V. V. Leushin

Speckle interferometric binary system HD375; Is it a sub-giant binary?

Atmospheric modeling is used to build synthetic spectral energy distributions (SEDs) for the individual components of the speckle interferometric binary system HD375. These synthetic SEDs are combined together for the entire system and compared with its observed SED in an iterative procedure to achieve the best fit. Kurucz blanketed models and the measurements of magnitude differences were used to build these SEDs. The input physical parameters for building these best fitted synthetic SEDs represent adequately enough properties of the system. These parameters are: Teffa = 6100 ± 50 K, Teffb = 5940 ± 50 K, log ga = 4.01 ± 0.10, log gb = 3.98 ± 0.10, Ra = 1.93 ± 0.20R⊙, Rb = 1.83 ± 0.20R⊙, Mva = 3·m26 ± 0.40, Mvb = 3·m51 ± 0.50, La = 4.63 ± 0.80 L⊙, and Lb = 3.74 ± 0.70 L⊙, in accordance with the new estimated parallax π = 12.02 ± 0.60 mas. A modified orbit of the system is built and compared with earlier orbits, and the masses of the two components are calculated as Ma = 1.35M⊙ and Mb = 1.25M⊙. Based on the estimated physical and geometrical parameters of the system, which are confirmed by synthetic photometry, we suggest that the two components are evolved subgiant (F8.5 IV and G0 IV) stars with the age of 3.5 Gyr, formed by fragmentation.

Chemical composition of the He-w stars HD 37058, 212454, and 224926

Our spectrophotometric analysis of the atmospheres of HD 37058, HD 212454, and HD 224926 shows these objects to be typical He-w stars with close-to-zero microturbulence velocities, very different magnetic fields, and wide scatter of chemical anomalies. However, one of the main manifestations of separation is that helium moves from the outer layers of the atmosphere into the star’s interior.Our analysis of the stars HD 212454 and 224926 with Be<100 G shows that despite their weak magnetic fields they have the same degree of chemical anomaly as highly magnetized stars. Chemical composition varies over a wide range for stars with the same magnitude of magnetic field. We find the conditions in the temperature interval 13000–16000 K to be the most favorable for the formation of He-w type stars. Helium underabundance is the strongest near the maximum of the distribution and it is observed in stars with weak as well as strong fields. Because of the scatter mentioned above the degree of chemical anomalies is not strictly related to the magnitude of the magnetic field, although the field has an appreciable effect on the formation of chemical inhomogeneities at the star’s surface. Its influence is minimal in stars with very weak magnetic fields and the presence of strong chemical anomalies indicates that microturbulence in these stars is sufficiently weak even without the effect of the magnetic field. It is plausible to assume that the anomalies arise due to slow rotation.The temperature dependences of rotation velocity vsini for stars with weak magnetic fields show no apparent trends associated with the magnitude of magnetic field. The rotation velocities vsini of almost all stars are lower than those of normal stars, except for HD 131120, 142096, 142990, and 143669, which rotate with the same velocity or even faster than normal stars. These objects do not obey the general rule and their example shows that stable atmospheres can also be found among fast rotators and that magnetic field takes no part in the spin-down of CP stars. We believe that CP stars inherited their slow rotation from protostellar clouds.

Atmospheric elemental abundances for the components of the multiple system ADS 11061. 41 Draconis

We obtained speckle interferometric and spectroscopic observations of the system 41 Dra during its periastron passage in 2001. The components’ lines are resolved in the spectral interval 3700–9200 Å. The observed wavelength dependence of the brightness difference between the components is used to estimate the B-V indices separately for each of the components: B-V = 0.511 for component a and B-V = 0.502 for component b. We derived improved effective temperatures of the components from their B-V values and hydrogen-line profiles. The observations can be described with the parameters for the components Teffa = 6370 K, log ga = 4.05 and Teffb = 6410 K, log gb = 4.20. The iron, carbon, nitrogen, and oxygen abundances in the atmospheres of the components are log N(Fe)a = 7.55, log N(Fe)b = 7.60, log N(C)a = 8.52, log N(C)b = 8.58, log N(N)a = 8.05, log N(N)b = 7.99, log N(O)a = 8.73, log N(O)b = 8.76.

Young massive binary θ1 OriC: Radial velocities of components

We succeeded in separating the absorption lines of both the primary C1 and the secondary C2 component in the spectra of the young massive binary θ1 OriC (O6Vp + B0V, mass sum 44 ± 7M⊙), obtained during the period from November 1995 to February 2013 with different telescopes. These observations allowed us to derive, for the first time, the radial velocities of both components. The orbitalmotion of the secondary star is traced through its weak (the line depth is approximately 0.01–0.02) absorption lines of CII, NII, OII, Si III, which are broadened by fast rotation of the star. Silicon absorptions Si III λλ 4553, 4568, and 4575 are better suited for radial velocity measurements than the other lines. From the velocity curves, we obtained the systemic velocity of the system, γ = 31 ±2 kms−1, and semi-amplitudes of the C1 and C2 velocities: K1 = 15 ± 2 kms−1, K2 = 43 ± 3 kms−1. This leads to individual component masses of M1 = 33 ± 5 M⊙ and M2 = 11 ± 5 M⊙, based on the adopted mass sum. At present, the combined spectroscopic-interferometric orbital solution cannot be obtained because of the large scatter of velocity measurements caused by chaotic line shifts in the spectrum of the primary star and by the weakness of wide absorptions from the secondary. New spectroscopy with a resolution of R ≥ 30000 and S/N ratio over 200 performed in the period close to the periastron passage in the second half of 2013, as well as additional long-baseline interferometry, will be decisive in refining the parameters of θ1 OriC. We expect that as a result of this campaign, masses and luminosities of the components will be determined with an accuracy of 2–3%.

Physical and geometrical parameters of the binary system gliese 150.2

The speckle interferometric binary system Gl 150.2 (HIP17491) is analyzed using atmosphere modeling and dynamical analysis simultaneously. A synthetic spectral energy distribution (SED) for each of the two components of the system is built using Kurucz blanketed models. These SEDs are combined together to form the total flux, which is compared with the observed one in an iterative method to get the best fit. The parameters of the individual components which lead to the best fit are: TeffA = 5350 ± 50 K, TeffB = 4400 ± 50 K, log gA = 4.40 ± 0.05, log gB = 4.68 ± 0.05, RA = 0.95 ± 0.06R⊙, RB = 0.58 ± 0.06R⊙, and π = 38.63 ± 0.79 mas, as given by the modified Hipparcos measurement. A modified orbit of the system is introduced and compared with earlier orbits. Hence, the masses of the two components are derived from the coincidence between the atmosphere modeling and dynamical analysis. Based on the estimated physical and geometrical parameters of the system, which are confirmed by synthetic photometry, the spectral types and luminosity classes of the two components are found to be G9.5V and K7V for the primary and secondary stars respectively, with an age of about 8 Gyr. Finally, the positions of both components on the H-R diagram are plotted, and the formation and evolution of the system are discussed.

Distribution of helium and silicon in the atmospheres of Bp stars HD168785 and HD21699

We present a study of stratification of helium and silicon in the atmospheres of CP stars HD 168785 (He-r) and HD 21699 (He-w). The distribution of these elements with depth is well described by the mechanism of diffusion under the effect of gravity, radiation pressure and stellar wind. We studied the stratification of these elements in different regions of the surface of HD 21699. We demonstrate that as the star rotates the abundance of He and Si changes in the antiphase. The position of the abundance maximum varies within small limits with optical depth as well.

Atmospheric chemical abundances and the evolutionary status of the spectroscopic and speckle-interferometric binary 9 Cyg

We have performed speckle interferometry with the 6-m telescope of the Special Astrophysical Observatory and spectroscopy (at 3700–9200 Å) with the 2-m telescope at Peak Terskol of the spectroscopic and interferometric binary 9 Cyg, which is a composite-spectrum star with an orbital period of 4.3 yrs. The atmosphere of the system’s primary component is analyzed in detail. The luminosities of both components estimated to be L1 = 103.8 L⊙, L2 = 55.2 L⊙, where L⊙ is the solar luminosity, and their effective temperatures to be Te(1) = 5300 K and Te(2) = 9400 K. The abundances of C, N, O, Fe, and other elements in the primary’s atmosphere have been derived. The chemical composition shows signatures of mixing of material from its atmosphere and the region of nuclear reactions. The evolutionary status of 9 Cyg has been determined. The binary’s age is about 400 million years; the brighter star is already in the transition to becoming a red giant, while the secondary is still in the hydrogen-burning stage near the zero-age main sequence. We suggest an evolutionary model for the binary’s orbit that explains the high eccentricity, e = 0.79.

Chemical composition of the atmosphere and evolutionary status of the spectroscopic and speckle-interferometric binary 12 Persei

The system 12 Per is a spectroscopic and speckle-interferometric binary with the components of similar spectral classes. The parameters of its orbit were determined quite accurately over nearly a century of observations. To refine the atmospheric abundances of its components and their evolutionary status, we obtained the spectra of the star in the 3500–9600 Å spectral region using the echelle spectrometers of the 6-m BTA telescope of the SAO RAS and 2-m Zeiss-2000 telescope at Terskol Peak. Based on the luminosities (L1 = 3.02 L⊙, L2 = 1.86 L⊙) and effective temperatures (Teff1 = 6195 K and Teff2 = 6000 K) we have estimated the evolutionary status of the system’s components. The age of the system is 12.1 Byr, the components are at the stage of hydrogen burning near the zero-age main sequence. The resulting element abundances in the atmospheres of 12 Per components indicate enhanced metallicity of both stars: [Fe/H] ≥ 0.35. We consider a scenario in which the initially circular short-period orbit of the pair turns into an eccentric large-period orbit due to the transfer of angular momentum of the components to the angular momentum of orbital motion over one billion years.

Evolutionary Status and Chemical Composition of the Atmosphere of the Spectroscopic and Speckle Interferometric Binary HD 10009

HD 10009 is a spectroscopic and speckle interferometric binary with almost identical solar-type components. It was studied via speckle interferometry using the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and had its spectrophotometry performed in the 3500–9600 Å wavelength interval with the 2-m telescope of the Terskol Branch of the Institute of Astronomy of the Russian Academy of Sciences. A detailed analysis of the atmosphere of the primary component (component 1) of the binary yielded the abundances of some of the elements. The luminosities and temperatures of the components are found to be L1= 2.9 L⊙, L2= 1.0 L⊙ and Teff1=6017 K, Teff2=5930 K, respectively. The iron abundance is [Fe]=−0.27±0.05. Our results make it possible to assess the evolutionary status of the system. The binary is 7.9 Gyr old and the primary component is close to become a red giant, whereas the secondary component is still in the hydrogen-burning stage near the main sequence.

Atmospheric chemical abundances of the components of the quadruple system ADS 11061. 40 draconis

As part of our study of the components of the hierarchic quadruple system ADS 11061, we acquired spectroscopic observations of the binary 40 Dra. Echelle spectra showing the separation of the components’ lines were obtained in the spectral range 3700–9200 Å. Effective temperatures and surface gravities were derived for the components from BV photometry and the hydrogen-line profiles. The components of the 40 Dra system have parameters close to Teffa = 6420 K, log ga = 4.17, Teffb = 6300 K, and log gb = 4.20. We find the microturbulence velocity in the component atmospheres to be Vt = 2.6 km/s. The abundances of iron, carbon, nitrogen, and oxygen in the atmospheres of both components are estimated to be log N(Fe)a = 7.50, log N(Fe)b = 7.46, log N(C)a = 8.39, log N(C)b = 8.45, log N(N)a = 8.12, log(N)b = 8.15, log N(O)a = 8.77, log N(O)b = 8.74.