Searching for chemically peculiar stars in stellar associations

Supervisor: Dr. Ernst Paunzen

Contact information: ernst.paunzen@univie.ac.at 

Expected duration: 9 months

Project description & Goals:

Stellar associations are the youngest aggregates we know of. Therefore, they are just born and are very important for testing any theories dealing with the formation of stars and their characteristics. On the other hand, chemically peculiar (CP) stars of the upper main sequence are comprised of magnetic and non-magnetic stars showing overabundances of several orders of magnitude compared to the Sun for Silicon, Chromium, Strontium, and Europium, and for other heavy elements. The main characteristics of the classical CP stars are peculiar and often variable line strengths, the quadrature of line variability with radial velocity changes, photometric variability with the same periodicity and the coincidence of extrema. The theories explaining the abundances patterns are manifold. They are explained by the diffusion of elements and the disappearance of the outer convection zone associated with the helium ionization because of the gravitational settling of Helium. For the magnetic CP stars, due to additional magnetic diffusion, the chemical abundance concentrations at the magnetic poles, spectral and the related photometric variabilities are also easily understood, as are radial velocity variations of the appearing and receding patches on the stellar surface. To put tight constraints on the above-mentioned astrophysical processes, it is essential to identify CP stars in stellar associations. This will allow us to analysis, how and when organized magnetic fields are strong enough to produce surface spots, for example.

Working plan & Milestones (including final thesis):

  1. Get the mean central coordinates, distances and proper motions from the newest Gaia data release of the known close-by stellar associations
  2. Cross-match the list of known CP stars to determine actual members
  3. Search for a correlation of the age with the amplitude of the photometric variability, for example

Requirements / special skills: NA

References:

Carraro: https://arxiv.org/abs/2007.11213

Semenko et al.:https://www.pta.edu.pl/pliki/proc/vol11/v11p25.pdf