The massive binary CPD - 41° 7742

Sana, H.; Antokhina, É. A.; Royer, P.; Manfroid, Jean; Gosset, Éric; Rauw, Grégor; Vreux, Jean-Marie

doi:10.1051/0004-6361:20052746

Cited by 37 publications

(61 citation statements)

References 45 publications

(50 reference statements)

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“…We adopt the distance to NGC 6231 as V 0 − M V = 11.0 mag. This value is in excellent agreement with the value obtained by Sana et al (2005). Although there is a slight difference in the adopted reddening law, this value is identical to the value obtained by SBL98 and adopted by Sana et al (2006).…”

Section: Color-magnitude Diagrams and Distancesupporting

confidence: 90%

The Initial Mass Function and the Surface Density Profile of NGC 6231

Sung

Sana²,

Bessell

2013

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We have performed new wide-field photometry of the young open cluster NGC 6231 to study the shape of the initial mass function (IMF) and mass segregation. We also investigated the reddening law toward NGC 6231 from optical to mid-infrared color excess ratios, and found that the total-to-selective extinction ratio is R V = 3.2, which is very close to the normal value. But many early-type stars in the cluster center show large color excess ratios. We derived the surface density profiles of four member groups, and found that they reach the surface density of field stars at about 10 , regardless of stellar mass. The IMF of NGC 6231 is derived for the mass range 0.8-45 M . The slope of the IMF of NGC 6231 (Γ = −1.1 ± 0.1) is slightly shallower than the canonical value, but the difference is marginal. In addition, the mass function varies systematically, and is a strong function of radius-it is very shallow at the center, and very steep at the outer ring suggesting the cluster is mass segregated. We confirm the mass segregation for the massive stars (m 8 M ) by a minimum spanning tree analysis. Using a Monte Carlo method, we estimate the total mass of NGC 6231 to be about 2.6 (±0.6) × 10 3 M . We constrain the age of NGC 6231 by comparison with evolutionary isochrones. The age of the low-mass stars ranges from 1 to 7 Myr with a slight peak at 3 Myr. However, the age of the high-mass stars depends on the adopted models and is 3.5 ± 0.5 Myr from the non-rotating or moderately rotating models of Brott et al. as well as the non-rotating models of Ekström et al. But the age is 4.0-7.0 Myr if the rotating models of Ekström et al. are adopted. This latter age is in excellent agreement with the timescale of ejection of the high-mass runaway star HD 153919 from NGC 6231, albeit the younger age cannot be entirely excluded.

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Section: Color-magnitude Diagrams and Distancesupporting

confidence: 90%

The Initial Mass Function and the Surface Density Profile of NGC 6231

Sung

Sana²,

Bessell

2013

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“…The collision of the primary wind with the secondary surface could generate an X-ray emission associated with the secondary inner surface. The short timescale X-ray variability could then result from occultation effects very much like those observed for CPD−41 • 7742 (Sana et al 2005). Though this scenario seems to agree with the results of the Doppler tomography where we have seen that the emission is only due to the primary star, the position of the contact zone remains unknown because the wind parameters of the secondary star are uncertain.…”

Section: Colliding Wind and Non-thermal Radio Emissionsupporting

confidence: 83%

Evidence for a physically bound third component in HD 150136

Mahy

Gosset

Sana

et al. 2012

A&A

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Context. HD 150136 is one of the nearest systems harbouring an O3 star. Although this system was considered for a long time as a binary, more recent investigations have suggested the possible existence of a third component. Aims. We present a detailed analysis of HD 150136 to test its triple nature. In addition, we investigate the physical properties of the individual components of this system. Methods. We analysed high-resolution, high signal-to-noise data collected through multi-epoch runs spread over ten years. We applied a disentangling program to refine the radial velocities and to obtain the individual spectra of each star. With the radial velocities, we computed the orbital solution of the inner system, and we describe the main properties of the orbit of the outer star such as the preliminary mass ratio, the eccentricity, and the orbital-period range. With the individual spectra, we determined the stellar parameters of each star by means of the CMFGEN atmosphere code. Results. We offer clear evidence that HD 150136 is a triple system composed of an O3V((f * ))-3.5V((f + )), an O5.5-6V((f)), and an O6.5-7V((f)) star. The three stars are between 0-3 Myr old. We derive dynamical masses of about 64, 40, and 35 M for the primary, the secondary and the third components by assuming an inclination of 49 • (sin 3 i = 0.43). It currently corresponds to one of the most massive systems in our galaxy. The third star moves with a period in the range of 2950 to 5500 d on an outer orbit with an eccentricity of at least 0.3. However, because of the long orbital period, our dataset is not sufficient to constrain the orbital solution of the tertiary component with high accuracy. Conclusions. We confirm there is a tertiary star in the spectrum of HD 150136 and show that it is physically bound to the inner binary system. This discovery makes HD 150136 the first confirmed triple system with an O3 primary star.

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“…(a) Boyajian et al (2007); (b) Maíz-Apellániz et al (2004); (c) Sana et al (2013); (d) Sana et al (2012); (e) Rauw et al (2012); (f) De Becker et al (2012); (g) Sota et al (2014); (1) Kaltcheva & Hilditch (2000); (2) Smith (2006); (3) Herbst & Havlen (1977); (4) Sana et al (2005); (5) Sung et al (2013); (6) Prisinzano et al (2005); (7) Ibanoglu et al (2013); (8) Dufton et al (2006); (9) Benaglia et al (2006).…”

Section: Introductionmentioning

confidence: 99%

Resolved astrometric orbits of ten O-type binaries

Bouquin

Sana²,

Gosset

et al. 2017

A&A

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Aims. Our long-term aim is to derive model-independent stellar masses and distances for long period massive binaries by combining apparent astrometric orbit with double-lined radial velocity amplitudes (SB2). Methods. We followed-up ten O+O binaries with AMBER, PIONIER and GRAVITY at the VLTI. Here, we report on 130 astrometric observations over the last seven years. We combined this dataset with distance estimates to compute the total mass of the systems. We also computed preliminary individual component masses for the five systems with available SB2 radial velocities. Results. Nine of the ten binaries have their three-dimensional orbit well constrained. Four of them are known to be colliding wind, non-thermal radio emitters, and thus constitute valuable targets for future high angular resolution radio imaging. Two binaries break the correlation between period and eccentricity tentatively observed in previous studies. This suggests either that massive star formation produces a wide range of systems, or that several binary formation mechanisms are at play. Finally, we found that the use of existing SB2 radial velocity amplitudes can lead to unrealistic masses and distances. Conclusions. If not understood, the biases in radial velocity amplitudes will represent an intrinsic limitation for estimating dynamical masses from SB2+interferometry or SB2+Gaia. Nevertheless, our results can be combined with future Gaia astrometry to measure the dynamical masses and distances of the individual components with an accuracy of 5 to 15%, completely independently of the radial velocities.

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The massive binary CPD - 41° 7742

Cited by 37 publications

References 45 publications

The Initial Mass Function and the Surface Density Profile of NGC 6231

The Initial Mass Function and the Surface Density Profile of NGC 6231

Evidence for a physically bound third component in HD 150136

Resolved astrometric orbits of ten O-type binaries

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