Pavel Mayer

Tomographic separation of composite spectra. x. the massive close binary hd 101131

We present the first orbital elements for the massive close binary HD 101131, one of the brightest objects in the young open cluster IC 2944. This system is a double-lined spectroscopic binary in an elliptical orbit with a period of 9.64659 ± 0.00012 days. It is a young system of unevolved stars (approximately 2 million yr old) that are well within their critical Roche surfaces. We use a Doppler tomography algorithm to reconstruct the individual component optical spectra, and we apply well-known criteria to arrive at classifications of O6.5 V((f)) and O8.5 V for the primary and secondary, respectively. We compare the reconstructed spectra of the components to single-star spectrum standards to determine a flux ratio of f2/f1 = 0.55 ± 0.08 in the V band. Both components are rotating faster than synchronously. We estimate the temperatures and luminosities of the components from the observed spectral classifications, composite V magnitude, and cluster distance modulus. The lower limits on the masses derived from the orbital elements and the lack of eclipses are 25 and 14 M☉ for the primary and secondary, respectively. These limits are consistent with the somewhat larger masses estimated from the positions of the stars in the Hertzsprung-Russell diagram and evolutionary tracks for single stars.

The early-type multiple system QZ Carinae

We present an analysis of the early-type quadruple system QZ Car, consisting of an eclipsing and a non-eclipsing binary. The spectroscopic investigation is based on new high dispersion echelle and CAT/CES spectra of H and He lines. The elements for the orbit of the non-eclipsing pair could be refined. Lines of the brighter component of the eclipsing binary were detected in near-quadrature spectra, while signatures of the fainter component could be identified in only few spectra. Lines of the primary component of the non-eclipsing pair and of both components of the eclipsing pair were found to be variable in position and strength; in particular, the He ii 4686 emission line of the brighter eclipsing component is strongly variable. An ephemeris for the eclipsing binary QZ Car valid at present was derived Prim. Min. = hel. JD

HD 165246: an early-type binary with a low mass ratio

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Improved estimates of the physical properties of the O-star binary V1007 Sco = HD 152248 and notes on several other binaries in the NGC 6231 cluster ,

. The relative orbit of the two binary constituents of the multiple system is discussed. In contrast to earlier investigations we found radial velocity changes of the systemic velocities of both binaries, which were used -together with an O-C analysis of the expected light-time effect -to derive approximate parameters of the mutual orbit of the two pairs. It is shown that this orbit and the distance to QZ Car can be further refined by minima timing and interferometry.

Spectroscopic and Photometric Analysis of the O-Type Binary V1182 Aquilae: A Close Eclipsing System with a Luminous Third Body*

Analyses of 13 FEROS spectra from the ESO archive and 617 V-band photometric observations from the ASAS3 database allowed us to demonstrate that HD 165246 is a double-lined spectroscopic binary. As an earlier finding revealed, HD 165246 is also an eclipsing system. We were able to derive consistent orbital and light-curve solutions and all basic physical properties of the system. The period of this O8 V + B7 V binary is 4. d 592706 and the semiamplitudes of the radial-velocity curves are K 1 = 55. 5k m s −1 and K 2 = 321 km s −1 . As the mass ratio is small (0.173), the secondary lines cannot be seen directly in the spectra; however the application of spectral disentangling allowed us to detect weak Balmer and He i lines of the secondary component. The primary component rotates with a high projected velocity of v sin i = 243 km s −1 . A combined radial-velocity and light-curve solution led to the component masses and radii expected for the young stars of the given spectral types. Due to the high rotation velocity, the primary component might display changes in surface abundances of some elements. However, we did not find any significant differences with respect to the abundances of slowly rotating stars.

Physical elements of the eclipsing binary δ Orionis

Context. In spite of the importance of massive O-type stars for astrophysics, their accurate masses and other fundamental properties are still a matter of debate. Determining them reliably is hampered by various factors (stellar winds and other forms of circumstellar matter), and the agreement of derived properties with the model predictions is far from satisfactory. Careful studies of O-type binaries, especially of those in stellar clusters, are therefore desirable. Aims. Having obtained new series of electronic spectra and UBV photometry of V1007 Sco, we analysed these data in an effort to check whether the observed properties of V1007 Sco indeed disagree with the prediction of stellar evolutionary models. We briefly analysed data for a few other binaries in NGC 6231, too. Methods. Spectral reductions were carried out with the MIDAS program, photometry reduced using the HEC22 program, the orbital elements were derived with the FOTEL program and the final solutions obtained with the program PHOEBE. Results. Our analysis led to an accurate determination of the apsidal advance, u ω = (0.00884 ± 0.00012) deg d −1 , based on a simultaneous solution of all usable radial-velocity and photometric data. This implies an apsidal period of 111.5 years. It is also demonstrated that the orbital inclination must be close to 67 ◦ . We arrived at the following preliminary values for masses and radii: M1 = (29.5 ± 0.4) M� , M2 = (30.1 ± 0.4) M� , R1 = (15.8 ± 0.7) R� ,a ndR2 = (15.3 ± 0.5) R� . These values clearly indicate a log g of about 3.5 [CGS], implying that the stars are giants and not supergiants, as the standard spectral classification criteria indicate.

Large distance of ε Aurigae inferred from interstellar absorption and reddening

We obtained high-resolution spectroscopy and UBV photometry of the O-type eclipsing binary V1182 Aql. In the spectra lines of a third component were found; the presence of third light is also supported by the solution of the light curves. New masses for both components of the binary were derived: M1 = 31.0 and M2 = 16.6 M☉. These values differ considerably from those given by Bell et al., which were obtained by neglecting the presence of a third body. With Teff ~ 43,000 K the primary component is much hotter than expected for the previously assumed spectral type O8. Its classification has to be revised to O5.5, which makes V1182 Aql probably the earliest eclipsing binary in the Galaxy. The mass of the primary is smaller than suggested by evolutionary models, while the secondary parameters agree with a position close to the zero-age main sequence (ZAMS). The third body, which manifests itself by strong lines in the optical spectrum and by a third light contribution of ~17% as deduced from the light curve solution might be detectable by interferometric measurements.

HD 152246: a new high-mass triple system and its basic properties

For years, δ Orionis was considered a normal binary with an 09.5 II primary exhibiting apsidal-line advance. However, radial-velocity curves of both binary components have been derived from the IUE and optical spectra using the cross-correlation technique, and surprisingly low masses of 11.2 and 5.6 M ⊙ were found. We obtained new spectra in the red spectral region and new UBV photometry. Using all published photometry and radial velocities, we deduced more accurate orbital and apsidal line periods. The main result of this paper is to show that the observed line spectra of δ Orionis are composed of the lines of the O9.5 II primary and a similarly hot tertiary, while the lines of a cooler B-type secondary are too faint to be detected in the available spectra. The character of the light curve (low-amplitude partial eclipses and a non-negligible scatter of the data) does not allow for a unique light-curve solution. Nevertheless, we show that the assumption of normal primary-component mass and radius corresponding to the 09.5 II classification (25 M ⊙ , 16-17 R ⊙ ) leads to consistent parameters for the system.

ξTauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system

The long-period (P = 27.1 years) peculiar eclipsing binary e Aur, which has recently completed its two year-long primary eclipse, has perplexed astronomers for over a century. The eclipse arises from the transit of a huge, cool and opaque, disk across the face of the F0 Iab star. One of the principal problems with understanding this binary is that the very small parallax of p = (1.53 ± 1.29) mas, implying a distance range of d ∼ (0.4−4.0) kpc, returned by a revised reduction of the Hipparcos satellite observations, is so uncertain that it precludes a trustworthy estimate of the luminosities and masses of the binary components. A reliable distance determination would help solve the nature of this binary and distinguish between competing models. A new approach is discussed here: we estimate the distance to e Aur from the calibration of reddening and interstellar-medium gas absorption in the direction of the system. The distance to e Aur is estimated from its measured E(B −V) and the strength of the diffuse interstellar band 6613.56 A. Spectroscopy and UBV photometry of several B- and A-type stars (<1 ◦ of e Aur) were carried out. The distances of the reference stars were estimated from either measured or spectroscopic parallaxes. The range in distances of the reference stars is from 0.2 to 3.0 kpc. We find reasonably tight relations among E(B − V), EW, and Ic (6613 A feature) with distance. From these calibrations, a distance of d = (1.5 ± 0.5) kpc is indicated for e Aur. If e Aur is indeed at (or near) this distance, its inferred absolute visual magnitude of MV � (−9.1 ± 1.1) mag for the F-supergiant indicates that it is a very young, luminous and massive star. Noteworthy, the high luminosity inferred here is well above the maximum value of MV �− 6. m 2 expected for (less-massive) post asymptotic giant branch supergiant stars. Thus, based on the circumstantial evidence, the higher-mass model appears to best explain the properties of this mysterious binary system. As a by-product of this study, our spectroscopy led to the finding that two of the stars used in the distance calibrations, HD 31617 and HD 31894, are newly discovered spectroscopic binaries, and HD 32328 is a new radial-velocity variable.

Revised physical elements of the astrophysically important O9.5+O9.5V eclipsing binary system Y Cygni ,,

Analyses of multi-epoch, high-resolution (R ~ 50.000) optical spectra of the O-type star HD 152246 (O9 IV according to the most recent classification), complemented by a limited number of earlier published radial velocities, led to the finding that the object is a hierarchical triple system, where a close inner pair (Ba-Bb) with a slightly eccentric orbit (e = 0.11) and a period of 6.0049 days revolves in a 470-day highly eccentric orbit (e = 0.865) with another massive and brighter component A. The mass ratio of the inner system must be low since we were unable to find any traces of the secondary spectrum. The mass ratio A/(Ba+Bb) is 0.89. The outer system has recently been resolved using long-baseline interferometry on three occasions. The interferometry confirms the spectroscopic results and specifies elements of the system. Our orbital solutions, including the combined radial-velocity and interferometric solution indicate an orbital inclination of the outer orbit of 112{\deg} and stellar masses of 20.4 and 22.8 solar masses. We also disentangled the spectra of components A and Ba and compare them to synthetic spectra from two independent programmes, TLUSTY and FASTWIND. In either case, the fit was not satisfactory and we postpone a better determination of the system properties for a future study, after obtaining observations during the periastron passage of the outer orbit (the nearest chance being March 2015). For the moment, we can only conclude that component A is an O9 IV star with v*sin(i) = 210 +\- 10 km/s and effective temperature of 33000 +\- 500 K, while component Ba is an O9 V object with v*sin(i) = 65 +/- 3 km/s and T_eff = 33600 +\- 600 K.