We have performed a statistical test of the currently used accretion disk models for cataclysmic variables (CVs) using a set of 33 CVs with steady disks (10 old novae and 23 nova-like systems). The mass transfer rate (Ṁ) for each system was also calculated. Ultraviolet (UV) data were fitted by model spectra using a multiparametric optimization method, aiming to constrain theṀ values. It was verified that these accretion disk models fail to fit both color and flux simultaneously, as previously noted when composite stellar atmosphere models were fitted to the UV spectra of CVs by Wade. By applying such models to a sample of novae and nova-like CVs, we confirm that the limb-darkening effect must be taken into account when estimating mass transfer rates, especially for high-inclination systems. Important fitting degeneracies of the basic disk parameters are analyzed. Our simulations suggest that to reproduce the observations a revision of the temperature profile, at least in the innermost parts of the disk, seems to be required, and possibly the vertical distribution of the viscosity should be revised. In addition, an optically thin layer or an extended disk component should be considered. This component may be physically represented by a disk wind and/or a chromosphere. A physical description of the emission-line profiles may help to break the degeneracies that appear when only the continuum is analyzed. The average value ofṀ found for nova-like systems is $9:3 ; 10 À9 M yr À1 , while $1:3 ; 10 À8 M yr À1 is found for old classical novae. No clear evidence is found for either the presence or absence of a correlation betweenṀ and the orbital period. Such correlation analysis was performed for high accretion rate systems (15 nova-like systems and 10 old novae), but we were not able to find a well-defined correlation as found by Patterson. By measuring the equivalent width of the emission lines (C iv k1550 and He ii k1640) we found a lack of systems with lowṀ and strong UV emission lines. A correlation between the equivalent width of such lines and the orbital inclination (i) was also confirmed.

We present a multi-wavelength (X-ray to optical) analysis, based on non-local thermodynamic equilibrium photospheric+wind models, of the B0 Ia-supergiant: ǫ Ori.The aim is to test the consistency of physical parameters, such as the mass-loss rate and CNO abundances, derived from different spectral bands. The derived mass-losswhere f ∞ is the volume filling factor. However, the S iv λλ1062,1073 profiles are too strong in the models; to fit the observed profiles it is necessary to use f ∞ <0.01. This value is a factor of 5 to 10 lower than inferred from other diagnostics, and impliesṀ 1×10 −7 M ⊙ yr −1 . The discrepancy could be related to porosity-vorosity effects or a problem with the ionization of sulfur in the wind. To fit the UV profiles of N v and O vi it was necessary to include emission from an interclump medium with a density contrast (ρ cl /ρ ICM ) of ∼100. X-ray emission in H-He like and Fe L lines was modeled using four plasma components located within the wind. We derive plasma temperatures from 1×10 6 to 7×10 6 K, with lower temperatures starting in the outer regions (R 0 ∼3-6 R * ), and a hot component starting closer to the star (R 0 2.9 R * ). From X-ray line profiles we inferṀ < 4.9×10 −7 M ⊙ yr −1 . The X-ray spectrum ( 0.1 kev) yields an X-ray luminosity L X ∼ 2.0 × 10 −7 L bol , consistent with the superion line profiles. X-ray abundances are in agreement with those derived from the UV and optical analysis: ǫ Ori is slightly enhanced in nitrogen and depleted in carbon and oxygen, evidence for CNO processed material.

Compared to mass transfer in cataclysmic variables, the nature of accretion in symbiotic binaries in which red giants transfer material to white dwarfs (WDs) has been difficult to uncover.The accretion flows in a symbiotic binary are most clearly observable, however, when there is no quasi-steady shell burning on the WD to hide them. RT Cru is the prototype of such non-burning symbiotics, with its hard (δ-type) X-ray emission providing a view of its innermost accretion G. J. M. Luna et al.: RT Crucis; X-ray, UV, and optical observations. structures. In the past 20 years, RT Cru has experienced two similar optical brightening events, separated by ∼4000 days and with amplitudes of ∆V∼ 1.5 mag. After Swift became operative, the Burst Alert Telescope (BAT) detector revealed a hard X-ray brightening event almost in coincidence with the second optical peak.Spectral and timing analyses of multi-wavelength observations that we describe here, from NuSTAR, Suzaku, Swift/X-Ray Telescope(XRT) + BAT + UltraViolet Optical Telescope (UVOT) (photometry) and optical photometry and spectroscopy, indicate that accretion proceeds through a disk that reaches down to the white dwarf surface. The scenario in which a massive, magnetic WD accretes from a magnetically truncated accretion disk is not supported. For example, none of our data show the minute-time-scale periodic modulations (with tight upper limits from X-ray data) expected from a spinning, magnetic WD. Moreover, the similarity of the UV and X-ray fluxes, as well as the approximate constancy of the hardness ratio within the BAT band, indicate that the boundary layer of the accretion disk remained optically thin to its own radiation throughout the brightening event, during which the rate of accretion onto the WD increased to 6.7×10 −9 M ⊙ yr −1 (d/2 kpc) 2 . For the first time from a WD symbiotic, the NuSTAR spectrum showed a Compton reflection hump at E> 10 keV, due to hard X-rays from the boundary layer reflecting off of the surface of the WD; the reflection amplitude was 0.77±0.21. The best fit spectral model, including reflection, gave a maximum post-shock temperature of kT =53±4 keV, which implies a WD mass of 1.25±0.02 M ⊙ .Although the long-term optical variability in RT Cru is reminiscent of dwarf-novae-type outbursts, the hard X-ray behavior does not correspond to that observed in well-known dwarf nova.An alternative explanation for the brightening events could be that they are due to an enhancement of the accretion rate as the WD travels through the red giant wind in a wide orbit, with a period of about ∼4000 days. In either case, the constancy of the hard X-ray spectrum while the accretion rate rose suggests that the accretion-rate threshold between a mostly optically thin and thick boundary layer, in this object, may be higher than previously thought.

We have developed a spectrum synthesis method for modeling the UV emission from the accretion disk from cataclysmic variables (CVs). The disk is separated into concentric rings, with an internal structure from the Wade & Hubeny disk-atmosphere models. For each ring, a wind atmosphere is calculated in the co-moving frame with a vertical velocity structure obtained from a solution of the Euler equation. Using simple assumptions, regarding rotation and the wind streamlines, these 1D models are combined into a single 2.5D model for which we compute synthetic spectra. We find that the resulting line and continuum behavior as a function of the orbital inclination is consistent with the observations, and verify that the accretion rate affects the wind temperature, leading to corresponding trends in the intensity of UV lines. In general, we also find that the primary mass has a strong effect on the P-Cygni absorption profiles, the synthetic emission line profiles are strongly sensitive to the wind temperature structure, and an increase in the mass loss rate enhances the resonance line intensities. Synthetic spectra were compared with UV data for two high orbital inclination nova-like CVs -RW Tri and V347 Pup. We needed to include disk regions with arbitrary enhanced mass loss to reproduce reasonably well widths and line profiles. This fact and a lack of flux in some high ionization lines may be the signature of the presence of density enhanced regions in the wind, or alternatively, may result from inadequacies in some of our simplifying assumptions.

Aims. We present a database of 43 340 atmospheric models (∼80 000 models at the conclusion of the project) for stars with stellar masses between 9 and 120 M⊙, covering the region of the OB main-sequence and Wolf-Rayet stars in the Hertzsprung-Russell diagram. Methods. The models were calculated using the ABACUS I supercomputer and the stellar atmosphere code CMFGEN. Results. The parameter space has six dimensions: the effective temperature Teff, the luminosity L, the metallicity Z, and three stellar wind parameters: the exponent β, the terminal velocity V∞, and the volume filling factor Fcl. For each model, we also calculate synthetic spectra in the UV (900−2000 Å), optical (3500−7000 Å), and near-IR (10 000−40 000 Å) regions. To facilitate comparison with observations, the synthetic spectra can be rotationally broadened using ROTIN3, by covering v sin i velocities between 10 and 350 km s−1 with steps of 10 km s−1. Conclusions. We also present the results of the reanalysis of ϵ Ori using our grid to demonstrate the benefits of databases of precalculated models. Our analysis succeeded in reproducing the best-fit parameter ranges of the original study, although our results favor the higher end of the mass-loss range and a lower level of clumping. Our results indirectly suggest that the resonance lines in the UV range are strongly affected by the velocity-space porosity, as has been suggested by recent theoretical calculations and numerical simulations.

We present a database of 45,000 atmospheric models (which will become 80,000 models by the end of the project) with stellar masses between 9 and 120 M ⊙ , covering the region of the OB main sequence and W-R stars in the H-R diagram. The models were calculated using the ABACUS I supercomputer and the stellar atmosphere code CMFGEN. The parameter space has 6 dimensions: the effective temperature T eff , the luminosity L, the metallicity Z, and three stellar wind parameters, namely the exponent β , the terminal velocity V ∞ , and the volume filling factor F cl . For each model, we also calculate synthetic spectra in the UV (900-2000Å), optical (3500-7000Å), and near IR (10000-30000Å) regions. To facilitate comparison with observations, the synthetic spectra were rotationally broaden using ROTIN3, by covering v sin i velocities between 10 and 350 km/s with steps of 10 km/s, resulting in a library of 1 575 000 synthetic spectra. In order to demonstrate the benefits of employing the databases of pre-calculated models, we also present the results of the re-analysis of ε Ori by using our grid.

Purpose of research. Is to develop a layout of an experimental setup that allows conducting research with elastic elements by exercising a force impact on them as well as automatic data collection and analysis, which allows determining the stiffness coefficient and investigating simple harmonic oscillations.Methods. The developed device makes it possible to determine elasticity coefficient of the spring applying two methods – static and dynamic. The dynamic method requires strict adherence to a certain procedure of experimental stydy. In this case, the system under study is under the action of a restoring force directly proportional to the displacement, i.e. it is a simple generator of harmonic oscillations. The prototype of the experimental setup being created includes a supporting structure, a control system to which an ultrasonic distance measurement sensor is connected, and a special mobile application that allows visualizing and recording the results of measurements in a user-friendly form.Results. The developed prototype makes it possible to determine spring deformation by static and dynamic methods; the presence of a special mobile application for devices with the Android operating system allows the user to control the device from his mobile phone. The experimental device allows visualizing the obtained data graphically and export them to a file of variable values. Exported values are displayed in tabular form for further processing using statistical tools or numerical computing applications.Conclusion. To improve the quality of the educational and training process of physics students it is necessary to introduce special equipment for experimental research into the educational process. Such equipment can be applied in the studies conducted in various sections of mechanics, including kinematics, oscillatory motion, impact, elasticity, etc.

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