Proposed subjects of PhD theses for the year 2016
Subject: Bright fireballs captured by Polish Fireball Network
Advisor: Dr hab. Arkadiusz Olech (firstname.lastname@example.org)
The main goal of the PFN is to monitor regularly the sky over Poland to detect bright fireballs occurring over the whole territory of the country. The monitoring is performed by amateur astronomers associated with the Comets and Meteors Workshop and coordinated by astronomers from the Copernicus Astronomical Centre in Warsaw, Poland. Currently, there are over 20 fireball stations belonging to PFN, which operate during each clear night. Each year about 50000 meteors is detected and for almost 10000 of them precise orbits and trajectories are determined. Among these numbers there are over one dozen of especially bright fireballs which should be analyzed by the PhD student in terms of precise orbit and trajectory determination, analysing the light curve, looking for the parent body, estimating the possible meteorite fall area and analysing the spectrum of the bolide if recorded.
Subject: Beta Cephei stars seen with the eyes of TESS
Advisor: Prof. Gerald Handler (email@example.com)
TESS is the acronym for Transiting Exoplanet Survey Satellite, a NASA space mission to be launched in late 2017, performing an all-sky survey of bright stars for transiting exoplanets. TESS 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 as soon as the data are obtained and reduced. The purposes of the proposed project concerns Beta Cephei stars, hot, massive main sequence pulsators, and are manifold. The first is to generate an input catalogue of candidate Beta Cephei stars by mining existing data bases and photometric surveys. The second is to perform a survey of the pulsational properties of Beta Cephei stars with TESS data that will supersede all related previous studies. Finally, individual stars with the most interesting pulsation spectra shall be subjected to ground-based 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. Given the expected workload, this project can be shared, with different aspects, between two students.
Subject: Spectroscopy of symbiotic binary systems
Advisor: Prof. Joanna Mikołajewska (firstname.lastname@example.org)
Co-Advisor: Dr Cezary Gałan (email@example.com)
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) as well as possible new observations (especially using ESO telescopes and SALT). In particular, the project will include:
Subject: Relativistic astrophysics
Advisor: Prof. Włodek Kluźniak (firstname.lastname@example.org)
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. The student working on radiative MHD simulations is expected to visit Harvard University and/or MIT (Massachusetts Institute of Technology) to collaborate with Professor Ramesh Narayan and Dr. Aleksander Sądowski.
Subject: Understanding super-Eddington accretion flows
Advisor: Prof. Marek Abramowicz (email@example.com)
Analytical, semi-analytical and numerical models of accretion disk at extremely high accretion rates ("hyperaccretion") around black holes will be studied. Collimation and energetics of jets emerging from these structures, their stability, and their astrophysical origin will be particular issues of interest.
Analytical models will be based on a further improvement of the most recent versions of standard "thick" and "slim" accretion disk models developed in Warsaw and Harvard (Wielgus et al. 2015, Sądowski et al. 2015).
Numerical studies will be using the general relativistic radiation magnetohydrodynamical (GRRMHD) code KORAL developed at Harvard and MIT (Sądowski et al. 2013, 2014), which evolves gas and magnetic fields in the ideal MHD approximation, together with the radiation field under the so-called M1 closure scheme.
The observational motivations for this work is explaining the Ultra Luminous X-ray sources, in particular the nature of the accreting compact object.
Subject: Cataclysmic variables in globular clusters: confronting theory with observations
Advisors: Dr hab. Arkadiusz Olech (firstname.lastname@example.org)
Dr hab. Mirosław Giersz (email@example.com)
There are less than 20 confirmed cataclysmic variable stars (CVs) in globular clusters (GCs). This is surprisingly low number taking into account theoretical models which suggest that we should expect several tens or even houndreds of such objects. However recent simulations indicate that majority of CVs in GCs should be below period gap. Moreover almost all of them are faint and inactive period bouncers. Low number of observed CVs belonging to GCs might be then a selection effect casued by inadequate observing strategies or using too small telescopes.
The main tasks of the PhD student would be:
Polish presence in ESO and the resulting access to the world largest telescopes creates new opportunities for this type project and give us the chance to work with the best equipment.
Subject: Analysis and theoretical interpretation of ground and space-based observations of classical pulsators
Advisor: Prof. Paweł Moskalik (firstname.lastname@example.org)
Co-Advisor: Dr Radosław Smolec (email@example.com)
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: Energetics and magnetization of jets in quasars and radio galaxies
Advisor: Prof. Marek Sikora (firstname.lastname@example.org)
In many Active Galactic Nuclei (AGN) accretion of matter onto black hole is accompanied by production of narrow streams of matter called 'jets'. These jets are often relativistic and reach powers comparable to the accretion power. Their launching via Blandford-Znajek mechanism must involve fast rotating black holes and so strong magnetic fields that they may dynamically dominate over innermost portions of the accretion flow. This challenges the standard accretion disk models and supports the magnetically-arrested-disk scenario. The main purpose of the project is to verify consistency of such a scenario by studies of the jet energetics and magnetization at different distances from the black hole.
Subject: Kinetic simulations of relativistic magnetic reconnection
Advisor: Prof. Marek Sikora (email@example.com)
Co-Advisor: Dr Krzysztof Nalewajko (firstname.lastname@example.org)
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-cell’ 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 Dr. Dmitri Uzdensky, University of Colorado Boulder, USA; prof. Roger Blandford, Stanford University, USA; Dr Benoit Cerutti, CNRS Grenoble, France).
Subject: Formation and evolution of spiral arms in interacting galaxies
Advisor: Prof. Ewa Łokas (email@example.com)
The origin of spiral structure in galaxies is still an open question. One of the mechanisms that may lead to the formation of spiral arms involves tidal interactions of galaxies in groups and clusters. The PhD student will analyse and interpret existing and perform new N-body simulations of such interactions. The first project will concern the properties of spiral arms forming in massive disk galaxies evolving on different orbits in a galaxy cluster. Next, the student will work on modeling of spiral arms in galaxy M33 and investigating the effect of its interaction with M31 on the structure of the arms. The modeling methods developed will then be applied to other galaxy systems.
Subject: High-energy astrophysics of pulsars and their dissipative winds
Advisor: Prof. Bronisław Rudak (firstname.lastname@example.org)
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: Modeling outflows from evolutionarily advanced stars in three dimensions
Advisor: Prof. Ryszard Szczerba (email@example.com)
Co-Advisor: Dr Mirosław Schmidt (firstname.lastname@example.org)
Mass loss from evolutionarily advanced stars (on asymptotic branch giants or just behind) or massive ones (red supergiants, yellow hypergiants) leads to the formation of large molecular dusty envelopes. The development of observational techniques now allow for observations of circumstellar matter with high spatial resolution (eg. ALMA, the VLTI, etc). Observations in recent years have detected the presence of complex structures in the ejected envelopes, in particular, the presence of spiral or concentric rings and the appearance of streams / jets. Reason for appearance of these structures is one of the unsolved and pressing problems of stellar astrophysics.
The successful candidate will be involved in modeling, using existing numerical codes (SHAPE SHAPEMOL, LIME, etc), of recent observations in both continuum as well as in molecular lines. Recovering spatial distribution and kinematics of circumstellar matter should help in understanding the reasons for deviations from spherical symmetry. The candidate must demonstrate the ability and passion in programming and interest in stellar astrophysics. Prospective candidates are kindly requested to contact with Prof. R. Szczerba (email@example.com) or Dr. M. Schmidt (firstname.lastname@example.org).
Subject: Accretion in X-ray binaries
Advisor: Prof. Andrzej Zdziarski (email@example.com)
The physics of accretion in stellar binary systems containing a black hole or a neutron star still remains far from full understanding. In the case of black-hole binaries in particular, the location of the bulk of the X-ray emission remains unknown and is currently a subject of an intense controversy. Some current models place it on the rotation axis of the black hole and very close to the horizon, sometimes closer than one gravitational radius. On the other hand, another paradigm places the X-ray source within a hot flow, in which most of the gravitational energy is dissipated at about ten or more of gravitational radii. The subject of the thesis, being a part of a large project financed by an NCN grant, will be to resolve this controversy by performing theoretical modelling, analysing available observational data, and applying the model to the data. Another potential research subject is studying the relationship between the accretion flow and jets, symmetric twin ejecta of collimated matter. Here, the role of the black-hole spin vs. that of the accretion disc is debated. Yet another potential topic is studying differences in accretion flows in binaries containing either weakly magnetized neutron stars or black holes.
Subject: Neutron stars - observational constraints on dense matter theory
Advisor: Prof. Leszek Zdunik (firstname.lastname@example.org)
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: Gravitational wave data analysis and the physics of neutron stars
Advisor: Dr hab. Michał Bejger (email@example.com)
Recent first direct gravitational-wave detection opens a completely new 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 and rotating neutron stars are instabilities related to them. The potential for fundamental new discoveries in this field is substantial.
The topic of the PhD study project is the design and implementation of data analysis algorithms for gravitational wave detectors (in collaboration with the Polish Virgo group, member of the LIGO-Virgo collaboration), development of computational methods using massive parallelization in large clusters' and the grid environment (MPI and hardware acceleration with GPUs), and construction of realistic theoretical models of neutron stars, to compare the with current and future observations (like proposed Athena satellite) in order to put constrains on the very dense matter equation of state (in collaboration with CAMK neutron-star group).
Subject: Pulsar Astrophysics
Advisor: Dr hab. Jarosław Dyks (firstname.lastname@example.org)
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: Numerical simulations of star cluster evolution – “observational” analysis of the database of numerical simulations
Advisor: Dr hab. Mirosław Giersz (email@example.com)
Globular clusters are among the oldest and most structurally simple objects in the Milky Way. Unfortunately, their simple structure does not mean that they can be easily numerically modeled. Close, mutual, gravitational interactions between stars, star collisions, stellar and binary evolution, the galactic tidal field are only a fraction of physical processes which have to be considered in the numerical simulations of cluster evolution. The dynamical MOCCA code, is developed in the Nicolaus Copernicus Astronomical Center and is one of the best codes for star cluster evolution in the world. The code is able to simulate evolution of real star cluster on levels of precision and detail comparable to N-body codes, but much faster.
Tasks to be performed:
Subject: Superfluid neutron stars
Advisor: Dr hab. Michał Bejger (firstname.lastname@example.org)
Co-Advisor: Dr Brynmore Haskell (email@example.com)
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 the theoretical and computational study of superfluid neutron stars, with the goal of developing a spectral superfluid hydrodynamics code. This code will be used to interpret two particular astrophysical observations: ‚glitches’, or jumps in frequency, that appear in radio observations of magnetised neutron stars, and gravitational wave observations of neutron star modes of oscillation, i.e. neutron star asteroseismology.
Subject: Observational and instrumental astrophysics with a global network of robotic telescopes
Advisor: Prof. Maciej Konacki (firstname.lastname@example.org)
Thanks to the funding from the European Research Council ("Ideas" funding scheme, 1.5 mln Euro), FNP (FOCUS grant), MNiSW (supporting grant) and NCN (research grant) totaling over 2.5 million Euro, we have established a network of robotic telescopes (four 0.5-m telescopes - Australia, South Africa and Argentina). Project web page: Project Solaris. We are looking for a grad student who would enhance our group. Preference will be given to an astronomer with programing or technical skills or having interest in observational astronomy. However anyone is encouraged to apply.
Subject: Hot Universe in X-rays
Advisor: Dr hab. Agata Różańska (email@example.com)
The goal of this PhD is the research on different aspects of X-ray radiation for the future ATHENA mission. Almost half of the observed matter in the Universe is in the form of the hot gas with a temperature of millions of degrees. The hot matter is locked in the centers of galaxy clusters, it surrounds galaxies and their active nuclei, and it is located in the vicinity of black holes, the best example is the one in our Galaxy - SgrA*. Most of the hot gas is outflowing from the centers of galaxies in the form of hot, ionized winds, which nature is not fully understood. On Nov. 2013, a new generation X-ray telescope ATHENA (the Advanced Telescope for High Energy Astrophysics) was approved by European Space Agency as a large mission with a launch foreseen in 2028. In our research group we compute advanced numerical models of X-ray emission from AGH and galactic black hole binaries. The PhD student will be involved in making end to end simulations of modeled signal for ATHENA detectors. As a result, we will upgrade our model parameters to provide the best theoretical predictions for future observations. During the PhD, we plane to work with X-ray data from currently working missions and make activities in the ATHENA consortium.