Optical and Near-infrared Spectra of σ Orionis Isolated Planetary-mass Objects

  title={Optical and Near-infrared Spectra of $\sigma$ Orionis Isolated Planetary-mass Objects},
  author={Mar{\'i}a Rosa Zapatero Osorio and V'ictor J. S. B'ejar and Karla Pena Ram'irez},
  journal={The Astrophysical Journal},
We have obtained low-resolution optical (0.7–0.98 μm) and near-infrared (1.11–1.34 μm and 0.8–2.5 μm) spectra of 12 isolated planetary-mass candidates (J = 18.2–19.9 mag) of the 3 Myr σ Orionis star cluster with the aim of determining the spectroscopic properties of very young, substellar dwarfs and assembling a complete cluster mass function. We have classified our targets by visual comparison with high- and low-gravity standards and by measuring newly defined spectroscopic indices. We derived… 

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