In their third year bachelor students can enlist in a 15 ECTS research project between February and August. If you are interested or if you want to know more, please contact the project supervisor. For general questions please contact project coordinator Dr. Anna Watts.
1. Observational projects at the Anton Pannekoek Observatory (multiple projects)
Multiple projects are available, including:
1) Exoplanets/eclipsing binaries: combining photometry and spectroscopy to determine orbital parameters (night time observations) .
2) Constructing narrowband images of the sun using a spectroheliograph (daytime observations)
3) Studying the instrumental properties of the APO observatory to improve future observations (e.g. effects of stacking vs. long-time exposures, limiting magnitudes, use of filters, noise reduction, processing techniques, etc.)
2. Simulation of exoplanet atmospheres with the James Webb Space Telescope
The James Webb Space Telescope will be launched in 2021. It is thus timely to prepare the next set of observations of exoplanets with this new capability. The goal of this project is to use exoplanet atmospheric models to create template of atmospheres, then ingest these templates in the JWST simulator in order to produce realistic data. The student will use a model of exoplanet atmospheres, take these synthetic data and apply atmospheric retrieval models to retrieve the atmospheric properties, including the temperature structure and elemental abundances, of these modeled atmospheres. Ultimately, this project will teach us on the best observing strategy to adopt with JWST for each templates and draw common properties and strategies for each class of exoplanets.
3. The effect of host star spectral type on the detectability of exoplanet atmospheres at high spectral resolution
High-resolution spectroscopy is a powerful tool for characterizing exoplanet atmospheres, and may be our only way forward in the coming decades to find biosignatures on nearby rocky worlds. The technique uses the large Doppler shift of the planet during its orbit to disentangle its spectrum from its bright host star and our own planet’s atmospheric signatures. However, the star is often 10,000-1 million times brighter than the planet spectrum, and thus can have strong influence on how easily we can extract the planet spectrum. In the project, you will simulate datasets of high-resolution spectroscopy based on real observations, and inject your own planets to investigate which stars are the easiest to disentangle the planet spectrum from. You’ll use these results to determine which of the stars in our local neighbourhood are our best targets for studying planets in the habitable zone, and are thus prime targets for the Extremely Large Telescope and its Dutch-lead high resolution spectrograph: METIS.
4. Gaia observations of massive star-forming regions
Stars are not born in isolation. When star formation sets is, the parental molecular cloud produces many stars of different mass; in the case of massive stars often in binaries or multiple systems. The outcome of the star-forming process, as represented by the so-called initial-mass function (IMF), is an essential ingredient for stellar-population studies, and may even be a 'universal' property. It contains important information on the physics of the star-formation process, i.e. how is gas converted into stars, and is key to our understanding of the evolution of stars and galaxies as a whole. With Gaia data it becomes possible to identify the stars that are members of the group, and in this way obtain a clear view on the IMF. The aim is to focus on a number of young massive star-forming regions; though obscured, they provide the opportunity to study the upper part of the (zero-age) main sequence.
5. The cosmic-ray composition up to 1016 eV and the origin of cosmic rays
Cosmic rays are the particles that continuously bombard Earth, where they cause background radiation and higher up form a radiation hazzard for astronauts and pilots. At low energies (<10^14 eV) these particles are detected with instruments on balloons or by satellites whereas at hgher energies the cosmic rays cause extensive airshowers (a cascade of secondary particles) from which the properties of the primary cosmic rays are reconstructed.
The standard idea is that particles up to 1017 eV are originating from sources in the Milky Way, with supernova remnants being the dominant sources. Around 3x1015 eV the cosmic-ray spectrum has a spectral break (“the knee”) and the standard idea is that the sources in the Milky Way routinely accelerate protons to the knee, with more massive particles (helium to iron) making up most of the particles beyond the “knee”. There is, however, one problem: observations of supernova remnants show that they can accelerate up to 1014 eV, but are unlikely to accelerate up to 1015 eV.
One possible solution to the problem of maximum acceleration of cosmic rays, is that protons do not at all accelerate up to 1015 eV, but up to 1014 eV. The issue is that the cosmic-ray energy distribution can be well measured, but the composition is very difficult, especially above 1014 eV. However, the last ten years there has been a lot of progress in measuring composition of cosmic rays above 1013 eV to 1017 eV. So the question is: are these new measurements consistent with a maximum proton energy up to 1014 eV, or is a maximum energy up to 3x1015 eV still required? In other words: is the cosmic-ray knee a proton feature or does it come from other elements like He, and/or CNO elements?
The student will survey the literature to compile the best cosmic-ray data between 1012-1017 eV, in particular concerning cosmic-ray composition. Important experiments are: AMS, Pamela and KASCADE, as well as many balloon experiments. The compiled data will then be fitted with models for the cosmic-ray output from various sources with various cut-off energies depending on the cosmic-ray elements.
6. Can we derive the supernova spatial distribution in the Milky Way from the observed distribution of supernova remnants?
There was an attempt to do this by D. A. Green http://adsabs.harvard.edu/abs/2015MNRAS.454.1517G
However, the fitted function goes to zero for the Galactic Centre. Since there are supernovae and pulsar in the Centre this cannot be right. A problem is that the supernova remnant record is incomplete, and for many of them we do not have distance. In this project we take the sample of known remnants and investigate how to best tackle the problem, either using distances or only using the projected coordinates. And explore different types of distribution functions.
7. Electron and proton heating in solar system shocks
There are several spacecraft targeting cosmic rays and the solar wind. Whenever the Sun has a Coronal Mass Ejection, a shock wave is sent into space and if the spacecraft is the right location it passes through the shock, directly measuring the energetic particles, the electron temperatures and proton temperatures and magnetic fields. There is a lot of interest in these shocks, as shocks are everywhere in space, but only in the solar system we can directly measure the properties.
One thing we don’t know about astrophysical shock is whether they heat up all particles to the same temperature. Apparently it depends on the type and speed of the shock. Unfortunately for the solar system this aspect of research is ignored. For this project we will look at a variety of shocks measured by ACE (or other spacecrafts) and see if there are any trends of the electron/proton temperature ratio as a function of shock speed and magnetic field. Other aspects may also be explored, such as the particle acceleration properties, depending on the progress of the project.
8. Hunting gems in the sky: a study of Aluminum in the interstellar dust
Aluminum is mostly locked in dust grains in the interstellar medium and it may constitute the core of relatively large, multi-layer grains. The form that Al should take is not completely understood (oxides, silicates or precious gems) and may depend on the line of sight in the Galaxy. The X-ray band offers a view on a well visible Al feature, which may serve as chemistry diagnostic. This project will explore the potential of the high-resolution X-ray data from the Chandra X-ray observatory. Once verified that instrumental features are well calibrated, the Al feature will be modelled using laboratory measurements, newly acquired by our group. The X-ray spectrum, absorbed by Al and other abundant elements in the interstellar dust, is provided by bright X-ray sources in the background: accreting compact objects such as neutron stars and black holes.
The project will be carried out at SRON-the Netherlands Institute for Space Research, in Utrecht
Supervisor: Dr Elisa Costantini (email@example.com)
9. X-ray spectral modelling of winds in active galactic nuclei
Supermassive black holes (SMBHs) at the heart of active galactic nuclei (AGN) grow through accretion of matter from their host galaxy, thus releasing enormous amount of radiation. This radiation is often accompanied by outflowing winds of gas, which importantly couple the SMBHs to their host galaxy. However, the nature and origin of these winds are not fully understood. The X-ray bright AGN are excellent laboratories to uncover the uncertain properties of the wind through high-resolution X-ray spectroscopy and photoionisation modelling. In this project the student will carry out such an investigation using spectral modelling of X-ray observations to determine the physical properties of the AGN wind.
The project will be carried out at SRON-the Netherlands Institute for Space Research, in Utrecht.
Supervisors: Dr. Missagh Mehdipour (firstname.lastname@example.org) and Dr Elisa Costantini (email@example.com).
10. An X-ray look at accretion and jets launched by neutron stars
Description: X-ray binary systems are binaries where a compact object - either a black hole or a neutron star - and a normal star orbit around each other, and the compact object gravitationally attracts, or 'accretes', the outer layers of the star. Part of this gas reaches the compact object, but a significant fraction is launched away in narrow beams of matter travelling close to the speed of light: jets. Observations of the accreted gas, which emits X-ray radiation, and the jet, which is bright at radio frequencies, shows a clear correlation between the X-ray and radio luminosity for the black hole case. Such a correlation signals the coupling between infalling and expelled material. However, for the neutron stars, the picture is more complicated and the correlation between accretion and ejection is more scattered.
In this project, we will try to understand this complicated neutron star behaviour, by looking at the X-ray observations in detail. The student will aim to determine whether certain individual components in the X-ray spectrum correlate better with the radio emission than the total X-ray luminosity. As such, this project will involve X-ray data analysis, working with state-of-the-art astronomical observations, and statistical analysis.
11. A new type of transient X-ray event
Ever since 2006, the Swift satellite has been taking ~20-min X-ray snapshot images of the center of our Galaxy nearly every day. The Galactic center is a very rich environment to study accretion onto black holes and neutron stars. Not only does it harbor the supermassive black hole Sgr A*, the Swift campaign also covers about 15 X-ray binaries. In these X-ray binaries, a stellar-mass black hole or a neutron star is swallowing gas from a companion star. This usually happens in a transient fashion; the black holes and neutron stars typically feast on their companion for a few weeks at a time and then remain dormant for years before exhibiting another outburst of accretion. During accretion episodes an X-ray binary brightens by orders of magnitude; they can thus be seen to switch on and off. In addition, Sgr A* occasionally shows a brief burp of X-ray emission, which typically lasts a few hours, for which the origin is not known.
By now, more than 1000 X-ray images of the Galactic center have been obtained by Swift. We recently noticed a new type of transient X-ray event in two of these images; brief flashes of X-rays that are not associated with any known X-ray source. While the brightness of these flashes is similar to the accretion outbursts of X-ray binaries, their duration seems to be much shorter. In this project, you will have to experiment with statistical detection methods to search for more of these brief transient events in the Swift data of the Galactic centre. By characterise their basic properties (e.g. duration, X-ray spectral shape) and occurrence rate, the ultimate aim is to understand the nature of the brief X-ray flashes.
12. Why do outbursts from black hole X-ray binaries sometimes 'fail'?
Black hole X-ray binaries consist of a stellar-mass black hole that is in orbit with, and pulling (accreting) material from a companion star. This infalling matter spirals inwards towards the black hole forming an accretion disk, which is observed at X-ray wavelengths. However, not all of the inflowing material is consumed by the black hole, some of it is shot out in the form of fast, focussed beams, or jets, which are observed at radio wavelengths. While these accreting black holes spend the majority of their time in a low-luminosity or quiescent state, with a faint disk and jets, they occasionally go through short periods of bright outburst, which is due to an increased amount of accretion onto the black hole. During such outbursts the disk and jet emission brightens dramatically. However, the picture isn't quite so simple: sometimes these objects 'fail' to go into a full outburst, and instead return to their quiescence state before the disk completely fills-in. Understanding why this happens will provide new insight into black hole accretion on all physical scales, from stellar-mass black holes in X-ray binaries to supermassive black holes at the centres of galaxies.
During this project the student will analyse X-ray and radio observations of a black hole X-ray binary during both a full and a 'failed' outburst to determine if there are any notable (and possibly predictive) differences between these two types of outburst. The student will also apply these ideas to other black hole systems that have shown similar ‘failed’ outbursts to see if they hold across the general population.
13. NICER studies of accretion disk variability from close to black holes and neutron stars
Since 2017, the NICER X-ray telescope on board the International Space Station has been delivering remarkable observations of accreting black holes and neutron stars in X-ray binary systems, with simultaneously higher X-ray count rates, time resolution and better spectral resolution than any previous X-ray telescopes. One of the unique capabilities of NICER is that it can see down to low X-ray energies and study in detail the X-ray variability of the thermal-emitting accretion disk, which is thought (based on data taken by older telescopes at higher energies) to be linked to the plasma turbulence that drives the accretion process itself. In this project, you will use new data from NICER, together with Python code that you will write to help analyse the data, to shed light on the mysterious origin of the variability from the accretion disk, and test whether the picture based on the older data is really correct. This will be the first time that anyone has carried out such a study, so whatever the results, they are sure to be interesting!
14. Searching for fast (<1 minute time scale) to very fast (second) optical transients
The optical sky can be very variable (i.e., called transients), with many different source types (e.g., supernovae, gammay-ray bursts, accreting white dwarfs, flare stars, interacting binaries) exhibiting several to many orders of magnitude variability in the optical. Therefore, many sky surveys are currently active or in design to search and study such transient sources. However, nearly all surveys prober the long to very long time scales of hours to days to weeks, and only a small number of surveys can probe timescales down to a few minutes. Moreover, sub-minute (i.e., seconds) timescales are hardly probed. Therefore, we have designed a student project (a pilot study) to use a run-off-the-mill consumer camera to survey the fast (<1 minute) to very fast (seconds) timescales of the optical sky. The oservations will be done at night by the student and will cover, per exposure, a field-of-view of many tens of degrees, thus instantenously covering large part of the visible sky. Expected targets are prompt emission from explosive events like gamma-ray bursts down to fast variability from flare stars, and potentially unknown types of sources.