Proposed subjects of PhD theses 2017/2018

 

 

 

Subject: Relativistic astrophysics

Advisor: Prof. Włodek Kluźniak (wlodek@camk.edu.pl)

 

PhD studies in a range of topics in theoretical astrophysics are offered including, but not limited to, the astrophysics of black holes and neutron stars. These include phenomena as diverse as TeV emission, gamma-ray bursts (GRBs), gravitational waves, the (magneto)hydrodynamics of accretion disks and jets, and binary evolution. Work on these topics will be relevant to ongoing and future observations with several modern and planned instruments, including H.E.S.S., CTA, LOFT and a host of optical, radio and X-ray telescopes.
 

Among specific topics of current interest are studies of the variability and stability of accretion disks in the presence of strong radiation fields. Prospective graduate students would be welcome to perform radiative MHD simulations of accretion disks with existing codes, as well as to work on improving radiation routines.



 

Subject: Pulsar Astrophysics

Advisor: Dr hab. Jarosław Dyks (jinx@ncac.torun.pl)

 

The projects focus on the interpretation of radiative properties of pulsars, in particular: modelling of radio or optical polarisation, pulse profile morphology, the relation between radio and gamma-ray properties, analysis of temporal behaviour (subpulse drift or profile moding). Some of the projects are oriented mostly on high-level data analysis, others on numerical implementation of theoretical models.



 

Subject: Beta Cephei stars seen with the eyes of TESS

Advisor: Prof. Gerald Handler (gerald@camk.edu.pl)

 

TESS is the acronym for Transiting Exoplanet Survey Satellite, a NASA space mission to be launched in late December 2017. TESS will perform an all-sky survey of bright stars for transiting exoplanets, but it will also have an asteroseismology program. In this framework, high-precision measurements (of a quality compared to that of the Kepler mission, but for stars some five magnitudes brighter) with rapid time sampling will be available for millions of stars.
 

The purposes of the proposed PhD project concerns Beta Cephei stars, hot, massive main sequence pulsators. Preparatory work for TESS has recently more than doubled the number of known Beta Cephei stars to about 500. These stars need to be categorized homogeneously with the aid of ground-based observations to be acquired. Then, a survey of the pulsational properties of Beta Cephei stars with TESS data should be carried out that will supersede all related previous studies. Finally, individual stars with the most interesting pulsation spectra shall be subjected to follow-up observations for mode identifications and detailed seismic studies. In this way, our knowledge on Beta Cephei stars as a group, and as individual pulsators shall be considerably improved. This PhD work is expected to result in several high-impact publications and should establish the candidate in the scientific community. Financial support for the project is available through a MAESTRO grant (NCN).



 

Subject: Double-station observations of meteors and LEO satellites

Advisor: Dr hab. Arkadiusz Olech (olech@camk.edu.pl)

 

The main aim of the PhD student will be putting into operation two sets of sensitive cameras with fast lenses located at the distance of 200-300 km and observing 50x50 deg field of view, detecting meteors and LEO satellites. The collected data will be used for trajectory and orbits calculations of both meteors and satellites.



 

Subject: Kinetic simulations of relativistic magnetic reconnection

Advisor: Prof. Marek Sikora (sikora@camk.edu.pl)

Co-Advisor: Dr Krzysztof Nalewajko (knalew@camk.edu.pl)

 

Magnetic reconnection is one of the most promising dissipation mechanisms in relativistically magnetized plasma, that is thought to be present in most astrophysical sources of gamma-ray radiation: relativistic jets of active galaxies (blazars), gamma-ray bursts, pulsars, magnetars, etc. In recent years, a significant progress was made in understanding the particle acceleration and production of gamma rays during relativistic reconnection, mainly due to kinetic numerical simulations ('particle-in-cellÔÇÖ algorithm; PIC). Nevertheless, there are many outstanding problems regarding both numerical simulations as well as application of the numerical results to specific astrophysical situations. We seek PhD candidates with either numerical or theoretical skills. We offer introduction to: basic plasma physics, theory of magnetic reconnection, gamma-ray astrophysics, high performance computing, working with a PIC code (Zeltron), as well as prospects for international collaboration (Prof. Mitchell Begelman and Prof. Dmitri Uzdensky, University of Colorado Boulder, USA; Prof. Roger Blandford, Stanford University, USA; Dr Benoit Cerutti, CNRS Grenoble, France). We offer 2 four-year stipends funded from a National Science Centre grant.



 

Subject: Time-Domain and Spectroscopy Studies of Active Galactic Nuclei

Advisor: Prof. Aleksander Schwarzenberg-Czerny (alex@camk.edu.pl)

Co-Advisor: Dr Alex Markowitz (almarkowitz@ucsd.edu)

 

Active Galactic Nuclei are powered by accretion of gas onto a supermassive black hole, and we seek to obtain observational constraints on the morphology of circumnuclear gas and on the physical mechanisms associated with accretion in the regime of extreme gravity.
 

We study accretion disks, as traced by X-ray emission lines, and we search for clumps/clouds in the accreting matter by studying X-ray spectral variability. We will use data from eROSITA's all-sky X-ray survey as well as from current X-ray missions such as XMM-Newton and INTEGRAL. In particular, in preparation for upcoming "big-data" observing programmes such as LSST and SKA, we seek a student to evaluate the efficacy of statistical methods commonly used when searching for quasi- or strictly-periodic signals in AGN/quasar continuum light curves.
 

Students are encouraged to apply if they seek to become skilled in Time Domain Analysis methods, X-ray astrophysics, and/or black hole accretion studies.



 

Subject: High-energy astrophysics of pulsars and their dissipative winds

Advisor: Prof. Bronisław Rudak (bronek@camk.edu.pl)

 

I offer several PhD projects addressing current important issues in high-energy astrophysics of pulsars and their dissipative winds. The projects are either of observational or theoretical nature. In the former case, the student will join the H.E.S.S. Collaboration. Decision about the final choice of the subject will be taken mutually within the first year of the PhD programme.
 

Here is an example of a proposed theoretical project:
 

Title: "Transitional pulsars"
 

Transitional millisecond pulsars - a new class of pulsars in binary systems representing the long sought ‘missing link’ of the millisecond pulsar formation scenario. High-quality multi-wavelength (MWL) observations of these systems allow us to probe pulsar emission, pulsar relativistic winds, and interactions of the latter with matter infalling from the companion star.
 

The discovery and impact potential of such observations is very high, particularly in gamma-rays. We’ll aim at working out a detailed physical scenario of different states of the three transitional systems known to date: PSR J1023+0038, PSR J1824-2452I, and PSR J1227-4853. Methodology and techniques: Model development, numerical modelling, MWL data analysis.



 

Subject: Gravitational lensing of the cosmic microwave background

Advisor: Dr hab. Michał Chodorowski (michal@camk.edu.pl)

Co-Advisor: Dr Paweł Bielewicz (pbielew@camk.edu.pl)

 

Gravitational lensing of the cosmic microwave background (CMB) is a relativistic effect caused by the gravitational interaction of the CMB photons with matter inhomogeneities encountered during their travel from the last scattering surface to an observer. The result of this effect are deflection of the CMB photon paths and correlations of the photon deflection angles over the sky. These correlations can be used to reconstruct the gravitational potential of the lensing structures projected along the line-of-sight. It gives a unique image of the formation of the large scale structure at high redshifts and enables constraining total mass of neutrinos as well as testing general relativity and alternative gravity theories at large scales. On the other hand, CMB gravitational lensing effect also generates divergence-free component of CMB polarisation. It can be a serious obstacle for the detection of signal coming from primordial gravitational waves produced during the inflationary epoch. Hence, to be able to detect the latter, there is a need of very accurate measuring of the lensing effect and correcting CMB polarisation maps for the effect. Recently released data from the Planck satellite allowed estimating the gravitational lensing potential for almost all the sky. One of the objectives of the ongoing and near future CMB experiments is a significant improvement of the measurement of the lensing effect.
 

This PhD project involves research on different aspects of the CMB gravitational lensing including developing and implementation of algorithms for estimation of the gravitational lensing potential, modelling and simulations of the effect, crosscorrelations with other tracers of the large scale structure, testing modified gravity theories and correcting CMB maps for the lensing effect. The PhD student will analyse publicly available data from the Planck satellite and galaxy and radio surveys, such as DES (Dark Energy Survey), SDSS (Sloan Digital Sky Surveys) and NVSS (NRAO VLA Sky Survey). The student will also provide the best theoretical predictions for future experiments, including Advanced ACT (Atacama Cosmology Telescope), LiteBIRD, COrE (Comic Origins Explorer), Euclid and SKA (Square Kilometre Array). We seek strongly motivated PhD candidates with interest in cosmology, however an educational background in cosmology is not necessary. The candidates should demonstrate ability and passion in programming and have experience in numerical methods.



 

Subject: Superfluid neutron stars

Advisor: Prof. Leszek Zdunik (jlz@camk.edu.pl)

Co-advisor: Dr Brynmor Haskell (bhaskell@camk.edu.pl)

 

Neutron stars are one of the most exotic and exciting nuclear physics laboratories in the Universe. With a mass comparable to that of the Sun squeezed into a 10 km radius they have interior densities that exceed nuclear saturation density. These are conditions that we cannot replicate with laboratory experiments on Earth and allow us to catch a glimpse of the behaviour of matter at high densities and low temperatures, with exotic phases, such as deconfined quark condensates, expected in the core of these stars.
 

Despite internal temperatures of tens of millions of degrees Kelvin, the thermal energy of these objects is in fact small compared to the huge Fermi energy of the constituents, and large scale superfluid components are expected in the interior. Superfluidity has a strong impact on the dynamics of the star, as the superfluid can flow with little or no viscosity with respect to the ‘normal’ component. Quite strikingly these microscopic properties of matter can lead to large scale phenomena that are observable from Earth mainly with radio telescopes, X-ray and gamma-ray satellites, and, in the near future, gravitational wave detectors.
 

This PhD project involves, in collaboration with the group of Pierre Pizzochero in Milan, Italy, the theoretical and computational study of the interaction between crustal nuclei (pinning sites) and superfluid vortices. The results will be used to investigate the origin of pulsar glitches, and more generally to study the observational signatures (both electromagnetic and in the form of gravitational waves) of superfluid neutron stars.



 

Subject: Analysis and theoretical interpretation of ground and space-based observationsof classical pulsators

Advisor: Dr hab. Radosław Smolec (smolec@camk.edu.pl)

 

Classical pulsators (Cepheids and RR Lyrae stars) are among the most important variable stars in astrophysics. They are not only excellent distance indicators but also serve as a testbed for stellar pulsation and evolution theories. Still, some of the phenomena in pulsation of classical pulsators are not well understood (e.g. excitation of non-radial modes, long-term modulation of pulsation - the Blazhko effect in RR Lyr stars). The goal of the project is to perform analysis and theoretical interpretation of classical pulsator's pulsation. Ground-based observations (OGLE, MACHO, ASAS) and space observations from the Kepler satellite will be used.
 

The student will search for multiperiodic pulsation in both radial and non-radial modes, for possible period-doubling effect and for modulation of pulsation. Next, these phenomena will be modeled with the help of existing pulsation codes and stellar evolution codes (Warsaw codes and publicly available MESA code).
 

Experience in numerical programming is important and welcome for the project. The student will learn techniques of time-series analysis and will learn the theories of stellar structure and evolution, also in practice, through computation of stellar models.



 

Subject: Spectroscopy of symbiotic binary systems

Advisor: Prof. Joanna Mikołajewska (mikolaj@camk.edu.pl)

Co-Advisor: Dr Cezary Gałan (cgalan@camk.edu.pl)

 

Symbiotic stars are long-period interacting binaries composed of evolved red giant and a hot luminous companion ionizing a circumbinary nebula. The aims of this project are detailed spectroscopic analysis of symbiotic binaries in Milky Way and the Magellanic Clouds based on already obtained spectra in the optical (including SALT, VLT) and near infrared (Gemini-South, 4m KPNO, IRTF, NTT) as well as possible new observations (especially using ESO telescopes and SALT). In particular, the project will include:
 

i) determination of chemical abundances using spectral synthesis method and analysis including abundance peculiarities (CNO, 12C/13C, s-process);

ii) the first attempts of the detailed chemical composition analysis (3D-NLTE) in symbiotic giants and studies their atmospheres for stratification;

iii) determination of the parameters of binary components: rotational velocities, masses, effective temperatures, etc.



 

Subject: Neutron stars - observational constraints on dense matter theory

Advisor: Prof. Leszek Zdunik (jlz@camk.edu.pl)

 

Neutron stars, observed as radio pulsars, X-ray bursters, X-ray pulsars, and magnetars, are cosmic laboratories for studying properties of matter under extreme astrophysical conditions. The goal of the project is to confront recent observations of neutron stars properties (mass of the neutron star, fast rotation, cooling) with theories describing these processes. The project involves the study of the properties of the crust of neutron stars using methods of theoretical physics, and performing numerical simulations of the crust structure and dynamics. The crust plays very important role in neutron star evolution and dynamics and its properties are crucial for neutron star cooling and surface temperature. Another subject is the study of spin-up of a neutron star by accretion, including the impact of the properties of superdense matter on the rotational evolution. The problems listed above should be solved for a broad range of possible models of dense matter.



 

Subject: Connection between accretion and jets in microquasars

Advisor: Prof. Andrzej Zdziarski (aaz@camk.edu.pl)

 

The relationship between black-hole accretion flows and jets is one of major unsolved problems of contemporary astrophysics. Matter falling from large distances onto the black hole loses its angular momentum and forms a disc-like inflow with a complex structure. However, a part of that matter is channelled into narrow bipolar outflows, i.e., jets. Jets are formed around both supermassive black holes (in active galactic nuclei, quasars, blazars) and stellar-mass black holes in interacting binary systems (called microquasars). The subject of the thesis will be studies of phenomena taking place close to the black hole in the region of jet formation. The way jets are formed and their emission are still not well understood. In particular, it has been disputed whether X-ray emission of microquasars originates in the accretion flow or in the jets. A recent popular model has been the 'lamppost', a compact X-ray source located on the black-hole rotation axis, and thus forming the jet base. This model is so far relatively undeveloped, and the thesis work may include studies of its dynamics, ways it can be formed, and electron-positron pair production within it. The theoretical results will be then compared to observations, e.g., X-ray spectra, radio/X-ray correlations, variability power spectra, and time lags between different spectral bands. A major feature in the observed X-ray spectra is an Fe fluorescent line, around 6-7 keV, originating from re-emission of X-ray radiation striking the surrounding accretion disc. Relativistic distortion of the line due to gravity and motion around the black hole is then used to infer the extent of the disc and the spin of the black hole.



 

Subject: Stellar astronomy and eclipse timing

Advisor: Prof. Maciej Konacki (maciej@ncac.torun.pl)

 

The aim of the project is to characterize with high precision eclipsing binary stars and search for circumbinary companions (stellar and planetary) thanks to the timing measurements of their eclipses. Determined parameters of the components of the binaries will be combined with the distances from the Gaia mission and used to test the models of stellar structure and evolution. Both parts of the project will be based on a vast database of photometric and spectroscopic measurements from the “Solaris” project. These database contains over 1.8 million frames (thousands of nights) of photometry and about 300 nights of echelle spectroscopy (11 different spectrographs, several thousand high resolution spectra for nearly 400 eclipsing binaries).
 

These tasks can be enhanced with new observing campaigns. The “Solaris” network consists of 4 robotic telescopes (0.5-m, 2 in South Africa, one in Argentina and one in Australia) with Johnson-Cousins (UBVRI) and Sloan (u’g’r’i’z’) filter sets. Additionally, one of the telescopes in South Africa is equipped with a medium resolution (R = 20 000), high throughput echelle spectrograph suitable for stellar astronomy up to about 11 mag.



 

Subject: Astronomical instrumentation in application to space sector

Advisor: Prof. Maciej Konacki (maciej@ncac.torun.pl)

 

The “Solaris” network of robotic telescopes offers considerable opportunities for development and deployment of small astronomical instruments. Additionally, this is supported by a recent opening of a laboratory at CAMK Toruń fully equipped to carry out small instrumentation projects. Telescopes of our network are capable of observing satellites and space debris on all orbits (LEO-GEO). The project will encompass (1) development of instruments enhancing the capabilities of our telescopes to observe and characterize resident space objects (RSO), (2) undertaking observing campaigns to detect, monitor and catalogue RSOs. We are looking for a candidate with an engineering degree and experience in astronomy.



 

Subject: Neutron-star transient gravitational-wave emission: data analysis and astrophysical models

Advisor: Dr hab. Michał Bejger (bejger@camk.edu.pl)

 

Recent direct gravitational-wave detections open a completely new and exciting observational window to our Universe: gravitational-wave astronomy. The network of Advanced LIGO and Advanced Virgo interferometric detectors is gathering the most sensitive data to date, in a broad range of frequencies corresponding to the emission of gravitational waves by binary systems of black holes, neutrons stars, supernova explosions, rotating neutron stars and instabilities related to them. The potential for fundamental new discoveries in this field is substantial.

 

The PhD study project is divided into two parts: first is the design and implementation of data-analysis algorithms for gravitational wave detectors aimed at the transient gravitational-wave phenomena related to neutron stars (in close collaboration with the Polish Virgo group, full member of the LIGO-Virgo collaboration) with the use of modern data-analysis techniques: deep-learning neural network methods implemented on graphical-processing units (GPUs). Second, complementary part of the project is related to the construction of realistic theoretical models of neutron stars - sources of the gravitational-wave emission - to be used in the gravitational-waves data analysis, and in order to put constrains on their physical properties and their very dense matter equation of state (in collaboration with CAMK neutron-star group members).



 

Subject: Variable stars in selected globular clusters

Advisor: Dr hab. Arkadiusz Olech (olech@camk.edu.pl)

 

The main goal will be reduction and photometric analysis of CCD images of selected globular clusters (mainly Omega Cen) gathered by CASE project in 1996-2016. The PhD student will search for variable stars in these clusters and will analyse their light curves. The particular interest will be given to pulsating variables (RR Lyr and others).



 

Subject: Comparing Star Cluster Simulations with Observations

Advisor: Dr hab. Mirosław Giersz (mig@camk.edu.pl)

 

Stellar and dynamical evolution of extremely dense star clusters produces a myriad of interesting astrophysical objects. Observations of objects like globular clusters reveal that these systems not only contain stars at different stages of stellar evolution but also harbour exotic stars and binary systems like blue stragglers, cataclysmic variables and X-ray binaries. In recent years, numerical simulations of star clusters using N-body and Monte Carlo codes have become increasingly more realistic and can be used to evolve clusters with up to millions of stars. At the same time, technological developments in optics and instrumentation have lead to in-depth and detailed observations of numerous star clusters in our Galaxy and its neighbourhood. In upcoming years, systems like globular clusters will be observed in unprecedented detail with the advent of the James Webb Space Telescope and the European Extremely Large Telescope.
 

Comparing these detailed observations with numerical simulations of theoretical star cluster models can provide useful insights that can significantly help to improve our knowledge of stellar systems like globular clusters by providing constraints on their initial conditions and properties. This project will focus mainly on transforming the data provided by state-of-the-art numerical simulations of star cluster models (provided by the MOCCA code for star cluster evolution) into synthetic observations. The main task of the student will be to further develop the COCOA (Cluster simulatiOn Comparison with ObservAtions) code which can create simulated observations from numerical snapshots provided by star cluster simulation codes. The student will work on analysing and reducing the synthetic observations in the same way as observers would do in order to obtain global cluster parameters and properties. This will include developing pipelines to determine the luminosity function, surface brightness profile, various scale radii, binary fraction, completeness and colour magnitude diagrams of hundreds of star cluster models. The student may also work on comparing observational properties of specific populations of stars and binary systems like variable stars, evolved giants, blue stragglers and eclipsing binaries from simulated models with real observations. This will be vital in understanding the formation and evolution of such interesting stars and binaries.
 

The student will work under the supervision of Mirek Giersz, who has been actively developing the MOCCA code for star cluster simulations at NCAC in Warsaw. Student will also closely collaborate with Abbas Askar, who has been developing the COCOA code for creating simulated observations. Prior knowledge of reducing observational data (specifically photometric data) will be extremely useful for this project.