Constraining the interiors of exoplanets by measuring the Love numbers k2, h2

• Applicant: Szilárd Csizmadia, Ph.D.
• Subject Area: Astrophysics and Astronomy ; Geophysics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 280637173

Mass and radius measurements provide the planetary mean densities, a prime planet parameter. Yet, mass, radius and mean density are degenarate when it comes to determining the interior structure of planets (e.g. radial density profiles and composition models). To provide further observational constraints on interior structure, as proposed here, is therefore of high scientific value.To provide such a further observable, one possibility is to measure the Love numbers h2 and k2 of exoplanets which depend on the internal density profile. They put additional constraints in the interiors. While h2 can be measured from transit light curve (TLC) observations, k2 can be measured from radial velocity (RV) and/or transit timing variation (TTV) observations. However, no measurements of exoplanetary Love numbers combining all three techniques (TLC, RV, and TTVs) have been attempted to date. Therefore, it is now essential to build a self-consistent and coherent tool to precisely and accurately estimate h2 and/or k2 from observations, understand the error sources on those measurements, and provide possibilities to improve the precision. Such an approach would use all available pieces of information and would increase the precision of Love number measurements.We plan to utilize the already existing archive RV, TTV and TLC measurements obtained by different spectrographs (HARPS, CORALIE, FIES, etc) and photometric TLC and TTV observations (ground-based telescopes, Kepler, TESS, future JWST). We were successful to get telescope time on HARPS for this project and we plan to extend the archive data with new RV-measurements by submitting new telescope time proposals.The results of our work provide the basis for close collaborations with other members of the Research Unit to explore the ranges of possible interior models for carefully selected exoplanets. In some cases, information on the energy dissipation and orbital evolution of the planet may be derived. The expected key result of this subproject SP6 is an estimate of the Love numbers h2 and/or k2 of selected exoplanets using combined techniques (TLC, RV and TTV). These measurements will be carefully interpreted in terms of interior parameters in close collaboration with subprojects SP4 and SP5. This subproject SP6 will provide invaluable as yet precisely and accurately not so often measured parameter to further constrain planetary interiors: the Love numbers of selected exoplanets.

• DFG Programme: Research Units
• Subproject of: FOR 2440: Matter Under Planetary Interior Conditions - High-Pressure, Planetary and Plasma Physics
• Co-Investigators: Professorin Dr. Heike Rauer; Dr. Frank Sohl