Velocity Curve Analysis of Spectroscopic Binary Stars AI Phe, GM Dra, HD 93917 and V502 Oph by Nonlinear Regression

We introduce a new method to derive the orbital parameters of spectroscopic bi-nary stars by nonlinear least squares of (o-c). Using the measured radial velocity data of the four double lined spectroscopic binary systems, AI Phe, GM Dra, HD 93917 and V502 Oph, we derived both the orbital and combined spectroscopic elements of these systems. Our numerical results are in good agreement with the those obtained using the method of Lehmann-Filhe's.     

Surface images of the short period contact binary AE Phe

We present high resolution Doppler images of the short period (P = 0.362 d) contact binary AE Phe. Using least squares deconvolution, we make use of the information content of the several thousand lines in each échelle spectrum to obtain the necessary S/N and time resolution required to resolve individual starspot features. A single pair of rotationally broadened profiles (free of sidelobes due to blending) with a typical S/N of 3000 ‐ 4000 per spectrum is thus obtained. With 300 sec exposures we achieve a cadence of 350 sec which is equivalent to sampling the rotation phase every 4°. We derive images for four nights of data which reveal starspots at most latitudes on both components of the common envelope system. Individual starspots evolve significantly on very short timescales, of order one day; significantly faster than the week timescales found on active single stars and the Sun. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Velocity curve analysis of the spectroscopic binary stars PV Pup,HD 141929, EE Cet and V921 Her by nonlinear regression

We use the method introduced by Karami & Mohebi (2007), and Karami & Teimoorinia (2007) which enable us to derive the orbital parameters of the spectroscopic binary stars by the nonlinear least squares of observed vs. curve fitting (o-c). Using the measured experimental data for radial velocities of the four double-lined spectroscopic binary systems PV Pup, HD 141929, EE Cet and V921 Her, we find both the orbital and the combined spectroscopic elements of these systems. Our numerical results are in good agreement with those obtained using the method of Lehmann-Filhés.     

An analysis of v sin (i) correlations in early-type binaries

We use information on the   v sin ( i )  values of early-type binaries in order to search for correlations which may constrain the relative orientation of the stellar spin axes in binary systems. We find correlations in the case of close binaries which suggest that tidal synchronization is effective for binaries whose separation exceeds the stellar radius by more than an order of magnitude, in line with the theoretical predictions of Goldreich & Nicholson and the previous observational analysis of Giuricin et al. In the case of wide binaries, the   v sin ( i )  values are not well correlated, which requires that the magnitude of the spin speeds is not tightly correlated. Under this assumption, we then find that the data provide no significant constraints on the degree of alignment of spin axes. The data are therefore compatible with scenarios (such as disc fragmentation or capture) which differ widely in the expected degree of spin alignment.     

Mass loss and orbital period decrease in detached chromospherically active binaries

The secular evolution of the orbital angular momentum (OAM), the systemic mass  ( M = M ₁+ M ₂)  and the orbital period of 114 chromospherically active binaries (CABs) were investigated after determining the kinematical ages of the subsamples which were set according to OAM bins. OAMs, systemic masses and orbital periods were shown to be decreasing by the kinematical ages. The first-order decreasing rates of OAM, systemic mass and orbital period have been determined as     per systemic OAM,     per systemic mass and     per orbital period, respectively, from the kinematical ages. The ratio of d log  J /d log  M = 2.68, which were derived from the kinematics of the present sample, implies that there must be a mechanism which amplifies the angular momentum loss (AML)     times in comparison to isotropic AML of hypothetical isotropic wind from the components. It has been shown that simple isotropic mass loss from the surface of a component or both components would increase the orbital period.     

Contribution to the search for binaries among Am stars – VII. Orbital elements of seven new spectroscopic binaries, implications on tidal effects

We present the results of a radial-velocity study of seven Am stars (HD 3970, 35035, 93946, 151746, 153286, 204751 and 224002) observed at the Observatoire de Haute-Provence (OHP) and the Cambridge Observatories with CORAVEL instruments. We find that these systems are single-lined spectroscopic binaries whose orbital elements are determined for the first time. Among this sample, HD 35035 and 153286 have long periods, with   P = 2.8  and 9.5 yr, respectively, which is rather unusual for Am stars. Four systems have orbits with large eccentricities (with   e ≥ 0.4  ). Physical parameters are inferred from this study for the primaries of those systems.
We then investigate the influence of tidal interaction, which has already led to the synchronism of the primaries and/or to the circularization of the orbits of some systems belonging to this sample. We extend this study to the list of 33 objects studied in this series of papers and derive values of the critical fractional radii   r = R / a   for circularization and synchronization of Am-type binaries. We find that the stars with   r ≳ 0.15  are orbiting on circular orbits and that synchronism is likely for all components with   r ≳ 0.20  .     

Contribution to the search for binaries among Am stars – V. Orbital elements of eight short-period spectroscopic binaries

We present the results of a radial-velocity study of eight Am stars (HD 341, 55822, 61250, 67317, 93991, 162950, 224890 and 225137) observed at Observatoire de Haute-Provence with the CORAVEL instrument. We find that these systems are single-line spectroscopic binaries whose orbital elements are determined for the first time.     

Contribution to the study of composite spectra: XI. Orbital elements of some faint systems

We present the results of a radial‐velocity study of nine new faint SB1 spectroscopic binaries with composite spectra: HD 137975‐6, 177984, HDE 226489, 231613‐4, 255387‐8, 256138‐9, 264997‐8, 276787 and 293041‐2. The observations were made at Haute‐Provence and Cambridge observatories with CORAVEL instruments between 1982 and 2006. From the radial‐velocity measurements of the cool components, we derive the orbital elements of those spectroscopic binaries for the first time. Using all the available data, we propose a model for each system that describes the nature of the individual components, with an estimation of the angular separation and orbital inclination. Finally we discuss the rotation–revolution synchronism of the cool components. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Contribution to the study of composite spectra: XII. Spectroscopic orbits of eight southern stars

We present the results of a radial‐velocity study of eight southern SB1 spectroscopic binaries with composite spectra: HD 34318‐9, HD 47579‐80, HD 70442‐3, HD 74946‐7, HD 102171‐2, HD 120901‐2, HD 168701‐2, and HD 174191‐2. The observations were made at Haute‐Provence observatory with the CORAVEL instrument between 1982 and 2006. From the radial‐velocity measurements of the cool components, we derive the orbital elements of those spectroscopic binaries. Using all the available data, we obtain an estimation of the orbital inclination and the angular separation of the two components. Finally we discuss the rotation‐revolution synchronism of the cool components. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Physical parameters of the O6.5V+B1V eclipsing binary system LS 1135

The 'All Sky Automated Survey' (ASAS) photometric observations of LS 1135, an O-type single-lined binary (SB1) system with an orbital period of 2.7 d, show that the system is also eclipsing performing a numerical model of this binary based on the Wilson–Devinney method. We obtained an orbital inclination     . With this value of the inclination, we deduced masses   M ₁∼ 30 ± 1 M_⊙  and   M ₂∼ 9 ± 1 M_⊙  , and radii   R ₁∼ 12 ± 1 R_⊙  and   R ₂∼ 5 ± 1 R_⊙  for primary and secondary components, respectively. Both the components are well inside their respective Roche lobes. Fixing the T _eff of the primary to the value corresponding to its spectral type (O6.5V), the T _eff obtained for the secondary component corresponds approximately to a spectral type of B1V. The mass ratio   M ₂/ M ₁∼ 0.3  is among the lowest known values for spectroscopic binaries with O-type components.     

The detection of binary companions to subdwarf B stars

Intermediate dispersion spectroscopy of a sample of 40 hot subdwarf B stars between 5500 and 9000Å has been obtained. The sample includes a large fraction of targets which have been studied photometrically. Seven targets show strong lines arising from the infrared Ca  ii triplet, the unequivocal signature of a cool companion. The positive Ca  ii identifications include known photometric binaries and new targets; all are associated with a photometric red excess. Assuming a canonical value for the subdwarf luminosity, all of the detected companions are overluminous compared with the main sequence. The detection procedure indicates an improved and more secure method for the measurement of the binary frequency of hot subdwarfs.     

The nearest star of spectral type O3: a component of the multiple system HD 150136

From radial velocities determined in high signal-to-noise digital spectra, we report the discovery that the brightest component of the binary system HD 150136 is of spectral type O3. We also present the first double-lined orbital solution for this binary. Our radial velocities confirm the previously published spectroscopic orbital period of 2.6 d. He  ii absorptions appear double at quadratures, but single lines of N  v and N  iv visible in our spectra define a radial velocity orbit of higher semi-amplitude for the primary component than do the He  ii lines. From our orbital analysis, we obtain minimum masses for the binary components of 27 and  18 M_⊙  . The neutral He absorptions apparently do not follow the orbital motion of any of the binary components, thus they most probably arise in a third star in the system.     

More than two hundred and fifty thousand spectroscopic binary or variable star candidates discovered by LAMOST

About 786.4 thousand stars were observed by LAMOST twice or more during the first stage of its spectroscopic survey. The radial velocity differences for about 256 thousand targets are larger than10 km s^-1 and they are possible spectroscopic binary or variable candidates(SBVCs). It is shown that most SBVCs are slightly metal poorer than the Sun. There are two peaks in the temperature distribution of SBVCs around 5760 K and 4870 K, while there are three peaks in the distribution of the gravitational acceleration at 2.461, 4.171 and 4.621 cm s^-2. The locations of SBVCs on the [Fe/H]-T, [Fe/H]-log g, log g-T and H-R diagrams are investigated. It is found that the detected SBVCs could be classified into four groups. The first group has higher log g～4.621 and lower T ～ 4870 K which are mainly cool red dwarf binaries. The second group of SBVCs has logg around 4.171 cm s^-2 that includes binaries and pulsating stars such as δSet and γ Dor variables. The gravitational accelerations of the third group of SBVCs are higher and some of them are below the zero-age main sequence. They may be contact binaries in which the primary components are losing energy to the secondaries in the common envelopes and are at a special stellar evolutionary stage.The last group is composed of giants or supergiants with log g around 2.461 cm s^-2 that may be evolved pulsating stars. One target(C134624.29+333921.2) is confirmed as an eclipsing binary with a period of 0.65 days. A preliminary analysis suggests that it is a detached binary with a mass ratio of 0.46. The primary fills its critical Roche lobe by about 89%, indicating that mass transfer will occur between the two components.