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List of Bachelor Projects for 2021

In their third year bachelor students can enlist in a 15 ECTS research project between February and August. If you are interested in a project and want more details, please contact the project supervisor. For general questions please contact project coordinator Dr. Antonia Rowlinson (B.A.Rowlinson@uva.nl)

Project for Double Bachelors with Mathematics:

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1.  Spherical geometry on the Space Station

Supervisors: Prof. Anna Watts (API) and dr. Raf Bocklandt (KdVI)
Contact:  A.L.Watts@uva.nl, R.R.J.Bocklandt@uva.nl

NASA's NICER telescope, installed on the International Space Station, provides us with superb quality X-ray data from neutron stars. The X-rays come from hot spots formed as particles accelerated in the neutron star's magnetosphere impact the surface at the star's magnetic poles. By modelling this emission, which propagates towards us through the relativistic space-time of the star, we are able to infer the neutron star's mass and radius, and make a surface map of the hot spots. This tells us about both the dense nuclear matter inside the star and its magnetic field configuration.

One ingredient in our models is a prescription for the shape and size of the magnetic polar caps. At present we use parameterized models of likely shapes such as circles, rings, and crescents on the spherical surface of the star. We specify prior ranges for the parameters and must exclude configurations that would be duplicates or where the emitting regions would overlap. This involves spherical geometry, which needs to be expressed in computationally efficient algorithms. At present we assume a maximum of two emitting regions for a fixed set of possible shapes. 

This project will involve defining comprehensive parameter conditions to broaden the range of allowed models. For two emitting regions, our current parameter ranges exclude some feasible configurations, such as very large arcs. We would like to broaden this, and then generalize to three or more emitting regions. The project will include working out the correct geometric conditions, and then coding them up for implementation into our existing relativistic ray-tracing simulation package.

Prof. A.L. (Anna) Watts

Faculty of Science

Anton Pannekoek Institute of Astronomy

Dr. R.R.J. (Raf) Bocklandt

Faculty of Science

KDV

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2.  Revealing the massive star population in the Galaxy with Gaia

Supervisors: Prof. Lex Kaper (API) & Prof. Frank Pijpers (KdVI)
Contact:  l.kaper@uva.nl f.p.pijpers@uva.nl

In the Spring of 2022 the third data release of Gaia is planned. The Gaia satellite was launched in 2014 and is measuring the position of more than a billion stars with unprecedented accuracy. By scanning the sky about a hundred times per year, the parallax (distance) and proper motion of the individual stars is obtained; a small spectrograph onboard the satellite provides information on the radial velocity (for the brighter stars) and the spectral type of the stars. For the first time it is possible to get a full census of the stellar population within about a kpc around the Sun. Because of their short lifetime, massive stars trace the star-formation sites in the Galaxy. With the accurate parallax, the distance to individual massive stars can be obtained, which should in principle allow us to reconstruct the (local) spiral arm structure of the Galaxy. However, several issues need to be addressed, such as interstellar extinction and potential biases (Lutz-Kelker and Malmquist) that affect the distance determination. Furthermore, stars are usually formed in clusters: cluster membership can be established by searching for concentrations in the 6-dimensional space spanned by location and velocity of the stars. A significant fraction of the massive stars is expected to be runaways, i.e. they escaped from the parental cluster due to dynamical ejection or a supernova explosion in a binary system.

The goal of this project is to obtain a census of the massive star population in an area of about 2 kpc centered on the Sun, and to estimate the ratio of the field and cluster population. If the data allow a mapping of the more active starformation sites over time, this project will contribute to an understanding of the starformation process in terms of complex dynamical reaction-diffusion systems.

Prof. dr. L. (Lex) Kaper

Faculty of Science

Anton Pannekoek Institute of Astronomy

Prof. dr. F.P. (Frank) Pijpers

Faculty of Science

KDV

Project for Bachelors Astronomy:

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1.  Interpretation of residual correlation patterns in the context of X-ray emission from neutron stars

Supervisors: dr. Serena Vinciguerra & Prof. Anna Watts
Contact: s.vinciguerra@uva.nl,  A.L.Watts@uva.nl

The NICER mission aims to reveal the composition of neutron stars through the detection of the X-ray pulsed thermal emission generated at the surface of neutron stars. The analysis of NICER data is carried out by the application of pulse profile modelling techniques. The core of these analyses consists in comparing the detected energy and time evolution of the neutron star thermal emission to models in order to derive quantities such as mass and radius of the emitting neutron star. Measurements of masses and radii of neutron stars are crucial for providing constraints on the composition of neutron star cores. Indeed, the equation of state that governs cold high-density matter can be uniquely mapped to a mass-radius relation through relativistic structure equations.

The goodness of the best fitting models is then inferred by a qualitative inspection of the difference between the NICER data and the proposed model(s), the so-called residuals. If the model is good, no correlation structure is expected, and the residuals are dominated by Poisson noise. 

This project will give you the opportunity to dive in into advanced data analysis and statistical techniques, currently used to advance our understanding of neutron stars and cold dense matter. During this project you will study the imprint of neutron star thermal emission in the time-energy plane and how it depends on the different parameters which are involved in the modelling of the signal. Your task consists in designing and implementing an algorithm, which statistically evaluates if correlations are present in the residuals, and, in that case, which model parameters are most likely responsible for such structure. Your algorithm is expected to contribute to the current analysis of the data that NICER is collecting from the Space Station. 

Dr S. (Serena) Vinciguerra

Faculty of Science

Anton Pannekoek Institute of Astronomy

Prof. A.L. (Anna) Watts

Faculty of Science

Anton Pannekoek Institute of Astronomy

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2.  Observational Astronomy with the Anton Pannekoek Observatory

Supervisor: Mr. Rasjied Sloot
Contact: M.R.Sloot@uva.nl  

The student will gather (most of) his or her own data using telescopes and instruments available in our Observatory.

Students can come up with their own research topic. A few suggestions are:

Exoplanet transits:

  • determining orbital parameters of planetary systems
  • Determine stellar properties of pulsating stars
  • Eclipsing binaries: modeling stellar properties
  • Determining the age and distance of open clusters of globular clusters
  • Measure the redshift objects at large distances

Solar topics:

  • Spectroheliography
  • High-resolution spectroscopy of the sun using the APO Heliostat
M.R. (Rasjied) Sloot MSc

Faculty of Science

Anton Pannekoek Institute of Astronomy

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3.  The impact of stellar radiation on evaporating exoplanet atmospheres

Supervisors: Mr. Dion Linssen, dr. Antonija Oklopcic
Contact: : d.c.linssen@uva.nl

Many of the discovered exoplanets are very different from the planets in our own solar system. For example, we commonly find gas giant planets that orbit close to their host star and are therefore very hot. Under these conditions, the intense stellar radiation can cause the atmospheres of these planets to evaporate in a planetary outflow: a process called photo-evaporation. In the literature, different approaches have been taken to model this process, but they usually involve quite a few simplifying assumptions in the way the stellar light interacts with the planetary atmosphere. This project will test the validity of these assumptions, by modeling the photo-evaporative process using a detailed code. By including or excluding certain processes, we can find which ones are the most important and in this way inform other modeling efforts.

D.C. (Dion) Linssen BSc

Faculty of Science

Anton Pannekoek Institute of Astronomy

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4.  Shedding light on a mysterious radio transient source

Supervisors: Ms. Iris de Ruiter & dr. Antonia Rowlinson
Contact: : i.deruiter@uva.nl, b.a.rowlinson@uva.nl 

The low-frequency radio sky is relatively unexplored and harbors many mysterious sources, some of which are transient in nature, such as fast radio bursts (FRBs), flare stars, (magnetic) cataclysmic variables, X-ray binaries, supernovae and gamma-ray bursts (GRBs). This list includes some of the most violent events in the Universe and studying them allows us to learn about physics of extraordinary and extreme environments. The Low Frequency Array (LOFAR) is a cutting-edge radio telescope located in the east of the Netherlands, which can be used to search for astronomical objects that are transient in nature. Stewart et al. (2016) [2] discovered such a transient source, which exhibited an extremely bright radio flare, that lasted a few minutes. This transient was discovered using LOFAR low band antennas (LBA). The astrophysical origin of this event is still unknown, but it is likely a neutron star or flare star. 

In this project you set out to analyze additional measurements of this source to see if we can identify repeating radio emission, which could possibly help to constrain the astrophysical nature of the source. These additional observations are of much better quality than the data used for the original detection, as they were taken with the full frequency bandwidth, instead of just one sub-band as in Stewart et al. (2016). Furthermore, we’ll preform a transient search over the whole patch of sky that was observed, which will yield a transient search at one of the lowest radio frequencies to date. This is a data analysis project, you’ll mainly use Python to analyze results of the transient finding software (TraP [3]) and inspect images and sources.

[1]: van Haarlem et al. 2013 https://www.aanda.org/articles/aa/pdf/2013/08/aa20873-12.pdf
[2]: Stewart et al. 2016  https://academic.oup.com/mnras/article/456/3/2321/1092386
[3]: Swinbank et al. 2016 https://arxiv.org/pdf/1503.01526.pdf

I. (Iris) de Ruiter

Faculty of Science

Anton Pannekoek Institute of Astronomy

Dr. B.A. (Antonia) Rowlinson

Faculty of Science

Anton Pannekoek Institute of Astronomy

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5.  Unsupervised machine learning for (radio) transient detection

Supervisors: Mr. David Ruhe & dr. Antonia Rowlinson
Contact: :d.ruhe@uva.nl, b.a.rowlinson@uva.nl

Transient hunting is among the most promising areas in astronomy. Transient events such as fast radio bursts (FRBs), flare stars, (magnetic) cataclysmic variables, X-ray binaries, supernovae and gamma-ray bursts (GRBs), are some of the most extreme events in the Universe, and studying them allows us to learn about physics of extraordinary and extreme environments. However, to do so, reliable detection of such events in extremely large and noisy datasets is necessary. In recent years, many datasets that allow supervised machine learning algorithms have become available. However, in practice, supervised data-sets are not available. As such, new approaches using unsupervised learning have to be considered.

In this project you will consider a dataset of light-curves that includes labels (i.e., whether a segment contains a transient or not). You will explore literature and existing methods for detecting these transients in an unsupervised setting, i.e., without using the labels. Implementing some of these methods, you will compare their performance and summarize the results.

[1] Webb et al., https://academic.oup.com/mnras/article/498/3/3077/5903285?login=true
[2] Villar et al., https://arxiv.org/abs/2103.12102

D.J.J. (David) Ruhe MSc

Faculty of Science

Informatics Institute

Dr. B.A. (Antonia) Rowlinson

Faculty of Science

Anton Pannekoek Institute of Astronomy

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6.  Search for dispersed radio flares in AARTFAAC-12 data

Supervisors: Mr. David Ruhe & Prof. Ralph Wijers
Contact: d.ruhe@uva.nl, r.a.m.j.wijers@uva.nl

Using efficient software developed by Ruhe and Kuiack, we found some tantalizing dispersed flares in AARTFAAC-6 radio data, which are of yet unknown origin. Such transient events (e.g., fast radio bursts (FRBs), flare stars, (magnetic) cataclysmic variables, X-ray binaries, supernovae, and gamma-ray bursts (GRBs)), are some of the most extreme events in the Universe, and studying them allows us to learn about physics of extraordinary and extreme environments. In this project, we aim to search the much higher-quality AARTFAAC-12 data with an adapted pipeline to investigate these phenomena further, trying to determine whether they are ionospheric or of (extragalactic) astrophysical origin. 

You will familiarize yourself with the software and apply it to AARTFAAC-12 data. Where needed, minor adjustments for better applicability on AARTFAAC-12 data should be made. You will apply the pipeline to AARTFAAC-12 images and investigate the data products. If interesting flares are detected, a follow-up analysis will be performed.

[1] Ruhe et al., https://www.sciencedirect.com/science/article/pii/S2213133721000664
[2] Kuiack et al., https://academic.oup.com/mnras/article-abstract/505/2/2966/6287590?redirectedFrom=fulltext&casa_token=Lx1r1KnnUQQAAAAA:JkDluISMySYgBv4p11va4Ec_RABse7nowtMwFmhGzWbsH2-mpIgBxHQ6G51IdIx0jcMldHRL47tH

D.J.J. (David) Ruhe MSc

Faculty of Science

Informatics Institute

Prof. dr. R.A.M.J. (Ralph) Wijers

Faculty of Science

Anton Pannekoek Institute of Astronomy

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7.  Early radio flashes from GRB reverse shocks and flares

Supervisor: Prof. Ralph Wijers
Contact: r.a.m.j.wijers@uva.nl

It has been suggested that radio flashes due to coherent or highly boosted radiation from the central source or reverse shock could accompany prompt or reverse-shock emission from GRBs and GW sources. Finding them with wide-field rapid-alert telescopes such as LOFAR could greatly help constrain their sources. However, the developing forward shock is also synchrotron self-absorbed and may stop this emission from reaching us. Using the simplest analytical approximations, this project will explore how much of an issue this is. 

skills: student should be theoretically minded, more capable with analytical work than numerical

Prof. dr. R.A.M.J. (Ralph) Wijers

Faculty of Science

Anton Pannekoek Institute of Astronomy

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8.  Using NICER to find the waveform of X-ray oscillations from accreting black holes

Supervisor: dr. Phil Uttley
Contact: p.uttley@uva.nl

The X-ray emission from accreting stellar mass black holes originates from close to the black hole in the accretion disk and a mysterious hot corona, which may form the base of a relativistic jet. The emission often shows nearly-periodic oscillations on time-scales of seconds or less. These oscillations are now thought to correspond to changes in the geometry of the inner emitting regions, possibly a 'wobble' in the corona/jet-base that is caused by general-relativistic frame-dragging in the extreme gravitational field around the spinning black hole. Testing this picture is difficult, because X-ray variations linked to turbulence in the accretion flow are also present and are hard to disentangle from the oscillations. The aim of this project is to combine state-of-the-art Fourier analysis techniques with state-of-the-art data, to reconstruct the shape or 'waveform' of the oscillations and remove other types of variation. You will do this using Python code applied to data from the NICER X-ray telescope on board the International Space Station, which offers a unique view of the disk and coronal X-ray variations from black hole systems.

Dr. P. (Phil) Uttley

Faculty of Science

Anton Pannekoek Institute of Astronomy

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9.  Characterizing the UV source population in the center of the MilkyWay and the Magellanic Clouds 

Supervisors: Prof. Rudy Wijnands & Mr. David Modiano
Contact:  r.a.d.wijnands@uva.nl, d.modiano@uva.nl

The characteristics of the sources visible in the optical sky (wavelengths between 400 and 1000 nm) have well been determined since the dawn of astronomy. Unfortunately, the ultraviolet sky (< 400 nm) is much harder to observe (and therefore to characterize) because radiation with these short wavelengths is strongly or even completely absorbed by the atmosphere of the Earth making ground based observations impossible (or challenging in the 300-400 nm wavelength range). However, several current generations of space and ground based observatories have the ability to perform detailed studies of the UV source populations of specific areas on the sky. In the proposed BSc projects, the goal is to characterize the UV source population in the inner 1 degree of the MilkyWay and of the center of the Small and Large Magellanic Clouds (both nearby dwarf galaxies and satellites of the MilkyWay). I.e., what are the spectral types of the UV emitting sources as well as their evolutionary states (i.e. are they mostly main sequence stars or evolved ones).  The UV sources will initially be detected using the UV/Optical telescope (UVOT) aboard the Swift satellite (for the MilkyWay; in the wavelength range 150-400 nm) and the MeerLICHT telescope in South Africa (for the Magellanic Clouds; wavelength range 350-400 nm). The detected UV sources will then be characterized using data obtained with the Gaia telescope (e.g., distances for the source in the MilkyWay; UV-g band colors; estimates of surface temperatures) and with the multicolor information provided by UVOT and MeerLICHT themselves. If time permits, also longterm UV light curves will be created from the UVOT and MeerLICHT data to search for variability in the sources to further characterize them. 

Additional information: Up to 3 students can work on this project (one for each galaxy). All will work independently on their own data set but with close collaboration between the students. The student(s) will have weekly meetings with the supervisors as well as participate in the weekly group meetings. 

Software packages used: Python on any type of operating system (Windows, Linux, MacOS)

Prof. dr. R.A.D. (Rudy) Wijnands

Faculty of Science

Anton Pannekoek Institute of Astronomy

D. (David) Modiano

Faculty of Science

Anton Pannekoek Institute of Astronomy

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10.  The progenitors of supernova type Ia 

Supervisor: dr. Silvia Toonen
Contact:  S.G.M.Toonen@uva.nl

Supernovae type Ia (SNIa) are on of the most mesmerizing type of transients in astronomy; They can be used to measure distances on cosmological scales, which lead to the discovery of the accelerated expansion of the Universe. Besides this, they are the main production side of iron and iron-group elements. And despite the high rate of SNIa events, the origin of SNIa is still a mystery. Recently, the origin of SNIa has been linked to a peculiar star: hybrid white dwarfs: white dwarfs with a large carbon-oxygen core and a thick layer of helium on top. In this project the student will perform calculations with our stellar and binary code to model the formation of SNIa from hybrid white dwarfs. In the project you will learn about stellar evolution and interactions, and how to model that using an existing code. You'll mainly work with python and the terminal. 

Dr. S.G.M. (Silvia) Toonen

Faculty of Science

Anton Pannekoek Institute of Astronomy

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11. Test particle methods in simulations of astrophysical plasma

Supervisors: Mr. Sebastiaan Selvi & dr. Oliver Porth
Contact:  o.j.g.porth@uva.nl, s.c.selvi@uva.nl

High energy astrophysical phenomena are shaped by the properties of relativistic particles, giving rise to non-thermal emission and cosmic rays.  For a full description of the particle spectrum and dynamics, it is necessary to solve the set of (kinetic) equations which is quite costly.  It has been argued however that much of the particle acceleration process can be understood with much more affordable "test-particle" simulations.  
In this project, you will study how charged test particles embedded in an astrophysical flow can be accelerated into high energy cosmic rays.  We are keenly interested to explore the advantages and drawbacks of this method to build better models for a variety of sources, observed e.g. by the EventHorizonTelescope, the GRAVITY interferometer or the NICER X-ray satellite.  

Dr. O.J.G. (Oliver) Porth

Faculty of Science

Anton Pannekoek Institute of Astronomy

S.C. (Sebastiaan) Selvi

Faculty of Science

Anton Pannekoek Institute of Astronomy

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12.Two populations of faint X-ray transients in the center of the Milky Way?

Supervisors: dr. Nathalie Degenaar & Ms. Stefanie Fijma 
Contact:  N.D.Degenaar@uva.nl  

Ever since 2006, the Swift satellite has been taking ~20-min snapshot X-ray images of the center of our Galaxy nearly every day. The Galactic center is a very rich environment to study compact objects: black holes, neutron stars, and white dwarfs. Apart from our supermassive black hole Sgr A*, the Swift campaign also has about 15 X-ray binaries in its field-of-view. 

X-ray binaries are binary star systems that contain a black hole or a neutron star that gravitationally attracts, or 'accretes', the outer layers of its companion star. Typically, the black hole or neutron star is feeding off its companion for a few days, weeks or months. During these episodes, which we call accretion outbursts, it produces bright X-ray radiation and will show up on Swift’s X-ray images. After its meal, however, an X-ray binary goes into hibernation and becomes too faint to be detected by Swift’s X-ray camera. White dwarfs in binaries that are accreting are called cataclysmic variables and these can also exhibit transient outbursts that produce X-rays, albeit fainter than their black hole and neutron star cousins.

Between 2006 and 2021, Swift has seen about two dozen different accretion outbursts of about 10 X-ray transients. Strikingly, the duration and brightness of these outbursts seem to fall into two different groups (with longer outbursts being fainter). In this BSc project, you will study the energy distribution of the emitted X-ray light, i.e., the X-ray spectra, of all these accretion outbursts. You will work with X-ray observations obtained with the Swift satellite and software from NASA to reduce these data. The aim is to investigate if the X-ray spectra show a dichotomy too. If so, this could indicate that there are two different populations of X-ray transients in the center of our Milky Way, possibly neutron stars or black holes on the one hand, and white dwarfs on the other. 

Dr N.D. (Nathalie) Degenaar

Faculty of Science

Anton Pannekoek Institute of Astronomy

S.C. (Stefanie) Fijma MSc

Faculty of Science

Anton Pannekoek Institute of Astronomy

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13. Using neural networks to determine the properties of short gamma-ray burst afterglow light curves.

Supervisors: Mr. Oliver Boersma & dr. Joeri van Leeuwen
Contact: o.m.boersma@gmail.com, leeuwen@astron.nl

GW170817 was the first gravitational-wave source to also be detected across the electromagnetic spectrum. One of the other emission types that was detected was the afterglow of the short gamma-ray burst interacting with the interstellar medium. Various computer models have been developed to analyze the emission of short gamma-ray bursts but this can take a lot of time. In this project, we would like to explore how neural network-type models could be used to speed up the analysis. We will use recent short gamma-ray burst models to train a neural network for this task. Topics to explore are: what kind of neural network is suited for this task? How can you best train such a neural network? Are there real benefits of using neural networks over more traditional methods?

O.M. (Oliver) Boersma

Faculty of Science

Anton Pannekoek Institute of Astronomy

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14. Applying astrophysics of tenuous plasmas applied to laboratory settings used for chip lithography

Supervisor: dr. Jacco Vink
Contact: j.vink@uva.nl

Supernova remnants consists of a shell of hot plasma, 10^6 - 10^8 Kelvin.  These X-ray emitting plasmas have interesting physical processes:  the density is so low (1 atom cm^{-3}) and the time scale so short (few hundred to few thousands years) that the number of  atom-electrons collisions is very limited. As a result the gas may not be in ionisation equilibrium (low ionisation given despite the high temperature) and the gas may not be in thermal equilibrium: electrons and ions have different temperatures, or perhaps even have a non-thermal distribution. The parameter  that governs  these processes is n_e t (electron density times age). 

For this project we are going to explore the same physics, but in the context of a laboratorium setting, which is used to explore the chip lithography physics by for example ASML. In order to create EUV light lasers vaporise tin droplets creating a tin plasma, which shines in EUV. 

In this case the plasma is much denser (10^19 atoms cm^-3) but the time scales much shorter. So a question is whether the tin plasma is out of equilibrium as well. For this project we are going to use the tools of X-ray spectroscopy of supernova remnants and apply them to tin plasma’s.

We do this in collaboration with Oscar Versolato and John Sheil  from the ARCNL lab (a UvA joint venture with ASML). The work has some some data analysis and theoretical aspects. 

All projects can be found here with hyperlinks and images:
https://staff.fnwi.uva.nl/j.vink/bachelor_projects.html

Dr. J. (Jacco) Vink

Faculty of Science

Anton Pannekoek Institute of Astronomy

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15. The X-ray signatures of dust destruction in supernova remnants

Supervisor: dr. Jacco Vink
Contact: j.vink@uva.nl

The supernova remnant Cas A contains a lot of silicate dust grains. According to some most silicon can even be locked up in grains. However, in the hot plasma this dust is being destroyed due to collisions with ions and electrons. This should leave an X-ray spectral signature that we should be able to detect with the upcoming X-ray satellite mission XRISM. The reason is that the destruction leads to continuous injection of weakly ionised silicon atoms, which radiate a different spectral energy than the silicon injected from the start. 

In this project we are going to model this effect. We estimate the silicon injection rates, and calculate the distribution of n_e t (see previous described project) for silicon, compared to elements not in grains. And then we simulate what the X-ray spectrum at high spectral resolution (for XRISM) will look like.

All projects can be found here with hyperlinks and images:https://staff.fnwi.uva.nl/j.vink/bachelor_projects.html

Dr. J. (Jacco) Vink

Faculty of Science

Anton Pannekoek Institute of Astronomy

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16. Principal component analysis of X-ray data from supernova remnants

Supervisor: dr. Jacco Vink
Contact: j.vink@uva.nl

Principal component analysis (PCA) is a statistical tool to describe the variations  in a data set. For this project you use PCA on X-ray images made with very specific energies, in order to characterise the spectral variation.  We then use the PCA to identify important spectral components and will extract spectra from regions in the supernova remnant where a certain PC is very prominent.

The supernova remnants considered are Kepler’s SNR, Cas A, Tycho’s SNR, MSH 11-54. This project will be co-supervised by postdoc Amael Ellien.

All projects can be found here with hyperlinks and images:https://staff.fnwi.uva.nl/j.vink/bachelor_projects.html

Dr. J. (Jacco) Vink

Faculty of Science

Anton Pannekoek Institute of Astronomy

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17. Hydrogen line formation in disks around massive young stellar objects

Supervisors: Prof. Alex de Koter & Mr. Frank Backs
Contact: A.deKoter@uva.nl, f.p.a.backs@uva.nl

The evolution of high-mass protostars and their evolutionary descendants the massive Young Stellar Objects (mYSOs) is very fast (e.g., Hosokawa & Omukau 2009) and, until very late in the build-up process, hidden from view as it unfolds deep down in dusty natal clouds. Though for these reasons much is still unclear about the mechanism that leads to the assembly of a massive star, most theories agree on the need for a dense and massive accretion disk (e.g., Tan et al. 2014; Beltran & de Wit 2016).

The main diagnostic of the properties and structure of the inner dust-free regions of the disks of mYSOs are hydrogen recombination lines. The line formation mechanism in this phase is however complex, as the ionization mechanism transitions from being chemically dominated for relatively early mYSO evolution (when the stars are still relatively cool) to photo-ionization dominated in relatively late phases, when the star further contracts and heats up.  It is however presently unknown at what central star (and disk) properties this transition occurs.

Using the radiation thermo-chemical code ProDiMo (Woitke et al. 2009; Kamp et al. 2010, 2017) we will investigate this problem constructing a series of models where the mYSO contracts and heats towards the zero age main sequence. We will identify the hydrogen ionizing mechanism at every point in the inner disk and establish the region from where hydrogen line emission originates. This will allow us to map out the region in pre-main sequence evolution where photo-ionization is the main mechanism of H line formation.

Prof. dr. A. (Alex) de Koter

Faculty of Science

Anton Pannekoek Institute of Astronomy

F.P.A. (Frank) Backs MSc

Faculty of Science

Anton Pannekoek Institute of Astronomy

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18. Searching for Fast Radio Bursts with the LOTAAS Survey 

Supervisors: Prof. Jason Hessels & dr. Pragya Chawla
Contact: j.w.t.hessels@uva.nl, p.chawla@uva.nl

Fast radio bursts (FRBs) are among the most puzzling phenomena in the field of astrophysics today. These micro-to-millisecond duration bursts are detectable at radio frequencies, being produced by sources of unknown origin. The detection of hundreds of FRBs at frequencies above 400 MHz motivates searches at lower frequencies, where only a handful of detections have been made. Observations at low frequencies are important to determine the properties of the local environment of FRBs and constrain the mechanisms which generate these bursts.

This project involves searching for FRBs with the Low Frequency Array (LOFAR) telescope in observations conducted as part of the LOFAR tied-array all-sky survey (LOTAAS). We intend to search for low-frequency emission in LOTAAS observations at the locations of FRB sources which are known to emit at higher frequencies. The student will develop scripts in Python and Bash to access and search the LOTAAS data. During the course of the project, the student will learn standard techniques used in FRB searches and also help adapt the existing tools to efficiently search for low-frequency FRB emission.

Prof. J.W.T. (Jason) Hessels

Faculty of Science

Anton Pannekoek Institute of Astronomy

P. (Pragya) Chawla

Faculty of Science

Anton Pannekoek Institute of Astronomy

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19. Visualization and analysis of binary neutron-star merger simulations 

Supervisor: dr. Philipp Moestra
Contact: p.moesta@uva.nl

This project will involve developing and running python-based analysis and 3D visualization tools to analyze output data from a set of binary neutron-star merger simulations. The simulation data consists of large datasets with full 3D fields for the state variables of the simulations (density, temperature, magnetic fields, etc). The student will work on calculating additional quantities like the total mass ejected in outflows from these simulations, perform 3D ray-casting visualizations, and learn how to postprocess the simulation data with nuclear reaction networks to analysis the elements formed in these events. These outputs will then be used to interface with observational data for gravitational waves, EM counterparts, and nucleosynthesis from these events.

Dr. P. (Philipp) Moesta

Faculty of Science

Anton Pannekoek Institute of Astronomy

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20. GPU-accelerated magnetohydrodynamics

Supervisor: dr. Philipp Moestra
Contact: p.moesta@uva.nl

This project will involve porting and profiling individual computation kernels for our GPU-GRMHD code GRHydro-X. GRHydro-X is a dynamical-spacetime general-relativistic magnetohydrodynamics code for simulation binary neutron-star mergers and supernova explosions. The project is flexible and can be focused on performance testing and optimization of existing modules of the code for specific GPU architectures or developing new physics modules (e.g. neutrinos, equation of state, magnetic fields). The former will give the student experience working with state-of-the-art GPU systems and gain insights into modern GPU programming while the latter also involves algorithm development for computational physics in astrophysical magnetohydrodynamic simulations.

Dr. P. (Philipp) Moesta

Faculty of Science

Anton Pannekoek Institute of Astronomy

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21. Using transiting exoplanet atmospheres to understand giant planet formation

Supervisor: dr. Jean-Michel Desert
Contact: J.M.L.B.Desert@uva.nl

TThis project focuses on studying atmospheres of ultra hot-Jupiters (T> 2000K) for which both refractory and volatile materials are in gas phases. Refractory elements, as traced by Fe, Mg and Si can be a measured in the NUV while the volatiles are measured through their molecular signatures (H2O, CO, CO2 CH4, NH3), which are present in the near- and mid-IR. By combining both the refractories and volatiles, it is possible to learn about how gas giants planets form. However, which specific species must be measured to constrain planet formation models? Is it that all of them are mandatory? or a subset of them would be enough? The proposed project will address these questions by using both observations and simulated data, and atmospheric models. 

Dr. J.M.L.B. (Jean-Michel) Desert

Faculty of Science

Anton Pannekoek Institute of Astronomy