- ID:
- ivo://CDS.VizieR/J/A+A/462/123
- Title:
- VLT/Flames spectroscopic data of NGC 6530
- Short Name:
- J/A+A/462/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mechanisms regulating the evolution of pre-main sequence stars can be understood by studying stellar properties such as rotation, disk accretion, internal mixing and binarity. To investigate such properties, we studied a sample of 332 candidate members of the massive and populous star forming region NGC 6530. We want to select cluster members by using different membership criteria, to study the properties of pre-main sequence stars with or without circumstellar disks. We use intermediate resolution spectra including the LiI6707.8{AA} line to derive radial and rotational velocities, binarity and to measure the Equivalent Width of the lithium line; these results are combined with X-ray data to study the cluster membership. Optical-IR data and H{alpha} spectra, these latter available for a subsample of our targets, are used to classify CTTS and WTTS and to compare the properties of stars with and without disks. We find a total of 237 certain members including 53 binaries. The rotational velocity distributions of stars with IR excesses are statistically different from that of stars without IR excesses, while the fraction of binaries with disks is significantly smaller than that of single stars. Stars with evidence for accretion show circumstellar disks; youth of cluster members is confirmed by the lithium abundance consistent with the initial content. As indicated by the disk-locking picture, stars with disks have in general rotational velocities lower than stars without disks. Binaries in NGC 6530 seem have undergone a significant disk evolution.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/456/623
- Title:
- VLT-FLAMES survey of massive stars
- Short Name:
- J/A+A/456/623
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new observations of 470 stars using the Fibre Large Array Multi-Element Spectrograph (FLAMES) instrument in fields centered on the clusters NGC 330 and NGC 346 in the Small Magellanic Cloud (SMC), and NGC 2004 and the N11 region in the Large Magellanic Cloud (LMC). A further 14 stars were observed in the N11 and NGC 330 fields using the Ultraviolet and Visual Echelle Spectrograph (UVES) for a separate programme. Spectral classifications and stellar radial velocities are given for each target, with careful attention to checks for binarity. In particular, we have investigated previously unexplored regions around the central LH9/LH10 complex of N11, finding ~25 new O-type stars from our spectroscopy. We have observed a relatively large number of Be-type stars that display permitted Fe II emission lines. These are primarily not in the cluster cores and appear to be associated with classical Be-type stars, rather than pre main-sequence objects. The presence of the Fe II emission, as compared to the equivalent width of H{alpha}, is not obviously dependent on metallicity. We have also explored the relative fraction of Be- to normal B-type stars in the field-regions near to NGC 330 and NGC 2004, finding no strong evidence of a trend with metallicity when compared to Galactic results. A consequence of service observations is that we have reasonable time-sampling in three of our FLAMES fields. We find lower limits to the binary fraction of O- and early B-type stars of 23 to 36%. One of our targets (NGC 346-013) is especially interesting with a massive, apparently hotter, less luminous secondary component.
- ID:
- ivo://CDS.VizieR/J/A+A/437/467
- Title:
- VLT-FLAMES survey of massive stars
- Short Name:
- J/A+A/437/467
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce a new survey of massive stars in the Galaxy and the Magellanic Clouds using the Fibre Large Array Multi-Element Spectrograph (FLAMES) instrument at the Very Large Telescope (VLT). Here we present observations of 269 Galactic stars with the FLAMES-Giraffe Spectrograph (R~=25000), in fields centered on the open clusters NGC 3293, NGC 4755 and NGC 6611. These data are supplemented by a further 50 targets observed with the Fibre-Fed Extended Range Optical Spectrograph (FEROS, R=48000).
- ID:
- ivo://CDS.VizieR/J/A+A/466/277
- Title:
- VLT-FLAMES survey of massive stars
- Short Name:
- J/A+A/466/277
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of high-resolution FLAMES spectra of approximately 50 early B-type stars in three young clusters at different metallicities, NGC 6611 in the Galaxy, N 11 in the Large Magellanic Cloud (LMC) and NGC 346 in the Small Magellanic Cloud (SMC). Using the TLUSTY non-LTE model atmospheres code, atmospheric parameters and photospheric abundances (C, N, O, Mg and Si) of each star have been determined. These results represent a significant improvement on the number of Magellanic Cloud B-type stars with detailed and homogeneous estimates of their atmospheric parameters and chemical compositions. The relationships between effective temperature and spectral type are discussed for all three metallicity regimes, with the effective temperature for a given spectral type increasing as one moves to a lower metallicity regime. Additionally the difficulties in estimating the microturbulent velocity and the anomalous values obtained, particularly in the lowest metallicity regime, are discussed. Our chemical composition estimates are compared with previous studies, both stellar and interstellar with, in general, encouraging agreement being found.
- ID:
- ivo://CDS.VizieR/J/A+A/479/541
- Title:
- VLT-FLAMES survey of massive stars
- Short Name:
- J/A+A/479/541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to provide the atmospheric parameters and rotational velocities for a large sample of O- and early B-type stars, analysed in a homogeneous and consistent manner, for use in constraining theoretical models. Atmospheric parameters, stellar masses, and rotational velocities have been estimated for approximately 250 early B-type stars in the Large (LMC) and Small (SMC) Magellanic Clouds from high-resolution VLT-FLAMES data using the non-LTE TLUSTY model atmosphere code. This data set has been supplemented with our previous analyses of some 50 O-type stars (Mokiem et al., 2006A&A...456.1131M, 2007A&A...465.1003M) and 100 narrow-lined early B-type stars (Hunter et al., 2006, Cat. <J/A+A/466/277>, Trundle et al., 2007, Cat. <J/A+A/471/625>) from the same survey, providing a sample of ~400 early-type objects.
- ID:
- ivo://CDS.VizieR/J/A+A/471/625
- Title:
- VLT-FLAMES survey of massive stars
- Short Name:
- J/A+A/471/625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of high resolution VLT-FLAMES spectra of 61 B-type stars with relatively narrow-lined spectra located in 4 fields centered on the Milky Way clusters; NGC3293 and NGC4755 and the Large and Small Magellanic cloud clusters; NGC2004 and NGC330. For each object a quantitative analysis was carried out using the non-LTE model atmosphere code TLUSTY; resulting in the determination of their atmospheric parameters and photospheric abundances of the dominant metal species (C, N, O, Mg, Si, Fe). The results are discussed in relation to our earlier work on 3 younger clusters in these galaxies; NGC6611, N11 and NGC346 paying particular attention to the nitrogen abundances which are an important probe of the role of rotation in the evolution of stars. This work along with that of the younger clusters provides a consistent dataset of abundances and atmospheric parameters for over 100 B-type stars in the three galaxies. We provide effective temperature scales for B-type dwarfs in all three galaxies and for giants and supergiants in the SMC and LMC. In each galaxy a dependence on luminosity is found between the three classes with the unevolved dwarf objects having significantly higher effective temperatures. A metallicity dependence is present between the SMC and Galactic dwarf objects, and whilst the LMC stars are only slightly cooler than the SMC stars, they are significantly hotter than their Galactic counterparts.
- ID:
- ivo://CDS.VizieR/J/A+A/496/841
- Title:
- VLT-FLAMES survey of massive stars
- Short Name:
- J/A+A/496/841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have previously analysed the spectra of 135 early B-type stars in the Large Magellanic Cloud (LMC) and found several groups of stars that have chemical compositions that conflict with the theory of rotational mixing. Here we extend this study to Galactic and Small Magellanic Cloud (SMC) metallicities. We provide chemical compositions for ~50 Galactic and ~100 SMC early B-type stars and compare these to the LMC results. These samples cover a range of projected rotational velocities up to ~300km/s and hence are well suited to testing rotational mixing models. The surface nitrogen abundances are utilised as a probe of the mixing process since nitrogen is synthesized in the core of the stars and mixed to the surface.
17138. VLT-FLAMES Tarantula Survey
- ID:
- ivo://CDS.VizieR/J/A+A/530/A108
- Title:
- VLT-FLAMES Tarantula Survey
- Short Name:
- J/A+A/530/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our scientific motivations and give an overview of the survey targets, including optical and near-infrared photometry and comprehensive details of the data reduction. One of the principal objectives was to detect massive binary systems via variations in their radial velocities, thus shaping the multi-epoch observing strategy. Spectral classifications are given for the massive emission-line stars observed by the survey, including the discovery of a new Wolf-Rayet star (VFTS 682, classified as WN5h), 2' to the northeast of R136. To illustrate the diversity of objects encompassed by the survey, we investigate the spectral properties of sixteen targets identified by Gruendl & Chu (2009, Cat. J/ApJS/184/172) from Spitzer photometry as candidate young stellar objects or stars with notable mid-infrared excesses. Detailed spectral classification and quantitative analysis of the O- and B-type stars in the VFTS sample, paying particular attention to the effects of rotational mixing and binarity, will be presented in a series of future articles to address fundamental questions in both stellar and cluster evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A70
- Title:
- VLT-FLAMES Tarantula Survey: B supergiants
- Short Name:
- J/A+A/575/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Model atmosphere analyses have been previously undertaken for both Galactic and extragalactic B-type supergiants. By contrast, little attention has been given to a comparison of the properties of single supergiants and those that are members of multiple systems. Atmospheric parameters and nitrogen abundances have been estimated for all the B-type supergiants identified in the VLT-FLAMES Tarantula survey. These include both single targets and binary candidates. The results have been analysed to investigate the role of binarity in the evolutionary history of supergiants. TLUSTY non-local thermodynamic equilibrium (LTE) model atmosphere calculations have been used to determine atmospheric parameters and nitrogen abundances for 34 single and 18 binary supergiants. Effective temperatures were deduced using the silicon balance technique, complemented by the helium ionisation in the hotter spectra. Surface gravities were estimated using Balmer line profiles and microturbulent velocities deduced using the silicon spectrum. Nitrogen abundances or upper limits were estimated from the NII spectrum. The effects of a flux contribution from an unseen secondary were considered for the binary sample. We present the first systematic study of the incidence of binarity for a sample of B-type supergiants across the theoretical terminal age main sequence (TAMS).
- ID:
- ivo://CDS.VizieR/J/A+A/558/A134
- Title:
- VLT-FLAMES Tarantula Survey. 30 Dor luminous stars
- Short Name:
- J/A+A/558/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VLT-FLAMES Tarantula Survey has an extensive view of the copious number of massive stars in the 30 Doradus (30 Dor) star forming region of the Large Magellanic Cloud. These stars play a crucial role in our understanding of the stellar feedback in more distant, unresolved star forming regions.
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