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PhD Projects 2004

Pulsars provide the nearest thing to a physicist's dream come true. Being the end-point of stellar evolution, they are densest bodies next to black holes and give us an insight into the most extreme physical conditions of matter density, pressure and magnetic field observable by man. They also provide the most precise clocks known to humankind for undertaking unique experiments of gravitation and general relativity. Furthermore, they can be used as probes of the distribution of ionised material and magnetic field in the Galaxy with a precision which nothing else can. We use the telescopes at Jodrell Bank, Parkes (Australia) and Arecibo (Puerto Rico) in this work and frequently travel to the foreign instruments to make observations. The pulsar group at Jodrell Bank are arguably the most productive in the world in this area and have discovered more than three-quarters of the known population of these elusive and fascinating objects.

There are several main active areas of research in the general area of pulsar astronomy which would support projects which would be ideal for students, starting in September 2004. We outline each of these areas below.

Searching for Extreme Binaries

The most exciting pulsars to be discovered are arguably pulsars in very tight compact orbits around massive companions. Such systems are the ideal - and only - test-bed to study gravitational physics in the strong field limit. Most of the current pulsar search strategies have difficulties in finding such binary systems with large orbital accelerations. In fact, the search codes usually assume that the pulse period is constant during the observing time, while in practice it may be doppler-shifted by a rapidly varying amount for a fast binary pulsar. Only so-called acceleration searches are able to search for an unknown orbital acceleration. These algorithms are computationally costly and are hence rarely done, but the systems that they find are likely to be most extreme and test the very frontiers of relativistic dynamics and the physics of gravitation. The figures below show the effects of acceleration on the detected pulse shape without correction (left) and with correction applied (right).

Nevertheless, recently we have made significant progress in the analysis of the data of our Parkes Multibeam Survey which has lead to the discovery of some very exciting binary systems. We want to continue this success story by developing and exploring new algorithm that can be applied to the data to find even more exotic object in the data. Hence, the student working on this project will get involved in this most successful pulsar search in history and will have chance to search for the most extreme binary systems existing.

Please contact Andrew Lyne (, Michael Kramer ( or Dunc Lorimer ( for further details.

The Galactic Pulsar Population

The Parkes Multibeam pulsar survey led by Jodrell Bank's pulsar group in collaboration with the ATNF in Australia has been the most successful survey in pulsar history. Just completed, it is a sensitive survey of a 10 deg-wide strip of the Galactic plane from Galactic longitude l=260 deg to l=50 deg. Using a 13-beam receiver on the 64-m Parkes radio telescope in Australia, it has already discovered about 700 new pulsars. We expect that after processing of all data that this one survey will finally have found as many pulsars as all previous pulsar surveys put together (see red points in figure below). Obviously, the newly discovered pulsars form an extremely valuable sample for studies of Galactic population of pulsars.

The observed population is biased by certain selection effects and does not necessarily represent the true population of pulsars in the Galaxy. However, by modelling the well-known selection effects, the salient properties of the underlying population (distribution in space, spin period, magnetic fields, luminosities etc) can be determined, allowing important conclusions relevant for the population and evolution of massive stars. This project would be ideal for a student with a good background in programming, and an interest in statistical methods in astronomy.

Please contact Dunc Lorimer ( or Michael Kramer ( for further details.

A new class of radio pulsars

The pulsar group at Jodrell Bank performs the world's most important timing program, monitoring a large number of known radio pulsars. Among the monitored sources is a seemingly ordinary pulsar which, after a close study, was recognized to be something very special: Unlike normal pulsars, this strange source is not visible for a substantial fraction of the time. It can disappear from one moment to the next, making it a very elusive object to observe.

An analysis of our data spanning many years shows that the pulsar is usually ``on'' for typically 3 to 10 days or so, followed by an ``off''-period of about 30 days. Moreover, most interestingly, these sequences appear in a quasi-periodical fashion (see figure below where "on" phases are marked in red). A spectral analysis of our data reveals significant periodicities at 30 and 40 days. In summary, we now know one pulsar which is not visible for a significant fraction of time, lasting weeks, but shows outbursts of emission in a seemingly regular fashion.

It is not clear as to what causes this phenomenon, whether it is caused by precession of the pulsar, whether some debris around the pulsar causes some physical interaction with the magnetosphere, or whether it is intrinsic to the emission process. The time-scales are not compatible with anything that has been studied before. Clearly, this interesting source represents a new class of pulsars.

In order to understand what is happening, we clearly need to identify more pulsars which demonstrate this phenomenon. Other sources may have a similar behaviour on different time-scales, and identifying other properties which might occur, then perhaps allows us to separate these otherwise normal pulsars from the rest. With more than 700 new pulsars discovered in the Parkes Multi-beam Survey, the number of known pulsars has increased to over 1500, and it is most likely that some of these newly discovered pulsars also exhibit similar properties. Indeed, we have identified further possible candidates, which we have started to study with the Parkes radio telescope in Australia.

In this project, the student would study this class of new radio pulsars. The aim is to identify new sources, to determine the occurring time-scales, and to explore the possible origins of the unexplained phenomenon. Significant contributions to this project can be made within an MSc thesis but the scope of the addressed question also leaves plenty of room to extend the research on the level of a PhD thesis.

Please contact Andrew Lyne ( or Michael Kramer ( for further details.

Multi-wavelength studies of a massive binary pulsar

One of the most exciting discoveries from the Parkes Multibeam Pulsar Survey is pulsar J1638-4725. This pulsar appears to be in a binary system with a long orbital period and high-mass stellar companion. We detect large changes in the dispersion measure and amount of scattering towards this pulsar as its radio pulses interact with the mass outflow from its companion, likely a Be star. This interaction is so severe that, at periastron, the pulses are undetectable at low frequencies, making this only the second known eclipsing binary system of this kind.

Multiwavelength study of this system will provide unique insights into the interaction of the pulsar with the Be star wind and into the compositions and kinematics of these winds and the geometry of the binary system. A student taking up this project would have the opportunity to analyze multiwavelength observational data and also develop theoretical models for the binary interaction. The student would begin by inspecting existing radio data on this pulsar, characterizing the DM and scattering changes and attempting to fit for an orbit that will explain these changes. Fitting for binary orbital parameters is essential for determining fundamental pulsar properites such as spin-down rate and position.

If the student would like to continue with this work after one year, he/she can become involved in the dense observations we plan to make around the periastron of this system, occurring roughly one year from now. These observations will utilize a new state-of-the-art receiver at the Parkes telescope in Australia. This receiver is capable of sensitive observations at the high radio frequencies needed to combat the extreme scattering at periastron. We also plan to study to X-ray emission from this system. Near periastron, we expect copious X-rays emission from the shock-powered emission produced as the relativistic pulsar wind interacts with the stellar outflow. This project would provide a student with a broad yet detailed introduction to both multiwavelength observational work and theoretical modeling and interpretation.

Please contact Andrew Lyne ( or Maura McLaughlin ( for further details.

Probing the Interstellar Medium using Pulsars

The interstellar medium is not uniform but shows a small degree of clumpiness in its contents of free electron. These density fluctuations responsible for scintillation and scattering of radio signals propagating through the interstellar medium (ISM). Scattering of pulsar signals causes the signal to arrive from different, multiple ray paths with different geometric lengths leading to a temporal broadening of the pulse shape commonly known as the scatter broadening time. Further, along different ray paths the radiation acquires random phases which cause interference in the plane of the observer to produce diffraction patterns which are easily observable as intensity variations.

These effects are a strong function of frequency, which allows to determine the physical quantities involved in direction of a given pulsar. Using multi-frequency observations made with the Parkes radio telescope and the Giant Metrewave Radio Telescope (GMRT) in India (shown on the right), the student working on this project would determine the scattering parameters and produce a model of (enhanced) scattering regions in the Galaxy to explore the still not-well known turbulence spectrum of the interstellar medium. Understanding the turbulence towards different directions of the Milky Way is very important when studying and modelling the observed population of radio pulsars. Only with a correct model of the ISM can we attempt to understand how pulsars are born and distributed in the Galaxy and can make predictions for future surveys of the sky.

With the already available data significant contributions to this project can be within a MSc project. The scope of the addressed scientific question would allow to extend this project to a PhD thesis.

Please contact Michael Kramer ( or Maura McLaughlin ( for further details.

Towards a pulsar virtual observatory - an e-science studentship

PPARC e-Science Studentship (Available October 2004) Department: Department of Physics and Astronomy: University of Manchester (in collaboration with eScience NorthWest (ESNW)) Principal Supervisor: Professor Andrew Lyne (JBO), co-supervisor: Dr John Brooke (Department of Computer Science)

Overview and required skills

This studentship, available at the University of Manchester from October 2004, is one of the PPARC e- Science studentships announced under Phase 2 of the PPARC eScience programme. The studentship will be held in the Department of Physics and Astronomy but with close collaboration with the Department of Computer Science. The successful applicant will have gained or expect to gain a 1st class (or good 2.1) degree in a subject such as computer science or a numerate discipline (e.g. physics or mathematics) that includes exposure to modern object-oriented computer languages (e.g. Java, C++). Consideration will also be given to other relevant qualifications, for example a relevant Masters qualification in Computer Science or Computation. The studentship will provide tuition fees and stipend for maintenance for UK-based students.

Description of Project: "Workflow Requirements in Virtual Observatory Applications"

The topic of scientific workflows is attracting great interest in the UK e-Science programme. Some examples of workflows used in physics are Chimera used in high-energy physics applications and Triana used in the analysis of gravitational waves and signals from pulsars. Examples from other disciplines include prominent applications in bioinformatics. These workflows need to be enacted on multiple resources providing computing processing power, data storage, network bandwidth. The project workplan will be to analyse such workflows in the context of applications related to Virtual Observatories so that the amount of resources at all points in the workflow can be predicted from knowledge of the amounts of data or rates of dataflow which will be processed in the workflow. This assessment of resource needs will then be passed to agents such as resource brokers that can reserve the required resources ahead of the time at which they are needed. The workflows to be examined will be based on the creation of a Pulsar Virtual Observatory permitting the integration of high-resolution multi-channel time series covering a large area of the radio sky. This will enable such data to be integrated with the AstroGrid VO framework since it will permit users who are not specialists in pulsar data analysis to access the data via selecting workflows for appropriate purposes. This generalises to other time based data that can be linked to deep sky fields, in a manner that reuses key components from AstroGrid and GridPP. The workflow analysis will be centred predominantly around Triana, since this is already used in the PPARC e-Science programme and in European work on gravitational wave analysis via the EU GridLab project (it is also being assessed by US-based projects). Contacts with the Grid1D project indicate that the signal analysis methods of gravitational waves and pulsar signals are fundamentally similar and Triana can be applied to both. However the methodology of analysing a workflow by its needs for computational power, memory, secondary storage, and networking bandwidth requirements of each component of the workflow generalises to other workflow engines. Until now AstroGrid applications have not faced the problem of resource availability. The pulsar data is an excellent template for such analysis since it involves requirements for heavy computational processing in multiple stages.

PhD Training

The Pulsar Virtual Observatory applications will provide PPARC e-Science aspects of training given by staff at Jodrell Bank Observatory; ESNW support at the Department of Computer Science and Manchester Computing will provide exposure to modern computing languages, software engineering techniques, advanced computational science and networking. There will also be opportunity for the student to conduct some astronomical research on pulsars if they feel so inclined. See the following links for more details: Jodrell Bank Pulsar group and ESNW.

Further Information

For further information, or informal discussions about the studentship, please contact Professor Lyne or Dr Brooke at the email addresses at the top of the page, or via telephone 0161-275-6814 (Dr Brooke) 01477-571321 (Professor Lyne).
Last updated Thu Oct 28 18:46:48 BST 2004