Hide and seek with brawling stellar couples
Julia Bodensteiner, Jakub Klencki & Henri Boffin
Massive stars are the energetic engines of the Universe. Most of them are born in tight pairs in which they strongly interact with their partners, one of them sometimes acting as a vampire. Join us on a journey to the cores of young star clusters in one of our neighboring galaxies, the Large Magellanic Cloud, to hunt for stars that are the products of such brawls.
Massive stars are the true cosmic engines of the Universe. With their extreme luminosities, strong outflows, and supernova explosions, they provide feedback and chemical enrichment that shape the evolution of entire galaxies. Despite their great importance, the evolution of massive stars still poses many questions. One of the main unknowns is the role of multiplicity: observations have shown that the majority of massive stars are born, and live, in binary or higher-order multiple systems. If the systems are tight enough, the two companions will interact during their life, for example by transferring mass from one star to the other. In more violent cases, the stars may even merge. Such interactions will thus drastically affect the evolution of both components. The large number of interacting binary systems also implies that in a given, old-enough population, there should be many stars that experienced such binary interactions in the past. However, while theoretically predicted in large numbers, observational constraints are still lacking.
In this project, we want to hunt for such products of binary interactions in one of our neighboring galaxies, the Large Magellanic Cloud. We will look at different star clusters of different ages for which theoretical models predict a large number of stars to have been affected by binary interaction. In a first step, we will focus on the population of blue supergiants, which are evolved massive stars. After identifying them, we will determine their main properties such as their effective temperatures, surface gravities, and rotation rates, and we will try to establish whether they are single or binary stars.
For this, we will use cutting-edge observations of the cores of these clusters. The observations were obtained with the integral-field spectrograph MUSE mounted at the Very Large Telescope in Chile. MUSE allows us to extract spectra for all stars in the field of view – spectra that can be used to infer the properties of the stars. Those will then be compared to theoretical predictions of stellar and binary evolution. First, we will use pen and paper to make simple, back-of-the-envelope estimations of the expected stellar content of the observed clusters. Then, we will carry out a comparison with numerical models of massive stars and binary systems computed with a state-of-the-art (and, yet, easy to use) stellar-evolution code, MESA. At the end of the project, we will be able to understand how binarity affects the evolution of massive stars.
#MassiveStars #StellarEvolution #BinaryInteractions #MUSE #IntegralFieldSpectroscopy