Mariana V. Sastre

Research projects

Geodynamical regimes in Earth-like exoplanets: A parameter study for linking the internal structure with atmospheres

Solid-state convection of rocky planetary mantles is essential to a planet's habitability over geological timescales. The starting point of main events, such as plate tectonics, is mainly controlled by this heat transfer efficiency. To understand better how this particular tectonic regime came about in Earth's evolution, and how this can be extrapolated to our understanding of the dynamical regime of Earth-like exoplanets and especially their outgassing, it is necessary to investigate under which conditions Earth-sized planetary mantles can produce enough melt that might deliver volatiles to the surface. In this study, I model the internal structure of Earth-sized exoplanets that serve as a basis for 2D heat transfer numerical simulations to explore the parameter space of different silicate mantle sizes and dynamical regimes. In this way, I investigated the optimal candidates for internal structure configurations and compositions, to break the primitive basaltic crust considering different heat sources. I applied my model to the particular case of the TRAPPIST-1 planets to constrain tidal dissipation that can be produced within their mantle according to different core sizes. I showed that Earth-like exoplanets with big cores are the best candidates to produce melt efficiently and consequently deliver more water content to the atmosphere.

Mapping the Sun’s active regions from SDO images to HARPS-N solar spectra

Active regions are the main observable of magnetic activity in the Sun, these zones include structures such as faculae, sunspots and plage, the first two are located at the photosphere and the third one at the chromosphere, respectively. The aim of this work was to perform an analysis to determine if there’s any individual contribution to the relative spectra driven by Sun’s activity. Besides that, correlate the disc-integrated spectra (HARPS-N) with the spot and plage filling factors measured with images taken by the Solar Dynamics Observatory (SDO). Using a previous code (YAMORI, Cretignier et. al in prep), we found that there’s no clear evidence of sensitivity to sunspot-faculae activity due to an interference pattern and systematics from the detector. Nevertheless, an equivalent of a stellar surface-tomography analysis was performed during the process and it was possible to observe strong features in spectral lines affected by plage and spot at the same time.

Searching for disintegrating planets in the TESS data

Catastrophically Disintegrating Exoplanets (CDEs) are Mercury-size rocky bodies that due to the close distance with their host star, these planets can heat up to high temperatures, allowing the sublimation of the planet’s surface. Only less than 10 exoplanet candidates has been confirmed as CDE’s in the last 10 years. Taking into account that these planets have very short periods (4-30hr), observations could miss/confused them with other big planet transits and stellar phenomena. In this case, we are looking to identify this type of transits using light-curves from TESS telescope data. Through the implementation of a pipeline, we can detect them in an automatically way, we use an exponential model that considers a set of orbital parameters that are fit through an optimization method. This one, was selected from three different routines tested during the work. Finally, we evaluate the entire method in 500 systems from which we obtain a final list of candidates for CDE’s

Astrophotography gallery