Fast radio bursts (FRBs) last for much less than the blink of eye and originate in distant galaxies, billions of lightyears away. We are still trying to understand what produces the FRBs. The hyper-magnetic neutron stars known as magnetars are a leading contender, but can they explain the variety of different FRBs we have observed? Some FRBs repeat, whereas others apparently do not. Some FRBs are found near star-forming regions in their host galaxies, whereas others live where only old stars are expected. This is confusing, and suggests that there may be multiple types of FRB sources. Recent years saw the discovery of longer-than-typical FRBs with durations up to a few seconds. Are they a distinct class of bursts or are they produced by the same sources and physical processes?

OBJECTIVE: This project aims to find longer-duration FRBs using data from the CHIME and/or LOFAR telescopes. You'll get access to prerecorded data sets and will work on the visualization tools and algorithms to first identify and then characterize astrophysical bursts.

PREREQUISITES: No prior knowledge of the field is required but experience with programming in Python or another language is strongly preferred.

RESOURCES: This project can be performed using a consumer laptop that runs Python; you will get remote access to one of our compute clusters for more demanding processing tasks. We will lend a laptop computer if need be.

Cosmology predict that supermassive black hole (SMBH) binaries frequently form as a result of galaxy mergers. However, the mechanisms driving these binaries from kiloparsec separations to the gravitational wave (GW) radiation-dominated regime remain a topic of active debate—this is known as the final parsec problem. Key open questions include the expected merger rates and the parameter space distribution of these systems, both of which are crucial for near-future GW observatories, such as the Laser Interferometer Space Antenna (LISA).
A promising mechanism that could accelerate the binary evolution is the interaction with gas in galactic centers, leading to the formation of circumbinary accretion disks. These disks can exert significant torques on the binary, potentially altering their inspiral and coalescence dynamics. Recent advances in high-resolution hydrodynamic simulations have provided insights into disk-driven torques, particularly in thin-disk models across a range of binary mass ratios. However, the impact of such environmental effects on the gravitational waveform -- especially in the late inspiral phase where GW emission dominates -- remains largely unexplored. This will be a crucial question facing LISA in the upcoming decades.

OBJECTIVE: This project aims to compute the impact of gas-induced torques on the gravitational waveforms of SMBH binaries and assess their detectability by LISA. Specifically, we seek to:
-- Quantify the influence of circumbinary disks on the evolution of binary orbits and resulting GW signals.
-- Identify possible degeneracies and systematic biases in GW parameter estimation due to unmodeled gas-induced environmental effects.
-- Explore whether gravitational waves can provide new insights into SMBH accretion physics and how these observations complement electromagnetic (EM) signatures from active galactic nuclei.
By addressing these questions, this project will contribute to understanding the role of environmental interactions in SMBH binary evolution and their implications for multi-messenger astrophysics.

PREREQUISITES: Some experience with Python would be helpful, particularly for data analysis.

RESOURCES: A standard laptop with a working Python installation will be sufficient for the computational tasks involved.

Since the Event Horizon Telescope's first published image of M87's supermassive black hole, there has been a renewed interest in observing black holes at various wavelengths. We now have at our disposal a multitude of multiwavelength data from various black hole sources, including M87*, Centaurus A*, and our galaxy's own Sgr. A*. But what drives the emission that we see across these many wavelengths? Using these data to develop models of the underlying physics, we can seek to unravel the complex interplay of mechanisms that work together to produce the observed radiation exhibited by these extreme environments.

OBJECTIVE: This project aims at bringing the observations across a broad range of frequencies together with our expectations from first principle simulations. In particular, you will be using existing simulation results of the plasma around a black hole and help improving the general relativistic ray tracing approach that creates images at all the observed frequencies from the plasma distribution. At the same time you will be involved in improving the complex comparison between the data and the simulated images.

PREREQUISITES: No prior knowledge of the field is required but experience with programming in Python or another language is strongly preferred. Some knowledge of Julia or C++ may be helpful but is not required.

RESOURCES: This project can be performed using a standard laptop; remote access to one of our compute clusters will be provided as necessary for more demanding processing tasks. A loaned laptop can be provided if necessary.

This project will be focussed on visualizing simulation data from binary neutron-star merger simulations. These simulations include general relativity, gas dynamics, nuclear and neutrino effects, and magnetic fields. You will use a visualization software that we develop in the group and look into finding the best way to visualize the physics happening in these extreme collisions. This will include looking at how heavy elements like gold can be made and how electromagnetic radiation in the form of kilonovae and gamma-ray bursts can be generated.

OBJECTIVE: Visualizing simulation data and looking at generation of very heavy elements and EM radiation.

PREREQUISITES: Knowledge in coding with Python.

RESOURCES: The project can be carried out on local compute resources, but needs a laptop for interface.

Circumbinary disks have long been observed around numerous binaries, but recently it was realised that they also affect their host binaries in more than one way. Here we will use the latest results to study the long term evolution of these binaries, to test of we can explain their enigmatic eccentricities.

OBJECTIVE: In this project you will learn to work with one of our codes, adjust it to your needs, and model the evolution of such systems.

PREREQUISITES: Rudimentary knowledge in coding with Python is beneficial. Some basic experience with Linux is also helpful, but not required.

RESOURCES: The student will be connecting to computer resources in Amsterdam, so a standard computer or laptop is sufficient. Linux or OS operating system is ideal

In high-mass X-ray binaries (HMXBs) a massive OB-type star is orbited by a compact object, a neutron star or a black hole. Accretion of material from the massive-star wind, or via Roche-lobe overflow, produces X-ray emission. HMXBs can be divided in two classes: (i) the OB supergiant systems and (ii) the Be/X-ray binaries. In the latter systems the X-ray emission is often transient, i.e. X-rays are only observed when the compact star passes through the equatorial disk of the Be star. HMXBs are expected to move away from their birthplace after the supernova preceding the formation of the compact star (often an X-ray pulsar) in the system. With the supernova mass is lost from the system leading to a recoil velocity of the order of the orbital velocity before the supernova.
It has been suggested that the kinematic properties of Be/X-ray binaries depend on the detailed supernova mechanism producing the neutron star in the system (Knigge et al. 2011): so-called electron-capture supernovae are produced by the collapse of a (lower-mass) oxygen-neon-magnesium core while the more massive progenitors undergo an iron-core collapse supernova. Thus, it may be that Be/X-ray binaries can be subdivided in two populations: one hosting X-ray pulsars with short spin and orbital periods in a relatively circular orbit (electron-capture supernova), and the other with relatively long and eccentric orbits. The prediction is that these two subpopulations would exhibit an observable difference in kinematical properties.

OBJECTIVE: The goal of this project is to measure the space motion of Be/X-ray binaries using Gaia astrometry and radial-velocity data. We will also investigate whether we can identify the origin of (some of these) Be/X-ray binaries, such that we can reconstruct the evolutionary history of these systems.

PREREQUISITES: Some experience with Python would be helpful.

RESOURCES: The student will use a terminal in the student room and access the Gaia Data Release 3 database through the ESA Gaia archive.

Observations have shown that almost 20% of the massive stars in our Galaxy, that is stars with more than 8 times the mass of our Sun, are spinning so fast around their own axis that they almost break apart. This leads to the formation of a gaseous disk around them, which can be observed through the strong emission lines in their optical spectra that make these stars stand out in observations.
It remains, however, a mystery how these so-called classical Be stars gained this rapid rotation. One of the proposed theories is that they previously interacted with a companion star, which in turn lost most of it’s envelope and is now difficult to spot observationally.

OBJECTIVE: In this project, you will use mostly optical spectroscopy from the Mercator telescope, but also other multi-wavelength datasets such as Gaia, X-ray and/or radio surveys to look at one such classical Be star. You will use these datasets to search for different potential signatures that could indicate the presence of a hidden companion around the star. You will learn to analyze optical spectra and combine your findings with other data sources, and thereby interpret your results in a broad astrophysical context.

PREREQUISITES: No prior knowledge of the field is required but some experience with programming in python would be beneficial.

RESOURCES: The project can be performed using a standard laptop, preferably operating on Linux or OS, although Windows should also be possible (less preferred, but there are alternative options if need be).