The detection and characterization of highly magnified stars with JWST: Prospects of finding Population III

Understand

Gravitational lensing may render individual high-mass stars detectable out to cosmological distances, and several extremely magnified stars have in recent years been detected out to redshifts $z\approx 6$.

• Here, we present Muspelheim, a model for the evolving spectral energy distributions of both metal-enriched and metal-free stars at high redshifts.
• Using this model, we argue that lensed stars should form a highly biased sample of the intrinsic distribution of stars across the Hertzsprung-Russell diagram, and that this bias will typically tend to favour the detection of lensed stars in evolved stages characterized by low effective temperatures, even though stars only spend a minor fraction of their lifetimes in such states.
• We also explore the prospects of detecting individual, lensed metal-free (Population III) stars at high redshifts using the James Webb Space Telescope (JWST).