Skip to Main content Skip to Navigation

Mise en oeuvre de détecteurs à avalanche pour l’interférométrie astronomique en proche infra-rouge : application à la multiplicité des étoiles massives

Abstract : From their interaction with their environment, the massive stars contribute significantly to the evolution of their host galaxy. However, their formation process is still unknown. To better constrain the formation models of those stars, the study of their multiplicity is essential. While photometry and spectroscopy allow studying the multiple systems separated from a few milliarcseconds (mas), and direct imaging allows to probe the separations above 50 mas, the range between a few mas and 50 mas of separation could not be probed until recently. This range can be resolved by the optical long baseline interferometry (OLBI), but this technique was limited in sensitivity and was able to observe only a dozen of massive stars a few years ago. Performing a statistical study on the multiplicity of massive stars requires to observe a larger number of objects.The goal of this thesis is to improve the sensitivity of the OLBI technique to conduct a survey on the multiplicity of Northern hemisphere massive stars.First, I actively participated in the implementation of two C-RED ONE cameras in the interferometric instruments MIRC-X and MYSTIC for the CHARA array of the Mount Wilson Observatory, in California. These cameras, based on the avalanche photodiode (APD) technology, have been used in astrophysics only for a few years; our knowledge on how they work is quite limited. During my thesis, I performed a full characterization of these cameras. I built a model of the signal distribution of the APD detectors to better understand the obtained results. This model and the classical characterization methods highlighted significant differences between the gain and excess noise factor that I measured and those provided by the manufacturer. Even if this makes individual photon counting impossible, the characteristics of these cameras remain exceptional, with a total noise below the electron for a frame rate up to kilohertz, which is fundamental to get rid at best of the atmospheric turbulence.These performance lead to a consequent sensitivity improvement: MIRC-X reaches a limiting magnitude of H = 7.5, to be compared with H = 5 for its predecessor MIRC. This limiting magnitude is confirmed by the demonstration survey on 44 massive stars. During this survey, I could observe routinely several targets with magnitudes of H = 7.5, and up to H = 8.1 with really favorable atmospheric conditions. In these observations, I detected 27 companions for a total of 21 multiple systems, with separations between 0.5 and 50 mas. This demonstration survey confirms the possibility to use MIRC-X to look for companions in the range of separation not covered by the other observational techniques, and this on a large number of massive stars (> 100).This demonstration survey corresponds to the first phase of the large survey on Northern hemisphere massive stars with a magnitude H < 7.5 that I prepared. I have thus selected 120 systems that are observable with the CHARA array, which will allow a statistical analysis of the massive stars multiplicity, as a complement of the SMASH+ survey in the Southern hemisphere. This kind of surveys is essential to constrain the formation models of those stars.
Complete list of metadatas

Cited literature [169 references]  Display  Hide  Download
Contributor : Abes Star :  Contact
Submitted on : Monday, May 25, 2020 - 8:34:15 PM
Last modification on : Wednesday, October 7, 2020 - 1:15:21 PM


Version validated by the jury (STAR)


  • HAL Id : tel-02619757, version 1



Cyprien Lanthermann. Mise en oeuvre de détecteurs à avalanche pour l’interférométrie astronomique en proche infra-rouge : application à la multiplicité des étoiles massives. Instrumentation et méthodes pour l'astrophysique [astro-ph.IM]. Université Grenoble Alpes, 2019. Français. ⟨NNT : 2019GREAY060⟩. ⟨tel-02619757⟩



Record views


Files downloads