master thesis proposals - ago.ulg.ac.be

Important notice!
The present catalogue is especially relevant for master theses in the Research focus. Its content is not exhaustive, and students are encouraged to contact specific teachers/researchers to ask them about potential alternatives if they are interested in other topics.
For the Professional focus, the master thesis must be an internship and there is no specific offer prepared in advance. Students are encouraged to search for opportunities out of the AGO Department. To do so, contacting other institutes is highly recommended, including
- Liège Space Centre (Sart-Tilman) : http://www.csl.uliege.be (or via S. Habraken, C. Barbier) - Belgian Institute for Space Aeronomy (Brussels) : http://www.aeronomie.be/en/ - Royal Observatory of Belgium (Brussels) : https://www.astro.oma.be/en/ - Royal Institute for Meteorology (Brussels) : https://www.meteo.be/en/ - The AMOS company (Sart-Tilman) : https://www.amos.be/ - The Aerospacelab company (Mont-Saint-Guibert): https://www.aerospacelab.be/
… or any other company involved in space activities.
About master theses out of ULiège...
Students involved in internships (abroad, in Belgium, and even at the Centre Spatial de Liège) have to fill in an internship agreement and a risk analysis sheet. These documents must be completed in concertation with the person responsible for the internship at the host institution, with the agreement of the teacher/academic supervisor in ULiège.
Link to the required documents : https://www.enseignement.uliege.be/cms/c_9413472/en/etape-4-fiche-d-analyse-de-risque-et- convention
For any question or request for assistance, the contact person for the Faculty of Sciences is Mrs Kristel Karremans: [email protected]
In addition, for a stay abroad it is mandatory to follow an on-line procedure to officially request the authorization to the Rector of the University. This is necessary for the validation of the activity abroad in the student programme and for benefiting of an insurance coverage. The request should be introduced at least one month (sooner is better!) before the expected date of departure.
Contact person : J.R. Cudell
Office: 4/44 (B5a)
Availability: most afternoons in May or June. Check via e-mail if you want to be sure,
Thematics : Cosmology and astroparticles
Description:
A number of possibilities exist (in particle physics, astroparticle physics, dark matter, gravitational waves,…), and I encourage interested students to come and see me.
Contact person : Prasanta Char
Office:
Availability: Online meeting can be set up with appointment by email
Thematics : Nuclear Astrophysics
Description:
In this project, we will study the properties of rotating neutron stars, their oscillations and the associated instabilities. In particular, we investigate the r-mode oscillations that are known to become unstable and emit gravitational waves. We will analyze the growth, saturation and damping of r-modes, and their dependence on the microphysical details of the neutron stars. We will also examine different scenarios such as new-born young pulsars, and accreting millisecond pulsars: their spin evolution, and the detectability of the emitted gravitational waves.
References:
1. M. G. Alford and K. Schwenzer, 2014 Astrophys. J. 781 26 2. C. Cuofano and A. Drago, 2010 Phys. Rev. D 82 084027 3. Ch. C. Moustakidis, 2015 Phys. Rev. D 91 035804 4. A. Mytidis et al, 2015 Astrophys. J. 810 27
Magnetars and their structure
Contact person : Prasanta Char
Office:
Availability: Online meeting can be set up with appointment by email
Thematics : Nuclear Astrophysics
Description:
Magnetars are neutron stars with extremely high magnetic fields. In this project, we will study how the magnetic field affects the spherical structure of the neutron stars. We will examine different configurations of magnetic fields and the associated deformations. We will compute stable models of such objects using realistic equations of state for different magnetic field strengths. We will also investigate gravitational wave emission from the spin evolution of the magnetically deformed stars.
References:
1. K. Ioka and M. Sasaki, 2004 Astrophys. J. 600 296 2. A. Colaiuda et al, Mon. Not. R. Astron. Soc. 385, 2080–2096 (2008) 3. L. Gualtieri et al, Class. Quantum Grav. 28 (2011) 114014
Deciphering a gravitational lens with MUSE
Contact person : Dominique Sluse
Office: B5c, +1/10
Availability: The interested student(s) should contact me by email to organise a meeting.
Thematics : Cosmology, Astrophysics; Instrumentation and methods
Description:
Gravitationally lensed quasars are exceptional astrophysical laboratories. They can be used e.g. to measure the expansion rate of the Universe, quantify the dark matter content of distant galaxies, or probe the structure of AGNs on scales inaccessible with classical instrumentation. Wide Field Integral Field Spectroscopy (IFS) of lensed systems is revolutionizing gravitational lens related science. IFS data allow one to simultaneously study, with an exceptional level of details, the lensing galaxy, the lensed quasar, and the other galaxies along the line-of-sight that contribute to the gravitational lensing effect. For this project, the student will work with recently obtained IFS data of a lensed quasar obtained with the MUSE instrument mounted on one of the 4 very large telescopes operated by ESO at the Paranal observatory. Those data will be used to study this system on multiple scales. By deblending the light from the quasar images from the light of the foreground lensing galaxy, it will be possible to perform, for the first time, a measurement of the lens redshift and of the lensing galaxy mass in that system. In addition, those data will enable the study of the spectral deformation of the quasar spectrum induced by gravitational microlensing but also establish its main physical properties based on the detected emission lines. In addition, it will be possible to measure the redshifts of all the galaxies detected in the field of view and quantify their impact on the strongly lensed system. The details of the project may be adapted (focusing on some specific aspects) depending of the student’ scientific interest and skills. The students are strongly encouraged to contact me to discuss this project. Other projects related to extragalactic astrophysics and/or gravitational lensing are possible.
Prerequisites: Experience with python programming (e.g. via SPAT0002-1: Programming techniques, numerical methods and machine learning) is needed. Other recommended courses (not mandatory): Extragalactic astrophysics (SPAT0011-1), Astrophysical observations (SPAT0068- 1), Traitement de données (PHYS0931-1).
The investigation of colliding-wind binaries through high resolution radio imaging
Contact person : Michaël De Becker
e-mail : [email protected]
Office: B5c, +1/8
Description:
Massive stars produce strong stellar winds with typical velocities of 2000-3000 km/s. In binary, or higher multiplicity systems where massive stars orbit their commn centre of mass, stellar winds collide and produce strong shocks. Such systems are valuable laboratories to study shock physics in astrophysical plasmas. In particular, tens of systems of that kind are known to be particle accelerators: they accelerate charged particles up to relativistic velocities. In the presence of the local magnetic field, relativistic electrons produce synchrotron radiation revealed in the radio domain. This non-thermal emission component is produced in the colliding-wind region close to the shocks where particles are accelerated. The investigation of the radio emission from these systems allows us therefore to study their non-thermal physics.
Beside that, stellar winds are also thermal radio emitters, and what we measure through most radio observations is a composite spectrum made up of synchrotron radiation from the colliding- wind region and bremsstrahlung from the individual stellar winds. In addition, the stellar winds are efficient absorbers of the synchrotron photons produced in the colliding-wind region. This makes the behavior of these systems quite complex to interpret. However, if the stellar separation is long enough, high resolution radio imaging allows us to spatially separate the synchrotron emission region from the stellar winds. This is quite useful to achieve a clearer view of these systems.
This master thesis work will consist in the processing, analysis and interpretation of data obtained with the European VLBI Network for a couple of massive binary systems. Some important steps of the work will require to spend a few days at JIVE/ASTRON, in the north of The Netherlands.
The main objective will be to check how such observations can help in retrieving relevant information about these complex systems. A significant part of the work will consist in discussing the outcome of the observations in the appropriate scientific context.
Recommended courses: SPAT0069-1 Radio astrophysics (M. De Becker) SPAT0008-1 Interstellar medium (M. De Becker, V. Van Grootel)
What does the study of populations of pulsars tell us about them and about the interstellar medium?
Contact person : Michaël De Becker
Office: B5c, +1/8
Description:
Since the discovery of pulsars several decades ago, their study constitutes a very important contribution to modern astrophysics. In particular, pulsars are emblematic targets for radio observatories. Among other quantities, the radio study of pulsars allows us to determine their period, their spin-down luminosity, their minimum magnetic field, an estimate of their age, and their braking index.
Beside the study of pulsars specifically, radio measurement provide us with a wealth of information on the medium that is travelled through by their radiation. In particular, the study of pulsar time series allows us to retrieve valuable information on the electron number density and on the magnetic field.
This master thesis work will consist in the use of large data bases of pulsar to extract information on pulsar populations. In addition, a significant part of the work will aim at deriving valuable information on the interstellar medium, specifically on the basis of measurments of the dispersion measure and of the rotation measure. The importance dedicated to pulsars themselves of the interstellar medium will depend on the wish of the student and on prelimnary results obtained in the frist steps of the master thesis work.
A visit at ASTRON (north of The Netherlands) could be organized for a short observation session with the Dwingeloo telescope.
A significant part of the work will consist in discussing the outcome of the results in the appropriate scientific context.
Recommended course: SPAT0069-1 Radio astrophysics (M. De Becker)
The impact of atmospheric eclipses on the light curves of close massive binaries
Contact person : Gregor Rauw
Office: B5c, 2/2
Availability: Interested students should contact me by e-mail to arrange an appointment on Lifesize or Skype.
Thematics : Stellar astrophysics
Description:
The vast majority of massive stars reside in binary or higher multiplicity systems. Eclipsing binaries are especially important as they allow to infer the fundamental properties (masses and radii) of the stars. The overwhelming majority of the studies of such systems assume that the stars are opaque and that their shapes can be described by the Roche potential. However, massive stars feature dense, partially optically thick stellar winds. In close binary systems, these winds can absorb some of the light of the companion, producing a so-called atmospheric eclipse and leading to situations where the surface corresponding to optical depth unity (τ=1) lies beyond the Roche lobe. Both effects (atmospheric eclipse and R(τ=1) larger than the radius of the Roche lobe) are not accounted for in the codes based on the Roche model. The goal of this project is to implement a numerical code for the calculation of light curves of close binaries which accounts for the shape of the stars (based on the Roche potential), the mutual eclipses of the opaque stellar surfaces and the atmospheric eclipses and to compare the results with existing data. Attending the course on “Variable Stars” is highly recommended.
Photometric and spectroscopic studies of an Algol binary
Office: B5c, 2/2
Thematics: Stellar astrophysics
Description:
Algol-type binaries are systems where a cool evolved star is overflowing its Roche lobe and is transferring material to a B-type main sequence companion. This mass-transfer process episodically leads to the formation of an accretion disk around the mass gainer. We propose here an in-depth study of such an Algol binary where we combine photometric and spectroscopic observations to specify the fundamental parameters of the stars.
The student is asked to
• get acquainted with the subject of Algol-type binaries, and with the existing literature on the target of the study, • process and normalize the spectroscopic observations of the system that have been collected by our team, • perform the spectral disentangling of the series of spectroscopic observations and classify the components of the system, • based on the results of the previous point, analyse the photometric lightcurve of the system and establish the error bars on the inferred parameters, • perform a Doppler tomography of the Hα line in order to search for signatures of an accretion disk or other accretion structures, • summarize the results, compare them with the literature and discuss their implications.
Attending the course on “Variable Stars” is highly recommended.
Line profile variability in peculiar massive stars
Office: B5c, 2/2
Thematics: Stellar astrophysics
Description:
Some massive OB stars display variations of their spectral lines that hint either at (non-radial) pulsations at their surface or structures inside their circumstellar environment. Studying these phenomena opens up new avenues to learn more about the fundamental properties of these stars. Indeed, the properties of pulsations reflect the internal structure of the star, whilst the structures in stellar winds bear information about the dynamics of stellar winds and the possible impact of magnetic fields. Observationally studying these phenomena requires long series of high-quality spectroscopic observations. Over recent years, our team has collected such data for several peculiar massive stars. And we propose here an in-depth study of some of these objects.
The student is asked to
get acquainted with the subject of spectral line profile variability in massive stars, and with the current knowledge of the variability of the targets,
reduce and normalize the spectroscopic observations that have been collected to study the variability of the targets,
apply a series of tests to the time series of spectra of each of the stars to search for vari - ability, specify its significance level and to establish possible periodicities,
and finally, compare the results with what is known about the stars in the literature and discuss the implications of the results.
Attending the classes on “Variable Stars” (SPAT0007) is certainly helpful.
Seismic probing of subgiant stars with mixed modes
Contact person : Marc-Antoine Dupret
Office: B5c +1/12
Thematics : Astrophysics: Stellar physics, Asteroseismology
Description:
Context: Once their central hydrogen is exhausted, low-mass stars leave the main sequence, become subgiants and next red giants. At this evolutionary stage, stars are composed of a small-sized helium core in contraction located below a thin hydrogen-burning shell, all surrounded by a diluted expanding envelope. Due to their core-envelope structure, they exhibit a peculiar kind of stochastically-excited oscillations called mixed modes. These modes can propagate in the central radiative region, where they behave as gravity modes, and in the convective envelope, where they behave as acoustic modes. Unlike pure acoustic modes in main-sequence stars, the frequency pattern of mixed modes in the subgiant and red giant phase gives us the unique opportunity of probing the properties not only of their outer envelope, but also of their inner layers. Space missions like CoRoT and Kepler revealed such very rich spectra of oscillation including mixed modes.
Proposed work: In the team ASTA, we have very recently developed the software EGGMiMoSA, a unique tool for the asteroseismic probing of subgiants and red giants with mixed modes. We also have our own stellar evolution code CLES and stellar adiabatic oscillation code LOSC. The aim of this Master Thesis project is to use these tools for the first seismic probing of well-chosen subgiants with very rich oscillation spectra observed by Kepler. The work of the student will first consist in determining the set of relevant seismic indicators and measure their observational values for the selected targets. Next, he/she will compute a grid of stellar models encompassing these targets and study how the seismic indicators depend on the global parameters of these models. Finally, he/she will use EGGMiMoSA for an automatic search of the stellar models best reproducing the seismic observations. As key results of this study, the mass, age, chemical composition, extra-mixing (the so-called overshooting) of these stars will be accurately determined for the first time. This work could constitute a first step before a PhD thesis dedicated to the detailed seismic study of numerous subgiants and red giants observed by Kepler.
Recommended courses: Stellar structure and evolution I SPAT0044-1 (& II SPAT0045-1) & Stellar stability and asteroseismology SPAT0005-1 (M-A Dupret)
Deformation and break-up of fast rotating stars
Contact person : Marc-Antoine Dupret
Office: B5c, room 1/12
Thematics : Astrophysics: stellar physics
Description:
Context:
Many stars are rotating fast. A typical example is given by Be stars, among which some are close to the rotation velocity break-up. As a consequence, they are strongly deformed by the centrifugal force. However, this deformation is neglected in nearly all current stellar models. Taking it into account would enable significant progress towards a more accurate modelling of fast rotating stars and their oscillations.
Proposed work:
The main task will be to implement a code modelling accurately the centrifugal deformation of a rigidly (or cylindrically) rotating star. This problem has the appropriate level for a master thesis thanks to a significant simplification: for rigid (or cylindrical) rotation, the fluid is barotrope and the pressure and density are constant on equi-potentials. Spherically symmetric models computed with the Code Liégeois d’Evolution Stellaire (CLES) will be taken as initial models. Next, solving iteratively the Poisson equation will provide the final centrifugally deformed model. Once the code works correctly, comparison with the approximate Roche models will be considered (centrifugal deformation, gravity-darkening) for models encompassing a wide range of masses and evolution stages. Finally, a very efficient student could consider the generalization to the non-conservative, non-barotropic case. This subject is ideal for a student who likes solving physical problems by himself and interpret the results. It could also constitute a first step before a PhD thesis, which would focus on the 3D modelling of close binary stars deformed by both rotation and tidal effects.
Recommended courses: SPAT0045-1 Stellar structure and evolution I and II (M.A. Dupret)
Modeling TESS data of extreme horizontal branch stars by asteroseismology
Contact person: Valérie Van Grootel
e-mail: [email protected]
Office: B5c, room 1/13.
Description:
The TESS satellite from NASA gathers since December 2018 high-quality photometric data on various stars, for searching transiting exoplanets but also for asteroseismology. Asteroseismol- ogy is the study of stellar oscillations in order to tightly constrain the physics inside stars and hence, to refine the models of the structure and the evolution of stars.
Among these stars, TESS observes each month (one Sector of the sky each 27 days) dozens of extreme horizontal branch stars, and discovers/confirms pulsations in a few of them. Extreme horizontal branch stars, also known as subdwarf B (sdB) stars, represent an advanced stage of stellar evolution. These hot (Teff=20,000-40,000 K) and compact (log g=5.2-6.2) objects burn helium in their cores into carbon and oxygen and are surrounded by an extremely thin H-rich envelope. Understanding the formation of sdB stars is one of last big mysteries of stellar evolution.
The proposed master thesis concerns the asteroseismic modeling of sdB stars observed by TESS. First step will consist in selecting the most promising targets for asteroseismic modeling: presence of a rich pulsation spectrum, availability of good spectroscopic constraints. The second step is preliminary asteroseismic analyses on the most promising targets, in order to select one that will be studied in depth during this master thesis in the third step. The asteroseismic modeling consists in quantitatively comparing the computed oscillation periods for large sets of stellar models to the observed periods. By optimizing this comparison (through genetic algorithms that have been developed for this purpose) to find the best-fitting model to the observations, the seismic modeling will yield the global parameters (e.g. stellar mass and radius) and internal structure and composition (e.g. envelope layering, core composition) of the star. Results will then be exploited, by comparing them to those of other sdB stars modeled by asteroseismology and by interpreting them in a context of sdB formation. All the tools are available and ready for a direct application to these TESS data.
This subject is well-suited for a student who like to work on concrete applications of asteroseismology and space-based observations.
Recommended courses: SPAT0005-1 Stellar Stability and asteroseismology, SPAT0045-1 Stel- lar structure and evolution II (M.A. Dupret)
Contact person: Valerie Van Grootel, Francisco J. Pozuelos
e-mail: [email protected] ; [email protected]
Tel: Valerie: +32 4 3669730 but contact preferably by email; Fran: +32 4 3669738
Office: B5c +1/13 & /17
Availability: Any time by email for a first contact. Due to the COVID-19 situation, video-calls will be preferred. The preferable time slot is from 10am to 1pm (Monday to Friday).
Thematics: Planetology and planetary systems
Description:
Theories concerning the formation and evolution of planetary systems are, at a certain level, well understood. However, little is known about how planetary systems end their lives. Indeed, the evolution of a given planetary system depends upon its host star, including when the star leaves the main sequence and starts the red giant branch (RGB) phase, when it expands and may engulf close-in planets. The question of what happens to these engulfed planets is of vital importance for understanding the fate of planetary systems. The most promising targets to address this question are hot subdwarfs, which are hot and compact post-RGB stars with typical sizes of 0.1-0.3R_sun and masses of 0.47M_sun.
In this research project the student will join our team and contribute to our transit survey in the search for transiting exoplanets orbiting hot subdwarfs. This research makes use of data collected by space telescopes such as TESS (Transiting Exoplanet Satellite Survey), Kepler and K2. The student will make use of dedicated pipelines to scrutinize a pre-existing target list in the search for signals which might hint at the presence of planets. For each event that overcomes the vetting process, a ground-based follow-up campaign with the TRAPPIST telescopes will be proposed and executed to rule out potential sources of false positives and strengthen the evidence of their planetary nature. More information on the project can be found in this paper : http://arxiv.org/abs/2104.10462 Recommended course: SPAT0063-1 Introduction to exoplanetology (M. Gillon)
Contact person: Valerie Van Grootel, Francisco J. Pozuelos
e-mail: [email protected] ; [email protected] Tel: Valerie: +32 4 3669730 but contact preferably by email; Fran: +32 4 3669738
Office: B5c +1/13 & /17
Availability: Any time by email for a first contact. Due to the COVID-19 situation, video-calls will be preferred. The preferable time slot is from 10am to 1pm (Monday to Friday).
Description:
Theories concerning the formation and evolution of planetary systems are, at a certain level, well understood. However, little is known about how planetary systems end their lives. Indeed, the evolution of a given planetary system depends upon its host star, including when the star leaves the main sequence and starts the red giant branch (RGB) phase, when it expands and may engulf close-in planets. The question of what happens to these engulfed planets is of vital importance for understanding the fate of planetary systems. The most promising targets to address this question are hot subdwarfs, which are hot and compact post-RGB stars with typical sizes of 0.1-0.3R_sun and masses of 0.47M_sun.
In this research project the student will join our team and contribute to our transit survey in the search for transiting disintegrating exoplanets. After the RGB phase of its host star, an underlying hot rocky exoplanet may suffer a body-disruption event, which could produce an elongated tail of dusty material. This research makes use of data collected by space telescopes such as TESS (Transiting Exoplanet Satellite Survey), Kepler and K2. We now have a performing tool to detect the transits of evaporating bodies, which will be used by the student to scrutinize a pre-existing target list in the search for signals which might hint at the presence of disintegrating exoplanets. For each event that overcomes the vetting process, a ground-based follow-up campaign with the TRAPPIST telescopes will be proposed and executed to rule out potential sources of false positives and strengthen the evidence of their nature. More information on the project can be found in this paper : http://arxiv.org/abs/2104.10462
Recommended course: SPAT0063-1 Introduction to exoplanetology (M. Gillon)
Contact person : Laetitia Delrez, Francisco J. Pozuelos
e-mail: [email protected], [email protected]
Tel: Laetitia Delrez: +32 4 366 97 63 / Francisco Pozuelos: +32 4 366 97 38
Office: Laetitia Delrez: B5c -1/2 / Francisco Pozuelos: B5c +1/15
Availability: Interested students should contact us by email to arrange a meeting
Description:
Exoplanets transiting bright and nearby stars are key objects for advancing our knowledge of planetary formation and evolution. Thanks to their special geometry and the brightness of their host star, we can indeed measure their radius, mass (in combination with radial velocity measurements or via transit timing variations), and orbital parameters, and we can also study their atmosphere. In particular, multi-planetary systems with several planets transiting the same bright star are targets of paramount importance, as they make it possible to compare several planets in the same system and better constain their properties and histories.
Launched in April 2018, NASA’s Transiting Exoplanet Survey Satellite (TESS) is searching the whole sky for small planets transiting bright nearby stars. As of April 2021, TESS has identified 2650 planet candidates, also known as TESS Objects of Interest (TOIs), of which 122 have been confirmed so far. The detection of a transiting planet around a given target enhances the probability that other planets in the system - if any - are also transiting (assuming small mutual inclinations between the orbital planes of the planets). However, these extra planets may have been missed by the TESS automatic detection pipeline if they produce transit signals that are below the set detection threshold. This can happen for planets with long orbital periods (with only a few transits covered by the TESS data) and/or small radii (shallow transits). The goal of this project is to scrutinize the TESS light curves of a selected number of targets for which the TESS pipeline detected at least one TOI, to search for possible signals that may hint at the presence of other planets. We will focus here on bright Sun-like stars that could be followed up with ESA’s new Characterizing ExOPlanets Satellite (CHEOPS, launched in December 2019). Unlike previous exoplanet detection missions, like TESS, CHEOPS is an exoplanet follow-up mission, designed to collect ultra-high precision photometry of known transiting planets (or candidates) around bright stars (a single star observed at a time). Thanks to its high precision and versatility, CHEOPS is perfectly suited to follow up and confirm the promising low signal- to-noise TESS candidates that may be found in the framework of this project.
Facilities, tools, and supervision: The student will be provided with a work station in the existing students’ office and all the tools needed to analyse the TESS data. The student will meet with the supervisors ideally every week to perform a weekly progress review of the project, where he/she will be able to discuss difficulties, new ideas, etc. The student will be invited to join meetings of the ExoTIC group (Exoplanets in Transit : Identification and Characterization), where other exoplanet-related topics are discussed.
Recommended course: SPAT0063-1 Introduction to exoplanetology
Tel : +61 3990 20 767
Office: Currently at Monash University (Australia). Back at ULiège in September 2021.
Availability: Availability by email or through zoom.
Thematics : Planetology and planetary systems
Description:
The indirect discovery of thousands of exoplanets with different masses, radii and orbital separations suggests a variety of pathways for the evolution of planetary systems. But do giant planets share common formation mechanisms? The advent of a new generation of sub-mm and high-contrast infrared instruments have recently provided direct images of protoplanetary discs, the birth environment of planets, revealing a wealth of structures potentially related to embedded planets (gaps, spiral arms, asymmetries). In only one system have protoplanets been unambiguously confirmed so far though, limiting our understanding of planet formation.
In this project, the student will use archival data obtained with the SPHERE high-contrast imaging instrument of the Very Large Telescope on a sample of discs showing hints of planet presence. The student will learn how to reduce data using the supervisor's pipeline, and test novel image processing techniques to model and subtract the bright emission from the star in order to produce new high-fidelity images of protoplanetary discs to identify new direct (point source) or indirect evidence (e.g.: spiral arms) of embedded protoplanets. The project will heavily rely on routines implemented in an open-source python package of high-contrast imaging routines developed in Liège, called VIP. The project will also involve adapting existing routines in order to further push the performance of high-contrast imaging processing algorithms.
Recommended background (albeit non-exclusive):
Contact person : Olivier Absil, Carl-Henrik Dahlqvist, Valentin Christiaens
Tel : 04/366.97.24
Office: B5c +2/19
Availability: I’m working mostly from home. Please contact me by email if you wish to meet (either face-to-face at B5c, or by videoconference).
Description: Despite the advent of new-generation, extreme adaptive optics systems like VLT/SPHERE and Gemini/GPI, the number of directly imaged exoplanets is still less than about 20. Any new detection is still therefore a very important step in our knowledge of planetary system architectures and planetary evolution. Among the reasons for this low detection rate are the poor sensitivity of direct imaging instruments at small orbital separations where most of the planets are supposed to be found (1-10 au), and poor sensitivity to cold, mature planetary systems (> 100 Myr). Part of these limitations can be overcome by observing nearby, young stars in the thermal infrared, where exoplanets are supposed to produce most of their thermal emission. This was the aim of the ISPY survey, carried out over about 130 nights in 2015-2019 with the ULiège vortex coronagraph installed on the NACO camera at the Very Large Telescope (VLT). While the ISPY survey is already largely analysed, and partly published by the coordinating team (Launhardt et al. 2020), the results so far were obtained with standard post- processing techniques, such as Principal Component Analysis. Within the PSILab group at the STAR Institute, we have recently proposed a new technique (the RSM map, Dahlqvist et al. 2020, 2021) to process high-contrast imaging data, which was shown to perform better than state-of-the-art algorithms, based on the “Exoplanet Imaging Data Challenge” (Cantalloube et al. 2020). The RSM map has recently been improved to run in a fully automatic way (Dahlqvist et al., in prep). The goal of this project is to revisit the ISPY archive and search for faint companions that would have been missed by standard post-processing techniques to date. The main tasks of the master student will be: (i) to identify all the suitable stars in the ISPY survey archive maintained by ESO, (ii) to calibrate the NACO data using the calibration pipeline developed by Valentin Christiaens, and (iii) to process all the calibrated data with the new auto-RSM package developed by Carl-Henrik Dahlqvist. The main outcome of the project will consist of a list of candidate companions, and of improved sensitivity limits for all the selected stars. Depending on the pace of the progress, some of these candidate companions could be confirmed by using other data sets, or by requesting new observing time at major observatories (e.g., VLT, Keck, LBT). Another follow-up would be to use the new sensitivity limits to revisit the constraints on exoplanet populations.
Recommended background: (SPAT0063) Introduction to exoplanetology (M. Gillon), (SPAT0067) Atmospheric and adaptive optics (O. Absil), Programming experience with python is also recommended.
Contact Person: Jehin Emmanuël
Description:
The TRAPPIST telescopes installed at the la Silla observatory in Chile in 2010 and in Morocco in 2016 by our team are dedicated to the research and the study of exoplanets in transit and the study of the small bodies of the Solar System (comets and asteroids). Each night, since 10 years in Chile and 4 years in Morocco we collect hundreds of images of one or two fields during several hours to search for exoplanets in transit. This constitutes a unique dataset of about 2.5 million images to be explored to discover new asteroids and comets. In this work we propose the fine tuning and the use of a recently developed pipeline to detect as many moving objects of the Solar System as possible in those archive images. Among these objects most will be already known asteroids but sometimes also a new object still unknown will be found. As some fields are observed several nights in a row and for many hours it will be possible to build rotation light curves for many of these objects. By adapting the pipeline it is also possible to find objects that move more slowly like distant comets and Trans-Neptunian objects or faster like Near Earth asteroids.
Objectives: adapt the detection strategies according to the type of objects to detect (close Near Earth Asteroids (NEA), or very distant Trans-Neptunian Objects (TNO)) and run the pipeline for automatic detection on the archive database. Collect from the results of the pipeline for each night the astrometric data and check the identification of the objects found. Submit the measurements of the unknown objects to the Minor Planet Center (MPC). Collect also the photometric measurements for each target found and build their light curves to try to find the asteroid rotation period. Most of these rotation light curves will be new and might be published in a paper.
https://www.trappist.uliege.be/
Study of the chemical composition of comets atmospheres using the TRAPPIST telescopes
Contact person: Jehin Emmanuël
Description:
Comets are among the best preserved specimens of the primitive solar nebula. This status of “fossils” gives them a unique role in understanding the origins of the solar system. The success of the Rosetta space mission was very important and is changing our knowledge about comets. But it showed also that observations from the ground continue to be important: they make it possible to supplement the data in situ by obtaining information on larger scales of the coma and tails, and for a much larger number of comets, which is necessary to extrapolate the results to the entire cometary population. The link between the composition of comets and their dynamic history must still be clarified and a complete comet classification is still missing.
In this context, we propose the observation and analysis of the coma of two or three bright comets with the TRAPPIST telescopes network. These robotic telescopes installed by our team in Chile (in 2010) and in Morocco (in 2016) are equipped with narrow band filters to isolate the emissions of different gases and dust contained in the atmosphere of comets. The student will have to prepare the observations, calibrate the data and calculate the production rates of the different gases using the so-called Haser model (1957). The necessary tools for this kind of measures have already been developed in our team. The student will have to become familiar with the various techniques, adapt and improve if necessary the reduction procedures and scripts and run the models. The results might lead to the publication of a short article.
The work will be done in the comet group of the OrCa Service (+1) and the TRAPPIST team https://www.trappist.uliege.be/
Building an atlas of cometary emission lines and identifying unknown emissions in comet spectra
Contact person: Jehin Emmanuël
Description:
Comets are among the best preserved specimens of the primitive solar nebula. This status of “fossils” gives them a unique role in understanding the origins of the solar system. The success of the Rosetta space mission was very important and is changing our knowledge about comets. But it showed also that observations from the ground continue to be important: they make it possible to supplement the data in situ by obtaining information on larger scales of the coma and tails, and for a much larger number of comets, which is necessary to extrapolate the results to the entire cometary population. The link between the composition of comets and their dynamic history must still be clarified and a complete comet classification and surface composition of nuclear ices is still missing.
To pursue this goal a complete inventory of the emission lines present in cometary spectra is for instance needed and as strange as it might seems, in the high resolution spectra of comets, hundreds emission lines are still to be identified. In this context, we propose to the student to build an atlas and a catalogue of the thousands of emission lines known and belonging to molecular species like OH, NH, CH, CN, C2, etc. using one of the best spectrum of a comet obtained in the visible with the UVES high resolution spectrometer of the Very large Telescope (VLT) by our team. This spectrum of comet C/2003 T7 (LINEAR) covers all the optical range from 300 nm to 1000 nm at high resolution and high signal-to-noise. The work will consist to understand the processes of line emissions in comets, the components of a comet spectrum (dust and gas), to find the list of lines for all the known species and identify them in the spectrum of the comet, and list them. The lines not identified will be indicated and searched for in atomic and molecular line databases for possible matches. The final goal is to make an atlas similar to the comet deVico atlas from Cochran 2012 displaying the spectrum with the lines identified and build a catalogue with those lines detected (identified or not identified). If time allows this atlas and catalogue will be made available through a webpage that could be queried to display given spectral regions selected by the user (with the help of our IT support). No new data reduction will be requested but the student needs to work with several software of his choice to display the spectra, be able to make detailed graphics, do bibliographic search, and work on long line list tables among other things.
The work will be done in the comet group of the OrCa Service (+1)
Characterising the different components of the Jovian aurorae with Juno-UVS observations
Contact person : Bertrand Bonfond
Office: B5c 0/2
Availability: From Monday to Thursday afternoon. Please send an email in advance. Skype is also a possibility.
Description:
Juno is a NASA mission dedicated to the exploration of the planet Jupiter. It orbits around the giant planet since July 2016, bringing a wealth of discoveries and unprecedented observations. Among its instruments sits an imaging spectrograph (Juno-UVS) dedicated to the observations of the Jovian aurorae. The most prominent feature of the Jovian aurorae is an incomplete curtain centred around the magnetic pole and called the main emissions. The main emissions also mark the boundary of the two other regions of the aurorae: the polar emissions and the outer emission, equatorward of the main emissions. The student will use the image processing tools developed at the Laboratory for Planetary and Atmospheric Physics (www.lpap.uliege.be) to monitor the evolution of the emitted power, the brightness and the UV color in these three regions on the Juno-UVS dataset. The student will then characterize the global morphology of the aurora and interpret their meaning in terms of magnetospheric physics.
The courses SPAT0028-2 and/or SPAT0023-1, as well as SPAT0032-2 are highly recommended.
Contact person : Denis Grodent
Office: B5c – 0/5
Thematics : Planetology and planetary systems; Instrumentation and methods.
Description: The auroras and magnetospheres of Jupiter and Saturn
The Laboratory for Planetary and Atmospheric Physics has gained a great deal of experience in the atmospheres, auroras and magnetospheres of Jupiter and Saturn, among other planets. The international reputation of the laboratory has allowed it to be involved in major planetary missions such as Cassini, Juno ou JUICE, and to be regularly selected for observations with space telescopes such as HST, Chandra or XMM-Newton. The quantity and variety of data acquired or being acquired allows us to propose tailored subjects for master thesis (or doctoral thesis) according to the students’aspirations. For example, the topics can be based on:
- the analysis of dynamic auroral images using existing procedures or those to be improved
- the development of new analysis techniques, including Machine Learning - analysis of in-situ data (other than images) - modelling of magnetospheric and/or auroral (atmospheric) phenomena involving a non-
negligible amount of programming.
This work may be carried out at LPAP under the guidance of LLPAP specialists: - Denis GRODENT - Bertrand BONFOND - Benjamin PALMAERTS - Ruilong GUO
Such research projects may be illustrated with the following original study papers involving LPAP members: D. Grodent et al. (2018) “Jupiter’s aurora observed with HST during Juno orbits 3 to 7”, http://hdl.handle.net/2268/221312
B. Bonfond et al. (2019) “Bar Code Events in the Juno-UVS Data: A Signature of ~10 MeV Electron Microbursts at Jupiter”, http://hdl.handle.net/2268/229352
B. Palmaerts et al. (2018) “Auroral storm and polar arcs at Saturn – Final Cassini/UVIS auroral observations”, http://hdl.handle.net/2268/225773
R. Guo et al. (2018) “Rotationally driven magnetic reconnection in Saturn’s dayside”, https://doi.org/10.1038/s41550-018-0461-9
Contact person : Murielle Kirkove
Description:
Critical for marine security, logistic management, and eco-sociological issues, the near-real time monitoring of ships in coastal areas is an important subject. Ship monitoring is usually performed based on the use of the Automatic Identification System (AIS) normally embarked on board of most ships. Nevertheless, some ships are not equipped with such systems, and may have the intention to harm citizens or materials. This is particularly the case in conflict zones or areas with high a significant economic potential (piracy, human trafficking, or armed conflict). These reasons pushed governments, researchers, and NGOs in developing techniques to identify these ships and compare them with AIS data.
Many of these techniques are based on RAdio Detection And Ranging (RADAR). In particular, the important increase of Synthetic Aperture Radar (SAR) satellites such as Sentinel allows a near- real time operational ship monitoring systems. Potential targets are localized either automatically or through a simple visual inspection of SAR images. A few years ago, at the Centre Spatial de Liège (CSL), we implemented a processing technique for automatically detecting potential ships within open seas areas using SAR data. This technique is based on simple detection algorithm (CFAR) and includes selector to limit detection to open sea surfaces. Since then, machine learning, and deep learning in particular, drastically push the accuracy limit obtainable by the current state-of-the-art approaches. In this context, we are looking for a motivated master student to explore different ways to detect ships from SAR Remote Sensing and Machine Learning Techniques. The student will benefit from the expertise of the signal processing group of CSL, under the supervision of Murielle Kirkove and Quentin Glaude.
The master student will be responsible for developing an automatic tool to download and preprocess SAR images including ships from the Sentinel database, labeling these images according to their ship content identified by AIS data, constructing a database from this labelization and choosing the best Machine Learning technique for the automatic detection of ships. This work can also include a comparison with the results obtained by our current method. The outcomes of the master thesis are expected to contribute to the field of automatized object detection and classification in SAR imaging. Recommended skills/courses: SPAT0032-1: Remote sensing, ELEN0062: Introduction to Machine learning, INFO8004-1: Advanced machine learning
Remark : topic highly appropriate for the professional focus
Whitening of Doppler data in Radioscience
Contact person: Promotor: Véronique Dehant; Co-Promotor: S. Le Maistre
e-mail: [email protected] and [email protected]
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:
The ground stations tracking satellites on Earth, the DSN (Deep Space Network - NASA) and ESTRACK (European Space Tracking – ESA) communicate directly with the spacecraft (S/C) using uplink (Earth → S/C) and downlink (S/C → Earth) radiosignal in X-band, S-band or Ka-band.
When the Earth is in the field of view of the S/C antennas, when the S/C is in the field of view of the Ground station (GS) antennas, and when programmatic allows it, the S/C transmit their data in a limited time (telemetry) and the GS transmit the commands for operating the S/C and its instruments. The scientific data that we are interested in in this case are the tracking Doppler data provided by the downlink at the DSN and ESTRACK either in One-Way (S/C → Earth or Two-Way (Earth → S/C → Earth). Data are often temporally correlated and therefore require pre-processing. The objective of this master thesis is to apply an algorithm of data whitening in order to decorrelate them and better dig out the Doppler signal out of the noise.
The method will be tested on and applied to the NASA InSight radioscience data (on the surface of Mars since November 2018).
This work can lead to a publication and be continued into a PhD thesis (application to real data of other radioscience data such as the future ExoMars 2020 data of the Belgian instrument LaRa).
Task description:
Examine the different whitening algorithms that allow to process highly noisy data and compare their respective performance.
Implement in MATLAB the whitening algorithm that will minimize the noise present in the Doppler data (DSN and ESTRACK files).
Application to the Radioscience InSight data.
Contact person: Promotor: Véronique Dehant; Co-Promotor: S. Le Maistre and N. Bergeot
e-mail: [email protected], [email protected], and [email protected]
Tel: 02 373 0266 (V. Dehant)
Description: The aim of this study is to analysis the effects of plasma turbulence in the solar wind on Doppler radio measurements from interplanetary spacecraft. A spacecraft receives an uplink signal at X-band (7.3 GHz), and transmits data (telemetry or science data) to Earth at X-band (8.4 GHz). In addition, a small amount of downlink power is transmitted at S-band (2.3 GHz) for evaluating the link performance. The two-way communication involves a 34-m ground station on the Earth that is equipped to emit an X-band signal and to receive both X- and S-band signals. At the ground station a loop tracker records carrier phase at both downlink carriers and this data is analyzed to examine the effect of charged particles, from solar plasma and the Earth’s ionosphere, on Doppler passes typically used for tracking and navigation of interplanetary spacecraft. The Doppler tracking data allows, for example, calculating the gravitation field of the planet around which the spacecraft is orbiting. The experimental data set that will be used in this study are dual-frequency tracking of the European Space Agency’s (ESA) Mars Express (MEX) spacecraft.
Task Description :
Based on the power spectral analysis of the dual-band data, the objective of this work is to determine an appropriate model for treating charged particles in single-band Doppler tracking. The statistic of phase variations will be described in terms of Allan variances (root-mean-square differenced-phase variations) and classical frequency variance. A realistic modelling of the charged particle variations should be adopted in good agreement with current models developed to estimate the solar plasma variations as a function of SEP angle.
This work can lead to a publication and can be continued in a PhD thesis.
Contact person: Promotor: Véronique Dehant; Co-Promotors: S. Le Maistre, M. Yseboodt
e-mail: [email protected] [email protected] et [email protected]
Tel: 02 373 0266 (V. Dehant)
Description:
The SBI (Same Beam Interferometry) technique can provide very precise measurements of the distance difference between two spacecraft or landers. This involves simultaneously tracking two or more landers with identical transponders from a single antenna on Earth. The radio signals emitted are relayed by the landers to the Earth station, where they are recorded and then combined in an interferometric mode to form a differential phase measurement. Since the media crossed by the two signals (for example the interplanetary plasma or the Earth's atmosphere) are the same, these sources of error are largely canceled out in the case of an SBI measurement.
These measurements will make it possible to observe precisely the deformations of the surface of Mars due to the tides as well as its rotation, which will add precise constraints on the interior of Mars (such as the state and the size of the nucleus for example) as well as on mass exchanges between the polar ice caps and the atmosphere.
For the proposed work, simulations will be carried out to quantify the contribution of this type of measurement on our knowledge of the parameters of rotation and tide. Measurements are generated and then used to extract interesting information and to see what level of precision is possible. This allows to test different mission configurations and see which one is most conducive to the experience.
It will also be asked to test new configurations such as for example a lander on Mars, the second being on Phobos, one of the moons of Mars.
The software used was developed at the Royal Observatory of Belgium in the case of Doppler and SBI measurements between a Martian lander and the Earth. The orbital movement of Phobos around Mars will have to be added to the software then simulations will have to be performed and analyzed for many configurations, in order to see which is the best mission strategy.
This work can lead to a scientific publication.
Task description:
Get familiar with existing codes for computing SBI measurements Compute the associate Mars interior parameters Determine the best strategy to obtain the best information.
This work can lead to a publication and can be continued in a PhD thesis.
Contact person: Promotor: Véronique Dehant; Co-Promotors: Ozgur Karatekin, Nicolas Bergeot, Florian Bodranghien
e-mail: [email protected] [email protected] [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Description:
The satellites of the American GPS system are at an altitude of about 20,000 km, those of the Russian GLONASS system at an altitude of about 19,000 km, and those of the European GALILEO system at an altitude of about 23,000 km. All these GNSS satellites (Global Navigation Satellite System) actually overlook a large number of low satellites equipped with GNSS receivers, including nanosatellites which will be launched in the future (> 2019) by the firm Aerospacelab. The radiofrequencies used are each time at least greater than 2; this makes it possible to combine the frequencies to obtain the TEC (Total Electron Content), that is to say the electron content of the ionosphere. The Earth's ionosphere is a region outside the atmosphere that contains a high concentration of free electrons. We now know that electrical events occur when clouds of charged particles are projected by the solar wind or by a solar flare or Coronal Mass Ejection (CME). When the eruption is intense, if the Earth is in the path of charged particles, the result can be catastrophic for all communication systems. It is therefore necessary in the future to monitor the activity of the Sun and its effects on our atmosphere (we speak of space weather), and in particular to measure the TEC. In this context, Aerospacelab has equipped and will equip its nanosatellites with GNSS receivers. The master thesis consists in studying the geometry of the orbits of the different satellites in play to see what can bring future nanosatellites to our knowledge of the ionosphere and in particular in the layers close to the height of cube-satellites. If data is already available, we can also apply what will be developed.
This work can lead to a scientific publication and extend into a doctoral thesis.
Task description:
Get familiar with GNSS data analysis and TEC Use the geometry of the GNSS to determine TEC
Determine what this can bring to TEC maps
Contact person: Promotor: Véronique Dehant; Co-Promotors: Ozgur Karatekin, Sébastien Le Maistre, Orkun Temal
e-mail: [email protected] [email protected] [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Description:
The Martian atmosphere is very thin but participates in the process of sublimation and condensation of the polar caps. A quarter of this atmosphere condenses in the poles according to the seasons. These mass movements induce variations in the rotation of Mars and a polar motion. This movement has seasonal components. There is also a free oscillation mode, the Chandler wobble, which would be excited by the atmosphere. The master thesis consists in calculating the amplitudes of the polar motion linked with the Chandler wobble using the outputs of a general circulation model of the Martian atmosphere. This work can lead to a scientific publication and extend into a doctoral thesis.
Task description:
Get familiar with GCM of the Martian atmosphere Compute polar motion excitation Compute CW excitation
e-mail: [email protected] [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Description:
The Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique exploits the radio transmitting capabilities of spacecraft from the most modern space science missions. A very high sensitivity of Earth-based radio telescopes (see Figure) involved in astronomical and geodetic Very Long Baseline Interferometry (VLBI) observations and an outstanding signal stability of the radio systems allow PRIDE to conduct precise tracking of planetary spacecraft. The data from individual telescopes are processed both separately and jointly (involving correlators) to provide Doppler and VLBI observables, respectively. The accurate examination of the changes in phase of the radio signal propagating from the spacecraft to each of the ground radio telescopes on Earth make the “open-loop” Doppler observables derived from each telescope very useful for different fields of planetary research. The Doppler data are called “open-loop” as the receiving ground station does not lock on the signal but receives the signal as it is in a frequency band around the expected received signal. “Closed-loop” Doppler data obtained by deep space tracking networks, such as the NASA Deep Space Network (DSN) and the ESA tracking station network (ESTRACK), are routinely used for navigation and science applications. The Doppler data are called “closed-loop” as the receiving ground station has the technical capability to lock on the signal.
For the future LaRa (Lander Radioscience) experiment that will be launched to Mars in 2022, we envisage to use this “open-loop Doppler” technique in order to increase the precision on the data. By tracking the LaRa signal, Earth-based radio telescopes involved in the PRIDE experiment can provide open-loop Doppler tracking data. The technique of processing the data is very different for “open-loop Doppler” compared to “closed-loop” Doppler, and will have to be fully developed. The partnership with JIVE (Joint Institute for VLBI ERIC) and the Technical University Delft will help us to use existing codes and not to start from scratch.
Task description:
Get familiar with open-loop data processing Application to LaRa Computing of the improvement

master thesis proposals - ago.ulg.ac.be

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