Hugues Sana

The VLT-Flames Tarentula survey
The 30 Dor region in the Large Magellanic Cloud is the nesting place of thousands of massive stars. It is the perfect laboratory to put on the testbed our understanding of massive star evolution and, more specifically, of key parameters such a rotation and multiplicity. In this context, an international consortium led by Chris Evans from Edinburgh has teamed up to obtained multi-epoch spectroscopy of 1000 massive stars using the Flames instrument from the ESO Paranal observatory. While many projects are linked to this observing campaign, the specific role of Amsterdam is to quantitatively analyse the hundreds of O stars observed, to accurately derive their stellar parameter and their chemical composition. Find out about the project status and our first results on the project homepage...

The massive star binary fraction in young open clusters

Typical parameter space for massive binaries. Relevant VLT instrumentation has been overlaid. Read more here...

One of the most striking properties of the massive O stars is their large degree of multiplicity. Most of them are indeed forming a close pair with another massive OB star, revolving around their common mass centre in time scales of days to (tens of) years. While this fact is widely accepted, the exact binary fraction i.e., the fraction of massive stars having a close-by companion, is not accurately known, neither is the distribution of their orbital parameters and whether these properties are universal or are depending on, e.g., the environment of the star. We are thus engaged in a longstanding effort to detect and characterize the massive binary population in young open clusters. Check out our most recent publications on the topics here...

Two-color NIR image (H and Ks band) of Trumpler 14, one of the young open clusters of the Carina nebula region and a nest for a dozen massive stars. Among them, HD 93129A, the brightest star in the field, is one of the very rare O2 supergiants. A million time brighter than the Sun, its mass is probably about 80 solar masses and its temperature close to 45 000~K. The full mosaic image, covering a field of view of 2' in diameter, has been obtained by MAD, the ESO Multi-conjugate Adaptive optics (AO) Demonstrator. By contrast with current AO facilities that use only one star, MAD relies on three natural guide stars to correct for atmosphere turbulence over a wider field of view. This image has an average quality (FWHM) of 0.2" while the actual seeing in K band was about 0.90". This image is the largest AO-corrected mosaic ever acquired. Read more here ...

Modelling the telluric spectrum
Ground-based spectroscopic observations in the red and in the infrared (IR) are inevitably affected by the atmosphere layer that the light has to cross to reach the observer. The scientific spectrum of a particular target of interest is thus polluted by the many telluric lines whose strength depends of the properties of the atmosphere at the time of the observations. Traditionally, this problem is circumvented by the observation of a telluric standard star obtained as close in time and direction as possible to the main target, and used to callibrate the atmospheric signature. Such observations are a necessary 'waste' of time and, in the current era of large ground-based telescopes, is particularly costly. With this project, we aim at providing an accurate tool to model the telluric spectra to optimize the preparation, observation and analysis phases for red and IR spectroscopy. Read more in the proceedings of the IAU...

The Liège Orbital Solution Package
LOSP is a FORTRAN77 numerical package that allows its user to compute the orbit of spectroscopic binaries. The algorithm has mostly been developed at the Liège University during my PhD. The code and the package has now been made sufficiently robust and user friendly to be released to the public. More details and package download on the LOSP page...