Radial Velocities of Galactic O-Type Stars. I. Short-Term Constant Velocity Stars

Gies, Douglas R.; Hillwig, Todd C.; McSwain, M. Virginia; Huang, W.

doi:10.1088/0004-6256/142/5/146

Cited by 12 publications

(7 citation statements)

References 55 publications

(72 reference statements)

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“…However, we do not observe the usual line doubling in our spectra. All recent data (our work and literature; Williams et al 2011) are very similar with RVs between −70 and −90 km s −1 ; old RV measurements (Feast & Thackeray 1963;Kilkenny & Hill 1975) differ from these, reaching higher and lower values. However, even after discarding them, the RV changes are found to be significant hence we classify this star as RV variable.…”

Section: C27 Hd 124979supporting

confidence: 83%

Chemical abundances of fast-rotating massive stars

Cazorla

Morel

Nazé

et al. 2017

A&A

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Aims. Recent observations have challenged our understanding of rotational mixing in massive stars by revealing a population of fastrotating objects with apparently normal surface nitrogen abundances. However, several questions have arisen because of a number of issues, which have rendered a reinvestigation necessary; these issues include the presence of numerous upper limits for the nitrogen abundance, unknown multiplicity status, and a mix of stars with different physical properties, such as their mass and evolutionary state, which are known to control the amount of rotational mixing. Methods. We have carefully selected a large sample of bright, fast-rotating early-type stars of our Galaxy (40 objects with spectral types between B0.5 and O4). Their high-quality, high-resolution optical spectra were then analysed with the stellar atmosphere modelling codes DETAIL/SURFACE or CMFGEN, depending on the temperature of the target. Several internal and external checks were performed to validate our methods; notably, we compared our results with literature data for some well-known objects, studied the effect of gravity darkening, or confronted the results provided by the two codes for stars amenable to both analyses. Furthermore, we studied the radial velocities of the stars to assess their binarity.Results. This first part of our study presents our methods and provides the derived stellar parameters, He, CNO abundances, and the multiplicity status of every star of the sample. It is the first time that He and CNO abundances of such a large number of Galactic massive fast rotators are determined in a homogeneous way.

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Section: C27 Hd 124979supporting

confidence: 83%

Chemical abundances of fast-rotating massive stars

Cazorla

Morel

Nazé

et al. 2017

A&A

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“…Radial velocity variations have been reported for this object from low‐resolution monitoring (Combi et al 2011; Williams et al 2011), suggesting the star to be a binary. With the information at hand before this study, X‐rays linked to a wind–wind collision might at first seem a good explanation for the observed high‐energy characteristics.…”

Section: Resultsmentioning

confidence: 63%

“…Moreover, HD 93250 displays large X‐ray variations (Rauw et al 2009), which reinforces the suspicion of a binary nature. Though radial velocity variations have never been observed up to now (see Rauw et al 2009; Williams et al 2011, and references therein), a close companion was recently detected using interferometry (Sana et al 2011). HD 93250 now appears to be composed of two similar stars, whose winds collide, in a long‐period, eccentric orbit.…”

Section: Resultsmentioning

confidence: 99%

Magnetometry of a sample of massive stars in Carina★

Nazé¹,

Bagnulo²,

Petit³

et al. 2012

Monthly Notices of the Royal Astronomical Society

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X-ray surveys of the Carina nebula have revealed a few hard and luminous sources associated with early-type stars. Such unusual characteristics for the high-energy emission may be related to magnetically confined winds. To search for the presence of magnetic fields in these objects, we performed a limited spectropolarimetric survey using the Focal reducer and low dispersion spectrograph (FORS) instrument. The multi-object mode was used, so that a total of 21 OB stars could be investigated during a one-night-long run. A magnetic field was detected in two objects of the sample, with a 6σ significance: Tr16-22 and 13. Such a detection was expected for Tr16-22, as its X-ray emission is too bright, variable and hard, compared to other late-type O or O+OB systems. It is more surprising for Tr16-13, a poorly known star which so far has never shown any peculiar characteristics. Subsequent monitoring is now needed to ascertain the physical properties of these objects and enable a full modelling of their magnetic atmospheres and winds.

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“…This suggests an orbital period around 8.5 years, making 9 Sgr one of the spectroscopic O-type binaries with the longest orbital period so far. Williams et al (2011) recently presented a set of 16 RV measurements of 9 Sgr, obtained over 13 consecutive nights in May-June 2004, i.e. near maximum RV separation.…”

Section: Discussionmentioning

confidence: 99%

9 Sagittarii: uncovering an O-type spectroscopic binary with an 8.6 year period

Rauw

Sana

Spano

et al. 2012

A&A

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Context. The O-type object 9 Sgr is a well-known synchrotron radio emitter. This feature is usually attributed to colliding-wind binary systems, but 9 Sgr was long considered a single star. Aims. We have conducted a long-term spectroscopic monitoring of this star to investigate its multiplicity and search for evidence for wind-wind interactions. Methods. Radial velocities are determined and analysed using various period search methods. Spectral disentangling is applied to separate the spectra of the components of the binary system. Results. We derive the first ever orbital solution of 9 Sgr. The system is found to consist of an O3.5 V((f + )) primary and an O5-5.5 V((f)) secondary moving around each other on a highly eccentric (e = 0.7), 8.6 year orbit. The spectra reveal no variable emission lines that could be formed in the wind interaction zone in agreement with the expected properties of the interaction in such a wide system. Conclusions. Our results provide further support to the paradigm of synchrotron radio emission from early-type stars being a manifestation of interacting winds in a binary system.

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Radial Velocities of Galactic O-Type Stars. I. Short-Term Constant Velocity Stars

Cited by 12 publications

References 55 publications

Chemical abundances of fast-rotating massive stars

Chemical abundances of fast-rotating massive stars

Magnetometry of a sample of massive stars in Carina★

9 Sagittarii: uncovering an O-type spectroscopic binary with an 8.6 year period

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