Tuesday 23 Jan 2018Solving the M-Dwarf Luminosity Problem

Sam Morrell - University of Exeter

4th Floor Interaction Area 11:15-11:45

It is noted in the literature that Pre-Main Sequence stars with effective temperatures < 4000k have radii inflated by 10% when compared to models, leading to a 5% reduction in effective temperature (Lopez-Morales & Ribas 2005, Bell et al. 2012, Jeffries et al. 2017). One manifestation of this issue is presented Jeffries (2007), which finds a distribution of radii in members of the Orion Nebula Cluster corresponding to a spread of ages wider than the median age of objects within that cluster. Such large inconsistencies in fundamental stellar properties have a sizeable impact on studies of young stellar populations, disc lifetimes and planet formation timescales; as well as studies of the planets themselves.
This discrepancy persists beyond the poorly understood pre-main-sequence phase to relatively well-understood main-sequence stars. Studying main-sequence stars may, therefore, give us the our best opportunity to understand the source of the discrepancy. Hence, we are using robustly flux-calibrated spectra of stars on the lower main sequences of two clusters with well constrained memberships, ages and metallicities, the Pleiades and Praesepe, to study the physics underlying this effect. We are determining effective temperatures through two separate methods to verify that the rumoured radius inflation is indeed the cause of deviation from the models. The findings from this investigation will feedback into the development of stellar models, thus rectifying the affected parameter space.

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