Ultracool Subdwarfs: The Halo Population Downto the Substellar Limit

摘要

Ultracool subdwarfs are low luminosity, late-type M and L dwarfs that exhibit spectro-scopic indications of subsolar metallicity and halo kinematics. Their recent discovery and ongoinginvestigation have led to new insights into the role of metallicity in the opacity structure, chem-istry (e.g. dust formation) and evolution of low-temperature atmospheres; the long-term evolutionof magnetic activity and angular momentum amongst the lowest-mass stars; the form of the haloluminosity and mass functions down to the hydrogen-burning mass limit; and even fundamental is-sues such as spectral classification and absolute brightness scales. This Splinter Session was devotedto bringing advances in observational and theoretical ultracool subdwarf research to the attentionof the low-mass stellar and brown dwarf communities, as well as to share results among ultracoolsubdwarf enthusiasts.