Transmission Spectroscopy of Extrasolar Planets

• Applicant: Dr. Andreas Schweitzer, since 7/2021
• Subject Area: Astrophysics and Astronomy
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 362051986

We propose to study the atmospheres of extrasolar planets via high-resolution ground-based transmission spectroscopy in the optical and infrared regime. Since the discovery of the first exoplanet around a main-sequence star in 1995, the observational techniques are continuously being improved so that even the constituents and structure of planetary atmospheres can be analyzed today. A key method in this endeavor is the technique of transmission spectroscopy.Transmission spectroscopy can be carried out in transiting planetary systems. When the planet traverses the stellar disk, it is seen "against the light". Only then, a fraction of the stellar light reaching the Earth passes the planetary atmosphere and carries along its distinct spectral signature, which we plan to recover using high-resolution spectroscopy. Models and observations have shown that both the optical and infrared regime are rich in signatures of the planetary atmosphere.Our proposed program comprises the search for signatures of the planetary atmosphere via the sodium doublet lines, the H alpha line, and the molecular lines in the infrared regime. To carry out the analysis, we already collected a number of time-resolved, high-resolution spectral time series of the transiting systems HD 189733, WASP-69, and 55 Cnc suitable for the analysis, using the CARMENES spectrograph, the VLT-UVES spectrograph, and our own TIGRE spectroscopic telescope.Recent results demonstrate that transmission spectroscopy not only allows to detect individual elements in the planetary atmosphere but even to study details such as the temperature pressure profile and global circulation patterns. These results are highly promising and there is no doubt that future observations \emph{and} observatories, such as the E-ELT being constructed right now, will provide even more sensitive data sets. The atmosphere is the very environment we need to understand to characterize planets in the end even in terms of habitability. The scientific scope of the proposed program is fully covered by the funding guidelines of the priority programme 1992. With it, we take advantage of the existing capabilities to study planetary atmospheres and prepare for a future, which will see a lot more of such studies.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1992: Exploring the diversity of extrasolar planets
• Ehemaliger Antragsteller: Dr. Stefan Czesla, until 6/2021