- 2016/126c - Detection and characterization of planets orbiting oscillating red-giant stars with NASA’s TESS mission
- 2017/127 - Small planets around small stars: characterizing M-dwarfs in CHEOPS
- 2017/128 - Reflections from other worlds: detecting the atmospheres of other planets with high resolution spectroscopy
- 2017/129 - Characterizing exoplanet atmospheres with CHEOPS: combining theory and observations
- 2017/130 - Orbital evolution of planetary systems: from formation to today
- 2017/131 - Looking for rings and tides in transiting planets
- 2017/132 - Probing the architecture of multi-planetary systems
- 2017/133 - Unveiling the composition of exoplanets with atmosphere spectroscopy
- 2017/134 - Advanced statistical data analysis methods for the detection of other Earths
- 2017/135 - Planning observations for the detection and characterization of exoplanets
- 2017/136 - Characterization of Giant Planets Atmosphere Dynamics with Doppler Velocimetry and Cloud Tracking Techniques
For further details, please see the listing below, with abstracts and advisors. Prospective candidates are welcome to contact directly the proposers of the topics for inquiries and further details.
2017/126c - Detection and characterization of planets orbiting oscillating red-giant stars with NASA’s TESS mission
Advisers: Tiago Campante (Univ. Gottingen), Margarida Cunha (IA U.Porto), Nuno C. Santos (IA U.Porto & DFA/FCUP)
The Transiting Exoplanet Survey Satellite (TESS) is a NASA space mission, with launch scheduled for March 2018, that will perform an all-sky survey for planets transiting bright nearby stars. Furthermore, TESS’s excellent photometric precision, combined with its fine time sampling and long intervals of uninterrupted observations, will enable asteroseismology (i.e., the study of stars by the observation of their natural, resonant oscillations) of solar-type and red-giant stars. Asteroseismology is proving to be particularly significant for the study of red-giant stars while quickly maturing into a powerful tool whose impact is being felt more widely across different domains of astrophysics. A noticeable example is the synergy between asteroseismology and exoplanetary science. TESS hence offers the exciting prospect of conducting asteroseismology on a significant number of evolved exoplanet-host stars. The main goal of this project will be to use TESS photometry to systematically detect and characterize transiting planets orbiting oscillating red-giant stars. To that end, we propose an end-to-end PhD project that will provide the student with skills in transit photometry analysis, asteroseismic data analysis and stellar modeling, and radial-velocity/spectroscopic techniques. The implications of this project are far-reaching. The proposed systematic search for transiting planets orbiting oscillating red-giant stars is expected to provide new insights into some of the outstanding problems in exoplanetary science, namely, on the planet occurrence rate as a function of stellar mass/evolutionary state, on the correlation between stellar metallicity and planet occurrence around evolved stars and on the structural aspects of gas- giant planets.
Restrictions: This is a closed topic.
2017/127 - Small planets around small stars: characterizing M-dwarfs in CHEOPS
Advisers: Sérgio Sousa (IA U.Porto), Nuno C. Santos (IA U.Porto & DFA/FCUP), Elisa Delgado-Mena (IA U.Porto)
This project will be focused on the precise characterization of low mass stellar/planetary systems observed with CHEOPS. The characterization of the planets in these systems are strongly dependent on the correct knowledge of the host stars. Therefore the goal of this topic is strongly connected with the precise characterization of M stars. Although these cool M stars are the most common stars in our Galaxy they still represent an outstanding challenge in what regards their characterization and are currently the most crucial step for an accurate study of low mass stellar/planetary systems. To achieve this goal we will use ground-breaking spectroscopic analysis of near-infra-red (NIR) spectra of M-dwarf stars with the goal of deriving precise and homogeneous stellar parameters.
The knowledge of the stellar parameters of planet-hosts, in particular their radii, is essential for the derivation of the properties of the discovered planets. The goals of the present project will have important impact in the scientific community and are of great importance for the full success of future space missions like CHEOPS for which we have direct access to private/consortium data (80% of the telescope time), but also for TESS, which will have immediate public data, and later for PLATO.
With this in mind, the goal of the proposed project is to use methodologies for the spectroscopic analysis of near-IR high resolution spectra that are/will soon be available from new instruments such as SpiRou, CARMENES, and CRIRES+. Moreover, we intend to develop a method based on spectral synthesis that could be used as an alternative for this kind of stars. These methods will be applied to M stars hosting planets observed with CHEOPS/TESS. Besides the determination of precise stellar (and thus planetary) properties, one side important side project will be to further explore possible correlations between the properties of the stars and the presence of the planets, which can give important clues for planet formation models.
2017/128 - Reflections from other worlds: detecting the atmospheres of other planets with high resolution spectroscopy
Advisers: Nuno C. Santos (IA U.Porto & DFA/FCUP), Cláudio Melo (ESO Chile)
Are we alone in the Universe? To answer this question, several high-impact instruments and space missions are in current development, guaranteeing that exoplanetology will be in the front-line of astronomical research for many years to come. With the number of exoplanets increasing at a fast pace, the focus in this field is also starting to focus significant efforts towards the detailed characterization of these alien worlds. In particular, a number of different techniques have enabled the detection of the signature from exoplanet’s atmospheres for already a dozen of cases. The advent of a whole new generation of high-resolution spectrographs – working both in the optical and near-IR – is promising a bright future for this line of research, allowing to characterize increasingly smaller planets at larger distances.
ESPRESSO is a new high-resolution spectrograph for the ESO-VLT telescopes (the start of the operations is expected for late 2017/early 2018). Its unique stability and resolution, coupled with the high collecting area of the VLT telescopes, will allow us to detect and characterize exoplanets with masses similar to that of the Earth. Furthermore, ESPRESSO is expected to give us the possibility to detect the reflected light signal from distant exoplanets. A new window towards the study of exoplanet atmospheres will thus be open. Our team is deeply involved in ESPRESSO, having thus a unique access to this instrument and to its data.
In the present PhD offer the student the opportunity to lead the development of a methodology to detect the spectra of exoplanets using high-resolution spectroscopy, and in particular to study the reflectance of the exoplanet as a function of wavelength. The developed methods will be used with new data from ESPRESSO. Together with planet atmosphere models, the observations will allow us to probe and understand in unique detail the physical and chemical conditions of the observed planets, and shed new light into the physics of these distant worlds.
2017/129 - Characterizing exoplanet atmospheres with CHEOPS: combining theory and observations
Advisers: Nuno C. Santos (IA U.Porto & DFA/FCUP), Antonio García Muñoz (TU Berlin), Olivier Demangeon (IA U.Porto)
With the number of exoplanets increasing at a fast pace, the attention of exoplanetology is progressively focusing on their detailed characterization. This characterization effort will receive a major boost in the coming years, as a number of new telescopes both in space and on the ground become operative. To fully exploit the potential of the data to arrive, it is critical that similar efforts are spent on the development of theoretical tools that will enable the interpretation of the observations.
CHEOPS is a new ESA space mission (launch 2018) jointly developed by an European consortium whose goal is to characterize planets using high precision photometry. The exquisite photometric precision of CHEOPS will allow us to derive accurate radii for planets orbiting nearby bright stars, thus constraining with unprecedented accuracy their physical properties. Furthermore, CHEOP’s photometric precision will allow to detect the occultation signals of several planets. Occultations occur when the planet passes behind the star as seen by us. During that moment the light emitted/reflected by the planet does not arrive to the observer. The amount of light that is “lost” in such an event is deeply related to various atmospheric physical properties (e.g. composition, temperature, presence of clouds/hazes). The detection of occultations is currently one of the best avenues to study the atmospheres of exoplanets.
The present project proposes a combined theoretical and observational approach to use data from new instruments (and in particular from CHEOPS) to study the atmospheres of exoplanets. The student is expected to analyze CHEOPS’ data to detect and interpret the occultation signals (and maybe phase curves) for a variety of planets orbiting stars with different properties. A statistical analysis of the data, coupled with the model predictions, will allow him to explore new physical processes in the atmospheres of exoworlds.
During the project the student is expected to get involved in the exploration of CHEOPS data.
Type: This may correspond to a mixed fellowship (up to 1 year abroad).
2017/130 - Orbital evolution of planetary systems: from formation to today
Advisers: Alexandre Correia (CIDMA U. Aveiro), Vardan Adibekyan (IA U.Porto), Pedro Figueira (IA U.Porto)
The field of extrasolar planets research is tee-ming with activity. Very recently we celebrated the 20th anniversary of the discovery of the first planet outside our system, and yet we count already over 3000 confirmed planets and thausand of candidates to confirm. With a fast-growing discovery pace and a bright future ahead guaranteed by large number of ongoing and planned projects, it presents itself as the emerging astronomy topic of the new century.
As the planetary zoology continue, recent studies have shown that stellar properties (like, mass, evolutionary stage, and metallicity) also play a very important role not only on the formation of planets, but also on the orbital evolution. Several remarkable observational results can be outlined from these studies, that are still waiting for a solid explanation: planets in the metal-poor systems form/evolve differently appear to form farther out from their central star and/or they form later and do not migrate far; low-metallicity stars have a deficit of eccentric planets between 0.1 and 1 AU when compared to their metal-rich counterparts, because of either a less effective planet-planet interactions or due to the self-shadowing of the disk by a rim located at the dust sublimation radius (approx. 0.1 AU).
Planet-planet and planet-disk gravitational interactions during the formation process emerge as important orbit-shaping to be explored for a better understanding of the evolution of planetary systems. With this application we propose to study the impact of stellar metallicity on the orbital evolution of planetary systems from the observational point of view and to develop new simulations in which we consider the effect of disk and/or a companion planet’s presence on the planetary parameters. A linkage between theory and observations as presented here is uncommon, but crucial to understand our picture of extrasolar system. The different expertise of the supervisors will allow for a more encompassing work than before.
2017/131 - Looking for rings and tides in transiting planets
Advisers: Susana Barros (IA U.Porto), Nuno C. Santos (IA U.Porto & DFA/FCUP)
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.
2017/132 - Probing the architecture of multi-planetary systems
Advisers: Susana Barros (IA U.Porto), Olivier Demangeon (IA U.Porto)
The Kepler satellite has revealed that a large percentage of the known transiting exoplanets are in multi-planetary systems (∼40%). Multi-planetary systems are great laboratories to test theories of formation and migration of planetary systems. Many interesting systems found by Kepler and others recently found by the K2 mission are still awaiting detailed modeling due to the extra-complexity that the gravitational interaction between the different planets of the system introduce. This project aims at the study of the architecture of multi-planetary systems using detailed state of the art n-body simulations coupled with a Bayesian modeling.
The project is built on a photodynamic transit and radial velocity (RV) fitting tool developed by our group to study interesting known Kepler multi-planetary systems and/or new multi-planetary systems discovered by the K2 and TESS new surveys. A photodynamical analysis, accounting for the dynamical interactions between the planets of the system at the earliest stage of the data analysis, achieves a better precision and accuracy on the determination of the system parameters than usual methods. It is also more sensitive to the low masse planets. The goal of this project is to focus on the lowest mass planets (super-Earths and mini-Neptunes), for which it is not possible to determine masses with current RV instruments alone and will probe this fascinating population of planets.
Our group has developed a pipeline to reduce K2 data and compute high precision light curves combined with a transit search algorithm to search for planetary transits. Hence we have a competitive advantage to discover knew interesting systems from K2 or even TESS data. We are also involved in a collaboration to obtain precise radial velocities with the HARPS spectrograph to confirm and characterize these candidates. The student will study the most promising know systems and is also expected to be involved in the search and characterization of these new multi-planetary systems.
2017/133 - Unveiling the composition of exoplanets with atmosphere spectroscopy
Advisers: Olivier Damangeon (IA U.Porto), Susana Barros (IA U.Porto)
With already more than 3000 exoplanets detected, we know that exoplanets are ubiquitous in the galaxy. However, for most of them, their composition and atmospheric conditions (temperature, pressure, clouds, hazes, rain) are poorly known. Models exist which, given the density of the planet, assume the most likely composition and compute the most likely structure and temperature-pressure profile (Valencia et al 2007, 2010, Guillot et al. 1996). Unfortunately, all these models are degenerate with respect to the exact composition (Alibert 2016). The goal of this project is to raise some of those degeneracies by delivering insights in the composition of exoplanets.
If detecting exoplanets is already a challenging task due to the high contrast and low angular separation between a planet and its host star, obtaining their spectra requires state-of-the art instrumentation. The past decades have seen the emergence of three techniques capable of obtaining spectral informations of exoplanet: high-angular resolution and high contrast imaging (Marois et al 2008 , Lagrange et al. 2010), high-precision photometry (Charbonneau et al. 2002, Stevenson et al. 2014), and high-spectral resolution cross correlation techniques (Snellen et al. 2010, Martins et al. 2015).
For the ambitious objective of constraining exoplanet atmospheres, high-precision instruments are not enough. Extracting reliable spectral information on the observed exoplanet atmosphere requires advanced data reduction and analysis techniques coupled with state of the art modeling. This project proposes to the student, to benefit from the unique conditions offered by IA and our collaborators, to be at the junction between observation and theory. He will have to confront the data from several instruments enabling atmospheric characterization to the PHOENIX-BTSettl atmospheric models and extract robust information regarding the composition of exoplanets’ atmosphere. He will first start with archive and already published data from transit photometry (Sing et al. 2016 from WFC3@HST) and high-angular resolution and high-contrast data (Bonnefoy et al. 2016 SPHERE@VLT). Then he will analyze high-spectral resolution data using the cross correlation technique (Snellen et al. 2010 from CRIRES@VLT). An homogenous analysis of datasets coming from these different observational techniques has never been done before and will open new doors for atmospheric studies. The final step of this project will be to apply the developed analyses to different types of newly discovered planets and to explore trends in the atmospheric composition with respect to the characteristic of the observed planets, stars and observing techniques.
2017/134 - Advanced statistical data analysis methods for the detection of other Earths
Advisers: Pedro Viana (IA U.Porto & DFA/FCUP), Nuno C. Santos (IA U.Porto & DFA/FCUP)
For the past two decades, the radial velocity technique has been extremely successful, leading to the detection and characterisation of hundreds of exoplanets. In the process, its limits have been continuously challenged by a combination of new instrumentation and data analysis methods. The main objective has been to reach the precision needed to detect Earth-analogs, planets with mass and orbital period close to that of Earth, moving around a star similar to the Sun. This goal may become a reality within the next few years, as third-generation spectrographs become operational, e.g. ESPRESSO@VLT in 2018. However, it will only be accomplished through the implementation of more advanced statistical data analysis methods, capable of identifying a planetary-induced radial velocity signal in the presence of confounding signals an order of magnitude higher in amplitude, be they of instrumental origin or produced by stellar activity. In this project we propose to tackle these problems through the development of a new data analysis computational tool for the purpose of exoplanet detection and characterization using the radial velocity technique, built within the framework of Bayesian statistics and using the power of Gaussian Processes. This tool should be capable of jointly taking into account the information contained in any number of time-series, extracted from spectroscopic and photometric data, that may help disentangle the impact on radial velocity data of planetary motion and stellar activity, based on existing and newly developed indicators for the latter. As a result, it is expected the student will be at the forefront with respect to the detection and characterization of low-amplitude (e.g. below one meter per second) signals produced by the orbital motion of exoplanets. This could lead to the publication of high-impact papers, based on the analysis of HARPS and/or ESPRESSO data.
2017/135 - Planning observations for the detection and characterization of exoplanets
Advisers: Pedro Viana (IA U.Porto & DFA/FCUP), Sérgio Sousa (IA U.Porto)
The detection and characterization of planets around stars other than the Sun, also known as exoplanets, has been one of the most rapidly developing research topics within Astronomy for the past two decades. With third-generation spectrographs becoming operational in the next few years, e.g. ESPRESSO@VLT in 2018, and with the launch of space missions like CHEOPS (also in 2018), our knowledge of the exoplanet population will expand significantly, in particular towards the regime occupied by Earth analogs. However, in order for these instruments to be used in the most efficient way, it will be very important to carefully plan the sequence of observations to be made of any given star. The objective is to extract the maximum amount of information about any exoplanet orbiting the stars observed. This is most naturally achieved within the framework of Bayesian optimal experimental design, where the utility function to be maximized measures the expected information gain with the planned observations.
In this project we propose the development of a computational tool for planning observations aimed at the detection and characterization of exoplanets, using the radial velocity or transit techniques, and built within the framework of Bayesian experimental design. This tool should be capable of implementing batch and sequential planning, and take into account different types of prior data and information about the physical phenomena that affect the observables, namely when and in what conditions the stars that could be the targets of observation are visible. As a means of using existing transit data to inform the planning of radial velocity observations, and vice-versa, it is also proposed the characterization of the relation between exoplanet mass and radius using Gaussian Processes. As a result, the student is expected to participate in the planning of observations using the HARPS and/or ESPRESSO instruments, as well as by the CHEOPS satellite. The publication of several papers is expected, describing the planning methods developed, the derived relation between exoplanet mass and radius, and on the characteristics of the exoplanets discovered or re-observed based on the data acquired through the planned observations.
2017/136 - Characterization of Giant Planets Atmosphere Dynamics with Doppler Velocimetry and Cloud Tracking Techniques
Advisers: Pedro Machado (IA U.Lisboa), Agustin Sánchez-Lavega (Escuela Técnica Superior de Inginiaria de Bilbao)
The scientific objective of this PhD proposal is to help constrain the atmospheric dynamics of the Giant Planets (Saturn and Jupiter), detect and study atmospheric planetary waves, storms, measure wind velocities and their spatial and temporal variability.
Major objectives are:
1) to measure the latitudinal profile of the zonal winds and to search for wave motions through ground-based spectroscopic observations, using Doppler techniques;
2) to complement in-situ observations made by space missions (JUNO and CASSINI using cloud tracking techniques);
3) to better understand the nature of the processes governing the overall dynamics in the atmosphere of Saturn and Jupiter, in particular waves and wave-mean flow interactions;
4) to understand the atmosphere dynamics of Solar System Giant Planets as a case study in order to help constrain atmospheric models of gaseous-type exoplanets.
Type: This topic may correspond to a mixed fellowship (up to 1 year abroad).