Research :: PhD Topics for 2015 :: Planets

Topics under the thematic lineTowards the detection and characterization of other Earths” available for the 2015 Call (8 PhD Topics):

  • 2015/107 – From ESPRESSO to Plato: detecting and characterizing Earth-like planets in the presence of stellar noise
  • 2015/108c – Determination of stellar parameters for M-dwarf stars: the NIR approach
  • 2015/109 – Towards new worlds by portraying the tiny stars
  • 2015/110 – Orbital evolution of planetary systems: from formation to today
  • 2015/111 – Toward the statistical validation of Earth-like planets
  • 2015/112 – Planetary atmospheric characterization using ALMA capabilities
  • 2015/113 - Planetary atmospheres – From Solar System to Exoplanets: atmospheric characterization and search for chemical disequilibrium compounds
  • 2015/114 - Galactic stellar populations and planet formation with the Gaia-ESO Survey data

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.

2015/107 - From ESPRESSO to Plato: detecting and characterizing Earth-like planets in the presence of stellar noise

AdvisersNuno C. Santos (CAUP)

While the number and variety of discovered extra-solar planets is still an important asset for exoplanet research, the focus of extrasolar planet researchers is now moving towards two main lines: i) the detection of lower and lower mass planets, with the goal of finding an Earth sibling, and ii) the finest characterization of planets orbiting other stars, including their interior structures and atmospheres.

Despite the development of a whole new generation of instruments and space missions (like ESO- ESPRESSO and ESA’s CHEOPS and PLATO missions, on which our team is deeply involved), these goals are not easy to achieve. In particular, the “noise” introduced by stellar activity has been shown to be a strong source of difficulties for planet search and characterization programs using both high precision radial velocity or photometric transit observations.

The present project proposes to investigate the impact and role of stellar activity in precise planet search and characterization projects. For this, we expect the student to develop a tool to simulate the effects of stellar activity on precise photometric (transit) and radial velocity measurements. The tool will then be applied to real data (e.g. HARPS and Kepler). The impact of stellar activity on the derivation of precise planet parameters will be investigated in detail. The results of this project have crucial consequences for the full success of instruments like ESPRESSO, CHEOPS, and PLATO.

University: Porto

2015/108c - Determination of stellar parameters for M-dwarf stars: the NIR approach

Advisers: Sérgio Sousa (IA-U.Porto), Nuno C. Santos (CAUP)

This project is focused on the 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 correct 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 are thus of great importance for the full success of future space missions like TESS, CHEOPS, and PLATO.

With this in mind, the major goal of the proposed project is to adapt current methodologies, well established for the analysis of high resolution optical spectra of FGK dwarfs, to be used with near- IR high resolution spectra that will soon be available from new instruments such as SpiRou, CARMENES, and CRIRES+. In this context the student is expected to implement an automatic code to estimate stellar parameters directly from the measurement of line equivalent widths, and to apply it to M stars hosting planets. Besides the determination of precise stellar (and thus planetary) properties, the student will then 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.

University: Porto

Note: This is a closed project. It is also offered as project 215c in the line on Stars.

2015/109 - Towards new worlds by portraying the tiny stars

Advisers: Bárbara Rojas-Ayala (IA-U.Porto), Nuno C. Santos (IA-U.Porto)

The search and characterization of new worlds has a strong dependance on the characterization of the host stars. A large number of the most interesting rocky planets found until date orbit the smallest stars. The characterization of M dwarf stars has been a one of the hottest topics in the past 10 years, and it has been quite challenging, involving new and creative techniques based on empirical data of nearby M dwarfs. The goal of this 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 M dwarf targets of the PLATO 2.0 mission, and the proper characterization of their likely planetary companions.

University: Porto

2015/110 - Orbital evolution of planetary systems: from formation to today

Advisers: Alexandre Correia (U.Aveiro), Vardan Adibekyan (IA-U.Porto),  Pedro Figueira (IA-U.Porto)

The field of extrasolar planets research is tee-ming with activity. This year we will celebrate the 20th anniversary of the discovery of the first planet outside our system, and yet we count already over 1700 confirmed planets and hundreds 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.

University: Porto

2015/111 - Toward the statistical validation of Earth-like planets

Advisers: Alexandre Santerne (IA-U.Porto), Nuno C. Santos (IA-U.Porto)

Detecting a planet like the Earth is one of the main challenges of the next decade. To find such planets, new outstanding instrumentations are going to be built with an unprecedented precision (such as the ESPRESSO spectrograph for the ESO – VLT and the PLATO space mission from ESA). Their precision will make possible the detection of an exoearth signal. However, other astrophysical scenarios are able to mimic the signal of an Earth signal, like stellar variability (stellar activity, magnetic cycle, …), or multiple stellar systems.

The announcement of the first Earth-twin planet will thus require strong evidence that the detected signal is indeed of planetary origin. This can be done by statistically validating the planet signals. In this context, the PASTIS software is a unique, fully-Bayesian, tool that is able to validate small-size planets. However, today, the PASTIS tool is not able to statistically validate an Earth-analog planet without relying on their occurrence rate and statistics of physical properties. Statistics of such planets are however extremely poor since only one is known so far (the Earth).

The goal of this PhD will be to improve the capabilities of PASTIS to validate planets, down to Earth-size ones. This can be done by improving the constraints from the data on the various astrophysical scenarios. This will require to develop and/or implement more accurate models of the scenarios, especially of stellar activity. Then, the improved PASTIS software will be used by the PhD student to validate Earth-size planets already detected by the Kepler space telescope or small planets that are first to be detected in existing HARPS data. Then, it will also be used to prepare the validation of other Earth in the context of the ESPRESSO spectrograph, which will be commissioned at the end of the PhD.

University: Porto

2015/112 – Planetary atmospheric characterization using ALMA capabilities

Advisors: Pedro Machado (IA-U.Lisboa), Hugo Messias (IA-U.Lisboa)

The advent of ALMA brought new planetary systems atmospherics’ research perspectives to the scientific community. The already available spectroscopic and continuum analyses of Solar System objects from (sub-)millimeter observations with ALMA will allow the project research lines to be fulfilled. This a case of opportunity, since three of the Solar System bodies targeted by this project (Mars, Uranus, and Titan) are regularly used as a calibrating sources.

The main goals of the project are to assess the atmosphere dynamics and photochemistry as well as the search for minor species in Venus, Mars, Uranus, and Titan. More specifically: CO mapping and dynamics in all the targets; mesospheric winds in Venus and Mars; HDO, Chlorine and Sulphur species in Venus; HDO and H2O2 in Mars; and HCN mapping in Uranus and titan.

The data necessary to fulfil these goals are twofold: ALMA archive on a first stage of the on-going PhD works and dedicated ALMA observing proposals when in need for longer integration, specific spectral tuning or array configuration.

University: Lisboa

2015/213 – Planetary atmospheres – From Solar System to Exoplanets: atmospheric characterization and search for chemical disequilibrium compounds

Advisors: Pedro Machado (IA-U.Lisboa), Pedro Figueira (IA-U.Porto)

High-resolution visible and infrared (in the CO2 transparency windows) spectroscopic capabilities to the Solar System planets opens a new window by accessing atmospheric composition, mixing ratios and isotopic ratios, in particular, the measurement of the spectral lines’ Doppler shifts allows the retrieval of wind velocities and thus contribute to constrain planetary circulation dynamics.

Solar System observations and data reduction techniques, besides their own relevance research sake, serve as a stepping-stone for the study of extrasolar planets. In this project we propose to use them as a starting point for the development and test of atmospheric characterization tools. In a second phase the fine-tuned protocols will be adapted and applied to exoplanetary targets in order to constrain their atmospheric composition. The research will be focused in the presence of chemical disequilibrium compounds.

University: Porto & Lisboa

2015/114 - Galactic stellar populations and planet formation with the Gaia-ESO Survey data

Advisors: Sérgio Sousa (CAUP) and Vardan Adibekyan (CAUP)

The on-going Gaia-ESO Survey is a very ambitious project which uses ESO/VLT to obtain detailed spectra of about 100000 stars from all the Galactic stellar populations. We propose to use the data from this survey (for which we have privileged access) to study the chemical and kinematic properties of stellar populations. The goal is to understand the formation and evolution of the distinct populations that we can identify with the data. In addition, we propose to investigate the observed planet hosting stars to understand possible links between the different stellar populations and planet formation processes. This latter study should help us to better estimate the frequency of the different type of planets for each stellar population and in our Galaxy in general.

University: Porto

Notes: This topic is also offered as topic 210, under the thematic line on Stars.