Asteroseismology of Pulsating Star KPD 1930 2752 using Faulkes Telescope

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Asteroseismology of Pulsating Star KPD 19302752
using Faulkes Telescope
Ciara Quinn Sacred
Heart Grammar School Newry Nuffield
Science Bursary 2004
Methods and materials  To calculate the
frequencies present in the light curve of KPD
19302752, a Fourier transform is needed.
However, in order to complete this transform, I
need data concerning the change in magnitude of
KPD 19302752. I obtained this data though a
process called high-speed photometry. In this
process, a large number of short duration
exposures are taken of KPD 19302752, using a CCD
camera attached to Faulkes Telescope north in
Hawaii.
Introduction During my 6 week placement at
Armagh observatory, I was set the project of
studying the change in magnitude of a variable
star, KPD 19302752. KPD 19302752 is actually 2
stars, known as a binary system, it consists of 2
stars, one hot, bright sub-dwarf B star orbiting
round a smaller, denser white dwarf in a period
of 137 minutes. KPD 19302752 is known to be
pulsing. When the surface of the star contracts,
it becomes opaque. All the photons under the
surface become trapped. This causes the pressure
of the gas to increase and the volume expand. The
surface expands and becomes transparent, allowing
the photons to escape. The pressure drops and the
surface contracts again, becoming opaque. This
process is occurring all over the surface of KPD
19302752. There is another type of variation
present in the star. The hot sdB star is
physically distorted by the white dwarf star,
making it become egg shaped. This means that the
star is brightest when the viewed side on, I.e.
when more of the star is is view.
In total I was given three and a half hours on
Faulkes telescope to observe KPD 19302752. This
time was divided into two sessions, one 2 hours
long and the other 1½ hours. During this time I
was in control of the telescope. As each exposure
was read off the chip, the image recorded was
shown on the screen. This, along with the use of
a star map, allowed me to identify KPD 19302752.
The image below is an example of the images
provided by Faulkes Telescope, immediately after
the exposure has been taken. The circled star is
KPD 19302752. When all the imaged had been
captured, I used the photometry tool in AIP4WIN
to obtain numerical values for the change in
magnitude of KPD 19302752. Using this data, I
was able to produce 2 graphs showing the change
in magnitude of the star over time. I also used
this data to produce a Fourier transform of the
data in the computer program Period98.
Results The graphs below represent the change in
magnitude of KPD 19302752 over time. The first
graph shows the data collected during the first
observing period of 1 ½ hours and the second
graph the data collected during the second
observing session on Faulkes telescope which was
2 hours long.
The Telescope Faulkes telescope is a 2m reflector
telescope located on the mountain Haleakala on
the Hawaiian island Maui. It was set up to make a
research grade telescope available to school
children to enable them to carry out their own
research astronomy projects. The telescope is
controlled from a computer and the user can
choose the object to be viewed, the exposure time
of the image and the filter on the telescope. It
provides young astronomers with the invaluable
resource and the experience of controlling a high
quality, research telescope to carry out their
own research in an area of science that interests
them an experience that was previous unavailable.
The following graph is the Fourier transform
produced by Period98 from the data I collected
over 2 observing sessions on Faulkes
Telescope.The peaks on the graph represent the
individual frequencies present in the light
emitted from KPD 19302752.
Thanks to everyone at Armagh Observatory for all
their friendly help and advice especially Dr.
Simon Jeffery, project supervisor.