How much lanthanide mass did the GW170817 kilonova eject?
In plain words
The glow of the 2017 neutron-star merger depends on how much of the rare-earth elements (lanthanides) it made, which is uncertain because their atomic data are poor.
Precise statement
For AT2017gfo, the kilonova of GW170817, determine the ejecta mass, lanthanide mass fraction $X_{\mathrm{lan}}$ and the presence of specific elements (strontium identified; tellurium, lanthanum, cerium candidates) using radiative transfer with complete atomic line data and non-LTE physics. Answer: $X_{\mathrm{lan}}$ and ejecta mass with uncertainties, and whether the pattern matches the solar r-process pattern including the third peak.
What would settle it
Non-LTE radiative-transfer fits with laboratory-calibrated lanthanide atomic data applied to the full spectral series of AT2017gfo and later kilonovae.
Status in the literature
2019: strontium was identified in AT2017gfo; the full abundance pattern remains model dependent.