Spectroscopy of planetary mass brown dwarfs in Orion

Abstract

We report the results of near infrared spectroscopy of 11 luminosity selected candidate planetary mass objects (PMOs) in the Trapezium Cluster with Gemini South/GNIRS and Gemini North/NIRI. 6 have spectral types >=M9, in agreement with expectations for PMOs. 2 have slightly earlier types, and 3 are much earlier types which are probably field stars. 4/6 sources with types >= M9 have pseudo-continuum profiles which confirm them as low gravity cluster members. The gravity status of the other cool dwarfs is less clear but these remain candidate PMOs. The derived number fraction of PMOs with M=3-15 Mjup is 1-14%, these broad limits reflecting the uncertainty in source ages. However, the number fraction with M<20 Mjup is at least 5%. These detections add significantly to the body of evidence that a planetary mass population is produced by the star formation process.

Accepted by MNRAS Letters, 5 pages, 2 figures

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• Close encounters involving free-floating planets in star clusters
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• Youth analysis of near infrared spectra of young low-mass stars and brown dwarfs
• An optical spectroscopic H-R diagram for low-mass stars and brown dwarfs in Orion
• Binary Formation in the Orion Nebula Cluster: Exploring the Sub-stellar Limit
• Euclid: Early Release Observations -- A glance at free-floating new-born planets in the sigma Orionis cluster
• Rogue planets and brown dwarfs: Predicting the populations of free-floating planetary mass objects observable with JWST
• Do micro brown dwarf detections explain the galactic dark matter?
• Discovery of a brown dwarf with quasi-spherical mass-loss
• Simulation of images of protoplanetary disks after collision with free-floating planets
• Primordial Planet Formation