Student projects

Supervisor:

Karsten Frank Brogaard

Variabillity studies of open clusters in the Kepler field (with Rasmus Handberg)
The open clusters NGC6791 and NGC6819 have been observed by the Kepler mission. Due to the crowding in the clusters light curves were not extracted for most of the stars but only the pixel data is available. This means that many variable cluster stars have still not been investigated, including some that are potentially very interesting because of their unexpected positions in the colour-magnitude diagram.
The purpose of this project is to extract photometric light curves of cluster stars and analyse them. This can be giants showing solar-like oscillations, eclipsing binary stars, non-eclipsing binary stars, stars showing spot activity, or some other kind of variability.

Testing asteroseismic scaling relations using eclipsing binary stars with an oscillating giant component
You will use light curves from Kepler and radial velocities from spectra from the Nordic Optical Telescope to derive masses and radii of eclipsing binaries through a classical analysis and through asteroseismology in order to compare the two.

The true parameters of the active binary KOI-1003
The article adsabs.harvard.edu/abs/2016arXiv161000721R presents an interesting analysis of a magnetically active eclipsing binary star, KOI-1003. However, as part of a study of binary stars in the old open star cluster NGC6791 I have acquired spectra for this target, also known as V54, at the Very Large Telescope (VLT). A quick examination of the spectra has shown that the stellar parameters derived in the article must be revised.
The task of this project is to derive stellar masses, radii and effective temperatures of the components of KOI-1003 that are consistent with both photometry from Kepler (analysed in the article) and spectroscopy from the VLT. Both photometric and spectroscopic data is available.

Supervisor:

Victoria Antoci

Stellar surface gravities from granulation noise in gamma Dor stars
The surface gravity of a star is one of the most basic parameters crucial for any type of analyses, but it is not easy to be determined robustly. Recently two methods (Bastien et al., 2013, Nature, 500, 427, Kallinger et al., 2016, Science, DOI: 10.1126/sciadv.1500654) were presented to extract the logg value of a star from the granulation signatures observed in Kepler light curves of solar-type oscillators. In this project you will be applying the methods described in the articles mentioned above on gamma Dor stars. Your results will be used in upcoming publications (you will be a co-author, of course). Come by for more details!

Stellar surface gravities from granulation noise in delta Sct star
The gravity of a star is one of the most basic parameters crucial for any type of analyses, but it is not easy to be determined robustly. Recently two methods (Bastien et al., 2013, Nature, 500, 427, Kallinger et al., 2016, Science, DOI: 10.1126/sciadv.1500654) were presented to extract the logg value of a star from the granulation signatures observed in Kepler light curves of solar-type oscillators. In this project you will be applying the methods described in the articles mentioned above on delta Sct stars. Your results will be used in upcoming publications (you will be a co-author, of course). Come by for more details!

Determining the variability of a strange feature
Over hundred stars observed with the Kepler telescope show a strange feature in their amplitude spectra, which was interpreted to be caused by non-tranisting planets (Balona, L. 2014, MNRAS, 441, 3543). While there is no clear explanation for its origin, it is very unlikely that it is indeed caused by close-in companions. In this project you will measure the exact location of these features and be part of a collaboration trying to solve this mystery. Your results will be used in upcoming publications (you will be a co-author, of course). Come by for more details!

Supervisor:

Günter Houdek

Stellar-convection properties across the Hertzsprung-Russell diagram
Convective transport of heat and momentum plays an important role in any phase of stellar evolution. Currently adopted one-dimensional (1D) convection models in stellar evolution calculations are still very simplified and subject to various parameters that need calibration. Results from sophisticated three-dimensional (3D) hydrodynamical simulations of the outer stellar convection zones can be used to calibrate the simpler 1D  convection models. It is the aim of this project to investigate convection properties in stars located at different points in the Hertzsprung-Russell diagram by calibrating 1D convection models with results from 3D simulations.

Measuring the depths of surface convection zones in Kepler stars
High-quality frequency measurements in many solar-like stars were obtained from the NASA Kepler mission. With the help of asteroseismic diagnostic techniques, which make use of certain combinations of the measured stellar
frequencies, it is possible to determine the extent of the surface convection zones. The knowledge of the depth of the surface convection zone is of great importance for stellar evolutionary calculations. The aim of this project is
to measure the acoustic glitch properties of the base of convection zones in various Kepler stars with the help of a seismic diagnostic procedure.

Calibrating the location of the theoretical instability strip in the HR-diagram
Accurate measurements of stellar pulsations in classical variables (stars with overstable, heat-driven, oscillations) are now available thanks to the NASA mission Kepler and ground-based observation campaigns. A long-standing problem has been the modelling of the location of the cool edge of the classical instability strip in the Hertzsprung-Russell (HR) diagram. The aim of this project is to use an existing, advanced, pulsation programme for computing the location of the instability strip and to calibrate the convection parameters with the help of observational data.

Supervisor:

Simon Albrecht

Kepler-18: measuring planetary densities from high precision photometry alone
Measuring radii and masses of the smallest extra solar planet is challenging. However observations of planetary transits in front of their stars let us measure their radii. If additional planets are present in the system then their masses perturb the orbit of the transiting planets. In this project you will use photometry from the Kepler space mission to measure the masses and densities of planets in the Kepler-18 system

What can we learn about the interiors of small terrestrial extra solar planets
In this work you will review what we know about the structure of terrestrial planets inside and outside the solar system. Next you will try to constrain the type of material rocky extra solar planets made of.

Phase curve simulator
In this work you will write the code for a simulator which allows you to estimate how exoplanets will look in reflected star light at different orbital phases. You will use some simple assumptions about the surface properties. If time permits then you will also include the thermal emission form the planet in the simulator, and compare the results to phase curves from the Kepler space mission.

How to form Hot-Jupiter
A review of what we know (and not know) about the formation of gas giant planets like Jupiter and Saturn.  However these planets orbit their stars at a distance of 1/20 the Sun-Earth distance. The existence of Hot Jupiters is one of the most persistent problems in extra solar planet science.

Supervisor:

Carolina von Essen

Hands-on exoplanets: from raw data to transiting light curves
Transiting exoplanets offer an outstanding opportunity to study alien worlds in more detail. Combined with the radial velocity technique, from transiting light curves we can determine orbital and physical parameters such as the semi-major axis, the orbital period, the planetary size, mass and density and only lately, with more refined observing techniques, the chemical composition of their atmospheres. In this project you will work with real data already acquired using the 2.5m Nordic Optical Telescope. You will learn how to reduce them and how to extract a primary transit light curve. In this project we will use IRAF, python and gnuplot.

Supervisor:

Timothy White

Extraction of asteroseismic parameters from Kepler raw data (Bachelor/Master)

The development of algorithms to fast and efficiently analyze the data from space missions is the cornerstone for extracting accurate asteroseismic parameters. This project consists on further developing and optimizing the Aarhus Solar-like Asteroseismic Pipeline (ASAP) that will process the raw Kepler data until extraction of the two main asteroseismic quantities (the large frequency separation and frequency of maximum power). ASAP is mean to be the pipeline that will analyse all data from current and future space missions (Kepler, K2, TESS, and PLATO).

Asteroseismic Diagrams of Red Giants (Bachelor/Masters)

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.

Mode amplitudes of F stars (Bachelor/Masters)

F stars with solar-like oscillations appear to have broader and more complex pulsation envelopes, with more orders excited to higher amplitudes than in cooler stars, although this effect has not been quantified. As the peak of this pulsation envelope is used in determining asteroseismic surface gravities, there are implications for the accuracy with which stellar parameters are measured. In this project, properties of pulsation envelopes will be measured, and investigated for trends with temperature and evolutionary state.

Calibrating asteroseismic radii with interferometry (Bachelor/Masters)

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.

Supervisor:

Victor Silva Aguirre

Calibrating asteroseismic radii with Gaia and Kepler (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 use the first Gaia data release and compare the distances measured from parallaxes with those determined using a combination of asteroseismic radii and InfraRed Flux Method determined angular diameters.

Dissecting the Milky Way disc with SAGA and K2 (Bachelor/Master)

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.

One size fits all: determining stellar properties of solar-like oscillators (Bachelor/Master)

The way 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.

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.

Galactic archaeology with APOGEE and Kepler (Master)

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.

3D model atmospheres and their impact in stellar evolution (Master)

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.

Exploring the Initial Mass Function (IMF) with asteroseismology (Master)

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.

Supervisor:

Mads Fredslund Andersen

Software development and color imaging using the new SONG SkyCam – 2

A new small 6'' telescope + a CCD camera and a filter wheel will be mounted on the side of the SONG telescope on Tenerife in March 2016.  If you have a flair for programming or a high interest in learning how to, this project might be of interest. You will develop the control software for the CCD camera and filter wheel in the programming language of Python. Part of the project will be focused on characterizing the CCD and determine the daily automatic operation of the instrument. Another part of the time will be spent using the instrument to create color images of astronomical phenomenons like dust clouds, galaxies, nebulas etc.

 

Photometry of images collected using the SONG SkyCam – 1

A small CCD camera with a 180mm lens is attached on the side of the SONG telescope on Tenerife and has collected huge amount of data in the last few years. In this project you will deal with the basics of astronomical photometry. You will adapt existing packages in Python to produce an automated pipeline for the steady data flow coming from SkyCam – 1. The pipeline will be developed to handle the data which will start to come from the new SkyCam – 2 as well. Characterizing the photometry precision will be an essential part of the project.

 

Pointing system and astrometry precision of the SONG SkyCam – 1

The piggybag SkyCam – 1 and the coming SkyCam – 2 are mounted on the side of the 1m SONG telescope located at Tenerife and therefore points at the same field as the mother telescope. These two instruments can potentially  be used to correct the telescope pointing and be used when normal pointing procedures fail. This project will focus on determining the precision at which the pointing can be done using both SkyCam – 1 and SkyCam – 2. Implementing the new pointing system into the SONG robotic software will be an important part of the project.

Supervisor:

Frank Grundahl

SONG relateret

Generelt: høj-præcisions radial-hastigheder med ThAr metoden, som regel af binær-stjerner, bestemmelse af masser. Test af analyse-metoder og procedurer kan også være en mulighed.

Bi-sector analyse - '3rd signature of convection'

Her studeres hvordan konvektionen opfører sig i de ydre lag af    klare stjerner. Data fra SONG teleskopet.

Fotometri fra K2 af stjernehobe ( med Rasmus Handberg og Karsten Brogaard):

M67 - eftersøgning af variable, svinginger i røde kæmpestjerner

Bestemmelse af absorptionen i retning af Mælkevejens ældste stjernehobe

Analyse af linie-styrken for interstellare Na linier for at bestemme absorptionen i retning til udvalgte stjernehobe. Dette vil føre til forbedrede temperaturer for stjernerne i hobene og ultimativt bedre aldre.

Kom og snak om mulighederne!

Supervisor:

Christoffer Karoff

 

Aktivitets cykler i sol-liggende stjerner

Vi kender til aktivitets cykler i omkring 100 stjerner, der minder om Solens 11-års cyklus. Disse cykler er hovedsageligt observeret fra Jorden ved at studere emission i Farunhofer H & K linjerne, men de sidste par år har fotometriske observationer fra Kepler missionen skabt fundamentet for en revolution inden for feltet.

 Flere forskellige projekter vil være mulige indenfor dette område:

 -         Måling af stjerne cykler med asteroseismologi

-          Konstruktion af UV spektrograf til SONG teleskopet på Tenerife

-          Bestemmelses af ændringer i Solens UV udstråling ogeffekten af disse ændringer på Jordens klima

 

Superflares på sol-ligende stjerner

Kepler missionen har opdaget et stort antal såkaldte superflares på Sol-liggende stjerner.  Dette åbner mulighed for at Solen også kunne have oplevet en superflare. En sådan superflare ville med stor sandsynlighed have destrueret ozonlaget og dermed kunne have ført til evt. masseudryddelse.

Projektet vil gå ud på at analysere optiske spektra observeret med det Nordiske Optiske Teleskop på La Palma af sol-liggende stjerne med superflares for at afdække, hvor meget de faktisk minder om Solen.

 

Supervisors:

Christoffer Karoff and Stergios Mision

Using coupled climate models of the atmosphere and the oceans to model solar influence on the Atlantic Multidecadal Oscillation and the North Atlantic Oscillation.

Part of the project can be conducted at Imperial College London

Using coupled climate models of the atmosphere and the oceans to model the effects of superflares on atmospheric chemistry and climate.

Part of the project can be conducted at Imperial College London