curve. The parameters of the optical star are used to estimate the mass of the compact object in three ways. The masses derived based on information about the surface gravity of the optical companion and various observational data are 2.25 _?0.24 ^+0.23 M_⊙ and 2.14 _?0.56 ^+0.50 M_⊙. The masses based on the radius of the optical star, 21.9R_⊙, are 1.76 _?0.21 ^+0.20 M_⊙ and 1.65 _?0.56 ^+0.78 M_⊙. The mass of the optical component derived from the mass-luminosity relation for X-ray binaries, 27.4M_⊙, yields masses for the compact object of 1.41 _?0.08 ⁺ M_⊙ and 1.35 _?0.18 ^+0.18 M_⊙.     

Analysis of light curves of eclipsing systems with exoplanets: HD 189733

High-accuracy multicolor light curves of the binary system HD 189733, which contains an exoplanet, are analyzed. We have determined the radii of the star and the planet in the binary system, as well as the orbital inclination. The limb-darkening coefficients of the stellar disk were obtained in 10 filters in the wavelength interval λλ = 5500?10 500 Å. The uncertainties of the fitted parameters were estimated using the differential-correction and confidence-area methods. The wavelength dependence of the limb-darkening coefficients is compared to the corresponding theoretical function for a model thin stellar atmosphere. We confirm the wavelength dependence of the exoplanet’s radius found by Pont et al. (at the 1σ level). The exoplanet radius increases with decreasing wavelength, which seems to argue for the presence of an atmosphere around the planet.     

Exoplanet Transients: Possible Variations in the Limb-Darkening Coefficients of Eclipsed Stars at Short Time Intervals

Astronomy Reports - The interpretation of high-precision transit light curves of binary systems with exoplanets Kepler-5b, Kepler-6b, and Kepler-7b is performed for three different epochs. It has...     

Estimation of parameter errors in inverse problems. Determining limb-darkening coefficients in classical eclipsing systems

The estimation of parameters and their errors is considered using the observed light curve of the eclipsing binary system YZ Cas as an example. The error intervals are calculated using the differential-correction and confidence-region methods. The error intervals and reliability of the methods are investigated, and the reliability of limb-darkening coefficients derived from the observed light curve analyzed. A new method for calculating parameter errors is proposed.     

Masses of X-ray pulsars in binary systems with OB supergiants

We describe the results of a statistical approach to analyzing the combined radial-velocity curves of X-ray binaries with OB supergiants in a Roche model, both with and without allowance for the anisotropy of the stellar wind. We present new mass estimates for the X-ray pulsars in the close binary systems Cen X-3, LMC X-4, SMC X-1, 4U 1538-52, and Vela X-1.     

Estimate of the black-hole mass and orbital inclination from the radial-velocity curve of the X-ray binary Cyg X-1

Astronomy Reports - The results of a statistical approach to interpreting a master radial-velocity curve for the X-ray binary Cyg X-1 are presented. The dependence of the mass of the X-ray...     

Influence of Normalization Inaccuracy of Transit Light Curves on the Results of Their Interpretation

Astronomy Reports - Using the transit light curves of Kepler-5b, Kepler-6b, Kepler-7b, Kepler-8b as examples, we study the effect of the primary normalization errors regarding the observed transit...