Four PhD positions in Astrophysics
Applications are invited for four PhD positions at the Department of Astrophysics of the Radboud University Nijmegen, funded through the NOVA research school for astronomy.
Positions are available in the areas of (see below for details):
1) Modeling mass transfer in binary stars
2) Fundamental interactions and physics of energetic cosmic rays in the Galaxy
3) Interstellar medium of the Milky Way
4) Spectroscopy of extragalactic star clusters
Applications, consisting of a letter of interest and an extended CV should be submitted by e-mail (email@example.com), including the details of two possible references. Candidates with a preference for one or two of the positions above are advised to indicate this in their letter.
Candidate selection will commence on December 15, with interviews scheduled in early 2014.
The successful candidate will be integrated into the Department of Astrophysics, which is part of the Institute of Mathematics, Astrophysics and Particle Physics. The vibrant department consists of 13 faculty, ~10 postdocs, ~30 PhD students. Current research activities are concentrated in the fields of supermassive and stellar mass black holes, jets, compact binaries, optical and radio transients, gravitational-wave and radio astronomy, stellar and binary evolution, stellar clusters, Galactic structure and magnetic fields, cosmic-rays and astroparticle physics, and asteroseismology. The department is part of the Netherlands Research School for Astronomy (NOVA), and has access to major (inter)national research facilities (ESO, ESA, LOFAR/WSRT, ING telescopes, etc.) as well as to major compute facilities, either via a local cluster or national supercomputing facilities. It is located in the student town of Nijmegen, an old (Roman) city, well connected by road and rail to the rest of the Netherlands.
PhD positions in the Netherlands are for four years and include good medical and social benefits (including maternity and paternity leave and child care) plus holiday and end-of-year allowances. Salaries start at 2062 Euro gross/per month, excluding secondary benefits.
Submission Address for Resumes/CVs: firstname.lastname@example.org, to the attention of Prof.dr. P.J. Groot, Head of Department.
Mass transfer is crucial to our understanding of binary systems with compact objects. It drives the accretion process observed e.g. in X-ray binaries and cataclysmic variables, as well as the formation and evolution of these and other compact-object binaries. It also plays a pivotal role in many progenitor channels for Type Ia supernovae. The theory of mass transfer is well developed for circular orbits, but observations reveal that many binaries retain (or obtain) an eccentric orbit after a phase of mass transfer. This PhD project aims to improve our quantitative understanding of mass transfer in eccentric binaries by a combination of Roche-lobe overflow and stellar winds. The student will perform detailed simulations using the AMUSE software framework, which combines hydrodynamics, radiative transfer and stellar evolution, and compare the results to observed binary systems. The following questions can be addressed: How efficiently is mass accreted by the companion star, and how does this depend or the orbital parameters of the system? What is the geometry and structure of the circumstellar material formed by the mass that leaves the system? What are the long-term effects on the orbital evolution of the binary system, e.g. under what circumstances does the orbit shrink or expand, and can the eccentricity grow?
The most energetic cosmic rays probably come from outside our Galaxy. However, before they reach detectors on Earth they traverse part of the Galaxy, and can be deflected by the Galactic magnetic field, or interact with interstellar gas and radiation. This PhD project looks at these interactions from a theoretical point of view, and aims to model them using both analytic theory and simulations. The aim is to make firm predictions about the influence of propagation in the Galaxy on the observed signal in large-scale cosmic ray detectors like AUGER. Nijmegen is a member of the AUGER collaboration. We will focus on the influence of the particle energy, charge and mass as the present data still do not allow us to firmly determine the precise chemical composition of these energetic cosmic rays.
The Interstellar Medium of the Milky Way forms a complex ecosystem with many components in interaction: gas is dynamically coupled to magnetic fields, which are closely tied to cosmic ray electrons that emit the ubiquitous Galactic synchrotron radiation. The goal of this PhD research project is mapping the galactic cosmic ray distribution through different channels. Firstly, we will use the new low-frequency radio interferometer LOFAR to study HII regions at low radio frequencies. Their absorption characteristics will allow determining the synchrotron distribution, which can be translated into the cosmic ray distribution in the Galaxy. Secondly, cosmic ray electrons emit in the soft gamma-ray regime. Soft gamma-ray observations can thus give an independent estimation of the cosmic ray distribution. This research is part of a larger project named “LOFAR Imaging of the Galactic Plane” and will include close collaboration with other members in that project, as well as interaction with the broader LOFAR community.
The chemical composition of stellar populations in galaxies provides crucial constraints on their evolutionary histories. Iron-peak elements are mainly produced in Type Ia supernova on relatively long time scales, while alpha-elements (oxygen, magnesium, calcium, etc) are produced on shorter time scales in Type II Supernovae. The relative abundances of these and other elements therefore contain important information on the star formation histories of the parent galaxies. However, until now, the Milky Way has been the only (large) galaxy where it is possible to study chemical evolution in detail. Are other spiral galaxies (chemically) similar to the Milky Way? We simply don't know! This situation is now changing, thanks to instruments such as X-Shooter that make it possible to obtain high-quality spectra of stellar populations well beyond the Local Group, in particular for stellar clusters. In this project, the successful candidate will analyse X-Shooter spectra of stellar clusters in several nearby galaxies and carry out a detailed chemical abundance analysis. The measurements will be compared with data for chemical abundances in Milky Way and other Local Group galaxies.