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The surface chemical compositions of stars are affected by physical processes which bring the products of thermonuclear burning to the surface. Despite their potential in understanding the structure and evolution of stars, elemental abundances are available for only a few high-mass binary stars. We aim to enlarge this sample by determining the physical properties and photospheric abundances for four eclipsing binary systems containing high-mass stars: V1034 Sco, GL Car, V573 Car and V346 Cen. The components have masses 8-17 Msun and effective temperatures from 22500 to 32200 K, and are all on the main sequence. We present new high-resolution and high signal-to-noise spectroscopy from HARPS, and analyse them using spectral disentangling and NLTE spectral synthesis. We model existing light curves and new photometry from the TESS satellite, We measure the stellar masses to 0.6-2.0 percent precision, radii to 0.8-1.7 percent precision, effective temperatures to 1.1-1.6 percent precision, and abundances of C, N, O, Mg and Si. The abundances are similar to those found in our previous studies of high-mass eclipsing binaries; our sample now comprises 25 high-mass stars in 13 binary systems. We also find tidally-excited pulsations in V346 Cen. We reinforce our previous conclusions: interior chemical element transport is not as efficient in binary star components as in their single-star counterparts in the same mass regime and evolutionary stage, possibly due to the effects of tidal forces. Our ultimate goal is to provide a larger sample of OB-type stars in binaries which would enable a thorough comparison to stellar evolutionary models, as well as to single high-mass stars., Comment: Accepted for publication in Astronomy & Astrophysics

We present light-curve analyses of two newly identified detached eclipsing binaries, namely HD96609 and HD303734, in the region of the richly populated open cluster NGC3532. HD96609 is composed of two main sequence stars (B9-A0V + A2V) with masses and radii of M-1 = 2.66 +/- 0.02M(circle dot), M-2 = 1.84 +/- 0.01M(circle dot), R-1 = 2.740 +/- 0.006 R-circle dot, and R-2 = 1.697 +/- 0.005 R-circle dot. The positions of the components on logM - logR plane suggest log(age/yr) 8.55, corresponding 350 +/- 40 Myr of age, which agrees with the 300 +/- 100 Myr age of NGC3532 estimated in previous studies. We find the distance of HD96609 as 460 +/- 17 pc, which is consistent with the 484(-30)(+35) pc distance of NGC3532, estimated from Gaia parallaxes. HD303734 is an interesting totally eclipsing binary with a quite shallow secondary eclipse. Using photometric properties of the system in conjunction with theoretical calibrations, we estimate that HD303734 consists of A6V + K3V components. HD96609 and HD303734 are the second and third eclipsing binaries discovered in the region of NGC3532, after the first one, GV Car., NASA's Science Mission Directorate, I express my thanks to BarisHoyman for his help on production of some figures in this study. Iwould like to thank anonymous referee for his/her thoughtful comments and critically reading, which improve and clarify the manuscript. This paper includes data collected by the TESS mission, which are publicly available from the MAST. Funding for the TESS mission is provided by the NASA's Science Mission Directorate. This research has made use of NASA's Astrophysics Data System. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.

The analysis of eclipsing binaries with massive components enables to test stellar evolution models and track selected aspects of the structure of early-type stars. Stellar pairs with B-type components may serve to find tighter constraints on the mechanisms of convective core overshooting or masses ofβCephei-type stars. We present the results of an analysis of several eclipsing binaries – N Sco, LS CMa, andδVel – observed by BRITE-Constellation satellites and followed by a wide range of ground-based telescopes.

Algol-type binary systems are the product of rapid mass transfer between the initially more massive component to its companion. It is still unknown whether the process is conservative, or whether substantial mass is lost from the system. The history of a system prior to mass exchange is imprinted in the photospheric chemical composition, in particular in the carbon-to-nitrogen (C/N) ratio. We use this to trace the efficiency of mass-transfer processes in the components of a classical Algol-type system, $\delta$ Librae. The present analysis is based on new spectroscopic data (ground-based high-resolution \'echelle spectra) and extracted archival photometric observations (space-based measurements from the STEREO satellites). In the orbital solution, non-Keplerian effects on the radial-velocity variations were taken into account. This reduces the primary's mass by 1.1 \Msun\ ($\sim$23\%) significantly in comparison to previous studies, and removes a long-standing discrepancy between the radius and effective temperature. A spectral disentangling technique is applied to the \'echelle observations and the spectra of the individual components are separated. Atmospheric and abundance analyses are performed for the mass-gaining component and we found C/N $= 1.55 \pm 0.40$ for this star. An extensive set of evolutionary models ($3.5\times10^6$) for both components are calculated from which the best-fitting model is derived. It is found that $\beta$, the parameter which quantifies the efficiency of mass-loss from a binary system, is close to zero. This means that the mass-transfer in $\delta$ Lib is mostly conservative with little mass loss from the system., Comment: Accepted for publication in MNRAS, 17 pages, 11 figures

We find that the emission-line object OGLEJ005039.05-725751.4, a member of the cluster OGLE-CL SMC 64, exhibits a peculiar light curve pattern repeating with a recurrence time of 141.45 days. The light curve resembles periodic outbursts with a duty cycle of 20%. A second long cycle of 2500 days is also detected in the photometric data set. Two X-SHOOTER spectra obtained at minimum and maximum reveal a Be star dominating at minimum light resembling the Classical Be star 48 Lib. The larger Hα emission, the stronger Na D absorption and the appearance of emission in the infrared Ca II triplet at maximum, might indicate periodic mass transfer in a complex binary system., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata

We present the discovery of four low-mass ($M, 28 pages, 22 figures, 6 tables. Accepted for publication in ApJ

Contact binaries are close binary systems whose components are in physical contact and share an atmosphere. They comprise about ~ 10-20 % of all binaries in present photometric sky surveys like Kepler and OGLE and thousands of light curves and spectra of these stars are already available, a number that is expected to increase by several orders of magnitude with new all-sky surveys like Gaia and LSST. Despite being abundant, the structure of contact binaries puzzles astronomers to this day. The inconsistencies with observations and the mere complexity of the theoretical models of mass and heat transfer in these objects have resulted in their continuous neglect in modern tools of binary star analysis. The light curve analysis is instead carried out through populating the surface of the contact envelope with blackbody radiation properties, or model atmospheres computed under assumptions that apply to single stars. This Thesis highlights the key problems and inconsistencies of contact binary modeling today and proposes a framework that serves to bridge the gap between the large influx of observational data and the lack of accurate models for the analysis of said data. The basic principles of a newly developed and freely available generalized radiative transfer code are outlined and their application to different geometries and stellar structures is discussed. The final goal of this ambitious project is the computation of model atmospheres under the correct assumptions for contact binaries for use in modern binary star analysis codes. This will enable testing of the many theoretical models at hand on high-quality data that would not only reveal the true structure and populations of contact binaries, but if applied to the large samples of data from present and future large-scale sky surveys, will also uncover fundamental aspects of their formation and evolution. Kontaktne dvojne zvezde so tesne dvojnice, pri katerih sta zvezdi v fizičnem stiku in si delita atmosfero. Obsegajo približno ~ 10-20 % vseh dvojnih zvezd v dosedanjih fotometričnih in spektroskopskih pregledih neba, kot sta Kepler in OGLE. Na tisoče svetlobnih krivulj in spektrov teh zvezd je že na voljo in pričakujemo, da se bo število podatkov povečalo za nekaj redov velikosti z novimi pregledi celotnega neba, kot sta Gaia in LSST. Kljub velikemu številu podatkov kontaktnih dvojnic, njihova struktura še zmeraj ni v celoti razkrita. Sodobna orodja za analizo podatkov dvojnih zvezd ne upoštevajo teoretičnih modelov prenosa mase in toplote v kontaktnih dvojnicah, kar je posledica nedoslednosti in kompleksnosti problema. Namesto tega, analiza svetlobnih krivulj poteka z modeliranjem kontaktnih ovojnic s pomočjo modelov sevanja črnega telesa ali atmosfer enojnih zvezd. Disertacija poudarja ključne probleme in nedoslednosti modeliranja kontaktnih dvojnih zvezd danes ter predlaga način kako uskladiti veliki pritok opazovalnih podatkov in pomanjkanje natančnih modelov za analizo le-teh. Opisana so osnovna načela nove kode za sevalni prenos ter uporaba kode za modeliranje sevalnega prenosa v različnih geometrijskih in zvezdnih strukturah. Končni cilj tega ambicioznega projekta je izračun atmosferskih modelov kontaktnih dvojnih zvezd in njihova uporaba v sodobnih kodah za analizo dvojnic. To bo omogočilo preskušanje številnih teoretičnih modelov na visokokakovostnih podatkih iz sedanjih in prihodnjih obsežnih pregledih neba, ki ne bi le razkrili resnične strukture in populacije kontaktnih dvojnic, ampak tudi odkrili bistvene lastnosti njihovega nastanka in razvoja.

This is the third installment of the Galactic O-Star Spectroscopic Survey (GOSSS), a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ∼ 2500 digital observations selected from the Galactic O-Star Catalog. In this paper, we present 142 additional stellar systems with O stars from both hemispheres, bringing the total of O-type systems published within the project to 590. Among the new objects, there are 20 new O stars. We also identify 11 new double-lined spectroscopic binaries, 6 of which are of O+O type and 5 of O+B type, and an additional new tripled-lined spectroscopic binary of O+O+B type. We also revise some of the previous GOSSS classifications, present some egregious examples of stars erroneously classified as O-type in the past, introduce the use of luminosity class IV at spectral types O4-O5.5, and adapt the classification scheme to the work of Arias et al., Instituto de Astrofísica de La Plata, Facultad de Ciencias Astronómicas y Geofísicas

Aims. We study the O-type star HD 161853, which has been noted as a probable double-lined spectroscopic binary system. Methods. We secured high-resolution spectra of HD 161853 during the past nine years. We separated the two components in the system and measured their respective radial velocities for the first time. Results. We confirm that HD 161853 is an ~1 Ma old binary system consisting of an O8 V star (MA,RV ≥ 22 M⊙) and a B1–3 V star (MB,RV ≥ 7.2 M⊙) at about 1.3 kpc. From the radial velocity curve, we measure an orbital period P = 2.66765 ± 0.00001 d and an eccentricity e = 0.121 ± 0.007. Its V-band light curve is constant within 0.014 mag and does not display eclipses, from which we impose a maximum orbital inclination i = 54 deg. HD 161853 is probably associated with an H ii region and a poorly investigated very young open cluster. In addition, we detect a compact emission region at 50 arcsec to HD 161853 in 22 μm-WISE and 24 μm-Spitzer images, which may be identified as a dust wave piled up by the radiation pressure of the massive binary system. Fil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Astrofísica de la Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina Fil: Putkuri, C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Astrofísica de la Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina Fil: Morrell, Nidia Irene. Las Campanas Observatory. Carnegie Observatories; Chile Fil: Barba, Rodolfo Hector. Universidad de la Serena; Chile Fil: Arias, J. I.. Universidad de la Serena; Chile Fil: Maíz Apellániz, J.. Centro de Astrobiología; España Fil: Walborn, N. R.. Space Telescope Science Institute; Estados Unidos Fil: Sota, A.. Consejo Superior de Investigaciones Cientificas. Instituto de Astrofísica de Andalucía; España Fil: Alfaro, E. J.. Consejo Superior de Investigaciones Cientificas. Instituto de Astrofísica de Andalucía; España

Context. It appears that most (if not all) massive stars are born in multiple systems. At the same time, the most massive binaries are hard to find owing to their low numbers throughout the Galaxy and the implied large distances and extinctions. Aims. We want to study LS III +46 11, identified in this paper as a very massive binary; another nearby massive system, LS III +46 12; and the surrounding stellar cluster, Berkeley 90. Methods. Most of the data used in this paper are multi-epoch high S/N optical spectra, although we also use Lucky Imaging and archival photometry. The spectra are reduced with dedicated pipelines and processed with our own software, such as a spectroscopic-orbit code, CHORIZOS, and MGB. Results. LS III +46 11 is identified as a new very early O-type spectroscopic binary [O3.5 If* + O3.5 If*] and LS III +46 12 as another early O-type system [O4.5 V((f))]. We measure a 97.2-day period for LS III +46 11 and derive minimum masses of 38.80 ± 0.83 M⊙ and 35.60 ± 0.77 M⊙ for its two stars. We measure the extinction to both stars, estimate the distance, search for optical companions, and study the surrounding cluster. In doing so, a variable extinction is found as well as discrepant results for the distance. We discuss possible explanations and suggest that LS III +46 12 may be a hidden binary system where the companion is currently undetected., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata

Aims. We present the first orbital solution for the O-type supergiant star HD 74194, which is the optical counterpart of the supergiant fast X-ray transient IGR J08408-4503. Methods. We measured the radial velocities in the optical spectrum of HD 74194, and we determined the orbital solution for the first time. We also analysed the complex Hα profile. Results. HD 74194 is a binary system composed of an O-type supergiant and a compact object in a short-period (P = 9.5436 ± 0.0002 d) and high-eccentricity (e = 0.63 ± 0.03) orbit. The equivalent width of the Hα line is not modulated entirely with the orbital period, but seems to vary in a superorbital period (P = 285 ± 10 d) nearly 30 times longer than the orbital one., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata

Algol ($\beta$ Persei) is the prototypical semi-detached eclipsing binary and a hierarchical triple system. From 2006 to 2010 we obtained 121 high-resolution and high-S/N \'{e}chelle spectra of this object. Spectral disentangling yields the individual spectra of all three stars, and greatly improved elements both the inner and outer orbits. We find masses of $M_{\rm A} = 3.39\pm0.06$ M$_\odot$, $M_{\rm B} = 0.770\pm0.009$ M$_\odot$ and $M_{\rm C} = 1.58\pm0.09$ M$_\odot$. The disentangled spectra also give the light ratios between the components in the $B$ and $V$ bands. Atmospheric parameters for the three stars are determined, including detailed elemental abundances for Algol A and Algol C. We find the following effective temperatures: $T_{\rm A} = 12\,550\pm120$ K, $T_{\rm B} = 4900\pm300$ K and $T_{\rm C} = 7550\pm250$ K. The projected rotational velocities are $v_{\rm A} \sin i_{\rm A} = 50.8\pm0.8$ km/s, $v_{\rm B} \sin i_{\rm B} = 62\pm2$ km/s and $v_{\rm C} \sin i_{\rm C} = 12.4\pm0.6$ km/s. This is the first measurement of the rotational velocity for Algol B, and confirms that it is synchronous with the orbital motion. The abundance patterns of components A and C are identical to within the measurement errors, and are basically solar. They can be summarised as mean metal abundances: [M/H]$_{\rm A} = -0.03\pm0.08$ and [M/H]$_{\rm C} = 0.04\pm0.09$. A carbon deficiency is confirmed for Algol A, with tentative indications for a slight overabundance of nitrogen. The ratio of their abundances is (C/N)$_{\rm A} = 2.0\pm0.4$, half of the solar value of (C/N)$_{\odot} = 4.0\pm0.7$. The new results derived in this study, including detailed abundances and metallicities, will enable tight constraints on theoretical evolutionary models for this complex system., Comment: Accepted for publication in MNRAS

Knowledge of the chemical composition and absolute masses of Capella are key to understanding the evolutionary state of this benchmark binary system comprising two giant stars. Previous efforts, including our own 2009 study, have largely failed to reach an acceptable agreement between the observations and current stellar evolution models, preventing us from assessing the status of the primary. Here we report a revision of the physical properties of the components incorporating recently published high-precision radial velocity measurements, and a new detailed chemical analysis providing abundances for more than 20 elements in both stars. We obtain highly precise (to about 0.3%) masses of 2.5687 +/- 0.0074 and 2.4828 +/- 0.0067 solar masses, radii of 11.98 +/- 0.57 and 8.83 +/- 0.33 solar radii, effective temperatures of 4970 +/- 50 K and 5730 +/- 60 K, and independently measured luminosities based on the orbital parallax (78.7 +/- 4.2 and 72.7 +/- 3.6 solar luminosities). We find an excellent match to stellar evolution models at the measured composition of [Fe/H] = -0.04 +/- 0.06. Three different sets of models place the primary star firmly at the end of the core helium-burning phase (clump), while the secondary is known to be evolving rapidly across the Hertzprung gap. The measured lithium abundance, the C/N ratio, and the 12C/13C isotopic carbon abundance ratio, which change rapidly in the giant phase, are broadly in agreement with expectations from models. Predictions from tidal theory for the spin rates, spin-orbit alignment, and other properties do not fare as well, requiring a 40-fold increase in the efficiency of the dissipation mechanisms in order to match the observations., Comment: 15 pages in emulateapj format, including figures and tables, accepted for publication in The Astrophysical Journal

The detailed chemical composition of most metal-poor halo stars has been found to be highly uniform, but a minority of stars exhibit dramatic enhancements in their abundances of heavy neutron-capture elements and/or of carbon. The key question for Galactic chemical evolution models is whether these peculiarities reflect the composition of the natal clouds, or if they are due to later mass transfer of processed material from a binary companion. If the former case applies, the observed excess of certain elements was implanted within selected clouds in the early ISM from a production site at interstellar distances. Our aim is to determine the frequency and orbital properties of binaries among these chemically peculiar stars. This information provides the basis for deciding whether mass transfer from a binary companion is necessary and sufficient to explain their unusual compositions. This paper discusses our study of a sample of 17 moderately (r-I) and highly (r-II) r-process-element enhanced VMP and EMP stars. High-resolution, low signal-to-noise spectra of the stars were obtained at roughly monthly intervals over 8 years with the FIES spectrograph at the Nordic Optical Telescope. From these spectra, radial velocities with an accuracy of ~100 m/s were determined by cross-correlation against an optimized template. 14 of the programme stars exhibit no significant RV variation over this period, while 3 are binaries with orbits of typical eccentricity for their periods, resulting in a normal binary frequency of ~18+-6% for the sample. Our results confirm our preliminary conclusion from 2011, based on partial data, that the chemical peculiarity of the r-I and r-II stars is not caused by any putative binary companions. Instead, it was imprinted on the natal molecular clouds of these stars by an external, distant source. Models of the ISM in early galaxies should account for such mechanisms., Comment: 14 pages, 3 figures, accepted for publication in Astronomy and Astrophysics

The results of a search for eclipsing Am star binaries using photometry from the SuperWASP survey are presented. The light curves of 1742 Am stars fainter than V = 8.0 were analysed for the presence of eclipses. A total of 70 stars were found to exhibit eclipses, with 66 having sufficient observations to enable orbital periods to be determined and 28 of which are newly identified eclipsing systems. Also presented are spectroscopic orbits for 5 of the systems. The number of systems and the period distribution is found to be consistent with that identified in previous radial velocity surveys of " classical" Am stars. Fil: Smalley, B.. Keele University; Reino Unido Fil: Southworth, J.. Keele University; Reino Unido Fil: Pintado, Olga Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentina Fil: Gillon, M.. Université de Liege; Bélgica Fil: Holdsworth, D. L.. Keele University; Reino Unido Fil: Anderson, D. R.. Keele University; Reino Unido Fil: Barros, S. C. C.. Aix-Marseille Université; Francia. Centre National de la Recherche Scientifique; Francia Fil: Collier Cameron, A.. University of St. Andrews; Reino Unido Fil: Delrez, L.. Université de Liege; Bélgica Fil: Faedi, F.. University of Warwick; Reino Unido Fil: Haswell, C. A.. Open University; Reino Unido Fil: Hellier, C.. Keele University; Reino Unido Fil: Horne, K.. University of St. Andrews; Reino Unido Fil: Jehin, E.. Université de Liege; Bélgica Fil: Maxted, P. F. L.. Keele University; Reino Unido Fil: Norton, Andrew. Open University; Reino Unido Fil: Pollacco, D.. University of Warwick; Reino Unido Fil: Skillen, I.. Isaac Newton Group of Telescopes; España Fil: Smith, A. M. S.. Polish Academy of Sciences; Argentina Fil: West, R. G.. University of Warwick; Reino Unido Fil: Wheatley, P. J.. University of Warwick; Reino Unido

Black holes are now commonplace, among the stars, in Galactic centers, and perhaps other places. But within living memory, their very existence was doubted by many, and few chose to look for them. Zeldovich and Guseinov were first, followed by Trimble and Thorne, using a method that would have identified HDE 226868 as a plausible candidate, if it had been in the 1968 catalogue of spectroscopic binaries. That it was not arose from an unhappy accident in the observing program of Daniel M. Popper long before the discovery of X-ray binaries and the identification of Cygnus X-1 with that hot, massive star and its collapsed companion., Comment: Key Words: Black holes, collapsed stars, Cygnus X-1, HDE 226868, spectroscopic binaries Journal: The Zeldovich Universe Genesis and Growth of the Cosmic Web IAU Symposium 308, 23-28 June 2014, Tallinn, Estonia) http://iau.maido.ee/proceedings

The bright binary system YZ Cassiopeiae is a remarkable laboratory for studying the Am phenomenon. It consists of a metallic-lined A2 star and an F2 dwarf on a circular orbit, which undergo total and annular eclipses. We present an analysis of 15 published light curves and 42 new high-quality echelle spectra, resulting in measurements of the masses, radii, effective temperatures and photospheric chemical abundances of the two stars. The masses and radii are measured to 0.5% precision: M_A = 2.263 +/- 0.012 Msun, M_B = 1.325 +/- 0.007 Msun, R_A = 2.525 +/- 0.011 Rsun and R_B = 1.331 +/- 0.006 Rsun. We determine the abundance of 20 elements for the primary star, of which all except scandium are super-solar by up to 1 dex. The temperature of this star (9520 +/- 120 K) makes it one of the hottest Am stars. We also measure the abundances of 25 elements for its companion (Teff = 6880 +/- 240 K), finding all to be solar or slightly above solar. The photospheric abundances of the secondary star should be representative of the bulk composition of both stars. Theoretical stellar evolutionary models are unable to match these properties: the masses, radii and temperatures imply a half-solar chemical composition (Z = 0.009 +/- 0.003) and an age of 490-550 Myr. YZ Cas therefore presents a challenge to stellar evolutionary theory., Comment: Accepted for publication in MNRAS. 15 pages, 9 tables, 7 figures

We present a spectroscopic study of the eclipsing binary system AS Camelopardalis, the first such study based on phase-resolved CCD echelle spectra. Via a spectral disentangling analysis we measure the minimum masses of the stars to be M_A sin^3 i = 3.213 +/- 0.007 M_sun and M_B sin^3 i = 2.323 +/- 0.006 M_sun, their effective temperatures to be T_eff(A) = 12840 +/- 120 K and T_eff(B) = 10580 +/- 240 K, and their projected rotational velocities to be v_A sin i_A = 14.5 +/- 0.1 km/s and v_B sin i_B = 4.6 +/- 0.1 km/s. These projected rotational velocities appear to be much lower than the synchronous values. We show that measurements of the apsidal motion of the system suffer from a degeneracy between orbital eccentricity and apsidal motion rate. We use our spectroscopically-measured e = 0.164 +/- 0.001 to break this degeneracy and measure (d omega_obs / dt) = 0.133 +/- 0.010 deg/yr. Subtracting the relativistic contribution of (d omega_GR / dt) = 0.0963 +/- 0.0002 deg/yr yields the contribution due to tidal torques: (d omega_cl / dt) = 0.037 +/- 0.010 deg/yr. This value is much smaller than the rate predicted by stellar theory, 0.40--0.87 deg/yr. We interpret this as a misalignment between the orbital axis of the close binary and the rotational axes of its component stars, which also explains their apparently low rotational velocities. The observed and predicted apsidal motion rates could be brought into agreement if the stars were rotating three times faster than synchronous about axes perpendicular to the orbital axis. Measurement of the Rossiter-McLaughlin effect can be used to confirm this interpretation., Submitted to ApJL on 9 Feb 2011

If binaries are common among massive stars, it will have important consequences for the derivation of fundamental properties such as the cluster age, initial mass function, and dynamical mass. Making use of the multiplexing facilities of the Gemini Multi-Object Spectrograph, we were able to investigate the presence of binary stars within the ionizing cluster of 30 Doradus. From a seven-epoch observing campaign at Gemini South we detect a binary candidate rate of about 50%, which is consistent with an intrinsic 100% binary rate among massive stars. We find that single-epoch determinations of the velocity dispersion give values around 30 kms-1. After correcting the global velocity dispersion for the binary orbital motions, the "true" cluster velocity dispersion is 8.3 kms-1. This value implies a virial mass of about 4.5 × 105 M or 8% of the mass calculated using the single-epoch value. The binary corrected virial mass estimate is consistent with photometric mass determinations, thus suggesting that NGC2070 is a firm candidate for a future globular cluster., Facultad de Ciencias Astronómicas y Geofísicas

Context. WR 29 is a known WN7h+O double-lined binary system with a rather short period (3.164 days). Aims. We search for light variations to determine the inclination of the system and thus the absolute masses of both components. Methods. We observed photometrically the field of WR 29 between December, 2002, and February, 2006. Results. We find that the V light of WR 29 varies in phase with the spectroscopic period of 3.16412 days, presenting two minima corresponding to the conjunctions of the binary components. Numerical models fitted to the light curve indicate an orbital inclination of about 44◦, and masses of 53 M and 42 M for the O- and WN-type components, respectively. Fil: Gamen, Roberto Claudio. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina Fil: Fernandez Lajus, Eduardo Eusebio. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina Fil: Niemela, Virpi Sinikka. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina Fil: Barba, Rodolfo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentina

We present the results of a spectroscopic monitoring campaign devoted to three O-type stars in the Carina nebula. We derive the full SB2 orbital solution of the binary system Tr 16-112, an exceptional dissymmetrical system consisting of an O5.5-6V((f$^+$?p)) primary and a B2V-III secondary. We also report on low-amplitude brightness variations in Tr 16-112 that are likely due to the ellipsoidal shape of the O5.5-6 primary revolving in an eccentric orbit around the system's centre of mass. We detect for the first time a clear SB2 binary signature in the spectrum of HD 93343 (O8 + O8), although our data are not sufficient to establish an orbital solution. This system also displays low amplitude photometric modulations. On the other hand, no indication of multiplicity is found in the optical spectra of HD 93250. Finally, we discuss the general properties of multiple massive stars in the Carina OB1 association., Accepted for publication in MNRAS