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PhD research topics

This page lists the available PhD projects to begin in 2021. The deadline for applications has now passed.  Applicants will be informed whether they will be invited for interview by late-December/early January, with interviews to take place 18-19 February 2021.

API staff may be contacted with questions about projects, but please do not email unsolicited application materials to API staff. More information about the recruitment process can be found here


Multi-wavelength observations of X-ray binaries as a probe of binary evolution

Supervisor: Nathalie Degenaar

As endpoints of massive stars and remnants of supernovae, neutron stars and black holes allow us to probe key phases in stellar evolution and death. X-ray binaries provide a valuable anchor point for evolutionary paths that possibly lead to gravitational wave mergers, and can provide valuable constraints on supernovae explosion physics. In this PhD project, the successful candidate will employ observations obtained with various telescopes and satellites (e.g., the Very Large Telescope, the Hubble Space Telescope, XMM-Newton) to study key aspects of known X-ray binaries such as their mass loss through disk winds and the chemical composition of their companion stars. Furthermore, this project will leverage large-scale surveys at X-ray, optical, and radio wavelengths to find many new binaries that harbour a neutron star or a black hole.


Exoplanet atmospheres in the JWST era

Supervisor: Jean-Michel Désert

Exoplanet atmospheres allows us to learn about their composition and their overall physical properties. The main motivation of the proposed research is to answer fundamental questions about exoplanets : What is the nature, formation and evolution of the observed planetary systems? How can exoplanetology explain the origin and characteristics of our Solar System and the Earth?

To address these questions, the successful PhD candidate will develop observing programs, data analysis tools, and atmospheric models in order to study exoplanet atmospheres. This project will be supported by a portfolio of observational programs, centered around JWST and ground-based facilities, which will be used to determine the atmospheric composition, structure, dynamics, and weather patterns of exoplanets. The PhD candidate will use these new types of observations and techniques to map how planetary atmospheres respond to stellar irradiation and test fundamental predictions of atmospheric models. Ultimately, the aim of this project is to leverage exoplanet detections, as well as observational capabilities and theoretical frameworks, to deepen our understanding of (exo)planetary physics. 

We are looking for a motivated candidate with an interest in a PhD project that comprises observational and modeling expertise. The successful candidate will work within an international research collaboration. The PhD candidate will be part of a vibrant group on exoplanets and planet formation at the University of Amsterdam.


Modelling black hole accretion using the Event Horizon Telescope + Multiwavelength Observations

Supervisor: Sera Markoff

Black holes are the most extreme manifestations of general relativity, and despite being fairly common in astrophysics, there is much we do not understand about how they power the accretion systems around them. On the other hand we directly observe their consequences, whether via feedback they provide on galaxy evolution on the largest scales, or the powerful winds and jets they launch. In April 2019 the Event Horizon Telescope (EHT) collaboration unveiled the first image of a black hole, the monster residing in the centre of the M87 galaxy. Interestingly, it was our lack of understanding of the complicated physics of accretion that dominated the error on the mass determination, and similarly limits our ability to constrain general relativity (GR).

The complexity of the data handling and theoretical modelling/interpretation required years of work developing new codes and pipelines, and this process is ongoing as we continue to work on the data from M87 as well as our own Galaxy's central black hole Sgr A*, as well as several other nearby Active Galactic Nuclei with powerful jets. As part of newly formed Dutch Black Hole Consortium, we are looking for a motivated, independent and enthusiastic PhD student who is always curious about the Universe and wants to get involved with EHT-related science. The exact project will be defined together with the student and our collaborators, but generally will involve the extension/development and application to data of of new numerical (computational) models as well as software/pipelines for model fitting and optimisation, and the study of literature on black hole accretion and jet physics. Once allowed, there will be regular travel to collaborate and train with other national/international groups. The candidate will be embedded in a diverse and friendly research group focused on compact object accretion, jet launching and particle acceleration, covering both observational and theoretical aspects. Within the larger Consortium the student will get to know researchers in other fields related to black holes, including mathematicians, theoretical physicists and historians/philosophers of science, and be expected to contribute to societal outreach projects including the design of a museum exhibits on black holes.  


Cosmic explosions in the multimessenger era

Supervisor: Philipp Moesta

Extreme core-collapse supernovae and compact object mergers belong to the most energetic transients in the universe and are the primary sources for multi-messenger gravitational wave astronomy with advanced LIGO. Understanding the fundamental physics and observational signatures of these events is one of the key topics in modern theoretical astrophysics. The possible projects in this field will rely heavily on numerical simulations to reveal the engines driving these transient events and the connection of these engines to their observable signatures. A main focus will be on the modeling of lightcurves and spectra, but heavy-element nucleosynthesis, the connection to stellar evolution via progenitor systems, and more fundamental relativistic astro-/plasma- physics aspects can also be explored.


Gravitational wave cosmology

Supervisor: Samaya Nissanke

The emphasis of the PhD position is on using gravitational signals from coalescing binary objects (neutron stars and/or black holes) as “standard sirens” for cosmological measurements. The successful candidate will work with the groups of Dr. S. Nissanke (Nikhef, GRAPPA and University of Amsterdam) and Prof. Dr. C. Van Den Broeck (Nikhef and Utrecht University). While the successful candidate will be employed by the Institute of Physics and API, University of Amsterdam, you will be fully embedded in the Gravitational Waves group at Nikhef. Nikhef is the national institute for subatomic physics in The Netherlands. At Nikhef, approximately 175 physicists and 75 technical staff members work together in an open and international scientific environment. Together, they perform theoretical and experimental research in the fields of particle and astroparticle physics. The gravitational physics division at Nikhef (led by Prof. F. Linde) has close ties with gravitational wave researchers at universities and institutes across the Netherlands, which apart from instrumentalists includes astronomers, astrophysicists, and theorists, such as Baumann, Bertone, Caudill, Groot, Hinderer, Jonker, Levan, Moesta, and Nelemans. There is also vibrant collaboration with individuals and groups around the world.


Exoplanet atmospheres: the effects of stellar activity

Supervisor: Antonija Oklopčić 

Chemical composition and evolution of exoplanet atmospheres is shaped by the radiation and stellar wind originating from the planet’s host star. High-energy stellar radiation and stellar activity in general can have a profound influence on the planet's atmosphere by driving atmospheric escape and mass loss. Phenomena related to stellar activity can also significantly affect, and sometimes hinder, our ability to reliably characterize exoplanet atmospheres through transmission spectroscopy. The long-term stability of atmospheres of close-in exoplanets critically depends on the incident stellar flux, particularly in the extreme-ultraviolet range. However, this portion of the spectrum of exoplanet host stars cannot be directly observed and has to be derived empirically using observations in other spectral bands and theoretical models. The PhD candidate will work on theoretical modeling and spectroscopic observations of stellar radiation and its effect on exoplanet atmospheres, with the goal of advancing our understanding of planetary formation and evolution. 


Triple evolution towards transients

Supervisor: Silvia Toonen

Stellar mergers give rise to some of the most energetic events known in the universe; ranging from gravitational wave sources to electromagnetic transients (such as supernova type Ia and luminous red novae). Upcoming surveys such as aLIGO/Virgo and LSST will open unprecedented windows to these events, and directly provide information on their properties. However, the progenitors and their formation are often shrouded in mystery. In the past most of our efforts focused on modelling binary evolution, however, in the last few years our work demonstrated that a so far poorly explored part of the physics is very important; interaction of the binary with a third star. Our lack of a theoretical understanding of stellar triples leaves a major void in astronomy, and therefore a major opportunity! The aim of this project is to explore the evolution of triple systems, compute their properties and event rates using a computational approach, and finally set it against the results from gravitational wave and electromagnetic surveys to unravel the mysterious progenitors of stellar mergers.


Dense matter in neutron stars via X-ray Pulse Profile Modelling

Supervisor: Anna Watts

Densities in neutron star cores can reach up to ten times the density of a normal atomic nucleus, and the stabilising effect of gravitational confinement permits long-timescale weak interactions. This generates nucleonic matter that is extremely neutron-rich, and the exciting possibility of stable states of strange matter.  Our uncertainty about the nature of cold ultradense nuclear matter is encoded in the Equation of State (EOS), which can be mapped via the stellar structure equations to quantities like mass M and radius R that determine the exterior space-time.

One very promising technique for measuring the EOS exploits X-ray emitting hotspots that form on the neutron star surface due to the pulsar mechanism, accretion streams, or during thermonuclear explosions in the stellar ocean. As the neutron star rotates, the hotspot gives rise to a pulsation and relativistic effects encode information about the EOS into the pulse profile. Pulse Profile Modelling (PPM), which employs relativistic ray-tracing and Bayesian inference codes to measure M-R and the EOS, is being pioneered by NASA’s NICER telescope on the International Space Station.  We are part of the NICER team, and contributing actively to that mission.  We are also looking ahead to the next generation of large-area X-ray timing telescopes such as eXTP and STROBE-X.  The sources these larger missions will target, accreting neutron stars, pose challenges for PPM such as variability, surface pattern uncertainty, and polarimetric signatures.

We are offering a PhD position working on the PPM technique, with the goal of determining the nature of ultradense nuclear matter.  You will work as part of a dedicated team of researchers, and can expect to work closely with our colleagues in both nuclear physics and gravitational wave astrophysics.