Spectroscopy of B and Be stars in the diffuse stellar clusters NGC 6871 and NGC 6913

Malchenko, S. L.; Tarasov, A. E.

doi:10.1007/s10511-009-9061-9

Cited by 6 publications

(7 citation statements)

References 27 publications

(93 reference statements)

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“…In addition, Boeche et al (2004) published the first SB1 orbital solution for this star. This SB1 binary status was moreover confirmed by a recent analysis of Malchenko & Tarasov (2009). We obtained nineteen spectra of HD 229234 between Sep. 2008 (HJD = 4717.3892) and Aug. 2010 (HJD = 5421.4347).…”

Section: Hd 229234supporting

confidence: 77%

A spectroscopic investigation of the O-type star population in four Cygnus OB associations

Mahy

Rauw

Becker

et al. 2013

A&A

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Context. Establishing the multiplicity of O-type stars is the first step towards accurately determining their stellar parameters. Moreover, the distribution of the orbital parameters provides observational clues to the way that O-type stars form and to the interactions during their evolution. Aims. Our objective is to constrain the multiplicity of a sample of O-type stars belonging to poorly investigated OB associations in the Cygnus complex and for the first time to provide orbital parameters for binaries identified in our sample. Such information is relevant to addressing the issue of the binarity in the context of O-type star formation scenarios. Methods. We performed a long-term spectroscopic survey of nineteen O-type stars. We searched for radial velocity variations to unveil binaries on timescales from a few days up to a few years, on the basis of a large set of optical spectra. Results. We confirm the binarity for four objects: HD 193443, HD 228989, HD 229234, and HD 194649. We derive for the first time the orbital solutions of three systems, and we confirm the values of the fourth, showing that these four systems all have orbital periods shorter than 10 days. Besides these results, we also detect several objects that show non-periodic line profile variations in some of their spectral lines. These variations mainly occur in the spectral lines that are generally affected by the stellar wind and are not likely to be related to binarity. Conclusions. The minimal binary fraction in our sample is estimated to be 21%, but it varies from one OB association to the next. Indeed, 3 O stars of our sample out of 9 (33%) belonging to Cyg OB1 are binary systems, 0% (0 out of 4) in Cyg OB3, 0% (0 out of 3) in Cyg OB8, and 33% (1 out of 3) in Cyg OB9. Our spectroscopic investigation also stresses the absence of long-period systems among the stars in our sample. This result contrasts with the case of the O-type stellar population in NGC 2244 among which no object showed radial velocity variations on short timescales. However, we show that it is probably an effect of the sample and that this difference does not a priori suggest a somewhat different star forming process in these two environments.

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Section: Hd 229234supporting

confidence: 77%

A spectroscopic investigation of the O-type star population in four Cygnus OB associations

Mahy

Rauw

Becker

et al. 2013

A&A

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“…This study continues a series of papers on the population of Be-stars in young open clusters [6,7]. The purpose of this work is to study the Hα emission line of the Be-stars of these clusters and, where possible, identify new Be-stars.…”

Section: Introductionmentioning

confidence: 75%

“…The blue regions of the spectra were used to estimate the effective temperature T eff and the logarithm of the acceleration of gravity at the stars' surfaces, log g, without taking the possible contribution of HI emission to the continuum. (The methods used to determine these parameters are described elsewhere [6,7].) The spectra in the blue region of object 74 correspond to those of a cold star.…”

Section: Spectral Observations Of Members Of the Clustermentioning

confidence: 99%

B and Be-stars in the young open stellar clusters NGC 659 and NGC 7419

Malchenko

Tarasov

2011

Astrophysics

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The populations of B and Be-stars in the young open clusters NGC 7419 and NGC 659 are studied. Lowresolution spectral observations in the region of the Hα line are used to study 34 members of NGC 7419 and additional spectra in the range λ3700-6200 Å are obtained for 12 stars. During the period of our observations, four previously identified Be-stars manifested an absorption profile for the Hα line. Emission in the Hα line is observed in the spectra of 21 objects. The members of the cluster NGC 7419 are classified as to spectral type. The position of the Be-stars on a two-color IR diagram and a comparison with the position of the objects in other clusters with similar ages cast doubt on the existence of two starformation waves. Moderate resolution spectra were obtained for 22 stars in the cluster NGC 659 over wavelengths of λ4050-5200 Å and for 7 objects in the neighborhood of the Hα line. Emission is observed in both the Hα and Hβ lines for two of the five Be-stars that were studied, while faint emission appears only in the Hα line in one of the stars. The other members of the cluster show no signs of emission in these spectra. T eff , log g, and Vsini are estimated for the observed stars. It is found that 5 of the objects are not members of the cluster.

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“…This analysis focuses on WR 133, a relatively understudied binary classified as WN5o+O9I by Smith et al (1996), where the 'o' suffix denotes no measurable hydrogen in the WR spectrum and the 'N' denotes it as nitrogen-rich. The system is a bright member of NGC 6871 (Rosslowe & Crowther 2015), a cluster residing at a distance of 2.14±0.07 kpc according to Malchenko & Tarasov (2009). The system is used in the calibration of WR star parameters by Rosslowe & Crowther (2015).…”

Section: Introductionmentioning

confidence: 99%

The First Dynamical Mass Determination of a Nitrogen-rich Wolf–Rayet Star Using a Combined Visual and Spectroscopic Orbit

Richardson

Lee

Schaefer

et al. 2021

ApJL

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We present the first visual orbit for the nitrogen-rich Wolf-Rayet binary, WR 133 (WN5o + O9I) based on observations made with the CHARA Array and the MIRC-X combiner. This orbit represents the first visual orbit for a WN star and only the third Wolf-Rayet star with a visual orbit. The orbit has a period of 112.8 d, a moderate eccentricity of 0.36, and a separation of a= 0.79 mas on the sky. We combine the visual orbit with an SB2 orbit and Gaia parallax to find that the derived masses of the component stars are M WR = 9.3 ± 1.6M and M O = 22.6 ± 3.2M , with the large errors owing to the nearly face-on geometry of the system combined with errors in the spectroscopic parameters. We also derive an orbital parallax that is identical to the Gaia-determined distance. We present a preliminary spectral analysis and atmosphere models of the component stars, and find the mass-loss rate in agreement with polarization variability and our orbit. However, the derived masses are low compared to the spectral types and spectral model. Given the close binary nature, we suspect that WR 133 should have formed through binary interactions, and represents an ideal target for testing evolutionary models given its membership in the cluster NGC 6871.

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Spectroscopy of B and Be stars in the diffuse stellar clusters NGC 6871 and NGC 6913

Cited by 6 publications

References 27 publications

A spectroscopic investigation of the O-type star population in four Cygnus OB associations

A spectroscopic investigation of the O-type star population in four Cygnus OB associations

B and Be-stars in the young open stellar clusters NGC 659 and NGC 7419

The First Dynamical Mass Determination of a Nitrogen-rich Wolf–Rayet Star Using a Combined Visual and Spectroscopic Orbit

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