The Whole Earth Telescope project

The Whole Earth Telescope (WET) is an international collaboration between a number of groups with a common interest in the study of white dwarf structure, with Leicester being an active participant in the program. It complements the work we do on atmospheres by studying pulsation modes to determine their interior structure. The ability to resolve complex oscillations relies on having long, comparatively unbroken observations stretching over a few weeks. Hence, observations are conducted contemporaneously from a number of telescopes at sites distributed in longitude around the globe. We have now been involved in the project since is beginning and a number of important results have been obtained, including independent measurements of white dwarf masses and rotation rates.

Recently, we have extended the WET technique to deal with a newly discovered class of pulsating subdwarf stars. Follow-up observations of hot objects in the Edinburgh-Cape blue survey have revealed a new class of object comprising a hot pulsating subdwarf in a binary with and F or G companion. The origin of subdwarfs is something of a mystery. they may have evolved from the horizontal branch stars and it is thought that they could provide a possible route to the white dwarf sequence. These new discoveries appear to be multiperiodic pulsators and, hence, provide an opportunity to apply the techniques of asteroseismology to studying the structure of these stars. Two observing campaigns were conducted in October 1996 and May 1997, using the 1.0m Jacobus Kapteyn Telescope on La Palma. An example of this works is a paper (O'Donoghue et al., 1998, MNRAS vol 296 pg 296-305).