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High-speed CCD Photometry of Interacting Binary Stars

Interacting binary stars are dynamic objects which require high-speed observing techniques. For instance, they can show sharp features during eclipse that last only 30 seconds, or flare on shorter timescales still. While the advent in the early 1980s of CCDs brought many advantages, it was bad for high-speed work because of their slow readouts, and we are only now catching up. We have developed a new high-speed camera called ULTRACAM. ULTRACAM has several unique features which make it a world-leading instrument in astrophysics today. First, it operates at high-speed with what are called ``frame transfer'' CCDs. Second, it operates in three bands simultaneously. In 2005 we mounted ULTRACAM on the 8m VLT in Chile, making it the first visitor instruments to be mounted there. There are many possible PhD projects to do with ULTRACAM, all making use of its unique advantages of high-speed. See below for one example. Supervisor: Tom Marsh

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The movie (3MB) shows ULTRACAM's view of a remarkable eclipsing binary star called NN Serpentis. This star consists of a compact white dwarf (old stellar remnant comparable in size to the Earth) and a much larger cool companion. The companion reveals its presence when it passes between us and the white dwarf. The eclipse takes 12 minutes in real time; only 1 in 5 images are plotted here in order to keep the file size reasonable. The aim of this project was to measure angular momentum losses which are crucial for binary evolution. The results we have so far are extremely puzzling and seem to indicate that the loss rate may be much higher than expected.

Please fill in our PhD enquiries form if you are interested in studying for a PhD in Astronomy at Warwick.

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ULTRACAM at the 4.2m WHT on the island of La Palma in the Canary Islands.

ULTRACAM at the 8m VLT in Chile.