JWST Spectra of Brown Dwarf Candidates in the Orion Nebula Cluster

TL;DR

This study analyzes JWST NIRSpec spectra of 200 sources in the Orion Nebula Cluster to identify cluster members and classify their spectral types, including potential brown dwarfs, and clarifies the nature of previously identified JuMBO objects.

Contribution

First spectroscopic assessment of ONC sources using JWST data, clarifying cluster membership and brown dwarf candidates, and re-evaluating the nature of JuMBO objects.

Findings

53 likely cluster members identified

24 sources suggestive of brown dwarfs (>$M6$)

JuMBO objects are background sources, not brown dwarfs

Abstract

I present an analysis of archival spectra of 200 sources toward the Orion Nebula Cluster (ONC) that were obtained with the Near-Infrared Spectrograph (NIRSpec) on board the James Webb Space Telescope (JWST). I have used these data to assess cluster membership and measure spectral types for the targets. Fifty-three sources are classified as likely cluster members, 24 of which have spectral types that are suggestive of brown dwarfs ($>$M6). Seven of the NIRSpec targets were previously identified as "Jupiter-mass binary objects" (JuMBOs), all of which are background sources rather than brown dwarfs based on the NIRSpec data. The spectral classifications of those objects are consistent with the results of my recent study of the JWST photometry in the ONC, which found that only a few JuMBO components have the colors expected for brown dwarfs, none of which form pairs that have uniquely wide separations or low masses relative to known binary brown dwarfs.