A quantitative study of O stars in NGC 2244 and the Monoceros OB2 association

Martins, F.; Mahy, L.; Hillier, D. J.; Rauw, Grégor

doi:10.1051/0004-6361/201117458

Cited by 71 publications

(117 citation statements)

References 82 publications

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“…This result is combined and put in perspective with several other investigations of O-type stars in the Galaxy (Martins et al 2012(Martins et al , 2015Bouret et al 2012). Although this constitutes a set of heterogeneous studies, all the analyses use the same tool to determine the stellar parameters.…”

Section: The N Contentmentioning

confidence: 92%

“…For the UV domain, we focus mainly on N v 1240, Si iv 1394-1403, and C iv 1548-1551, and when FUSE spectra are available, we consider C iv 1169 and C iii 1176 as additional diagnostics to those lines for mass-loss rate determination. A single value ofṀ should allow a good fit of both types of lines even though a study by Martins et al (2012) has shown that this was not always the case. In our analysis, we reach a general agreement between UV and Hα lines by playing on other parameters such as the clumping or the β.…”

Section: Modellingmentioning

confidence: 99%

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

Mahy

Rauw

Becker

et al. 2015

A&A

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Aims. Having established the binary status of nineteen O-type stars located in four Cygnus OB associations, we now determine their fundamental parameters to constrain their properties and their evolutionary status. We also investigate their surface nitrogen abundances, which we compare with other results from the literature obtained for galactic O-type stars. Methods. Using optical spectra collected for each object in our sample and some UV data from the archives, we apply the CMFGEN atmosphere code to determine their main properties. For the binary systems, we have disentangled the components to obtain their individual spectra and investigate them as if they were single stars. Results. We find that the distances of several presumably single O-type stars seem poorly constrained because their luminosities are not in agreement with the "standard" luminosities of stars with similar spectral types. The ages of these O-type stars are all less than 7 Myr. Therefore, the ages of these stars agree with those, quoted in the literature, of the four associations, except for Cyg OB8 for which the stars seem older than the association itself. However, we point out that the distance of certain stars is debatable relative to values found in the literature. The N content of these stars put in perspective with N contents of several other galactic O-type stars seems to draw the same five groups as found in the "Hunter" diagram for the O and B-type stars in the LMC even though their locations are obviously different. We determine mass-loss rates for several objects from the Hα line and UV spectra. Finally, we confirm the "mass discrepancy" especially for O stars with masses smaller than 30 M .

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Section: The N Contentmentioning

confidence: 92%

Section: Modellingmentioning

confidence: 99%

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

Mahy

Rauw

Becker

et al. 2015

A&A

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“…HD 149757 (ζ Oph; O9.2 IVnn, Sota et al 2011; v sin i ∼ 378 km s −1 ) has been studied by Villamariz & Herrero (2005). In addition, the CNO abundances of two O-type supergiants, two O dwarfs, five additional O giants, and four other O-stars with v sin i ≥ 200 km s −1 have been derived by Bouret et al (2012), and Martins et al (2012bMartins et al ( , 2015b, respectively. The small number of high-resolution studies combined with the heterogeneity of the analyses has motivated us to undertake an in-depth study of bright OB stars with high rotational velocities.…”

Section: Rationale Of Our Studymentioning

confidence: 99%

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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“…Martins et al 2010) and the effects of stellar winds are of secondary importance (e.g. Martins et al 2012).…”

Section: Bubbles North Of η Car (Nb)mentioning

confidence: 99%