We report on the spectroscopic analysis of \object RAVE J183013.5 - 455510 , an extremely metal-poor star , highly enhanced in CNO , and with discernible contributions from the rapid neutron-capture process .
There is no evidence of binarity for this object .
At [ \mathrm { Fe } / \mathrm { H } ] = -3.57 , this is one of the lowest metallicity stars currently observed , with 18 measured abundances of neutron-capture elements .
The presence of Ba , La , and Ce abundances above the Solar System r -process predictions suggest that there must have been a non-standard source of r -process elements operating at such low metallicities .
One plausible explanation is that this enhancement originates from material ejected at unusually fast velocities in a neutron star merger event .
We also explore the possibility that the neutron-capture elements were produced during the evolution and explosion of a rotating massive star .
In addition , based on comparisons with yields from zero-metallicity faint supernova , we speculate that \object RAVE J1830 - 4555 was formed from a gas cloud pre-enriched by both progenitor types .
From analysis based on Gaia DR2 measurements , we show that this star has orbital properties similar to the Galactic metal-weak thick-disk stellar population .