A space-based near-infrared sky survey to study the oxygen abundance in cool stars

Cool stars, especially spectral-type M, are important probes across contemporary astrophysics, from the forma- tion history of the galaxy to the coalescence of rocky exoplanets. Main sequence M-dwarf stars are one of the most abundant stars in the galaxy, and evolved M-giant stars are some of the most distant stars that can be individually observed. The Emu sky survey, described here, will deliver critical stellar properties of these cool stars by inferring the oxygen abundance via measurement of the water band strength at 1.4 μm. A relatively wide field zenith-looking telescope with time delay integration capability can perform such a survey without active pointing but requires a fast and low-noise detector. Emu employs the paradigm-changing properties of the Leonardo SAPHIRA electron avalanche photodiode array, to provide these powerful new observations at the critical water absorption wavelength inaccessible to ground-based telescopes due to the Earth's own atmosphere. Here we will present Emu mission concept, science objectives, instrument details and simulation results.