Evolutionary state of W UMa-type systems

The evolutionary status of a sample of 31 W UMa-type systems (20 of W, 9 of A, and 2 of A/W sub-class) is examined and discussed on the basis of their positions in the H-R, mass-radius and mass-luminosity diagrams. The absolute elements of these systems have been evaluated by use of their spectroscopic and photometric data as they were found in the literature. Since different analysis methods have been used by the various investigators this gives the opportunity to make different H-R, mass-radius and mass-luminosity diagrams, according to the method used, and compare the results.Moreover, from the spectral type-period diagram of those systems that have spectral types from O to G2 it was found that all of them lie in the evolved region. Finally, the log (L _l/L _s) log (M _l/M _s) diagrams are presented and discussed.     

The minimum mass ratio of W UMa-type binary systems

When the total angular momentum of a binary system   J _tot= J _orb+ J _spin  is at a certain critical (minimum) value, a tidal instability occurs which eventually forces the stars to merge into a single, rapidly rotating object. The instability occurs when   J _orb= 3 J _spin  , which in the case of contact binaries corresponds to a minimum mass ratio   q _min≈  0.071–0.078. The minimum mass ratio is obtained under the assumption that stellar radii are fixed and independent. This is not the case with contact binaries where, according to the Roche model, we have   R ₂= R ₂( R ₁, a , q )  . By finding a new criterion for contact binaries, which arises from  d J _tot= 0  , and assuming   k ²₁≠ k ²₂  for the component's dimensionless gyration radii, a theoretical lower limit   q _min= 0.094–0.109  for overcontact degree   f = 0–1  is obtained.     

Variation in the orbital period of W UMa-type contact systems

The secular variation in the orbital period P_orb is studied as a function of the mass ratio q of the components in a sample of 73 contact systems of class W UMa constructed from a survey of current (1991–2003) published photometric and spectroscopic data. Almost all the W UMa-systems (>93% of this sample) are found to have a variation in their orbital periods P_orb which alternates in sign independently of their division into A-and Wsubclasses. A statistical study of this sample in terms of the observed characteristics dP_orb/dt and q showed that on the average the numbers of increases (35 systems) and decreases (33 systems) in the periods are the same, which indicates the existence of flows directed alternately from one component to the other and illustrates the cyclical character of the thermal oscillations. An analysis of the behavior of dP_orb/dt as a function of the mass interval of the primary component yields a more accurate value for the mass ratio, q ≈ 0.4 ÷ 0.45 at which contact binaries are separated into A-and W-subclasses. No correlations were observed between the fill-out factor for the outer contact configuration, the total mass of the contact system, and the mass ratio of the components, on one hand, and the sign of the secular variation in the period. The physical properties and evolutionary features of these systems are discussed. __________ Translated from Astrofizika, Vol. 49, No. 3, pp. 419–432 (August 2006).     

Fraunhofer line profiles

It is shown that comparing an observed Fraunhofer profile to a fitted gaussian yields more information on shape and asymmetry of the solar line than the simple bisector method.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

Alfven waves and sunspot line profiles

We investigate the effect of Alfven waves on the profile of the g = 0 lines FeI 5691.505 and FeI 5434.534. We find nonnegligible oscillation and distortion of the profile and vastly different lines. We calculate the theoretical profiles of these two lines under the action of Alfven waves, compare them with observations and hence verify preliminarily that sunspots are cooled by the propagation of Alfven waves.     

Jupiter: New retrieved thermal profiles and ammonia distributions

New thermal profiles of Jupiter are retrieved from recent far infrared spectral measurements and for H₂ mixing ratios varying from 0.8 to 0.94. The effective temperature corresponding to the inferred thermal profile is 123.15 ± 0.35°K. Far-infrared brightness temperature spectra computed from these profiles are compared to experimental data including measurements made at high spectral resolution in the NH₃ν₂ band at 10 μm and in NH₃ pure rotational bands between 40 and 110 μm. It is found that a strong depletion of NH₃ does occur in the Jovian stratosphere and that ammonia seems to be undersaturated in the upper troposphere.     

BV photometry of UX Arietis

DifferentialBV photometry of UX Ari obtained on 58 nights during 1984-85, 1985-86, 1986-87, and 1987-88 observing season is presented. We find that (B-V) is phase dependent with the system being reddest at the light maximum and we interpret this as due to the variable fractional contribution by the G5 V component to the total light at shorter wavelengths. An analysis of the available data indicates that at larger amplitudes of the photometric wave the brightness at maximum increases and that at minimum decreases and both converge to δV ≃ −1.0 mag at very low amplitudes. It implies that the low wave amplitudes are essentially due to more homogeneity in the surface distribution of spots rather than due to low levels of spot activity. The variation in wave amplitude is found to be near-sinusoidal with a period around 13–14 years     

Precise measurements of spectral line profiles

We present a method of precise measurements of spectral line profiles that was elaborated and tested on the Main Stellar Spectrograph (MSS) of the 6-m BTA telescope. The method allows discarding corrections for flat field. To take account of inhomogeneity of the CCD chip sensitivity, two spectra are recorded, shifted against each other along the dispersion by one column. Recurrent ratios between the photo responses of the CCD pixels let us determine their relative sensitivity and correct the line profiles. To eliminate various instability effects, the spectra are registered with the use of a cyclic shift procedure along the dispersion, and a synchronous electronic image transfer across the spectrum dispersion (along the CCD matrix columns).     

Modelling line profiles in infalling cores

Results are presented from a model of molecular line formation in collapsing star-forming cores. The study includes, for the first time, a self-consistent chemical and dynamical model which is then directly coupled to an appropriate radiative transfer model. The assumptions of chemical uniformity or simple monotonic variations within such cores are shown to be unacceptable. The results show that the abundance variations and the line profiles are highly sensitive to the assumed values of the free parameters in the chemical model. Extreme caution is therefore advised in the quantitative analysis of emission-line profiles from infall sources. The implied degeneracy can be overcome by multiple line-of-sight observations of many species and transitions.     

Turbulence in clusters of galaxies and X-ray line profiles

Large-scale bulk motions and hydrodynamic turbulence in the intergalactic gas that fills clusters of galaxies significantly broaden X-ray emission lines. For lines of heavy ions (primarily helium-like and hydrogen-like iron ions), the hydrodynamic broadening is appreciably larger than the thermal broadening. Since clusters of galaxies have a negligible optical depth for resonant scattering in the forbidden and intercombination lines of these ions, these lines are not additionally broadened. At the same time, they are very intense, which allows deviations of the spectrum from the Gaussian spectrum in the line wings to be investigated. The line shape proves to be an important indicator of bulk hydrodynamic processes. Doppler probing of turbulence becomes possible, because the cryogenic detectors of the X-ray observatories now ready for launch and being planned will have a high energy resolution (from 5 eV for ASTRO-E2 to 1–2 eV for Constellation-X and XEUS). We use the spectral representation of a Kolmogorov cascade in the inertial range to calculate the characteristic shapes of radiation lines. Significant deviations in the line profiles from the Gaussian profile (shape asymmetry, additional peaks, sharp breaks in the exponential tails) are expected for large-scale turbulence. The kinematic SZ effect and the X-ray line profiles carry different information about the hydrodynamic velocity distribution in clusters of galaxies and complement each other, allowing the redshift, the peculiar velocity of the cluster, and the bulk velocity dispersion to be separated.     

Variations in brightness and polarization of UX Draconis

Photoelectric observations of the brightness and polarization of the carbon star UX Dra in 1989–1993 are presented and discussed. The strong variations in this star’s period and the impossibility of determining it from our observations forced us to use an extrapolation of Vetešnik’s periodvariation curve. As in Vetesnik’s observations, our determinations of UX Dra’s brightness are satisfied far better by a period twice as long. The variations in UX Dra’s brightness and polarization parameters resemble most closely those of an RV Tau star, in our opinion. Translated from Astrofizika, Vol. 41. No. 4, pp. 561–568, October–December, 1998.     

Calculation of line profiles of inhomogeneous solar formations

A generalized equation was obtained for calculation of line profiles of solar formations in the assumption of their inhomogeneity. Line profiles of homogeneous formations are a particular consequence of this equation. Analysis of the equation and line profiles calculated from it was carried out.     

Theoretical line profiles from a symbiotic system

A model for a symbiotic system is presented which is not spherically symmetrical. The system consists of a cool, mass losing giant and a hot star. The stellar wind from the cool star is radiatively ionized by the hot companion, and the resulting nebular lines are emitted mainly close to the cool star. Due to the elliptical orbit, the line fluxes change with time because of the varying separation of the stars. The line profiles vary from symmetrical to asymmetrical, depending on the angle between the line of sight and the axis of symmetry. The calculated line profiles are compared with observed UV lines of the symbiotic star HBV 475.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables, Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Absorption line profiles and rotational velocities for 59 stars

Absorption lines of Heii, Hei, Mgii, and other ions have been measured in coudé spectral tracings for 59 slowly and rapidly rotating sourthern O, B and A stars on the Main Sequence. All 668 separate line profiles have been analyzed with a procedure of differential corrections by least-squares to yield the following parameters and their error estimates: half-width, central depth, equivalent width, and shape parameter. The shape parameter includes Voigt profiles and also ‘super-Gaussian’ and ‘super-damping’ profiles. In addition, separately-measured line profiles in each star have been superimposed to yield better composite profiles with smaller errors. In addition, a preliminary value ofv sini is derived for each line by deconvolving it with both the intrinsic and instrumental profiles, and a mean value (including error bar) is derived for each star. The resulting mean values ofv sini are only about 2/3 as large as the earlier results presented by Buscombe (1969). The inadequacies of the traditional procedure are discussed, and plans for using calculated non-LTE intrinsic line profiles including line limb darkening and also effects of rotational distortion, will be outlined.     

Calculation of 5250.216 Å line profiles in sunspots

The assumptions of pure absorption and local thermodynamic equilibrium are sometimes used to calculate approximate spectral line profiles in cases where a rigorous treatment is impractical or impossible. In certain conditions, the profile is not completely defined under these assumptions.This work was done under NASA contract No. NAS8-26376 for the Space Sciences Laboratory, George C. Marshall Space Flight Center, Huntsville, Ala.