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

Mayer, P.; Harmanec, P.; Nesslinger, S.; Lorenz, R.; Drechsel, H.; Morrell, N.; Wolf, M.

doi:10.1051/0004-6361:20078542

Cited by 26 publications

(48 citation statements)

References 38 publications

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“…The He ii 4686 Å emission in HD 152248 may also be due to gas streams in a close binary. This object was recently studied by Mayer et al (2008) and the stellar mass of 30 M in that paper is probably more accurate than the stellar mass listed in Table 2 (as it is simply derived from the binary motion). However, we find the Hα shape in HD 152248 very reminiscent of that in λ Cep and ζ Pup.…”

Section: Onfp Starsmentioning

confidence: 94%

On the presence and absence of disks around O-type stars

Vink¹,

Davies

Harries

et al. 2009

A&A

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Context. As the favoured progenitors of long-duration gamma-ray bursts, massive stars may represent our best signposts of individual objects in the early Universe, but special conditions seem required to make these bursters. These are thought to originate from the progenitor's rapid rotation and associated asymmetry. Aims. To obtain empirical constraints on the interplay between stellar rotation and wind asymmetry, we perform linear Hα spectropolarimetry on a sample of 18 spectroscopically peculiar massive O stars, including OVz, Of?p, Oe, and Onfp stars, supplemented by an earlier sample of 20 O supergiants of Harries et al. (2002, MNRAS, 337, 341), yielding a total number of 38 O-type stars. Our study's global aim is to characterize the differences between, and similarities amongst, different classes of peculiar O stars and to establish in how far they differ from garden-variety O stars. Methods. Our linear (Stokes QU) spectropolarimetry data should be regarded a geometric counterpart to (Stokes I) spectral classification, setting the stage for circular (Stokes V) polarimetric searches for magnetic fields. Results. Despite their rapid rotation (with v sin i up to ∼400 km s −1 ) most O-type stars are found to be spherically symmetric, but with notable exceptions amongst specific object classes. We divide the peculiar O stars into four distinct categories: Group I includes the suspected young zero-age main sequence OVz stars and related weak-winds objects, of which the magnetic star Θ 1 Ori C is the most famous member. These objects show no evidence for significant linear polarization. Group II includes the Of?p stars, in which one of its members, HD 191612, was also found to be magnetic. These objects show more linear polarization activity than those in Group I. Group III includes the Oe stars, which have been suggested to be the more massive counterparts to classical Be stars, and Group IV concerns the Onfp stars. Objects from the latter two groups are on the high-end tail of the O-star rotation distribution and have in the past been claimed to be embedded in disks. Here we report the detection of a classical depolarization "line effect" in the Oe star HD 45314, but the overall incidence of line effects amongst Oe stars is significantly lower (1 out of 6) than amongst Be stars. The chance that the Oe and Be datasets are drawn from the same parent population is negligible (with 95% confidence). This implies there is as yet no evidence for a disk hypothesis in Oe stars, providing relevant constraints on the physical mechanism that is responsible for the Be phenomenon. Finally, we find that 3 out of 4 of the Group IV Onfp stars show evidence for complex polarization effects, which are likely related to rapid rotation, and we speculate on the evolutionary links to B[e] stars.

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Section: Onfp Starsmentioning

confidence: 94%

On the presence and absence of disks around O-type stars

Vink¹,

Davies

Harries

et al. 2009

A&A

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“…These models are inspired by the following massive binaries: HD 93205, HD 93403, HD 101131, HD 152218, and HD 152248, and are named models E1, E2, E3, E4, and E5. The stars were studied by: Antokhina et al (2000), Rauw et al (2000), Gies et al (2002), Sana et al (2008), Mayer et al (2008), and Sana et al (2001). The parameters used for the computation are given in Table 4.…”

Section: Eccentric Modelsmentioning

confidence: 99%

“…References. From Antokhina et al (2000), Rauw et al (2000), Gies et al (2002), Sana et al (2008), Mayer et al (2008), and Sana et al (2001) for models E1 to E5. A sample of the phase-dependent behaviour of the mean radius, gravity, and temperature as well as their maximum and minimum values are shown in Figs.…”

Section: Notesmentioning

confidence: 99%

Spectral modelling of massive binary systems

Palate

Rauw

Koenigsberger

et al. 2013

A&A

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Context. The spectra of massive binaries may be affected by interactions between the stars in the system. These are believed to produce observational phenomena such as the Struve-Sahade effect. Aims. We simulate the spectra of massive binaries at different phases of the orbital cycle, accounting for the gravitational influence of the companion star on the shape and physical properties of the stellar surface. Methods. We used the Roche potential modified to account for radiation pressure to compute the stellar surface of close circular systems. We furthermore used the tidal interactions with dissipation of energy through shear code for surface computations of eccentric systems. In both cases, we accounted for gravity darkening and mutual heating generated by irradiation to compute the surface temperature. We then interpolated non-local thermodynamic equilibrium (NLTE) plane-parallel atmosphere model spectra in a grid to obtain the local spectrum at each surface point. We finally summed all contributions, accounting for the Doppler shift, limb-darkening, and visibility to obtain the total synthetic spectrum. We computed different orbital phases and different sets of physical and orbital parameters. Results. Our models predict line strength variations through the orbital cycle, but fail to completely reproduce the Struve-Sahade effect. Including radiation pressure allows us to reproduce a surface temperature distribution that is consistent with observations of semi-detached binary systems. Conclusions. Radiation pressure effects on the stellar surface are weak in (over)contact binaries and well-detached systems but can become very significant in semi-detached systems. The classical von Zeipel theorem is sufficient for the spectral computation. Broad-band light curves derived from the spectral computation are different from those computed with a model in which the stellar surfaces are equipotentials of the Roche potential scaled by the instantaneous orbital separation. In many cases, the fit of two Gaussian/Lorentzian profiles fails to properly measure the equivalent width of the lines and leads to apparent variations that could explain some of the effects reported in the literature.

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“…The very young and rich open cluster NGC 6231 (Sung et al 1998;Reipurth 2008;Kuhn et al 2017, and references therein) hosts a population of 15 massive O-type objects with a high incidence of short-period binaries (Sana et al 2008). The most emblematic O-star binary in NGC 6231 is probably the O7.5 III(f) + O7 III(f) system HD 152 248 (Sana et al 2001;Mayer et al 2008). The binarity of this star was discovered by Struve (1944), and its orbital period near 6 d was first established by Hill et al (1974).…”

Section: Introductionmentioning

confidence: 99%

Apsidal motion in the massive binary HD 152248

Rosu

Rauw

Conroy

et al. 2020

A&A

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Context. The eccentric massive binary HD 152248 (also known as V1007 Sco), which hosts two O7.5 III-II(f) stars, is the most emblematic eclipsing O-star binary in the very young and rich open cluster NGC 6231. Its properties render the system an interesting target for studying tidally induced apsidal motion. Aims. Measuring the rate of apsidal motion in such a binary system gives insight into the internal structure and evolutionary state of the stars composing it. Methods. A large set of optical spectra was used to reconstruct the spectra of the individual binary components and establish their radial velocities using a disentangling code. Radial velocities measured over seven decades were used to establish the rate of apsidal motion. We furthermore analysed the reconstructed spectra with the CMFGEN model atmosphere code to determine stellar and wind properties of the system. Optical photometry was analysed with the Nightfall binary star code. A complete photometric and radial velocity model was constructed in PHOEBE 2 to determine robust uncertainties. Results. We find a rate of apsidal motion of (1.843−0.083+0.064)° yr−1. The photometric data indicate an orbital inclination of (67.6−0.1+0.2)° and Roche-lobe filling factors of both stars of about 0.86. Absolute masses of 29.5−0.4+0.5 M⊙ and mean stellar radii of 15.07−0.12+0.08 R⊙ are derived for both stars. We infer an observational value for the internal structure constant of both stars of 0.0010 ± 0.0001. Conclusions. Our in-depth analysis of the massive binary HD 152248 and the redetermination of its fundamental parameters can serve as a basis for the construction of stellar evolution models to determine theoretical rates of apsidal motion to be compared with the observational one. In addition, the system hosts two twin stars, which offers a unique opportunity to obtain direct insight into the internal structure of the stars.

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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

Cited by 26 publications

References 38 publications

On the presence and absence of disks around O-type stars

On the presence and absence of disks around O-type stars

Spectral modelling of massive binary systems

Apsidal motion in the massive binary HD 152248

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