Asteroseismology from the ground
Project level: Honours; PhD
There is a second side to the ARC DECRA-supported research on naked-eye bright stars: using the Mount Kent Observatory, near Toowoomba, to measure the masses the brightest red giant stars in the sky. The Sun, like many other stars, rings like a bell, and its dominant note has a period of about 5 minutes. The turbulent motion of gas in the Sun couples to normal modes of acoustic oscillation and cause it to ring in a band of frequencies that are precisely diagnostic of conditions in the stellar interior. Larger stars, like larger instruments, have lower notes, so that many red giant stars might mainly ring at periods of days or weeks. The science of asteroseismology is about studying the interiors of stars through oscillations like this, and can be used to determine stellar masses and ages. It has been revolutionised by the Kepler Space Telescope's long, precise, uniform time series of stellar brightnesses.
On the ground-based side, we are interested in doing asteroseismology of the brightest red giant stars in the sky. With pulsation periods of about a week, they are too long to measure well with TESS (which observes most parts of the sky for a month at a time). The Mount Kent Observatory, near Toowoomba, hosts arrays of 0.7m robotic telescopes coupled to radial velocity spectrographs Minerva and SONG, which can automatically obtain RVs of many bright stars per night. In order to hit the whole sky, we want to conduct as few observations of each star as possible, while still getting enough to constrain their physics well - and as a consequence, we will typically only get sparse and irregularly-sampled time series of each star.
It turns out that Gaussian Process statistical models are well-suited to this, as my collaborators and I showed on the bright giant Aldebaran, a known planet host. By measuring its mass with asteroseismology to 5% precision, we showed that while its planet is now blasted with heat from the red giant, when it was a main sequence star the planet would have received a similar amount of sunlight to the Earth, and so it may have in the distant past been habitable.
Part of this ARC DECRA project is therefore to scale up what we did on one star (Aldebaran) to all the giants in the sky, and build a new tool for doing asteroseismology from the ground.
This project would be well suited to someone with an interest in statistics and programming in Python or Julia, and who wants to get to grips with Gaussian Process models, or the spectroscopic instruments SONG and Minerva at Mt Kent.
For more reading, see Aldebaran b's temperate past uncovered in planet search data
