Stellar ejecta of massive stars

Advisor: Michaela Kraus (AI CAS)

Funding: basic scholarship; additional top-up funding is granted until December 2022. Top-up funding beyond that period depends on the outcome of future grant applications.



Massive stars are key objects for the evolution of their host galaxies, because they deposit huge amounts of energy into their environment and enrich it with chemically processed material throughout their entire life path. Despite their importance, their evolution still faces major mysteries, as it comprises several phases with enhanced mass loss and eruptions of yet unknown origin. Optical and infrared imaging revealed that many of these stars are surrounded by hot gas and dust in form of shells, spiral-arms, ring nebulae, filamentary structures, unipolar, bipolar, or multiple-lobed nebula, witnesses of such prior phases of mass ejections. Understanding the physics behind mass eruptions and the associated energy and mass released to the environment during such outbursts is crucial for reliable predictions of the subsequent evolution and the final fate of the star, and of the galactic and cosmic evolution as a whole.

The goal of this project is to achieve a better comprehension of the chemical and dynamical evolution of the ejecta of massive stars in diverse evolutionary phases. To this aim, the student will perform a detailed study of the structure, chemical composition, and expansion properties of the ejecta surrounding a sample of selected massive stars from small to large scales and in diverse chemical states (atomic and molecular gas, solid dust grains). For this, new observational data in the optical and infrared spectral regions (imaging and long-slit respectively IFU spectroscopic data) will be acquired using world renowned facilities at ESO and GEMINI observatories and the Nordic Optical Telescope, along with satellite data of the forthcoming James Webb Space Telescope. These data will be combined with available data sets to cover suitable temporal baselines. Moreover, it is foreseen and desired that the student participates in the development of a numerical code for the investigation of the chemical evolution within the ejected material.

Figure description: Composite image, showing the distribution of the ejected material from the massive supergiant star MWC 137. The ionized gas is shown in blue and the surrounding dust in red. The optical and infrared images have been obtained with the Nordic Optical Telescope and the Spitzer Space Telescope, respectively. This image is taken from Kraus et al. (2017).


  1. Gvaramadze, V. V., Kniazev, A. Y., & Fabrika, S. 2010, MNRAS, 405, 1047
  2. Gvaramadze, V. V. & Menten, K. M. 2012, A&A, 541, A7
  3. Kraus, M., Oksala, M. E., Cidale, L. S., et al. 2015, ApJ, 800, L20
  4. Kraus, M., Liimets, T., Cappa, C. E., et al. 2017, AJ, 154, 186
  5. Lagadec, E., Zijlstra, A. A., Oudmaijer, R. D., et al. 2011, A&A, 534, L10
  6. Marston, A. P. & McCollum, B., 2008, A&A, 477, 193