High-contrast SB2 spectroscopic systems with peculiar early-type component(s)

Supervisor: Dr. Martin Vaňko (vanko@astro.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Stellar Department, Tatranská Lomnica
Syllabus
Focus of the research: The easiest proof that a system is a binary star is the presence of eclipses. The second most useful technique is radial-velocity (RV) variations. Such variations are typically detected within spectroscopic surveys, which result in a list of objects catalogued according to their specific stellar attributes. Once such a variation has been detected, targeted and systematic observations must be obtained to characterize the system. In the simplest case, the binary comprises two components of relatively close luminosity which results in two systems of spectral lines in the composed spectrum. When the components differ significantly in luminosity, spectral lines of the fainter secondary component become less evident. The situation gets especially difficult when the secondary is a fast rotator (> 100 km/s). Although the spectral lines of the fast-rotating secondary component are shallow and hard both to identify and model, its light boosts the continuum level, which uniformly reduces the depths of the dominant component’s spectral lines. More rarely, a star might be revealed to be double when discrepancies in the projected rotational velocity, v sin i, determined using spectral lines that have a different sensitivity to the atmospheric effective temperature are detected, e.g., the lines of Mg II at λ 4481 Å and Ca II H and K.
Objectives: Modelling the spectroscopic data of several peculiar, high-contrast, early-type systems on the main sequence with a combination of photometric measurements from the archive of the TESS satellite. The main goal is to determine the RVs and rotational velocities of the studied objects and the possible presence of other components. Our analysis will also be focused on characteristic of possible short-term (tens of minutes) or medium-term (several hours) pulsations of individual components, determination of their atmospheric parameters (surface temperature, metallicity, surface gravity) and absolute parameters (radius, mass, luminosity). Based on the obtained results, the evolutionary status of studied systems will be discussed.
Requirements: good knowledge of English, good knowledge of programming, ability to work independently with literature.
Research field: Binary and multiple stellar systems