DTPA Seminar: Pivoňková-Mondal-Xia

Department of Theoretical Physics and Astrophysics invites you to the department seminary. This time three talks are scheduled:

Kateřina Pivoňková – Structured Stellar Winds of Hot Stars

One of the most important physical processes governing the lifecycle of massive stars (initial masses exceeding approximately eight times the mass of the Sun) is mass loss, which predominantly occurs through stellar winds. Recent studies have revealed that stellar winds are not smooth, homogeneous outflows as was once believed. Instead, these winds exhibit a clumpy structure, with regions of higher density (”clumps”) interspersed with lower-density material (”voids”). In this project, I will focus on developing a comprehensive 3D radiative hydrodynamic model to study the clumping in stellar winds.

Prapti Mondal – Spectroscopy of Chemically Peculiar star

Chemically peculiar (CP) stars exhibit atypical chemical abundances in their atmospheres, often influenced by magnetic fields and processes such as radiative diffusion. These characteristics lead to unique spectral signatures, making classification essential for understanding their properties and evolution. My PhD includes an analysis of classification criteria for CP stars within the red spectral region, specifically from 4200 to 9000 Å. In general, spectral classification is done by comparing a star's line profiles and line ratios with the known profiles of standard stars with available astrophysical parameters. All classical classification criteria are based on the blue wavelength region, i.e., from 3800 to 4600Å. The new generations of spectroscopic instruments and detectors are much more sensitive in the red region, i.e., redder than 4200Å. Therefore, it is necessary to establish new classification criteria in this wavelength region using already well-known CP stars and their spectra, as an example from the LAMOST survey.

Caiyun Xia – Study of CP stars

A group of stars on the upper main sequence of Hertzsprung-Russell diagram exhibits an anomalous abundance of some chemical elements on their surface layers. We call this group of stars as chemically peculiar (CP). Peculiar abundance of elements leads to originating of photometric spots and variability of stellar flux as star rotates. The shape of light curves of mCP stars could remain unchanged even for decades. We will analyze light curves of selected CP stars using data from TESS mission.