Article

# The VLT-FLAMES Tarantula Survey

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09/2009; 574. DOI: 10.1051/0004-6361/201219621
Source: arXiv

ABSTRACT

The Tarantula Survey is an ambitious ESO Large Programme that has obtained
multi-epoch spectroscopy of over 1,000 massive stars in the 30 Doradus region
of the Large Magellanic Cloud. Here we introduce the scientific motivations of
the survey and give an overview of the observational sample. Ultimately,
quantitative analysis of every star, paying particular attention to the effects
of rotational mixing and binarity, will be used to address fundamental
questions in both stellar and cluster evolution.

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Available from: Hugues Sana,
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• "In order to ensure the accuracy of the NIR photometry, we compared the values with those of the VISTA VMC survey (Cioni et al. 2011; Rubele et al. 2012) and, for fields with strong nebulosity, with the ground-based photometry of Rubio et al. (1998) and the HST photometry of Walborn et al. (1999). In cases with significant discrepancies we adjusted the values and increased the uncertainties of the used photometry."
##### Article: The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars
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ABSTRACT: Context: The commonly used extinction laws of Cardelli et al. (1989) have limitations that, among other issues, hamper the determination of the effective temperatures of O and early B stars from optical+NIR photometry. Aims: We aim to develop a new family of extinction laws for 30 Doradus, check their general applicability within that region and elsewhere, and apply them to test the feasibility of using optical+NIR photometry to determine the effective temperature of OB stars. Methods: We use spectroscopy and NIR photometry from the VLT-FLAMES Tarantula Survey and optical photometry from HST/WFC3 of 30 Doradus and we analyze them with the software code CHORIZOS using different assumptions such as the family of extinction laws. Results: We derive a new family of optical+NIR extinction laws for 30 Doradus and confirm its applicability to extinguished Galactic O-type systems. We conclude that by using the new extinction laws it is possible to measure the effective temperatures of OB stars with moderate uncertainties and only a small bias, at least up to E(4405-5495) ~ 1.5 mag.
Astronomy and Astrophysics 02/2014; DOI:10.1051/0004-6361/201423439 · 4.38 Impact Factor
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##### Article: The VLT-FLAMES Tarantula Survey. VII. A low velocity dispersion for the young massive cluster R136
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ABSTRACT: Detailed studies of resolved young massive star clusters are necessary to determine their dynamical state and evaluate the importance of gas expulsion and early cluster evolution. In an effort to gain insight into the dynamical state of the young massive cluster R136 and obtain the first measurement of its velocity dispersion, we analyse multi-epoch spectroscopic data of the inner regions of 30 Doradus in the Large Magellanic Cloud (LMC) obtained as part of the VLT-FLAMES Tarantula Survey. Following a quantitative assessment of the variability, we use the radial velocities of non-variable sources to place an upper limit of 6 km/s on the line-of-sight velocity dispersion of stars within a projected distance of 5 pc from the centre of the cluster. After accounting for the contributions of undetected binaries and measurement errors through Monte Carlo simulations, we conclude that the true velocity dispersion is likely between 4 and 5 km/s given a range of standard assumptions about the binary distribution. This result is consistent with what is expected if the cluster is in virial equilibrium, suggesting that gas expulsion has not altered its dynamics. We find that the velocity dispersion would be ~25 km/s if binaries were not identified and rejected, confirming the importance of the multi-epoch strategy and the risk of interpreting velocity dispersion measurements of unresolved extragalactic young massive clusters.
Astronomy and Astrophysics 08/2012; 546. DOI:10.1051/0004-6361/201219471 · 4.38 Impact Factor
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##### Article: The VLT-FLAMES Tarantula Survey X: Evidence for a bimodal distribution of rotational velocities for the single early B-type stars
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ABSTRACT: Aims: Projected rotational velocities (\vsini) have been estimated for 334 targets in the VLT-FLAMES Tarantula survey that do not manifest significant radial velocity variations and are not supergiants. They have spectral types from approximately O9.5 to B3. The estimates have been analysed to infer the underlying rotational velocity distribution, which is critical for understanding the evolution of massive stars. Methods: Projected rotational velocities were deduced from the Fourier transforms of spectral lines, with upper limits also being obtained from profile fitting. For the narrower lined stars, metal and non-diffuse helium lines were adopted, and for the broader lined stars, both non-diffuse and diffuse helium lines; the estimates obtained using the different sets of lines are in good agreement. The uncertainty in the mean estimates is typically 4% for most targets. The iterative deconvolution procedure of Lucy has been used to deduce the probability density distribution of the rotational velocities. Results: Projected rotational velocities range up to approximately 450 \kms and show a bi-modal structure. This is also present in the inferred rotational velocity distribution with 25% of the sample having $0\leq$\ve$\leq$100\,\kms and the high velocity component having \ve$\sim 250$\,\kms. There is no evidence from the spatial and radial velocity distributions of the two components that they represent either field and cluster populations or different episodes of star formation. Be-type stars have also been identified. Conclusions: The bi-modal rotational velocity distribution in our sample resembles that found for late-B and early-A type stars. While magnetic braking appears to be a possible mechanism for producing the low-velocity component, we can not rule out alternative explanations.
Astronomy and Astrophysics 12/2012; 550. DOI:10.1051/0004-6361/201220273 · 4.38 Impact Factor