ABSTRACT

Atmospheric escape is an important process in the evolution of exoplanet atmospheres, especially those orbiting very close to their host stars. However, many aspects of atmospheric escape remain poorly understood, in part due to a limited number of direct observations of this process. Recently, the high-resolution transmission spectroscopy in the helium line at 1083 nm has been established as a powerful new diagnostic tool for studying the extended and escaping exoplanet atmospheres, providing valuable insights into the dynamics of the upper atmospheres. I will discuss how these observations may lead to a better understanding of the physical processes that drive atmospheric escape. In the second part of the talk, I will describe how radiation polarization in the helium 1083 nm line can be used as a probe of magnetic fields in exoplanet atmospheres. Linear and circular polarization signals in the helium line arise in the presence of a magnetic field due to atomic level polarization induced by anisotropic stellar radiation, and the combined action of the Zeeman and Hanle effects. Assuming magnetic fields with strengths comparable to the magnetic fields observed in solar system planets, polarization signals in the helium 1083 nm line could be detectable with current and next-generation high-resolution spectropolarimeters operating at NIR wavelengths.

BIO
Antonija Oklopčić completed her undergraduate studies in Physics in Zagreb, Croatia and obtained a PhD in Astrophysics from the California Institute of Technology. Between 2017 and 2020, she was a postdoctoral fellow and a NASA Hubble fellow at Harvard University. She recently started a new appointment as an Assistant Professor at the University of Amsterdam. Antonija’s research interests cover a broad range of topics in theoretical astrophysics, but her recent work has been focused on developing new diagnostic tools for studying exoplanet atmospheres.