PhD::SPACE Thesis

Recent years have seen a revolution in our knowledge of exoplanetary systems including many surprising discoveries. In contrast, several expected results have not yet been observed or confirmed. Among these is the existence of moons and rings, as well as of tidal deformations of the exoplanets that orbit very close to their parent star. This project aims at detecting these extreme systems taking advantage of the unprecedented precision of the ongoing and future transit missions K2, TESS, CHEOPS and Plato, as well as of new high-resolution spectrographs such as ESPRESSO.

Our team is now particularly involved in the CHEOPS (ESA) mission, to be launched in 2018. CHEOPS (CHarecterising ExOplanets Satellite) is a new ESA mission that will allow to observe key bright targets with extreme characteristics. The development of CHEOPS is also intimately related to our strong participation in the ESPRESSO (ESO) high-resolution spectrograph for the VLT telescopes.

ESPRESSO will allow deriving radial velocity measurements with an unprecedented precision, and hence it will permit to measure masses for the smallest known exoplanets. Together, CHEOPS and ESPRESSO will give us a unique opportunity to characterize the properties (mass, radius, composition, structure, shape) of exoplanets.

In particular, in this project we propose to upgrade a state of the art Bayesian transit and radial velocity fitting code to include rings, planetary occultations, Rossiter-McLaughlin effect, and tidal effects. Rings have never been detected around extra-solar planets, but their signature should be present in both the transit light and radial-velocity curves (through Rossiter-McLaughlin effect). The tidal star-planet interactions deform the planets, producing also significant deformation in the light curve (never detected, but expected for some short period planets). Hence, the code will allow searching for the signature of rings, planetary occultations, and tidal effects. All these effects have been predicted by theory but they were never observed: the new set of instruments will allow us to make a breakthrough in this domain.

Our team has privileged access to Cheops data hence the student will be able to access this unique dataset. Furthermore, the tools developed during this project we may also use for other datasets: NASA K2, TESS missions and in the future for ESA PLATO mission. The results of this project will increase the scientific exploitation of these state of the art missions and lead to a better understanding of planetary systems.

Fellowship: PD/00040/2012 – PD/BD/135226/2017 - FCT

Advisors: Susana C. C. Barros (IA-U.Porto), Nuno C. Santos (IA-U.Porto & FCUP)

The late-time cosmic accelerated expansion is one of the most important and challenging current problems in cosmology. Although models of dark energy are the most popular candidates responsible for the cosmic expansion, the latter may be due to modifications of General Relativity, which introduce new degrees of freedom to the gravitational sector itself. This research project will explore the viability of a plethora of modified gravity models, consistently analysing the reproduction of all the cosmological epochs. More specifically, we will consider generalizations of the Einstein- Hilbert action by including non-linear curvature invariants and Lagrangians that also include curvature couplings to the matter sector. Another class of theories under our scrutiny will be generalised scalar-tensor or vector-tensor gravity theories, where scalar or vector fields play gravitational roles that can also be perceived as couplings to matter in an appropriate frame. One fundamental goal of this project is to study the theoretical issues of the extra degrees of freedom of the theory and to analyse its astrophysical applications.

Fellowship: PD/00040/2012 – PD/BD/128017/2016 - FCT

Advisors: Francisco S. N. Lobo (IA-U.Lisboa), Diego Rubiera-Garcia (IA – U.Lisboa)

This PhD project concerns the model building and associated phenomenology of gravitational theories beyond the standard paradigm of General Relativity, focusing on general theories constructed out of a scalar field, known as generalised scalar-tensor theories. The student will learn and apply analytical and numerical tools, such as cosmological perturbation theory and statistical methods to make phenomenological predictions for the dynamics and structure of the Universe at very large scales, with the aim of testing the concordance cosmological model with current and future observational surveys like Euclid and Planck. On the same time, the student will have the opportunity to explore the implications of these theories for the Universe at its very first moments after the Big Bang, where quantum-gravitational effects become important.

Fellowship: PD/00040/2012 – PD/BD/128017/2016 - FCT

Advisors: Nelson Nunes (IA-U.Lisboa), Ippocratis Saltas (IA – U.Lisboa)

Abstract: The project consists in a comprehensive study of the NIR spectroscopic properties of M dwarf stars by studying a large number of binary systems composed of a solar type star and an M dwarf secondary. It involves the development and test of techniques to derive accurate and reliable effective temperatures, surface gravities and metallicities from APOGEE near infrared spectra. The goal of the project is to provide not only reliable measurements of the fundamental parameters for the tiny stars, but also provide consistency and estimate the real precision of the different methods involving photometry, spectroscopy and evolutionary models. This comprehensive study is fundamental for the proper and accurate characterization of the larger stellar component of the Galaxy, which will improve our knowledge of their nature and the chemical and dynamical evolution of the Milky Way.

Advisors: Barbara Rojas-Ayala (Universidad Andrés Bello, Chile), Elisa Delgado Mena (IA-U.Porto)

Fellowship: PD/00040/2012 – PD/BD/128050/2016 - FCT

Abstract: New insights on stellar evolution and stellar interiors physics are being made possible by asteroseismology, the study of stars by the observation of their natural, resonant oscillations. Asteroseismology is proving to be particularly significant for the study of solar-type stars, in great part due to the exquisite data that have been made available by NASA’s Kepler space telescope. The future looks even brighter, with NASA’s TESS and ESA’s PLATO space missions promising to revolutionize the field and increase the number of stars with detected oscillations by several orders of magnitude. The information contained in stellar oscillations allows the internal stellar structure to be constrained to unprecedented levels, while also allowing fundamental stellar properties (e.g., mass, radius, and age) to be precisely determined. In anticipation of the flood of observations from future space missions, the main goal of this project is to develop and test state-of-the-art asteroseismic techniques for the estimation of fundamental stellar properties. Particular attention will be focused on calibrating the determination of age, due to the strong dependence this quantity has on stellar physics. The goal is to address the critical requirement to obtain precise estimates of age for stars at different phases of evolution and/or with planetary systems where signatures of life are to be observed. A very important component of this project will be to understand the systematics on the derived properties that arise from changes in the input physics and the effects introduced by different evolutionary and pulsation codes. The implications of this project will be far-reaching. Not only should it provide important contributions to theories of stellar structure, stellar dynamics and evolution, but it will also play an important role in the characterization of planet-candidate host stars and their planetary systems.

Advisors: Mário J. P. F. G. Monteiro (IA-U.Porto & FCUP), Tiago L. Campante(University of Birmingham)

Fellowship: PD/00040/2012 – PD/BD/113744/2015 - FCT

Building up on current in-house knowledge, we propose to develop the methodologies required for the extraction of the maximum of information, and in particular the minute signals of exoplanets from nIR spectra. The risk of this ambitions program will be minimized by a thorough and gradual pathway to this objective. The intermediary tasks and objectives have been laid out and a significant amount of observational data has already been acquired and is fully available to be explored from day one.

The expertise gained through this project will give the PhD the ability to efficiently reduce and explore nIR spectroscopic data, an emerging field in astronomy, in particular in the domain of extrasolar planets. The results of this project will be used for the science verification of two upgraded infrared instruments: CRIRES+ and VISIR (both at the VLT-ESO).