Optical spectroscopy of isolated planetary mass objects in the sigma Orionis cluster

Abstract

We have obtained low resolution optical spectra of 15 isolated planetary mass objects (IPMOs) in the sigma Orionis cluster, and derived spectral types by comparison with nearby M and L dwarfs. The spectral types are in the range late M - mid L, in agreement with our expectations based on colors and magnitudes for bona fide members. Therefore, most of these objects have masses below the deuterium burning limit. About 2/3 show H(alpha) in emission at our spectral resolution. From our spectroscopic and photometric data, we infer that three IPMOs in this sample may be binaries with components of similar masses. These results confirm that the substellar mass function of the sigma Orionis cluster, in the form dN/dM, keeps rising in the planetary domain.

Astronomy and Astrophysics, accepted

References in corpus (3)

• The Limiting Effects of Dust in Brown Dwarf Model Atmospheres
• Infrared Spectroscopy of Substellar Objects in Orion
• The Substellar Mass Function in sigma Orionis

Cited by in corpus (55)

• Spitzer Space Telescope study of disks in the young $\sigma$ Orionis cluster
• Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5
• An empirical criterion to classify T Tauri stars and substellar analogs using low-resolution optical spectroscopy
• Spectroscopy of Very Low Mass Stars and Brown Dwarfs in IC2391: Lithium depletion and Halpha emission
• Lithium and Halpha in stars and brown dwarfs of sigma Orionis
• Identifying Young Brown Dwarfs Using Gravity-Sensitive Spectral Features
• New isolated planetary mass objects and the stellar and substellar mass function of the sigma Orionis cluster
• Near-infrared cross-dispersed spectroscopy of brown dwarf candidates in the Upper Sco association
• A Flaring L5 Dwarf: The Nature of HαEmission in Very Low Mass (Sub)Stellar Objects
• A Survey for Circumstellar Disks Around Young Substellar Objects
• Precision photometric monitoring of very low mass Sigma Orionis cluster members: variability and rotation at a few Myr
• The substellar mass function in sigma Orionis. II. Optical, near-infrared and IRAC/Spitzer photometry of young cluster brown dwarfs and planetary-mass objects
• The substellar population of the young cluster lambda Orionis
• Substellar Objects in Nearby Young Clusters (SONYC): The bottom of the Initial Mass Function in NGC1333
• Photometric variability of young brown dwarfs in the sigma Orionis open cluster
• The brightest stars of the sigma Orionis cluster
• Contamination by field late-M, L and T dwarfs in deep surveys
• Optical Spectroscopic Classification and Membership of Young M Dwarfs in Star-Forming Regions
• XMM-Newton observations of the sigma Ori cluster. II. Spatial and spectral analysis of the full EPIC field
• A census of very-low-mass stars and brown dwarfs in the sigma Orionis cluster
• Near-infrared low-resolution spectroscopy of Pleiades L-type brown dwarfs
• Towards Precise Ages and Masses of Free Floating Planetary Mass Brown Dwarfs
• The optical+infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association
• Dusty disks at the bottom of the IMF
• Photometric variability of a young, low-mass brown dwarf
• A deep look into the cores of young clusters I. sigma-Orionis
• Contamination and exclusion in the sigma Orionis young group
• X-ray Emission near the Substellar Limit: The sigma Orionis and Taurus Star Forming Regions
• Chemical abundances of late-type pre-main sequence stars in the $\sigma$-Orionis cluster
• Activity at the Deuterium-Burning Mass Limit in Orion
• Optical and Near-Infrared Spectra of sigma Orionis Isolated Planetary-mass Objects
• Can the masses of isolated planetary-mass gravitational lenses be measured by terrestrial parallax?
• Low-resolution spectroscopy and spectral energy distributions of selected sources towards sigma Orionis
• Spectroscopy of Young Planetary Mass Candidates with Disks
• A Pulsation Search Among Young Brown Dwarfs and Very Low Mass Stars
• Probing the Upper Scorpius mass function in the planetary-mass regime
• Are isolated planetary-mass objects really isolated? A brown dwarf-exoplanet system candidate in the sigma Orionis cluster
• Substellar Mass Function of Young Open Clusters as Determined through a Statistical Approach Using 2MASS and GSC Data
• A novel survey for young substellar objects with the W-band filter VI: Spectroscopic census of sub-stellar members and the IMF of $\sigma$ Orionis cluster
• A near-infrared survey for new low-mass members in Alpha Per
• New deep XMM-Newton observations to the west of the sigma Orionis cluster
• Young brown dwarfs at high cadence: Warm Spitzer time series monitoring of very low mass Sigma Orionis cluster members
• Testing the fragmentation limit in the Upper Sco association
• Very low-luminosity Class I/Flat outflow sources in sigma Orionis
• Euclid: Early Release Observations -- A glance at free-floating new-born planets in the sigma Orionis cluster
• USco1621 B and USco1556 B: Two wide companions at the deuterium-burning mass limit in Upper Scorpius
• Near-infrared photometry of WISE J085510.74$-$071442.5
• Infrared Spectroscopy of the Ultra Low Mass Binary Oph 162225-240515
• The first spectroscopically identified L dwarf in Praesepe
• Young nearby open clusters and their luminosity functions
• Photometric variable stars in the young open cluster NGC 6823
• Stars and brown dwarfs in the sigma Orionis cluster. III. OSIRIS/GTC low-resolution spectroscopy of variable sources
• A deep staring campaign in the Sigma Orionis cluster. Variability in substellar members
• A review on substellar objects beyond the deuterium burning mass limit: planets, brown dwarfs or what?
• Disk fraction among free-floating planetary-mass objects in Upper Scorpius