Are you fascinated by black holes and neutron stars? Do you want to learn how they swallow gas from their surroundings and spit it back into space? Do you want to find our how this can be achieved using astronomical observations obtained at different wavelengths? If you answer yes to these questions, a masterproject in my group might be something for you!
Within the overarching theme of “observational studies of accreting neutron stars and black holes” there is a wealth of possibilities for exciting projects using different analysis techniques. Think of high-resolution X-ray spectroscopy to study wind outflows, radio observations to study jet outflows, X-ray reflection studies to zoom in on the hot gas circling closest to black holes and neutron stars, and linking the X-rays to UV, optical or infrared emission to understand how the gas gets to the neutron star or black hole. To get a general idea of the research done within my group, visit my research page.
Below are some ideas for projects that I would love to dive into with a Master student. However, we can also tailor a project to your specific interests. Just stop by for a chat or drop me an e-mail if you’re interested in exploring possibilities.
Here are my slides of the MSc project presentations of April 2022 (~50 MB).
Possible Master projects
- The origin of the quiescent X-ray emission of neutron stars
Neutron stars and black holes are the gravitationally-collapsed remains of once massive stars that ended their life in a supernova explosion. In X-ray binaries, these stellar corpses accrete gas from a companion star, which makes them shine bright at X-rays and other wavelengths. However, neutron stars and black holes often only actively accrete during outbursts that last a few weeks to months. During intervening quiescent episodes little or no matter is being accreted, causing X-ray binaries to dim by orders of magnitude.
Whereas X-ray binaries are very dim in quiescence, their X-ray emission is often still detectable with sensitive X-ray telescopes like Chandra and XMM-Newton. For black holes, it is generally accepted that their quiescent X-ray emission is originating from a residual accretion flow. For neutron stars, on the other hand, it is not fully established what causes the quiescent X-ray emission. If the neutron star is hot, it may emit detectable thermal (black-body like) X-ray emission. If accretion is absent, this surface emission can be used to measure the radius of the neutron star and even to obtain information on the interior properties of neutron stars. However, quiescent neutron stars often display a second X-ray emission component that can be described by a power-law model and may either be generated in a residual accretion flow, or due to processes that involve the magnetosphere of the neutron star.
In this project, you will analyze a large sample of X-ray observations of quiescent neutron star X-ray binaries obtained with the Chandra and XMM-Newton satellites. The aim is to perform a systematic analysis of the X-ray spectra to determine if the power-law emission component has the same characteristic in every source or if there are clear differences between sources. This will give important insight into the origin of this emission component and will have implications for using quiescent X-ray spectra to determine the fundamental properties of neutron stars.
Keywords: Observational, X-ray, neutron stars, accretion
- Understanding accretion onto neutron stars with X-ray and infrared observations
Accretion is a very common process in the universe wherein an object attracts surrounding material through its gravity. For instance, in binary systems a neutron star can pull gas from a companion star and accrete this. Such systems are very interesting: we can study the stream of material as it accretes, test general relativity as the gas gets close to the neutron star, and probe the poorly understood interior of the neutron star when the gas hits the surface. This project will focus on understanding the accretion process itself, by comparing the radiation it emits in X-rays with the infrared emission coming from the entire binary system.
The project will be an observational one, meaning that you will work hands-on with astronomical data. You will analyse near-infrared images obtained for many different neutron stars with the 6.5-m Magellan telescope located in Chile, and X-ray spectra obtained for these neutron stars with different telescopes. By combining the near-infrared and X-ray results, you will investigate what the dominant emission processes are, and whether this changes depending on how fast the neutron star is accreting. You also compare your results for this large sample of neutron stars with the X-ray and near-infrared properties of accreting black holes, to see what the differences and similarities are.
Keywords: Observational, X-ray+near-infrared, imaging, spectroscopy, neutron stars, black holes, accretion
Related research blog: Changing emission mechanisms
- Developing a new tool to detect for weak disk wind features in X-ray binaries
Neutron stars and black holes are notorious for attracting and swallowing material from their surroundings. However, these stellar cannibals can also spit large amounts of matter and energy back into space via collimated jets or dense accretion disk winds. The emission from jets is directly detectable (most prominently in the radio band), but the disk winds typically reveal themselves by absorbing light from the accretion disk.
The presence of a disk wind causes narrow absorption features in (high-resolution) spectra taken at different wavelengths. Those features will show a blue-shift at a velocity corresponding to the speed of the wind, which is typically a few to a few tens of percent of the speed of light. However, such features may be very weak for various reasons, making them very difficult to find by eye.
In this project you develop an analytical tool to efficiently search for such weak absorption lines in X-ray spectral data obtained with the XMM-Newton and Chandra telescopes. You will then apply your own tool to a large number of data sets to perform the first-ever systematic search for such features in the X-ray spectra of a few tens of X-ray binaries. This study will serve as an important benchmark for strategizing new observations and searching for weak wind features in other data sets. This is a challenging project that requires good programming skills and your initiative on developing an efficient search technique.
Keywords: Observational, coding, X-rays, spectroscopy, neutron stars, accretion
Related research blog: Blown away by an accretion disk wind
- Mapping the UV properties of X-ray binaries
Neutron stars and black holes are extreme objects that are involved in the most explosive and energetic phenomena observed in the universe. When located in binary star systems, black holes and neutron stars can pull off and swallow gas from their companion star. This process, called accretion, converts enormous amounts of gravitational energy into electromagnetic radiation. These so-called X-ray binaries can therefore be observed at radio, infrared, optical, ultra-violet (UV), X-ray, and sometimes even gamma-ray, wavelengths.
Whereas X-ray binaries have been known and extensively studied for over 5 decades, little is known about their UV properties. However, in recent years several X-ray binaries have been observed at UV wavelengths with the Hubble Space Telescope and the Swift satellite. This observational project will focus on characterizing the UV properties of X-ray binaries, linking it to their X-ray properties, using astronomical data. You will work with satellite data obtained with the following observatories: Hubble Space Telescope, Swift, Chandra, XMM-Newton.
Keywords: Observational, UV+X-rays, imaging, spectroscopy, neutron stars, black holes, accretion
Related research blog: Changing emission mechanisms