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.
Possible Master projects
- 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
- Blown away by a thermonuclear X-ray burst
Neutron stars that are located in X-ray binaries are pulling off gas from their companion star. The stripped material forms a gaseous disk around the neutron star, where it spirals in at increasingly high speed until it finally plunges on to the neutron star. The plasma that accumulates on the surface of a neutron star undergoes thermonuclear reactions, which can cause an extremely energetic explosion and result in a bright flash of X-ray emission. Such “X-ray bursts” are extremely common: tens of thousands of such events have been recorded to date with different X-ray detectors. X-ray bursts typically last for a few minutes, up to a few hours, and on some neutron stars the explosions repeat every few hours.
X-ray bursts can be very bright and powerful. Possibly, X-ray bursts can be so powerful that it blows off material from the accretion disk that surrounds the neutron star. Such a “disk wind” may be observable as narrow absorption features in high-resolution X-ray and UV spectra. The aim of this project is to analyze high-resolution spectral data of neutron stars that show thermonuclear bursts, to search for evidence of such burst-driven disk winds. This will give valuable insight into the physics of the accretion process.
Keywords: Observational, X-rays, UV, high-resolution spectroscopy, neutron stars, accretion, outflows
- The origin of the quiescent X-ray emission of neutron stars
Neutron stars and black holes are often not continuously swallowing gas from their companion star. Many X-ray binaries are transient, implying that they are only actively accreting during months-long outbursts and spend the majority of their time in a quiescent state during which very little matter is being accreted.
X-ray binaries are very dim in quiescence, but 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, its thermal emission can be detected as 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, 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