Honours
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We are currently
accepting applications from suitably qualified students wishing to
undertake an Honours degree in the fields of Astrophysics or
Theoretical Physics. Applications for entry to the honours
year at the University of Tasmania for the 2006 Academic year close at
the end of October 2005, please check back later to see exactly when
applications are due. Below is a list of the projects we have to offer
for
2005/2006. Prospective students are encouraged to contact the
supervisor(s)
involved to obtain for information about the research component of the
program. Information on the requirements for honours can be found here.
Scholarships
The University of Tasmania offers 10 open scholarships valued at
$10,000 to the very best students commencing at the University. As only
10 are given across the entire university the competition is high for
these, however we encourage suitable applicants to apply. Further
information is available
here.
2005/2006
Honours Projects:
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Honours
Scholarships
UTas is offered two honours scholarships in Astrophysics for 2005. The
value of each scholarship was $4500 in addition to which $4000 would be
paid if the student relocated from another institution. There was one
scholarship for a project in Radio Astronomy and one for Optical
Astronomy. Details of what honours scholarships will be available
for students commencing in 2006 will be posted later in the year.
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Astrophysics
Theoretical Physics
 Propagation
of deformations along aperiodic biopolymers: |
Dr
Jim Bashford, Prof
Robert Delbourgo, Dr Peter Jarvis |
| Supersymmetric
quantum mechanics in Morse-like potentials?: |
Dr
Jim Bashford, Prof
Robert Delbourgo, Dr Peter Jarvis |
| Spin-charge
separation in 1-D metals. (Literature review topic): |
Dr
Jim Bashford, Prof
Robert Delbourgo, Dr Peter Jarvis |
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| Astrophysics |
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Kinematic
Analysis of the HR Supercluster: Dr Melanie. Johnston-Hollitt
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The
Horologium-Reticulum Supercluster (HRS) is one of the most massive
galaxy concentrations in the Southern sky. Dr Johnston-Hollitt is
working with a team of researchers from the US and Australia to study
the multi-wavelength properties of the HRS. In particular, under a
collaborative research effort involving Fleenor, Rose &
Christiansen (University of North Carolina), Hunstead (University of
Sydney) & Johnston-Hollitt (University of Tasmania) we are seeking
to evaluate the kinematics of the central part of the HRS around the
galaxy clusters A3125/A3128. We have an extensive existing
multi-frequency dataset for this region (optical, radio and X-ray) and
potential student projects include:
compuation of the radio luminosity function in the region and analysis
of the HRS structure through use of radial velocity measurements.
Students could also participate in new optical (spectroscopic) or radio
(ATCA) observation of the region as part of the on-going effort.
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Observing
Merging Southern Clusters of Galaxies: Dr Melanie Johnston-Hollitt
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Large-scale
structure in the Universe is thought to be assembled via accretion and
merging processes between clusters of galaxies. In some cases these
mergers appear violent and create shock waves on Mpc scales. These
shocks are thought to be responsible for the enigmatic phenomena
of Mpc-scaled "radio relics" which are seen in several clusters
(see the picture of A3667 to the right). In collaboration with Prof R.
W. Hunstead (Sydney) and Dr Corina Vogt (ASTRON) we are studying a
sample of Southern clusters containing these radio relics to try to
better understand their origin and generation. This project would
involved multi-frequency radio observations of several southern
clusters using the ATCA and associated analysis
Image: Abell 3667. The
coloured image shows hot
gas that lies between the galaxies. Yellow contour lines show the
regions of radio emission, produced by shock waves in the gas as two
clusters collided. (Radio data : Australia Telescope Compact Array,
wavelength 20 cm. X-ray data: ROSAT (PSPC). Composite image and
associated data belongs to Dr Melanie Johnston-Hollitt.)
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Magnetic
Fields in
Galaxy Clusters: Dr Melanie Johnston-Hollitt
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Galaxy clusters are
the largest coherent structures in the Universe and comprise of tens to
hundreds of galaxies embedded in hot (107K) thermal X-ray
emitting gas.
We know from direct observations that magentic fields exist in certain
parts of clusters (relics, halos, cold fronts) but there is current
debate in the literature about the strength of cluster-wide fields.
This project aims to add directly to our understanding of cluster
magnetic fields by examining the Faraday Rotation Measure of a sample
sources located behind clusters and superclusters. This is principally
a radio astronomy project and will make use of polarisation data
taken with the ATCA and possibly the VLA.
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Intraday
Variability of radio sources: Dr Simon Ellingsen
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The radio emission
from some distant quasars has been observed to vary on timescales of
hours to minutes. The brightness temperature implied from
light-travel arguments suggests that these variations cannot be
intrinsic to the source (the implied brightness temperature exceeds the
inverse Compton limit of 1012 K). This means that the
variations must be due to a propagation effect. For a number of
sources it has been proven that the variations are due to
scintillation. Stars viewed on Earth twinkle due to turbulence in
the Earth's atmosphere. Scintillation is a similar phenomena that
effects radio waves passing through interstellar space - variations in
the line of sight electron density produce destructive and constructive
interference and result in amplitude variations on Earth.
The timescale of scintillation induced amplitude variations depends
upon the speed at which the Earth is moving with respect to the screen
that introduces the phase variations. This velocity changes
throughout the year as the Earth moves around the Sun and produces an
annual cycle in the timescale. It is possible to use deviations
from the predicted annual cycle to determine information on the source
structure at microarcsecond resolution. This is approximately
10-100 times higher resolution than can be achieved using any
other technique at any wavelength.
The project would involve regular monitoring of a number of intraday
variable radio sources with the Mt Pleasant antenna to measure the
change in the characteristic timescale throughout the year. This
data would then be used to determine the annual cycle and deduce
properties of the source and the interstellar medium along the line of
sight to the source.
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Giant
Pulse Patrol: Professor John Dickey
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This project is to
search for pulses of exceptionally large amplitude from the Vela
pulsar. The Vela pulsar is monitored constantly by the 14m radio
telescope for pulse arrival times, but data is also collected on pulse
amplitudes. In addition, individual pulses can be detected with the 26m
telescope. By measuring the distribution of pulse strengths in thi and
other pulsars we can study the emission mechanism and find candidates
for giant pulses.
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Mapping
the Galactic plane: Professor John Dickey & Dr Simon Ellingsen
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Unlike optical
telescopes, individual radio telescopes cannot form an image simply by
pointing at a region of the sky. A radio telescope simply
measures the power level at that point in the sky. To form an
image the antenna must be scanned back and forth in order to measure
how the observed intensity changes with position. Since the
advent of interferometric arrays in the late 70's and early 80's single
antenna mapping has become increasingly rare. However, there have
been significant improvements in receiver and computing technology in
the same period, which make it possible to make much more sensitive
observations. In the same period there have been large advances
in high energy astronomy, but most X-ray and gamma-ray observations
have a resolutions no better than arc-minute scale, similar to that
achievable with single antenna radio mapping.
This project would involve the development of a continuum mapping
capability for the new Mt Pleasant antenna control and sampling
system. Once developed this system would be used for one or more
of a variety of interesting projects :
Mapping the Water
and Ammonia Emission of Cool Clouds: An example of a Galactic
plane mapping project is to tune the receiver and spectrometer to
detect spectral lines from the water or ammonia molecule. These are in
the frequency range 22 to 24 GHz. Starting from images produced by the
new Spitzer Space Telescope in the near infrared, we can determine
candidate regions of intense star formation in the innner Milky Way.
Very dense, cool interstellar cloud cores can be traced efficiently by
the ammonia molecule, and the velocity structure of the clouds obtained
from the Doppler shift of the spectral lines tells us about collapse
and rotation of the cloud.
Detection of
transient sources: By regularly mapping the inner Galactic Plane
it will be possible to search for transient radio sources, such as
microquasars and background extragalactic radio sources.
Image Processing:
Making a continuum image by raster scanning an antenna can take several
hours or longer. During this time the system gain will change due
to a variety of factors, including drifts in the receiver gain, changes
in the antenna efficiency with elevation. If not removed by image
processing or calibration this drift will severly limit the quality of
the images. One aspect of the project could be to study effectiveness
of different calibration and image processing techniques. There
are a large number of methods which could be evaluated, to the extent
that this could form the core of the project (depending upon the
interests of the student).
A study of extended
radio sources: By imaging a number of extended radio sources at
a number of different frequencies spectral index images can be
formed. These can be used to determine what the emission
mechanisms are in different parts of the source. Astrophysical
interpretation of these sources could also be aided by making
polarmetric images, and/or comparing the radio data with that from
X-ray and gamma-ray satellites.
Mapping of the
Galactic Plane: Recently the Parkes telescope has been used to
image large regions of the Galactic Plane at 2.4 GHz (for more
information see here).
It
is the most sensitive survey to date of the southern regions of our
Galaxy and detected many new and interesting features. The
resolution of the Mt Pleasant antenna at 6.7 GHz is well matched to
Parkes at 2.4 GHz. Mt Pleasant observations at 6.7 GHz would
provide vital information for interpreting some of the new and unusual
Galactic features discovered in the Parkes search.
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Variability
of Methanol Masers: Dr Simon Ellingsen
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An interstellar
maser (Microwave Amplification by Stimulated Emission of Radiation) is
a naturally occurring radio frequency laser. In some interstellar
gas clouds the physical conditions create a population inversion
between rotation levels in some molecules (the rotational energy of
molecules with a dipole moment is quantised). The geometry of the
methanol molecule means that it has hundreds of rotational transitions
in the frequency range 1-1000 GHz, and maser emission has been detected
from 15. The strongest transitions are at 6.7 and 12.2 GHz (the
6.7 GHz transition is the second strongest known masing transition from
any molecule).
Since its discovery in 1991 more than 400 6.7 GHz methanol masers have
been found, many of them using the Mt Pleasant antenna. High
resolution observations of the masing regions have shown that in some
cases the 6.7 and 12.2 GHz methanol maser arise from the same regions
within the gas cloud. This means that the same physical
conditions must be able to produce both masing transitions and this
information can be used to constrain theoretical models of the maser
pumping.
The aim of this project is to study the variability of a sample of 6.7
and 12.2 GHz methanol masers on time-scales of days-months. The
sample will mainly consist of sources which preliminary studies suggest
are likely to show marked variability. Observations will be made
using the Mt Pleasant antenna at each frequency approximately once per
fortnight for six months. Basic data processing will be performed
soon after the observations so that any sources which are undergoing
rapid variations can be identified and targeted for intensive
monitoring.
There is a lot of scope in the project for original research, topics
which could be investigated (depending upon the interests of the
student):
The shape of the
light curves:
 Are
there correlations between the light curves of different maser
features from the same source?
Are
there correlations between the light curves of the 6.7 and 12.2 GHz
masers toward the same source?
Can
the light curves be characterised (e.g. a sharp rise followed by an
exponential decay)?
Is
there any evidence for periodicity within the light curves?
Maser theory:
What
are the implications of the observed variability for proposed
pumping schemes?
What
is the nature of the variability, is intrinsic to the maser, or is
it extrinsic (a propagation effect)?
What
is the cause of the variability; is it due to disturbances
in the masing gas?
Do
the widths of the maser features show any variation with the line
intensity.
Statistics:
What
percentage of the maser features vary and what is the amplitude
and time-scale for the variations?
Are
the variations correlated with any other aspect of the masers, such
as their flux density, width etc?
Computational &
Calibration Techniques:
A
study of methods for calibrating the antenna between observation
epochs.
A
study of methods of obtaining power spectra of temporal variations
from unevenly sampled data (including wavelet analysis).
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3 cm ATCA
radio continuum image of the NGC6334F star formation region. The
location of the 6.7 GHz methanol masers are marked with blue crosses. (Ellingsen et al)
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Variability
of 22 GHz water masers: Dr Simon Ellingsen
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The 22 GHz
transition of water is the strongest and most variable of the maser
transitions and the Mt Pleasant telescope has a new sensitive receiver
capable of observing this transition. The 22 GHz water masers
transition is the most highly variable of all maser transitions and
large amplitude variations are frequently observed on timescales of
weeks or months.
The aim of this project is to study the variability of a sample of
water masers on time-scales of days-months. Observations will be
made using the Mt Pleasant antenna approximately once per week for six
months. Basic data processing will be performed soon after the
observations so that any sources which are undergoing rapid variations
can be identified and targeted for intensive monitoring. The
details of the sorts of analysis that could be undertaken with this
project are similar to those for the methanol variability project.
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Hydrodynamical
Modelling of HII regions: Dr Simon Ellingsen & Prof Larry Forbes
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High-mass stars form
deep within molecular clouds, which despite their name are largely made
of neutral hydrogen (HI). Once fusion commences in the core
of the forming star significant numbers of ultraviolet photons are
produce, these ionise the surrounding gas producing an HII
region. The dissociation of neutral hydrogen into an electron and
proton and the related heating of the ionise material means that it is
at a much higher pressure than the surrounding neutral material and so
rapidly expands. The rapid expansion means that compact HII
regions should be very short-lived and hence rare, however,
observations have found approximately an order of magnitude more of
these regions than expected for the current rate of high-mass star
formation in our Galaxy. This has come to be known as the
``lifetime problem'' for HII regions.
Over the last 15 years a number of mechanisms to extend the lifetime of
compact HII through various confinement mechanisms have been
proposed, however none have gained wide acceptance. As part of an
honours project in 2003 Stas Shabala investigated the lifetime problem
and found that modelling the parent molecular cloud with a hierarchical
density structure (a series of concentric spheres with density and
temperature decreasing with increasing radius) produced results that
agree well with observations. However, it also showed that the
expansion rate of the of HII regions is comparable to the sound
speed (which controlls the mixing). This means the assumption of
thorough mixing (implicit in the numerical modelling) is not valid and
hydrodynamical methods must be employed to accurately model the HII
region.
This project would involve building upon the earlier honours project by
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Implementing
a hydrodynamical model of the HII regions to see if they
produce compact cores surrounded by more diffuse gas as is
observed in many cases.
Implementing
more realistic initial conditions for the density
structure of the parent molecular cloud (power-law density gradients,
rather than constant density).
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Linear
methanol masers from shocks in rotating clouds: Dr Simon Ellingsen
& Prof
Larry Forbes
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High resolution
observations of 6.7 and 12.2 GHz methanol masers in star formation
regions have found that in many cases they show simple linear or curved
morphologies, sometimes with a monotonic velocity gradient. There
are three hypotheses as to why this might be the case :
The
masers form in edge-on disks.
The
masers form in outflows from the star forming region.
The
masers form in post-shock gas.
The first of these has been the most popular, however, there are a
number of problems with this hypothesis, in particular the common
association of methanol with OH masers which don't show the same simple
morphology. There is some observational evidence for an
association between methanol masers and shocks, however, the difficult
with shocks has been explaining the monotonic gradients. A recent
paper by Dodson, Ojha & Ellingsen (2004) suggests a solution to the
problem, with the methanol masers forming in shocks that propagate into
rotating clouds.
The aim of the project is to test the hypothesis of Dodson et al.,
modelling their scenario and determining if it can plausibly produce
maser emission. Topics for investigation would include :
What
types of shocks are consistent with the formation of methanol
masers (some types of shocks will dissociate the methanol)?
Is
the path length and velocity coherence in the rotating clump
sufficient to form bright masers?
What
effect does the angle of propagation of the shock with respect to
the line of sight have on the properties of the observed maser emission?
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Polarization
properties of masers: Dr Simon Ellingsen
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The intense emission
from strong methanol and water masers frequently
exhibits linear polarization at the level of a few - 10's of
percent. The polarization in the masers is produced by Zeeman
splitting in the magnetic field in the region where the masers
originate. Magnetic fields play an important role in many
astrophysical processes, including star and planetary formation,
however, they are frequently excluded from theoretical modelling due to
a lack of experimental information. Through observations of
masers it is possible to obtain information on magnetic field strength
and orientation at very high resolution and hence provide vital
information and constraints for theoretical models.
The Mt Pleasant and Ceduna telescopes now have state of the art
autocorrelation spectrometers which can form cross-product spectra and
can be used to determine the polarization characteristics of maser
spectra. Leith Godfrey, an honours student in 2003 has been
working on this project and the 2005 honours project would build upon
his achievements. The project would involve measuring the
polarization characteristics of a variety of maser sources and
transitions.
Some of the science questions which could be explored:
Do
the polarization characteristics of water masers vary depending upon
the astrophysical object they are associated with?
Does
the fractional polarization of methanol masers correlate with
their total intensity, or any other characteristic?
How
do the polarization characteristics of 6.7 and 12.2 GHz methanol
masers compare? Is the fractional linear polarization the same
for the two transitions?
How
does the variability of the polarized emission compare to that of
the total intensity spectra? Indications are that for strong
water masers the polarized component increases greatly during rapid
variation.
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A
search for new masers: Dr Simon Ellingsen
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Between 1993 and
1996 the Mt Pleasant antenna was used to search for 6.7 GHz methanol
maser emission toward selected regions of the Galactic Plane. In
total more than 50 square degrees of sky were searched and more than
120 masers detected, approximately half of these being new
detections. There is little to distinguish the newly detected
methanol masers from those which were already known, with the exception
that they on average have a slightly weaker peak flux density.
Searches of catalogues of other astronomical objects show that while
some are associated with known star formation regions, many are not
associated with any other known astrophysical object.
There are two possibilities for the origin of these sources:
1) They are associated with previously unknown star formation
regions. If this is the case then it will require revision of
estimated number of massive star formation regions within our Galaxy.
2) They are associated with a different type of object, possibly less
massive star formation regions, or massive star formation regions at an
earlier stage of evolution.
In order to determine which of these two hypotheses is correct we need
to make further observations of the entire sample of methanol masers in
different maser transitions and at other wavelengths to determine if
there are two or more classes of sources. Some work has already
been done toward this including high resolution imaging of the radio
continuum emission and a search for 22 GHz water masers.
The aim of this project is to search for 1665/1667 MHz OH masers , 12.2
GHz methanol masers and 22~GHz water maser towards the sample of
sources detected in the 6.7 GHz survey and compare the properties of
the sources. Observations will be made using the Mt Pleasant
antenna at each frequency. Comparison of the detection rates,
relative flux densities and velocity ranges would then be investigated
to determine if the new 6.7~GHz methanol masers exhibit different
characteristics than the previously known sources (which would indicate
that they represent a different class of source).
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22 GHz water
maser emission towards the nucleus of the Circinus galaxy. The
masers trace both a warped, edge-on accretion disk and a wide-angle
outflow (image courtesy
Lincoln Greenhill,
CfA)
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Interferometric
imaging of Methanol Masers: Dr Simon Ellingsen
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In addition to the
projects listed above there are also several data processing type
projects available. They differ from the other projects in that
they don't involve any observing and little or no development of data
reduction software, which is either a positive or a negative depending
upon your point of view.
These projects involve the reduction of previously collected
interferometry data using existing software packages. In order to
do this the student will need to develop an basic understanding of how
an interferometer works and synthesis imaging data reduction techniques
(including phase closure, self-calibration and non-linear
deconvolution). However, in the end the data reduction is only
the means to and end and the student will be expected to perform
astrophysical analysis on the reduced data.
There are two data reduction projects available :
1) Involves imaging a variety of methanol maser transitions towards the
ultra-compact HII region W3(OH). The purpose of the
project is to study at high resolution the distributions of the 6.7,
12.2, 23.1 and 107.0 GHz methanol masers. A second aspect of the
project is to examine the large scale structure of the maser emission
to try and understand the variety of scale sizes observed and to see
how these vary for the different methanol maser transitions.
2) Involves imaging of VLBA observations of an unusual 44.1 GHz class I
methanol maser which is distributed in the shape of a cross. The
purpose of the project is to image the maser emission at high
resolution and try and determine the kinematics of the masing region
and the astrophysical phenomena which is driving the maser emission.
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Anomalous
1720 MHz OH emission: Dr Simon Ellingsen
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In the 1970's large
scale surveys of the Galaxy were made at each of the 4 ground-state OH
transitions (1612, 1665, 1667 and 1720 MHz). One of the findings
of these surveys was that the 1720 MHz transition frequently exhibits
anomalous large-scale emission. Since that time very little
further work has been undertaken to study this phenomenon. This project
would involve making observations of the anomalous 1720 MHz transition
over a variety of scale sizes using both the Mt Pleasant telescope and
analysing data collected with the Australia Telescope Compact Array
(ATCA). These observations would then be compared with
observations of the same regions at a variety of wavelengths, to
determine where in the interstellar medium the anomalous emission
arises and the physical conditions that it requires.
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Optical
and Radio Pointing of the Mt Pleasant Antenna: Dr Simon Ellingsen
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A fundamental
question with any telescope is how well does it point? This is
extremely important in radio astronomy as in many cases we cannot 'see'
the source we are observing, so how do we know we are looking at
it. A new focus cabin and feed assembly has recently been
installed at Mt Pleasant which enables us to change rapidly from one
frequency of operation to another and provides three dimensional
control of the feed position. We have also installed a small
optical telescope whose axis is aligned with the radio telescope.
The aim of this experiment is to use radio and optical observations to
characterise this new assembly and determine the optimum position of
the feed in three dimensions for each source position. The
project could also be extended to examine temperature and other weather
effects on the pointing of the radio telescope.
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XTE J0929_314 is an accreting millisecond X-ray
pulsar with an orbital period of 42 minutes. Accretion has stripped the
envelope of the companion leaving a degenerate core with a mass which
may be as low as 10 times that of Jupiter. These systems are believed
to be the progenitors of millisecond radio pulsars but so far only
three have been optically identified.
XTE J0929_314 is a transient system which flared
up in May 2002 and faded below instrument thresholds about 5 weeks
later. We have the only detailed optical data on it. This includes
broadband BVRI spectra taken on 8 separate occasions. The spectrum is
unusual with strong B band absorption and a variable I band excess.
Much of the emission is believed to be from the disc but it seems lkely
that there is also synchrotron emission from bipolar jets during the
early phases of the outburst.
The primary objective is to develop an X-ray
heated accretion disc model based on tha standard Shakura-Sunyaev disc
with parameters from published X-ray data. This model will be fitted to
the observed spectra with V band interstellar extinction and orbital
inclination i as free parameters. This method has been successfully
applied to another system of the same kind by Wang et al (ApJ, 563,
L61, 2001). If, as expected, a satisfactory fit is obtained to the more
normal late outburst spectra it will be possible to further constrain
the system inclination angle and hence the companion star mass. The
model will also be used to test the hypothesis that there was a
separate non-thermal contribution to the spectrum during the early
phases of the outburst. Since ours is virtually the only optical data
on this system, satisfactory completion of this project will provide an
opportunity for publication of the results.
Students will also have an opportunity, if time
permmits, to conduct spectroscopy of other transients using the Mt
Canopus 1-m telescope. These occur frequently throughout the year.
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| Theoretical
Physics |
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Research in theoretical/mathematical physics is
concerned with fundamentals of quantum field theories used to model
systems with many degerees of freedom such as elementary particle
interactions and statistical mechanics -- especially aspects such as
gauge symmeties and quantisation, and the systematics of perturbation
and renormalisation theory. Topics thrown up often bear on related
algebraic, geometrical or combinatorial problems - for example
supersymmetry algebras, structure and representations or topological
aspects of Feynman integrals and diagrams.
Modern mathematical physics draws its methods
eclectically from a pantheon of upmarket higher mathematics; quantum
field theory itself requires a long lead time to digest and so often
fourth year projects do not grapple with these topics `head on'. Rather
there are many challenging and applicable problems dealing with
(relativistic) quantum mechanics and general relativity which are
accessible and feasible for fourth year. To support these topics,
lecture units on gravitation and cosmology and quantum computation
& quantum information are available.
The theory group comprises Dr Peter Jarvis
togetehr with Professor Bob Delbourgo (emeritus), Dr Jim Bashford
(Australian Postdoctoral Fellow), and currently 3 postgraduate
students, usually with one or two honours students. In addition,
because of our external research grants and overseas
collaborations we often have visitors in the group, who get to meet and
interact with the students.
Currently we have also embarked on a major
programme of applications of mathematical physics in relation to
problems of theoretical biology. Topics under study include the
systematics and origin of the genetic code, theoretical/numerical
aspects of stochastic phylogenetic branching models including many body
formulations and entanglement measures, and nucleic acid base pairing
models - RNA duplex free energy formation, DNA replication, RNA
secondary structure and so on.
2005
Theory Projects:
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Propagation
of deformations along aperiodic biopolymers: Dr Jim Bashford, Prof
Robert Delbourgo, Dr Peter Jarvis
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Non-linear,
1-dimensional lattice models have been traditionally used to model the
separation or melting of DNA double helices into single strands, with
some qualitative success. Over the past two decades several
claims have been made that localised melting at sequence sites
associated with gene transcription should behave differently from
ordinary DNA. Unfortunately these papers predict opposite
behaviours and, in the current bioinformatics boom, the
question of whether these claims are theoretical artifacts deserves
further investigation. Review of 1-d nonlinear lattice models
with emphasis on aperiodic structures (DNA se-quences, Josephson
junction arrays). Possible numerical analysis of kinks in lattice
model in-corporating sequence-specific geometric variations.
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Supersymmetric
quantum mechanics in Morse-like potentials?: Dr Jim Bashford, Prof
Robert Delbourgo, Dr Peter Jarvis
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The Morse function
is often used in molecular dynamical models of atomic bonding however,
depending on the application, other potentials (e.g. Lennard-Jones or
Buckingham-Hill) are also commonplace. A recent study of the
Schrödinger equation with Morse potential proposed a dynamical
superalgebra to describe the spectrum of bound and continuum states on
an equal footing. Short review of quantisation, dynamical
algebras. Attempt to construct another explicit example of a
model with a supersymmetric, unified description of bound and continuum
states.
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Spin-charge
separation in 1-D metals. (Literature review topic): Dr Jim
Bashford, Prof Robert Delbourgo, Dr Peter Jarvis
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In conventional
metals the elementary, or quasiparticle excitations of the system of
in-teracting electrons is described by the Fermi-liquid model.
Essentially the quasiparticles are electrons with an increased,
effective mass. However, when the electron system is confined to
one dimension the stable excitations are theorised to be spin and
charge. That is, extra electrons injected into the system decay
into spinons (chargeless spin quanta) and holons (spinless, charge
quanta) which propagate independently. The project will review:
the breakdown of the Fermi-liquid model, basic features of spin-charge
decoupling and may attempt to tie in empirical evidence.
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