Research :: PhD Topics for 2016 :: Stars

Topics under the thematic line Towards a comprehensive study of starsavailable for the 2016 Call (4 PhD Topics):

  • 2016/217 - Dissecting the atmospheres of low-mass stars: Precise stellar characterization with high- res NIR spectroscopy
  • 2016/218 - Detection and characterization of planets orbiting oscillating red-giant stars with NASA’s TESS mission
  • 2016/219 - A new tool for the asteroseismic characterization of large samples of pulsating stars
  • 2016/220c - Towards a comprehensive understanding of the tiny stars at NIR wavelengths

For details, please see below the abstract and advisors for each topic. Prospective candidates are welcome to contact directly the proposers of the topics for inquiries and further details.

2016/217 - Dissecting the atmospheres of low-mass stars: Precise stellar characterization with high- res NIR spectroscopy

Advisors: Sérgio Sousa (IA U.Porto), Elisa Delgado-Mena (IA U.Porto), Barbara Rojas-Ayala (IA U.Porto)

This project will be 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. Although these cool M stars are the most common stars in our Galaxy they still represent an outstanding challenge in what regards their characterization.

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 TESS, CHEOPS, and PLATO.

With this in mind, the goal of the proposed project is to use current methodologies for the spectroscopic analysis of near-IR high resolution spectra that 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. 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

Notes: This topic is also offered as topic 2016/119, under the thematic line on Planets.

2016/218 - Detection and characterization of planets orbiting oscillating red-giant stars with NASA’s TESS mission

Advisors: Tiago Campante (University of Birmingham, UK),  Margarida Cunha (IA U.Porto), Nuno Santos (FCUP & IA U.Porto)

The Transiting Exoplanet Survey Satellite (TESS) is a NASA space mission with scheduled launch for late 2017 that will perform a wide-field 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 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 (i) transit photometry analysis, (ii) asteroseismic data analysis and stellar modeling, and (iii) 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, (i) on the planet occurrence rate as a function of stellar mass/evolutionary state, (ii) on the correlation between stellar metallicity and planet occurrence around evolved stars or (iii) on the structural aspects of gas-giant planets.

University: Porto

Notes: This topic is for a mixed fellowship (up to 12 months  in Birmingham). This topic is also offered as topic 2016/120, under the thematic line on Planets.

2016/219 - A new tool for the asteroseismic characterization of large samples of pulsating stars

Advisors: Margarida Cunha (IA U.Porto), Pedro Avelino (FCUP & IA-U.Porto) and Dennis Stello (University of Sydney)

As a result of the launch of the CoRoT and Kepler satellites, the astronomical community has, today, exquisite asteroseismic data on thousands of red giant stars. The analysis of just a fraction of these data has already led to a number of very exciting new results, published in high-impact journals, such as Nature and Science.  Moreover, given the recent approval by ESA of the mission PLATO2.0 (launch around 2023), it is expected that in a decade the number of red giants with detected oscillations will increase by orders of magnitude. To exploit this large observational sample of stars, further development of asteroseismic tools is required. In particular, it is imperative that we have tools capable of modelling the pulsations in large grids of red giant models, covering a wide parameter space (in mass, age, metallicity), in a reasonable amount of time. In this context, a primary goal of this project is to develop a new linear adiabatic pulsation code, significantly more efficient than those currently available, that may be applied to large grids of red giant models, necessary to fully exploit the available data. The code will then be applied in the characterization of the red giant populations for which space-based data are already available, and in the study of particular aspects of the physics of these stars. The proposed tool will constitute a magnificent step forward towards the preparation for the exploitation of the data that will be acquired by the PLATO2.0 mission.

University: Porto

Notes: This topic is for a mixed fellowship (up to 12 months  in Sydney).

2016/220c - Towards a comprehensive understanding of the tiny stars at NIR wavelengths

Advisors: Bárbara Rojas-Ayala (IA U.Porto), Elisa Delgado-Mena (IA U.Porto),

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.

University: Porto

Notes: This is a closed topic.