Student projects

3D model atmospheres and their impact in stellar evolution

Master/PhD

Detailed hydrodynamical simulations of stellar atmospheres have recently become available. This sophisticated set of models includes all relevant physical processes that govern the evolution of convective outer layers and are of key importance to accurately predict stellar properties. This projects aims at coupling the average results of these simulations to 1D hydrostatic evolutionary codes and study its impact in physical and pulsation properties of stars.

SupervisorVíctor Silva Aguirre


Anchoring the asteroseismic age scale

Bachelor/Master

Asteroseismology is a powerful tool to determine precise stellar properties, including masses of red giant stars. This project aims at anchoring the zero-point of the asteroseismic age scale by comparing mass determinations (and thus ages) of solar-like oscillators in clusters with those predicted by isochrone fitting to the CMD.

SupervisorVíctor Silva Aguirre


Asteroseismic Diagrams of Red Giants

Bachelor/Master

The values of asteroseismic parameters depend on physical properties of stars. To date the phase of gravity modes (eps_g) in red giants has not been investigated for its diagnostic potential, but it is expected to probe the properties of the stellar core. This project will involving calculating eps_g for a grid of red giant models, and investigate how it varies with other stellar properties.

SupervisorTim White


Asymmetries of solar-like modes of oscillation

Bachelor/Master

An important part of asteroseismic analysis pertains to extracting parameters (including frequencies) of modes of solar-like oscillations for the purpose of asteroseismic inferences and modelling. When doing so, the individual modes are typically approximated as symmetric Lorentzian profiles when in fact they can be asymmetric due to activity. The project consists in measuring mode asymmetries from Kepler stars and try to find relations to other activity indicators and fundamental stellar parameters.

SupervisorMikkel Nørup Lund


Calibrating asteroseismic radii with interferometry

Bachelor/Master

Ensuring the accuracy of stellar parameters derived from asteroseismology is of fundamental importance to its subsequent use in studies of stellar physics and our Galaxy’s formation. This project will involve measuring angular diameters of bright stars with interferometry, which combined with parallaxes from the first Gaia data release provide stellar radii to be compared with those determined with asteroseismology.

SupervisorTim White


Constraining overshoot in intermediate mass stars

Master/PhD

An adequate prescription of mixing processes in stellar interiors is of crucial importance for precise predictions of stellar ages across the HRD. This projects will constrain the amount of non-canonical mixing from convective cores in stars from ~1.1-2.5 solar masses using frequency combinations in the main-sequence phase and gravity modes period spacing in the base of the red giant branch.

SupervisorVíctor Silva Aguirre


Dissecting the Milky Way disc with SAGA and Kepler/K2

Master/PhD

Combining Strömgren photometry with Kepler asteroseismic observations provides a powerful tool to determine self-consistent properties of thousands of stars. This project couples the SAGA observations with data from Kepler to study gradients and variations in the population of the Milky Way disc as a function of position and distance, revealing the main dynamical processes that formed the thin and thick discs.

SupervisorVíctor Silva Aguirre


Exploring the Initial Mass Function (IMF) with asteroseismology

Master/PhD

The IMF is an empirical function that describes the distribution of initial masses for a population of stars. So far its determination and test of its universality has been hampered by the difficulty in estimating stellar masses for a field stars across the Galaxy. In this project the student will use stellar masses derived from seismology to explore whether new constraints can be derived for the IMF.

SupervisorVíctor Silva Aguirre


Galactic archaeology with APOGEE and Kepler/K2

Master/PhD

Combining spectroscopy and asteroseismology to determine accurate stellar properties can provide stringent constraints into the formation and evolution of the Milky Way. This project uses the latest observations from the APOGEE survey and Kepler asteroseismic data of red giants to study correlations between age, composition, and velocity dispersions as a tracer of our Galactic history.

SupervisorVíctor Silva Aguirre


Mass loss along the red giant branch

Bachelor/Master

The efficiency of mass loss in stars is still very much unconstrained. In this project, the student will combine asteroseismic and classical stellar parameters to fit the spectral energy distribution of red giant stars and match observed multi-band photometry. The goal is to determine whether stars display any infrared excess, which could be the signature of mass-loss. The study of this excess will give insights on the mass-loss mechanism.

SupervisorVíctor Silva Aguirre


Measuring stellar granulation backgrounds

Bachelor/Master

For a solar-like oscillator we see in addition to the signal from oscillation modes also a broad background from stellar granulation. The properties of this granulation background correlates with the mode parameters of the star, because the convection that the granulation indicates also drive the excitation of the oscillations – much can therefore be learned about the star from measuring the parameters of the granulation. In addition to this, the actual shape of the granulation background is not agreed upon. The project consists in measuring the granulation backgrounds of Kepler solar-like oscillators, comparing different parameterisations, and establishing relations between the parameters of the granulation and fundamental stellar parameters.

SupervisorMikkel Nørup Lund


One size fits all: determining stellar properties of solar-like oscillators

Bachelor/Master

The manner in which properties of stars are determined from asteroseismology depends on the availability and quality of the data, as well as the evolutionary stage where the star is. The aim of this project is to refine and optimize the BAyesian STellar Algorithm (BASTA) for determining accurate stellar properties of solar-like oscillators across all evolutionary stages, as well as update its library of stellar isochrones and pulsation frequencies.

SupervisorVíctor Silva Aguirre


Photometry of Kepler superstamps of stellar clusters

Bachelor/Master

During the Kepler mission so-called superstamps, that is images with a large number of pixels, were obtained for the few open stellar clusters observed. A detailed photometric analysis of these still remains to be done. The project would consist in developing code, or modifying existing software, to extract light curves for cluster stars covered by the superstamps. From these light curves signs of rotational modulation or asteroseismic signatures will be sought for and analysed.

SupervisorMikkel Nørup Lund