Properties and evolutionary state of massive stars across the HR diagram

Dr. Michalis Kourniotis

Abstract

The advanced stages of high-mass stars are characterized by episodic mass loss shed during phases of instability. Key for assigning these stars a proper evolutionary state is to assess the composition and geometry of their ejecta alongside the stellar properties. I will speak about my work to increase the number of B[e] supergiants, Yellow Hypergiants and Luminous Blue variables in the Local Group by investigating circumstellar environments and exploring the evolutionary properties of high-luminous, dusty targets. By conducting and analyzing optical spectroscopy alongside fitting the spectral energy distribution, I derive stellar properties and infer the presence of circumstellar dust. In search of processed ejected material, modeling of the CO band heads in the K-band is further employed. Results of my work in M33 include the discovery of a strong Yellow Hypergiant candidate showing evidence of past eruption. Moreover, the insight into the surrounding molecular environment witnesses the presence of circumstellar/binary disks around post-supergiant/evolved stars. I highlight the importance of the infrared data to resolve the evolutionary status of massive stars and thus, to constrain the physics of the diverse pre-supernova stellar states. Finally, I will speak about my work at IAC regarding the photometric properties of OB stars in conjunction to the latest Gaia Data Release 2 and their possible link to the line-broadening status of the stars.

About the talk

Properties and evolutionary state of massive stars across the HR diagram
Dr. Michalis Kourniotis
Astronomical Institute of the Czech Academy
Thursday March 28, 2019 - 11:30  (Aula)
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