Projects

The research projects offered in ASPIRE cover a wide range of topics. You can choose up to three projects when you apply via the form (in descending order of interest). You can click on the supervisors name for contact information.

SgrA

Unleashing Jets from Black holes
Dr. Atul Chhotray (a.chhotray@uva.nl)

Black holes are the simplest and the most compact objects that exist in the universe. Their ability to trap and prevent both matter and radiation from escaping their gravitational pull is unparalleled. However, observations of black holes show a strikingly different picture. Besides accreting and consuming matter, focused streams of matter called ‘jets’ are seen flowing outwards from the vicinity of black holes. Many of these jets flow at speeds comparable to the speed of light and are observed to emit across the entire electromagnetic spectrum – from radio waves all the way to gamma rays, indicating the presence of energetic particles. The goal of this project is to use the laws of physics to understand and explore the extreme conditions leading black holes to propel and energize jets. The project involves learning magnetohydrodynamics (MHD), the theory of how magnetic fields influence the fluid flow. To study and understand the vital role magnetic fields play in launching jets in black hole environments - the student will learn how to combine General Relativity (GR) and MHD – leading to GRMHD equations that describe matter in the vicinity of black holes. This project involves developing analytical and computational skills along with collaboration with peers and supervisors. Skills learnt during this project will prime the student for a future career in physics / astrophysics and in many other areas.

OBJECTIVE: The student will develop and use state of the art semi-analytical methods to solve this complex system of GRMHD equations. The obtained solutions hold the key to understand the conditions that enable black holes to launch, propel, and energize matter to relativistic energies!

PREREQUISITES: Basic knowledge of General Relativity (coursework would suffice) is required. Some experience with MHD and coding experience (in C++, Python) would be preferred.

RESOURCES: If necessary, login access to one of our group computers

Massive star explosion

Modelling the evolution of a magnetic O-type star
Dr. Zsolt Keszthelyi (z.keszthelyi@uva.nl)

Surface magnetic fields are routinely detected in stars all across the Hertzsprung Russell diagram, from early to late evolutionary stages. In low-mass stars, the incidence rate of magnetism is 100%, and it is understood that these fields are generated by a dynamo mechanism powered by the convective envelope. In intermediate and high-mass stars, the incidence rate of magnetism is only 7%, and likely it is not a result of an active dynamo mechanism as massive stars possess radiative envelopes. While the origin of such fossil magnetic fields in massive stars is still unknown (part might be the result of stellar mergers), it has become clear that their presence drastically changes the physical properties of stars, particularly their mass loss and surface rotation. Consequently, the evolution of massive stars is significantly affected by fossil magnetic fields. There are, however, only a handful of known magnetic O-type stars, 11 as of now.

OBJECTIVE: The key goal of the project is to find how well current state-of-the-art stellar evolution models can be reconciled with a known magnetic O-type star, whether discrepancies can be identified, and if so, how these discrepancies may be resolved. The project will focus on one specific star. The project should establish a clear picture of the uncertainties/limitations in reproducing the evolutionary state of this star and detail which physical assumptions are critical. The candidate will have to collect observational data reported in the literature and compare them to new model calculations, with the final goal to be able to draw relevant conclusions from the comparison.

PREREQUISITES: Some knowledge of python (or similar programming tool) is required

RESOURCES: Linux/OS op. system is ideal; however, there will be alternative options for Windows users. Good connection is helpful but not vital for carrying out the project.


Protoplanetary disk

Imaging the cradles of planet formation
Dr. Christian Ginski (c.ginski@uva.nl)

Extended disks of gas and dust around young stars are the birthplaces of planets. To understand planet formation, we must therefore study the properties and evolution of these environments. In the past six years new instruments became available to observe disks around stars in unprecedented detail. Sub-structures like rings and spiral arms are found in most observed disks. Are those smoking guns indicating the presence of embedded forming planets? In this project the student will work with recently acquired near-infrared imaging observations of circumstellar disks. These observations were conducted with the world leading ground-based observatory, the ESO Very Large Telescope in Chile.

OBJECTIVE: The student will learn how these observations are conducted and how data needs to be post-processed to make the faint light received from the disks visible. Depending on the preferences of the student the project can either focus on the analysis of the disk structures, e.g., determining the vertical height of the disk, dust properties, fitting of spirals/rings, or on advanced post-processing to isolate possible light from embedded planets.

PREREQUISITES: Some basic programming knowledge in Python is required.

RESOURCES: Python installation on a standard PC or laptop. No heavy computational equipment is required.

Gravitational waves

Measuring cosmic expansion history with gravitational wave sources
Dr. Suvodip Mukherjee (s.mukherjee@uva.nl)

Multiple observations have indicated that about 95% of the Universe constituents of dark matter and dark energy. Both these quantities cannot be explained by the known laws of physics and particles discovered until today. As a result, independent measurements that are capable of bringing new insight to understand their properties are essential. Gravitational waves (GW) bring a new avenue to explore the constituents of the Universe by measuring the expansion history of the Universe with its redshift. Mapping the expansion history of the Universe makes it possible to estimate the present expansion rate of the Universe is known as the Hubble constant, the matter density in the universe, dark energy equation of state, and its redshift evolution.

OBJECTIVE: The project will involve the study of the constituents of the Universe using the GW signals detectable from the current generation GW detectors such as LIGO, Virgo, and KAGRA, and in the future from the upcoming space-based detector LISA. The project will involve the calculation of the impact of cosmological expansion on gravitational wave strain and estimating the capability of the gravitational wave detectors to do precision cosmology. The project will explore the requirements of accurate source modeling of the GW signal and its impact on the estimation of cosmological parameters. The project will last for a period of eight/ten weeks starting from the first week of June 2021.

PREREQUISITES: The project will involve both analytical and numerical calculations. So, experience in coding in either Python or Fortran, or C will be useful. The project will be accomplished with a project report and possibly a publication in an international journal. The project report and the paper will be prepared in Latex, and the candidates are expected to have preliminary experience in using Latex.

RESOURCES: The project will involve computation which is expected to be carried out on a laptop or desktop. Due to the remote format of the project, it is essential to have stable internet connections. Possible adjustments will be made during the project tenure to overcome any interruption due to the poor internet connection of the supervisor and/or the student. The project will be carried out remotely with online meetings with the supervisor using the Zoom application.


Pulsar

Exploring electromagnetic interaction of highly magnetised binary systems
Alex Cooper (a.j.cooper@uva.nl)

When conducting objects move through electromagnetic fields, these fields are disrupted, sometimes leading to the acceleration of particles. In this project, we look at what happens when conducting objects interact with the strongest magnetic fields we know of in the universe; highly magnetised neutron stars called magnetars. Conducting objects such as asteroids or other compact objects can be gravitationally attracted to magnetars. When the objects are close to collision, the motion of these objects through the strong magnetic field lines can result in observable astronomical signals. The aim of this project is to model the dynamical interaction of magnetars with different types of conductors, understand how the electromagnetic fields change and how particles can be accelerated. In the most interesting cases, these extreme fields result in exotic quantum phenomena which may be observable.

OBJECTIVE: The student will work on dynamical models of neutron stars interacting with different types of conductors using various initial conditions. We will explain in the electromagnetic interaction and the induced electric field, and make predictions of observable cosmological emission. The student will gain experience of theoretical research projects, and have the opportunity to advance programming skills.

PREREQUISITES: Some basic knowledge of Python is required, and experience using Latex would be preferred

RESOURCES: A fairly normal computer/laptop should suffice, with a working Python installation

Exoplanet atmosphere

Studying upper atmospheres of strongly irradiated exoplanets
Dr. Lorenzo Pino and Prof. Jean-Michel Desert (lorenzo.pino@inaf.it)

As of today we know thousands of exoplanets - planets around stars different from the Sun. Among the most studied are very irradiated planets: rocky words and gaseous giants that orbit very close to their parent stars (in hours or days!), and thus have temperatures exceeding thousands of Kelvin. Their extended atmospheres are a unique window into planetology, in a context that is not accessible in our Solar System. Yet, we still know little about them: are they evaporating away due to the extreme irradiation? What do they tell us about the chemical composition of their host planets?

OBJECTIVE: During this project, you will set up a code (in Python) to simulate the upper atmospheres of strongly irradiated planets (so called exospheres). You will include simple prescriptions to account for the effects of stellar radiation and atmospheric evaporation (Jeans escape and hydrodynamical outflows), building a flexible tool that can be applied to planets from Earth-sized to Jupiter-sized planets. This project will introduce the student to the field of upper atmospheres. Albeit simplified, the models developed can be used to make predictions about the detectability of different chemical species and the properties of atmospheres with current and upcoming high-resolution observations from space and from the ground. The expertise gained during this program will place the student in a good position to continue working in the field of exoplanets.

PREREQUISITES: No previous knowledge of the field is required. Knowledge in coding with Python is preferred but not mandatory.

RESOURCES: This project does not rely on heavy computational resources. It can be carried out on a regular commercial computer. It relies on coding with free software.


Transiting Exoplanet

Growing the planets by pebble accretion
Rico Visser (r.g.visser@uva.nl)

The stages of planet formation encompass a factor 10^40 mass increase from the smallest dust grains to the gas giants such as Jupiter and Saturn. Throughout these stages many physical processes play a role. Even today, coming up with a consistent theory that matches observational data from young protoplanetary disks remains challenging. For example, we encounter growth barriers already in the early stages of planetary growth. Classical planet formation scenarios such as core accretion have difficulty growing a planet within the lifetime of the gaseous protoplanetary disk. One promising new theory to overcome planetary growth barriers is Pebble Accretion. In Pebble Accretion, a small planetoid/asteroid (read body) is sweeping up small ‘pebbles’ in the young gaseous protoplanetary disk. It turns out that the gas damping produces large collision cross- sections for these small bodies since the gas slows down the pebbles in an encounter. The conspiracy between the small body’s gravity and the disk gas can lead to fast growth of the small body well within the disk lifetime.

OBJECTIVE: In this project you will build a basic model of pebble accretion. You will set up an N-body problem with a star, gas drag, small pebbles and a planetesimal in orbit around the star. As the pebbles are swept up by the planetesimal they transfer their spin angular momentum on impact. The goal is to investigate how much spin a planetesimal will accumulate from these pebbles when it is in eccentric and/or inclined orbit around the star. Can we explain current spin properties of (exo)solar system objects with the outcomes?

PREREQUISITES: Access is needed to a computer, Linux Ubuntu and Python. A stable internet connection is essential for clear communication during contact moments.

RESOURCES: The project will be done in REBOUND, an N-body solver. No specific knowledge of the field is required. Experience with programming in Python and writing up documents in Latex is useful.

Radio Galaxy

Variability of radio emission from isolated and cluster galaxies
Uddipta Bhardwaj (u.bhardwaj@uva.nl)

Studies involving radio galaxies tackle few of the outstanding research questions in Astrophysics. Individual galaxies are strong sources of a radio emission; however, depending on the clustering properties of radio-galaxy, the emissions display certain peculiar characteristics. The differences in radio emission from cluster galaxies and field ('isolated') galaxies are usually attributed to the interaction of the emission with the ICM (IntraCluster Medium) or to the proximity of the galaxies to the cluster core (eg. cD galaxies). Radio emission from galaxies are in the form of a compact radio source associated with the AGN (Active Galactic Nuclei) and extended regions of radio emission (radio lobes) diametrically opposite to and quite distant from the compact radio source. In galaxy clusters, the interaction of the gas outflow that forms the radio lobes with the ICM are thought to be responsible for the observed departures from usual radio lobe alignments. Studies of variations in properties of radio galaxies with respect to clustering amplitude and redshift as well variations amongst cluster galaxies depending on the mass, redshift as well as photometry of the cluster can shed some light into the peculiarity of radio galaxies belonging to a cluster as opposed to isolated radio galaxies.

OBJECTIVE: The aim of this project is to obtain a clear distinction between properties of radio emission from galaxies depending on their clustering amplitude and to search for variations amongst radio galaxies within a cluster. A secondary objective is also to look for physical and morphological properties of a galaxy cluster that the variability of radio galaxies may be attributed to.

PREREQUISITES: Basic knowledge of astrophysics. Basic Python experience or a general comfortability with programming.

RESOURCES: A reliable internet connection is preferred.Python installation on a normal PC.