Accretion disk in the eclipsing binary AU Mon

We analyze the CoRoT and V-passband ground-based light curves of the interacting close binary AU Mon, assuming that there is a geometrically and optically thick accretion disk around the hotter and more massive star, as inferred from photometric and spectroscopic characteristics of the binary. Our model fits the observations very well and provides estimates for the orbital elements and physical parameters of the components and of the accretion disk.Comment: Accepted for publication in MNRA

Landau model for uniaxial systems with complex order parameter

We study the Landau model for uniaxial incommensurate-commensurate systems of the I class by keeping Umklapp terms of third and fourth order in the expansion of the free energy. It applies to systems in which the soft mode minimum lies between the corresponding commensurate wave numbers. The minimization of the Landau functional leads to the sine-Gordon equation with two nonlinear terms, equivalent to the equation of motion for the well-known classical mechanical problem of two mixing resonances. We calculate the average free energies for periodic, quasiperiodic and chaotic solutions of this equation, and show that in the regime of finite strengths of Umklapp terms only periodic solutions are absolute minima of the free energy, so that the phase diagram contains only commensurate configurations. The phase transitions between neighboring configurations are of the first order, and the wave number of ordering goes through harmless staircase with a finite number of steps. These results are the basis for the interpretation of phase diagrams for some materials from the I class of incommensurate-commensurate systems, in particular of those for A$_2$BX$_4$ and BCCD compounds. Also, we argue that chaotic barriers which separate metastable periodic solutions represent an intrinsic mechanism for observed memory effects and thermal hystereses.Comment: 12 pages, 14 figures, LaTeX, to be published in Phys. Rev.

Physical parameters of close binaries QX Andromedae, RW Comae Berenices, MR Delphini, and BD +07{\circ} 3142

Aims. We analyze new multicolor light curves and recently published radial velocity curves for close binaries QX And, RW Com, MR Del, and BD +07{\circ} 3142 to determine the physical parameters of the components. Methods. The light curves are analyzed using a binary star model based on Roche geometry to fit the photometric observations. Spectroscopic parameters, such as the mass ratios and spectral types, were taken from recent spectroscopic studies of the systems in question. Results. Our findings provide consistent and reliable sets of stellar parameters for the four studied binary systems. Of particular interest is the BD +07{\circ} 3142 system, since this is the first analysis of its light curves. We find that it is an overcontact binary of W UMa type and W subtype, and that each component has a large cool spot in the polar region. QX And is an A subtype, and RW Com a W subtype W UMa binary, and in both systems we find a bright spot in the neck region between the components. MR Del is a detached binary with a complex light curve that we could model with two cool spots on the hotter component.Comment: 10 pages, 4 figures. Accepted for publication by A&

Light curve analysis of the late type binary V523 Cassiopeiae

We present the analysis of V and R light curves of the late type contact binary V523 Cas for the season of 2006. These observations make part of the monitoring program aimed at studying the long-term light curve variability in this system. Our results confirm that the system is in an over contact configuration, and include a bright spot in the neck region of the cooler and larger primary. We compare these results with the previous solution, obtained for the season 2005 dataset and discuss the differences

Light Curve Analysis of the Late Type Binary V523 Cassiopeiae

We present the analysis of V and R light curves of the late typecontact binary V523 Cas for the season of 2006. These observations make part of the monitoring program aimed at studying the long-term light curve variability in this system. Our results confirm that the system is in an overcontact configuration, and include a bright spot in the neck region of the cooler and larger primary. We compare these results with the previous solution, obtained for the season 2005 dataset and discuss the differences

On the modifications of oscillator strengths and damping constants of Fe I spectral lines from 500 nm to 510 nm

We modified oscillator strengths and enhancement factors of van der Waals damping constants for 84 moderately strong and weak neutral iron spectral lines between 500 nm and 510 nm, by fitting the solar synthetic spectrum to the observed one. We have found significant difference between the oscillator strengths and damping constants taken from an extensive spectral line list, frequently used for spectral synthesis, and their modified values. Our findings include: (1) the mean value of the distribution of the difference between our and listed oscillator strengths is -0.31dex and its width is 0.42 dex, (2) a decrease of this difference with increasing equivalent width of spectral lines, (3) unusually high values of the obtained enhancement factors in comparison with the results of other authors, (4) a decrease of enhancement factor with increasing excitation potential for lines with equivalent width greater than 7.5 pm, (5) a decrease of enhancement factors with increasing equivalent width and (6) a decrease of enhancement factors with increasing oscillator strengths

Identification of phase-independent spectral lines in close binary V455 CYG: I. Telluric lines

Spectroscopic observations of close binary star V455 Cygni reveal many lines that originate in interstellar and circumstellar medium and the atmo­sphere of the Earth; we found over two hundred such spectral features, and in this paper we present the list of telluric lines we identified through comparison with HITRAN database of molecular lines. The lines that remain unidentified or show peculiar behavior will be discussed in the second part of the paper.

Physical parameters of close binaries QX Andromedae, RW Comae Berenices, MR Delphini, and BD +07° 3142

Aims. We analyze new multicolor light curves and recently published radial velocity curves for close binaries QX And, RW Com, MR Del, and BD +07° 3142 to determine the physical parameters of the components. Methods. The light curves are analyzed using a binary star model based on Roche geometry to fit the photometric observations. Spectroscopic parameters, such as the mass ratios and spectral types, were taken from recent spectroscopic studies of the systems in question. Results. Our findings provide consistent and reliable sets of stellar parameters for the four studied binary systems. Of particular interest is the BD +07° 3142 system, since this is the first analysis of its light curves. We find that it is an overcontact binary of W UMa type and W subtype, and that each component has a large cool spot in the polar region. QX And is an A subtype, and RW Com a W subtype W UMa binary, and in both systems we find a bright spot in the neck region between the components. MR Del is a detached binary with a complex light curve that we could model with two cool spots on the hotter component

Program of telluric lines monitoring

A new observational program of telluric lines monitoring was introduced at Belgrade Astronomical Observatory. The ultimate goal of this program is to investigate the properties of Earth’s atmosphere through modeling the observed profiles of telluric lines. The program is intend to observe infrared molecular oxygen lines that were selected according to spectral sensitivity of the available CCD camera. In this paper we give the initial and the final selection criteria for spectral lines included in the program the description of equipment and procedures used for observations and reduction, a review of preliminary observational results with the estimated precision, and a short discussion on the comparison of the theoretical predictions and the measurements