NEW OPENING FOR A SEVERO OCHOA PhD POSITION: Constraining the populations of exoplanets that interact with their M dwarf hosts: indicators in the blue, optical and near-infrared and their relation to radio observations.

Supervisor: Pedro Amado (pja@iaa.csic.es)

IAA-CSIC offers a predoc contract in the framework of the Project “Severo Ochoa”. Candidates are expected to carry out their activity in the field of stellar physics and exoplanets.
Rocky planets in orbit around nearby late-type M-dwarfs are very promising targets to be studied with the new generation of telescopes with spectroscopic capabilities, such as the James Webb Space Telescope, from space, or with HIRES on the ELT, from the ground, notably to search for bio-signatures. Furthermore, thanks to their small sizes and low luminosities, M dwarfs allow for easier detection of these terrestrial-type planets inside their habitable zone with both radial velocity (e.g. with CARMENES) and photometric measurements (from NASA’s TESS). Both techniques are complementary when it comes to understanding the real nature of a given planet.
This is the case of super-Earths, a type of planet conceptually unknown because we do not have them in our Solar System. Observationally, their current population shows a number of intriguing features. One of them is that the less massive super-Earths (M < 4-5 MꚚ) tend to have small radii yielding high densities, in line with a rocky composition (rocky planets, with thin secondary atmospheres). Observations tend to confirm that these planets cannot have masses larger than ~10 MꚚ, in agreement with the results from population models. At higher masses, the fraction of objects with larger radii, above a “radius gap” at ~2 RꚚ, becomes more significant, showing that they can retain a significant envelope (sub-Neptunes and “water” worlds). Interestingly, another feature is that most multiple systems containing a super-earth only have one planet detected in transit, pointing towards a significant misalignment between the planets' orbits, which might be an indication for some type of interaction at work in the system. Naturally, the question rises if star-planet interaction (SPI) is at work to build these particularities in the super-Earth population.
Theoretically, according to Ahuir et al. (2021), three populations of star-planet systems emerge from the combined action of magnetic and tidal interactions: i) the “steady” population, with planets undergoing negligible migration being too further out from the star (large orbital periods, Porb, although it also depends on the rotation rate of the star, Prot), ii) the “young migrators” population, with planets migrating very close to their stars (strong interactions) during their pre-main sequence phase. They can eventually be engulfed or migrate to the steady population, and iii) the “old migrators” population with planets whose migration is highly dependent on the physical parameters of the system.
We propose a formative programme for a PhD student based on the investigation of CARMENES planetary systems, exploiting CARMENES data from its on-going Legacy-Plus project, to work on the precise characterisation of the parameters and dynamics of systems containing close-in super-Earths of nearby M dwarfs whose architecture and populations might have been sculpted by its interaction with the star. The results from this study will have the objective of testing the results of the SPI models and those from the radio SPI project also at IAA, eventually, understanding the population and observed distributions in the radius-mass and Prot-Porb planes of the CARMENES low-mass planetary systems.