Ross 458c
Ross 458c is a widely separated planetary mass companion at a distance of 1100 AU from its host binary, Ross 458AB. We obtained high-resolution (R∼2700) emission spectra of Ross 458c with JWST NIRSpec Fixed Slit in F070LP, F100LP, and F170LP filters. We fit these spectra to the Sonora Bobcat, Sonora Elf Owl, and ExoREM forward models, and we retrieved atmospheric properties using the POSEIDON retrieval code. The forward model grids preferred enhanced metallicity relative to the host, while the retrieval preferred a metallicity consistent with the host within 1σ. The retrieval provided a much better fit to the spectrum, so we inferred that Ross 458c likely formed through fragmentation of the molecular cloud that formed its host.
