Fundamental parameters of very low mass stars in eclipsing binary star systems observed with the CHEOPS satellite

Swayne, Matthew Iain

Abstract

Observations of low-mass stars have frequently shown unexpectedly large stellar radii when compared to the predictions from theoretical stellar structure models. This “radius inflation” problem may have consequences not just for stellar science but also for observations of exoplanets around low mass stars. In this thesis, I seek to explore this problem by analysing the light curves of eclipsing binaries with low mass companions (EBLMs) observed by the CHEOPS satellite. Using transit photometry I obtain precise radii for about 20 M-dwarf targets. To account for the effect of starspots on derived radii, I simulate the uncertainty caused by observed stellar flux variation and account for this in error calculations. I also derive their effective temperatures using their eclipse depths and PHOENIX model atmospheres. Combining these with already present spectroscopic measurements I also calculate stellar masses and therefore observe our target’s place on the mass-radius and mass-effective temperature diagrams. Observing that some of our targets show inflated radii and some do not, I then hunt for inflation-causing trends in our data. I find tentative suggestions of a trend with orbital period and a linear trend between metallicity and inflation of gradient −0.082±0.033. This thesis contributes to solving this long-standing problem in astrophysics, and towards aiding observation preparations for upcoming exoplanetary observations with low mass stellar hosts.

Citation

Swayne, M. I. (2023). Fundamental parameters of very low mass stars in eclipsing binary star systems observed with the CHEOPS satellite. (Thesis). Keele University

• Thesis Type: Thesis
• Deposit Date: Jul 20, 2023
• Publicly Available Date: Jul 20, 2023
• Award Date: 2023-06