Using Asteroseismology to Measure an Integrated Mass Loss for Evolved Stars in Globular Clusters
Wednesday 14 Sep 2022 @ 12:00 p.m., Level 6 Geoff Opat(+Zoom)
Madeline Howell, Monash; Email: Madeline.Howell1[at]monash.edu
Mass loss remains a major uncertainty in stellar modelling. In low-mass stars, mass loss is most significant on the red giant branch, and will impact the star’s evolutionary path and final stellar remnant. Directly measuring the mass difference of stars in various phases of evolution represents one of the best ways to quantify mass loss. Globular clusters are ideal objects for this, because they contain stars with essentially identical initial masses, metallicities and ages, and hence easily distinguishable evolutionary phases. M4 is currently the only globular cluster for which asteroseismic data exists for stars in multiple phases of evolution. The advent of space-based photometric missions have provided the opportunity to measure stellar masses with unprecedented accuracy using asteroseismology. Using photometry from the K2 mission, we report asteroseismic masses for 75 red giants in M4, the largest seismic sample in a globular cluster to date. From this sample, we measured a prec
ise integrated red giant branch mass loss. Our results for initial mass, horizontal branch mass, Reimers’ coefficient, and integrated red giant branch mass loss show a remarkable agreement with previous studies, but with higher precision through using asteroseismology. We also report preliminary detections of solar-like oscillations in a second globular cluster, M80. Because this cluster is more metal-poor than M4, we can test the potential mass loss-metallicity trend. We emphasise the importance of seismic studies of globular clusters which could potentially allow us to resolve major uncertainties in our understanding of stellar evolution. We discuss the prospects of using photometry from current and future space-based telescopes for this science objective.