Asteroseismology of White Dwarf GD358 Using Optical and Ultraviolet Light Curves

Asteroseismology is the study of the internal structure of stars. Similar to the way seismologists study the Earth’s vibrations during an earthquake to draw conclusions about the Earth’s inner structure, astronomers analyze a pulsating star’s light curve – the intensity of the light over time – to characterize its internal structure. Pulsating white dwarf stars are ideal for asteroseismology because they have relatively simple structures that make them easier to model. Asteroseismology relies on accurately identifying pulsation modes that are simultaneously present as a star vibrates. The goal of this project is to identify pulsation modes via “chromatic amplitude method”. Pulsating white dwarf star GD358 was observed simultaneously in the ultraviolet using the Hubble Space Telescope (HST) and in the optical by the Whole Earth Telescope (WET) – a network of telescopes from around the world that enable an object to be observed continuously for many days. The amplitude information is extracted from both the ultraviolet and optical data, and the ratios of the amplitudes are taken. Based on these ratios, the modes of GD358 will be identified. Identification of these modes will then be compared to the modes that were identified in previous studies using the period method – analyzing the distribution of periods. If the chromatic amplitude method accurately identifies previously known modes of GD358, it will serve as confirmation of a powerful new method for asteroseismology, especially in stars with few modes that are difficult to analyze with the period method alone.