PhD Level

Armagh Observatory is known world-over as a leader in the field of astronomical research; we welcome PhD Candidates every year.

Note: Applications for 2020 are now closed.

Candidate Information

Application Form

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About Armagh

Contribute to the growing wealth of astronomical research

PhD Application Information

Applications are invited for a 3.5 year postgraduate research studentship(s) tenable at Armagh Observatory & Planetarium from Oct 2020. Armagh Observatory, located in Northern Ireland, UK, is an astrophysical research institute founded in 1789. It has 8 staff astronomers, 2 post-doctoral fellows, a dozen PhD students and several visiting astronomers. Research interests include Solar Physics, Solar-System Science, Stellar, Galactic and Extra-galactic Astrophysics.

Candidates must have, or expect to obtain, at least an upper second class honours degree or equivalent, in an appropriate discipline (e.g. Physics, Mathematics, Astronomy or Astrophysics). Successful candidates will enroll at an appropriate university and carry out a research programme at the Armagh Observatory & Planetarium. Applications are encouraged from candidates of any nationality although eligibility may depend on funding source. The successful applicant(s) would receive a grant based on the United Kingdom Science and Technology Facilities Council rate (2019/20: £14,777 per annum). In addition, we would fully fund the university fees. Prospective candidates should fill in the application form available from this web site and ensure that their references are received by the administrator before the deadline.

First selection will take place as soon as possible after 15th May 2020. Presently, only STFC positions are available for UK residents (see eligibility requirements). The application form, CV and other supporting documents should be sent to the administrator (hr@armagh.ac.uk).

If potential applicants have questions they can be sent to the administrator or the potential supervisor for the project which are listed on our web site.

Current Research Projects

Time Domain Astrophysics

STFC, UK residents

Supervisor: Dr Gavin Ramsay

As one famous astronomer once said, if you monitor the brightness of a star with sufficient precision for a sufficently long time, every star
is 'variable'. I have been studying variable stars for many years and use the brightness information to investigate the properties of accretion discs around compact binary systems; how flare originate on
low mass stars; how frequent are flares from solar-type stars; search for activity cycles on stars and identify new explosive 'transient' sources from survey data.

 

A number of potential science projects are available but are expected to partly use data from the Gravitational-wave Optical Transient Observer (GOTO). This survey is an international project which Armagh is a founder partner and aims to detect the optical counterpart of gravitational wave events detected by the Advanced Ligo and Virgo detectors. Other projects could use data from the TESS satellite which is currently surveying the entire sky and providing a unique opportunity to study stellar variability.

These projects would suit someone interested in observational astronomy and ideally someone with experience of computing. languages. It is expected there would be opportunities for travelling to La Palma, Australia or South Africa to help commission new GOTO nodes or help make detailed observations of objects discovered in these surveys.

For further information contact: gavin.ramsay@armagh.ac.uk

Magnetic Fields of Degenerate Stars

STFC, UK residents

Supervisor: Stefano Bagnulo

White dwarfs (WDs) are the end point of 90% of stellar evolution. 15–20% of such stars possess strong magnetic fields. The fields range over five dex in strength, from below ten kG (one Tesla) up to about 1000 MG. The fields are roughly dipolar, and show no evidence of rapid secular changes. They seem to be “fossil fields”, produced in earlier evolution that evolve slowly by ohmic decay. At present, there is no single firmly established theoretical scenario that explains how prior evolution through the red giant and AGB phases can leave strong surface fossil magnetic fields in a significant fraction of WDs. Possibilities include retaining fields from earlier evolutionary phases, or field generation during binary mergers.

 

Using various facilities at the Very Large Telescope, at the Canada-France-Hawaii Telescope, and at the William Heschel Telescope, Armagh astronomers are performing a large survey of magnetic WDs in the vicinity of our solar system, with the goal to understand if and how magnetic fields evolve with time, and if they are correlated to other features of the stellar atmospheric chemistry, mass, and age. A PhD project is offered to help to obtain observational constraints that will be used to understand the origin of magnetic fields in WDs.

The student will learn how to use spectro-polarimetric techniques to detected and model stellar magnetic fields. She or he will help with the preparation of proposal for telescope time, with the execution and analysis of the observations, with the search for correlation between magnetic fields and other stellar parameters, and with the modelling of time series of polarised spectra and of surface magnetic field structure of of WDs. The project will be more theoretically or observationally oriented according to the preference and skills of the student.

For further information contact stefano.bagnulo@armagh.ac.uk

Nucleosynthesis and Hydrodynamics in Stellar Collisions

STFC, UK residents

Supervisor: Simon Jeffery

In 2016 LIGO observed the first double black hole collision, proving Einstein's prediction of gravitational wave radiation (GWR). Compact double star systems contain black holes, neutron stars or white dwarfs. Their orbit decay by emission of GWR until the components merge, often with an explosion. When two helium white dwarfs merge, a new star is formed, helium-burning is ignited in the collision, and new elements are created. Nuclear debris on the surface of the new star reveals this violent history, whilst pulsation and rapid evolution provide other clues. 

Artist's illustration shows three steps in the merger of a pair of white dwarf stars. 
Credit: Dana Berry, ST ScI Astronomy Visualization Laboratory

This project offers opportunities to explore nucleosynthesis in the highly dynamic regions of a double white dwarf collision (the ring of fire), to simulate the subsequent stellar evolution, to analyse the nuclear debris on the surfaces of stars believed to have survived such a collision, and to explore the hydrodynamics of pulsations in their atmospheres. Applicants with interests in nuclear astrophysics, radiation hydrodynamics, stellar structure and evolution and/or stellar spectroscopy are especially encouraged.   

For further information contact simon.jeffery@armagh.ac.uk

Supermassive Black Holes with Molecular Gas

STFC, UK residents

Supervisor: Marc Sarzi

Supermassive black holes (SMBH) are now known to nearly ubiquitous at the centre of galaxies. The finding of relations between their mass and various galaxy properties imply a tight connection between the growth of SMBHs and that of galaxies. However, the number of reliable SMBH mass measurements is still relatively small, and the number of independent measuring methods is even smaller. In this project, a student would join the WISDOM team (mm-Wave Interferometric Survey of Dark Object Masses) of researchers that has
recently shown how the dense molecular gas of galaxies traces very close the circular velocities dictated by the gravitational potential around galactic nuclei (e.g. the Nature paper of Davis et al. 2013) thus allowing to infer much more accurate and easier measurements for the central SMBH mass.

HST image of NGC4526 with its molecular gas disk overlaid in violet.
The disk extends all the way to the center allowing to weight the central SMBH.
From Davis et al. (2013)

As part of the WISDOM team (mm-Wave Interferometric Survey of Dark Object Masses), the student will pursue a programme of SMBH mass measurements in a large sample of local galaxies spanning a range of morphological types, masses, and nuclear activities. There are thus much data in hand already, primarily from the ALMA observatory, and the tools necessary to model the velocity fields and estimate uncertainties have already been developed. With these data and machinery, the student will explore how SMBH masses and galaxy properties correlate, in addition to probing the nuclear-scale gas dynamics that allows SMBHs to be fed.

For further information contact marc.sarzi@armagh.ac.uk

The Heaviest Stars and Black Holes in the Universe

STFC, UK residents

Supervisor: Jorick Vink

Some few hundred million years after the Big Bang the universe lit-up by the formation of the First Stars, which are thought to have been very massive owing to their pristine chemistry.

Despite their key role in setting the stage for the subsequent Cosmic chemistry, we know surprisingly little about the evolution & fate of the first few stellar generations.

 

The goal of this computational PhD project is to predict the amount of the mass the first stellar generations lose through stellar winds, and to determine the final masses of these stars as Black Holes.

The predicted black hole masses will be compared to data from gravitational wave observatories.

For further information contact jorick.vink@armagh.ac.uk

Physical studies of asteroids with photometric and polarimetric techniques

STFC, UK residents

Supervisor: Stefano Bagnulo

We are carrying out an intensive observing campaign to acquire new photometric and polarimetric data for various objects of the solar system, from comets to asteroids, to giant planets. Observations will be obtained from major facilities such as the VLT and the WHT, as well as two small to mid-size facilities: the observing station of Calern (a facility of the Observatory of Nice, France) and the Rozhen Observatory in Bulgaria.

 

We are seeking a PhD student to join an international collaboration, involving researchers from Italy, France, Bulgaria (for the observations) and Finland (for the theoretical modelling). After a training period requiring a stay in Calern and in Rozhen, the student will take care of a large part of the observations and of data reduction, and will learn the basic principle of data modelling, with particular emphasis on the derivation of some important physical properties of the asteroids. This project will require observational activities partly on site, but mostly in remote mode, for typically a few weeks per year.

For further information contact stefano.bagnulo@armagh.ac.uk

What happens to asteroids in resonances?

STFC, UK residents

Supervisor: Dr Apostolos “Tolis” Christou

The AOP solar system group is carrying out frontline astronomical research in the origin and evolution of the solar system and its small bodies. Highlights include: the discovery that the tenuous atmosphere of Mercury is modulated by impacts with debris from periodic comet Encke (Christou, Killen et al, GRL, 2015); using the distant moons of the giant planets to time key events in early solar system evolution (Li and Christou, Astron. J., 2017); and constraining the production and loss of Mars Trojan asteroids by collisions and radiation forces (Christou et al, Icarus, 2017; Icarus, 2020). Our research is grant-aided by the UK Science and Technology Facilities Council (STFC).

Work done by our group (Christou, Icarus, 2013; Borisov et al, MNRAS, 2017; Christou et al, Icarus, 2020) shows that the Yarkovsky effect causes significant orbit changes or even escape for asteroids in the 1:1 resonance with Mars - the so-called Trojans - while the physical bodies themselves break apart due to YORP spin-up, creating clusters of resonant asteroids. Outcomes of YORP-induced disruption are observed elsewhere, as orbital clusters of Main Belt asteroids (Pravec et al, 2010) and the active shedding of material (eg (6478) Gault, Hui, M-T et al, MNRAS Lett., 2019) while correlations between asteroid orbits and sizes point to size-dependent orbit evolution (Bolin et al, Icarus, 2017; Dermott, Christou et al, Nature Astronomy, 2018).

 

 

In this project we want to quantify resonant asteroid orbit and/or spin evolution under non-gravitational forces, applying our findings to different settings, make predictions and interpret observations. Breaking up of resonant or co-orbital asteroids near the Earth’s orbit may form compact orbital clusters (de la Fuente Marcos & de la Fuente Marcos, MNRAS Lett., 2019), contribute to debris structures observed at the orbits of the Earth (Dermott et al, Nature, 1994) or, more recently, Venus (Jones et al, Science, 2013; Pokorny & Kuchner, ApJ, 2019) and give rise to meteor showers. Outside the solar system, any debris co-orbital with close-in exoplanets would evolve significantly and rapidly, giving rise to features that may betray the presence of the planetary body.

The successful applicant will collaborate with Dr Christou in attacking this multi-faceted problem, with the scope and direction of the resulting PhD project depending primarily on the student's individual inclinations. Work methods will include, but are not necessarily limited to, intensive N-body numerical simulations. Some familiarity in the areas of dynamics, statistical methods or numerical analysis will be seen as an advantage.

For further information contact Apostolos.Christou@armagh.ac.uk

Off-limb line widths, Alfvén waves & ion-cyclotron heating

STFC, UK residents

Supervisor: Gerry Doyle

Background: What processes accelerate the fast solar wind and heat the solar corona?

To help answer this question, the measurement of spectral line widths off the solar limb can provide information concerning ion temperatures, sub-resolution turbulent motions and velocity fluctuations associated with magnetohydrodynamic waves in the corona. Ion-cyclotron absorption of high-frequency Alfvén waves is considered an important mechanism with regards to coronal heating and fast solar-wind acceleration. One of the limitations of current datasets is the large spatial binning (up to 5”) that is required in order to obtain good statistics for fitting the line profiles. Some of the emission contributing to these bins may come from warmer-than-average structures leading to significant ambiguity. To overcome this problem we will investigate observations from DKIST, a new 4m class solar telescope located in Hawaii, which commences science operations in the second half of 2020.

 

Credit: Solar Dynamics Observatory

DKIST can provide observations at higher spatial resolution with better statistics and may resolve some of these systematic issues regarding line width measurements. We plan to use the DL-NIRSP instrument to measure the line width of three coronal lines, Fe XIV 530.3 nm, Fe XI 789.2 nm, Fe XIII 1074.7 nm and Si X 1430.0 nm at the solar equator and at a northern coronal hole off-limb to ~0.3 solar radii. We also plan to use the atomic database ADAS to check on whether transient ionization is important for these coronal lines in the low density environment. In addition to DKIST, we plan to use data from Aditya-L1, an Indian solar mission due for launch in late 2020. One of the instruments on onboard is the Visible Emission Line Coronagraph which has a field of view of 1.05–3 solar radii and facilitates simultaneous multi-slit spectroscopy for three emission lines, viz. Fe XIV 530.3 nm, Fe XI 789.2 nm and Fe XIII 1074.7 nm.

As mentioned above, a number of mechanisms, including Alfven waves, have been shown to be consistent with such observations, however, we have not yet measured their relative contributions. Furthermore, these studies are mostly performed using space-based data at EUV wavelength range. A major short-comings at EUV wavelengths is that spectral lines are very narrow and in some cases instrumental broadening is comparable to the line width. The student will be based at Armagh Observatory & Planetarium, but enrolled at Northumbria University.

For further information contact gerry.doyle@armagh.ac.uk

Investigating the outflows of black hole progenitors in different galaxies

STFC, UK residents

Supervisor: Andreas Sander

Classical Wolf-Rayet (WR) stars are a rare, but important class of helium-burning stars. Their spectra are dominated by strong emission lines, indicating strong outflows. With mass-loss rates that are about ten times higher than those of O supergiants, just a few WR stars are enough to easily outweigh the feedback of a whole population of OB stars. Moreover, being the last long-lived stage before core collapse, helium-burning WR stars are inherently tied to our fundamental understanding of heavy black holes. The amount of mass lost by these stars defines the eventual black-hole masses but depends strongly with their metallicity environment and our understanding of how their mass loss is driven.

 

Credit: ESA/Hubble

This PhD project will combine observational and theoretical efforts to gain a better understanding of WR stars in different environments. To achieve this, the student will analyse WR stars in different galaxies with stellar atmosphere models, gaining first-hand experiences with a new generation of models that allow gaining direct insights on the driving of WR winds. Different treatments for wind physics in the derived model atmospheres will be investigated. By comparing observational data to the derived models, the project will not only yield descriptions of mass loss to constrain the nature of heavy black holes but provide fundamental theoretical insights on whether the nature of WR winds require different mechanisms in different environments.

For further information contact andreas.sander@armagh.ac.uk

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