Topics for Bachelor, Master and PhD Theses

Scheduled for release in December 2026, Gaia DR4 includes astrometry and photometry for objects in nine crowded fields. Due to source density, these regions required a special observing mode, as nominal observations could not resolve all objects. The resulting catalogue partly overlaps with other Gaia catalogues. This project aims to cross-match and harmonize these catalogues, opening the door to explore systematic effects, particularly how stellar blending influences measured parameters. Additionally, catalogues from external surveys may be incorporated to broaden the analysis.

Scheduled for release in December 2026, Gaia DR4 includes astrometry and photometry for objects in nine crowded fields. Due to source density, these regions required a special observing mode, as nominal observations could not resolve all objects. While this mode provides data for millions of additional sources, these objects have not undergone further processing within the standard Gaia pipeline. The goal of this master’s project is to identify, classify and characterise variable stars within these crowded field datasets.

Due to the geographical location, mirror performance, and optomechanical composition of a telescope, the light spot produced in the focal plane of the celestial object being examined always varies in size. This requires a fiber optic cable with a diameter that varies depending on the telescope it is used with and the wavelengths being examined. The function of the optical fiber is to guide light from the focal plane to a spectrograph. For various reasons, several components are required, including connectors that join the fibres together or to other components.

According to current research, there are connectors for various specific fiber optic diameters.

The aim of this Bachelor's/Master's thesis is to investigate and further develop an existing concept for a universal connector system for optical fibers.

Task:

• Design, simulate, prototype and validate a universal connector for optical fibers that works independently of the fibre diameter.
• Develop a universal connector that ensures high connection precision, low attenuation and robust mechanics.
• The manufacturing techniques for producing high-precision connectors will be evaluated and compared (e.g. manufacturing processes, surface treatment, material selection).
• Conduct laboratory and practical tests, potentially in collaboration with research institution partners.

Qualifications:

• Experience with CAD/design and simulation tools (e.g. 3D CAD and finite element simulations).
• Understanding of tolerances
• Ability to work independently and as part of a team.

We employ AIP’s Wide Field STELLA Imaging Photometer (WiFSIP) on the STELLA-I telescope in Tenerife for continuous monitoring of selected Open Clusters. Possible Master topics include the membership determination/verification based on metallicities and gravities (in the absence of radial velocities), the determination of rotational periods for selected clusters, the search for L-dwarfs from combined (stacked) CCD images, or the search for transits from extra-solar planets, a.o. The overall goal is to determine a mass-rotation and a rotation-activity relation and, later on, a mass-rotation-activity-age relation that shall constrain models of angular-momentum transport and evolution in the early phases of stellar evolution.

PLATO (PLAnetary Transits and Oscillation of stars) is ESA’s M3 mission for launch in 2026. It will search for extrasolar planets by means of ultra-high-precision transit photometry and addresses fundamental questions in exoplanet science. With our new robotic telescope BMK10k in Chile (see https://bmk10k.aip.de/), we aim supporting PLATO from the ground. A key planet parameter for the confirmation and characterisation
of planets is their mass, which can be determined by means of high-resolution spectroscopic observations providing precise radial velocities (RV). But additional photometric facilities will as well be useful to discard false positive scenarios. We will start monitoring the southern deep field with BMK10k by the end of 2024 and continue well beyond satellite launch. Individual Mastertheses are envisioned for several sub-aspects of the BMK10k data ranging from false positives detection, eclipsing binary statistics, periods for rotating and pulsating stars, to transient phenomena like stellar flares a.s.o., depending upon preference.

Solar limb darkening, or center-to-limb variation (CLV), is a well-known effect that causes the limb of the Sun to appear darker than its center. This phenomenon is caused by the variation in optical depth along the line of sight. It is strongly dependent on the wavelength, the observed target, and the spectral line being observed. While the CLV of the quiet Sun is well characterized, the limb darkening of active regions such as sunspots and plage remains poorly defined. Proper modeling of the CLV is critical for a wide range of astronomical quantities, such as exoplanet atmosphere parameters, stellar abundances, and rotation rates. A recent study by an undergraduate student in this department used data from the Solar Dynamics Observatory (SDO) to calculate the limb darkening coefficients of sunspots in a specific spectral line (Fe I 6173 Å). The current project aims to extend this work to other wavelengths using additional data from both space-based and ground-based telescopes.The project will use existing Python frameworks to analyze the limb darkening of active regions at multiple wavelengths. While some of the necessary code is already developed, some data sets will require careful handling to remove systematic effects. The project is modular so that more spectral lines can be analyzed as it progresses, and has the potential to result in a publication.

Ellerman bombs (EBs) are small-scale reconnection events found in active regions of the solar photosphere. These events are generally short-lived, with lifetimes of about a minute, but can last longer depending on their environment. They are thought to contribute to the heating of the higher layers of the solar atmosphere and are used as a tracer for the evolution of the active regions from which they originate. Despite their importance, they are poorly understood. Recent work by a master's student in this department has identified several EBs with extraordinarily long lifetimes of an hour or more, two orders of magnitude above the average. In this project, these long-lived EBs will be studied using satellite data from the Solar Dynamics Observatory (SDO) to analyze their intensity variations and those of their surroundings. The project involves the use of Python as an image processing and analysis tool, and has the potential to result in a publication.

Note: this topic has been allocated to a student and is not available any more.

Over 70% of all stars in existence are low-mass M dwarfs. Their lifetimes are longer than the age of the universe, and each of them hosts at least 1-2 planets. Some of these planets orbit in the habitable zone, where the basic conditions for life as we know it are met. The youth of young, low mass stars is of particular interest to astronomers because it sets the stage for the main sequence development of the entire star-planet system, and helps understand the conditions under which it formed.
TIC 206544316 is a young mid-M dwarf with a light curve that puzzles observers with its complexity. Several hypotheses exist to explain the persistent yet variable modulations of its optical emission. Some include magnetic spots on the rotating surface of the star and/or material in a disk or co-rotating clouds. Flares are a powerful natural spotlight that illuminates these local, dynamic magnetic structure as well as the material along the line of sight. In a recent observation by the Transiting Exoplanet Survey Satellite (TESS), a giant flare erupted on TIC 206544316. This presents a unique opportunity to discriminate between the proposed ideas about the nature of its magnetism and immediate surroundings.
The master project will involve analyzing this flare with an existing Python framework that was designed to localize flares on the surface from optical light curves of rapidly rotating stars. The student will then expand that framework to include the presence of material in the line of sight either in form of clouds or a misaligned disk that obscures the flare.
Basic scientific Python skills are required, i.e., familiarity with numpy, scipy, pandas, and matplotlib. Foundations of stellar magnetism and rotation are a bonus, but not mandatory.

Note: this topic has been given to a student and is no longer available.

In this thesis the student will learn about the wealth of information that is encoded in high-resolution spectra of exoplanetary systems. In real high resolution observations however, one is confronted with the complex problem of detecting and retrieving the tiny spectral signatures of an exoplanet. Advanced simulation will allow the student to model the spectral signatures of exoplanets around magnetically active host stars. Deep learning techniques offer a potential benefit to explore and analyze theses tiny spectral signatures. In a proof of concept case study based on simulated data and spectra the student will train and apply machine learning methods to retrieve characteristic parameters and information of the exoplanet and its active host star.

Note: this topic has been given to a student and is no longer available.

Stars in wide binary systems are formed at the same time, which provides us with two same-age (but not necessarily same-mass) stars. It is of high interest to stellar and exoplanetary science how the magnetic activity and X-ray emission of stars evolves over their main-sequence lifetime. In particular, the intrinsic scatter in this evolution of two stars that are otherwise very similar is important to understand the spin-down processes of stars. The goal of this thesis is to find archival X-ray data of wide binary stars and to measure the X-ray luminosity and other coronal properties of those stars. The student will then characterize the typical scatter within pairs of same-age stars and interpret this in the context of magnetic braking and spin-down of cool stars.

Different master thesis projects become available depending on the current research projects in the section. Please contact Prof. Poppenhaeger to check if thesis projects are currently available.

Different stellar populations in the Milky Way can be discriminated by their chemistry and by their kinematics. Thanks to the Gaia astrometric satellite mission, it is for the first time possible to track larger number of stars by their 3-dimensional orbits. This enables us to directly analyse the orbits of stars as function of their chemical abundance signatures. The project foresees to perform this analysis and compare findings with analogue relations seen in large-scale computer simulations of galaxy formation.

References: Buck, T., 2020 MNRAS 491, 5435; Guiglion, G., et al, 2020, A&A 644, 168; Steinmetz, M., et al, 2020 AJ 160, 183; Wojno, J., et al., 2018, MNRAS, 477, 5612

Central bars are present in about 2/3 of disk galaxies, including our Milky Way. Numerical simulations have shown that they are very important for the galactic chemo-dynamical evolution. This project will study the conditions under which bars form, using cosmological disk formation simulations. The time evolution of bar parameters, such as the pattern speed, length, and strength, will be linked to the disk phase-space structure discovered in the Gaia data, for the first time in the correct Local Group environment. The angular momentum redistribution induced by the bar in conjunction with the inner spiral structure will also be quantified. An ultimate goal of the project will be to resolve the longstanding controversy about the Milky Way’s bar length and pattern speed – is it long and slow or short and fast?

References: Minchev, I., et al., 2012, A&A 548, 126; Sanders, J. L., et al. 2019, MNRAS 488, 4552

The asymptotic giant branch (AGB) is the last evolutionary stage of intermediate-mass (1-8 M_sun) stars. The stars in this stage are extremely bright, so AGB stars are important luminosity contributors in stellar systems with intermediate ages (1-3 Gyrs). The luminosity contribution of AGB stars becomes even larger in near-infrared wavelengths due to their red colours. Models predict their luminosity and colour evolution, but they have significant uncertainty due to the complex internal stellar structure evolution, their rather cool atmospheres resulting in absorption lines of many elements and molecules, and circumstellar dust absorption effects. However, in preparation for the James Webb Space Telescope era it is important to calibrate the near-infrared luminosity and colours onto the models. Star clusters are useful tools to investigate the evolution, as they are assumed to have approximately the same age. There are resolved star photometry of stars clusters in the Large Magellanic Cloud and Andromeda galaxies, publicly available in the literature. We will select AGB stars in the star clusters in each galaxy, and investigate their luminosity and colour evolutions in Colour-Magnitude Diagrams. Detailed age-dependent properties, such as luminosity and colour of individual AGB stars, and total luminosity of AGB stars in star clusters in a given age bin, will be derived.

References: Radburn-Smith, D. J., et al. 2014, ApJ, 780, 105

Metal-poor stars in our Galaxy (those stars with at least 10 times smaller metal fraction than the Sun) hold important clues on the first steps of the formation and assembly of the Milky Way. It is now possible to use Gaia Mission Data Release 2 information combined with photometric information to find good candidates of metal-poor stars. This can be tested with samples for which the metallicity is known via spectroscopy (from many publicly available surveys). We will also study the effects of the different stellar evolutionary tracks on the outcome of the low metallicity candidates near and far way. This is a project to be carried out with the StarHorse code designed to determine stellar parameters (e.g., temperature, metallicity) from photometric and astrometric input values of millions of stars.

References: Queiroz, A., et al. 2018, MNRAS, 476, 2556

The stellar structure in the outermost regions of disk galaxies contains important clues about the disk formation and evolution. This project will involve examining a set of ~33 high-resolution disk formation simulations in the cosmological context, aiming to understand how the outer regions of galactic disks form and evolve with time. The student will write a code to split simulated stars by angular momentum, age, and chemical composition, and study the evolution of these parameters with cosmic time. The goal of this work will be to (1) understand the physical causes for the formation of different types of observed stellar density profiles: Type I (single exponential), Type II (down turning), and Type III (upturning) and (2) to find observational relations that can be used to distinguish different formation scenarios in observations of external galactic disk outskirts.

References: Minchev et al. 2012, A&A 548, 126