The optical+infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association

Abstract

We present the results of photometric and spectroscopic follow-ups of the lowest mass member candidates in the nearest OB association, Upper Scorpius (5-10 Myr; 145+/-17 pc), with the Gran Telescopio de Canarias (GTC) and European Southern Observatory (ESO) Very Large Telescope (VLT). We confirm the membership of the large majority (>80%) of the candidates selected originally photometrically and astrometrically based on their spectroscopic features, weak equivalent widths of gravity-sensitive doublets, and radial velocities. Confirmed members follow a sequence over a wide magnitude range (J=17.0-19.3 mag) in several colour-magnitude diagrams with optical, near-, and mid-infrared photometry, and have near-infrared spectral types in the L1-L7 interval with likely masses below 15 Jupiter masses. We find that optical spectral types tend to be earlier than near-infrared spectral types by a few subclasses for spectral types later than M9. We investigate the behaviour of spectral indices defined in the literature as a function of spectral type and gravity by comparison with values reported in the literature for young and old dwarfs. We also derive effective temperatures in the 1900-1600K from fits of synthetic model-atmosphere spectra to the observed photometry but we caution the procedure carries large uncertainties. We determine bolometric corrections for young L dwarfs with ages of ~5-10 Myr (Upper Sco association) and find them similar in the J-band but larger by 0.1-0.4 mag in the K-band with respect to field L dwarfs. Finally, we discovered two faint young L dwarfs, VISTAJ1607-2146 (L4.5) and VISTAJ1611-2215 (L5) that have H$\alpha$ emission and possible flux excesses at 4.5 microns, pointing towards the presence of accretion from a disk onto the central objects of mass below ~15 Jupiter masses at the age of 5-10 Myr.

arXiv comment40 pages, 10 Tables, 22 figures, accepted for publication to MNRAS, pending changes by Journal before appearance

References in corpus (153)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• Validation of the new Hipparcos reduction
• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The USNO-B Catalog
• The VizieR database of Astronomical Catalogues
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• A Hipparcos census of the nearby OB associations
• X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope
• The Limiting Effects of Dust in Brown Dwarf Model Atmospheres
• Models of Stars, Brown Dwarfs and Exoplanets
• The UKIRT Infrared Deep Sky Survey ZYJHK Photometric System: Passbands and Synthetic Colours
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• Evolutionary models for low-mass stars and brown dwarfs: uncertainties and limits at very young ages
• An Infrared Spectroscopic Sequence of M, L and T Dwarfs
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• A Census of the Young Cluster IC 348
• Constraining the Age-Activity Relation for Cool Stars: The SDSS DR5 Low-Mass Star Spectroscopic Sample
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• A Revised Age for Upper Scorpius and The Star-Formation History Among the F-Type Members of the Scorpius-Centaurus OB Association
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: the Effects of Temperature, Clouds, and Gravity
• Molecfit: A general tool for telluric absorption correction II. Quantitative evaluation on ESO-VLT X-Shooter spectra
• A Unified Near Infrared Spectral Classification Scheme for T Dwarfs
• L' and M' Photometry of Ultracool Dwarfs
• The WFCAM Science Archive
• Towards Spectral Classification of L and T Dwarfs: Infrared and Optical Spectroscopy and Analysis
• Stellar SEDs from 0.3-2.5 Microns: Tracing the Stellar Locus and Searching for Color Outliers in SDSS and 2MASS
• Preliminary Parallaxes of 40 L and T Dwarfs from the U.S. Naval Observatory Infrared Astrometry Program
• The Spectra of T Dwarfs I: Near-Infrared Data and Spectral Classification
• The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
• Meeting the Cool New Neighbors V: A 2MASS-Selected Sample of Ultracool Dwarfs
• The Mauna Kea Observatories Near-Infrared Filter Set. II. Specifications for a New JHKL'M' Filter Set for Infrared Astronomy
• A Catalog of Northern Stars With Annual Proper Motions Larger Than 0.15 Seconds of Arc (LSPM catalog - North)
• Fundamental Parameters and Spectral Energy Distributions of Young and Field Age Objects with Masses Spanning the Stellar to Planetary Regime
• A Near-Infrared Spectroscopic Study of Young Field Ultracool Dwarfs
• Pulkovo Compilation of Radial Velocities for 35495 Hipparcos Stars in a Common System
• The NIRSPEC Brown Dwarf Spectroscopic Survey. I. Low-Resolution Near-Infrared Spectra
• Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey
• Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5
• BANYAN. II. Very Low Mass and Substellar Candidate Members to Nearby, Young Kinematic Groups With Previously Known Signs of Youth
• A Population of very young Brown Dwarfs and free-floating Planets in Orion
• Low-Mass Star Formation and the Initial Mass Function in the Rho Ophiuchi Cloud Core
• Population Properties of Brown Dwarf Analogs to Exoplanets
• Infrared Spectroscopy of Substellar Objects in Orion
• Exploring Exoplanet Populations with NASA's Kepler Mission
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• The Disk Population of the Upper Scorpius Association
• Direct Imaging and Spectroscopy of a Planetary Mass Candidate Companion to a Young Solar Analog
• The Formation and Early Evolution of Low-mass Stars and Brown Dwarfs
• The Extremely Red, Young L Dwarf PSO J318-22: A Free-Floating Planetary-Mass Analog to Directly Imaged Young Gas-Giant Planets
• A Census of the Chamaeleon I Star-Forming Region
• Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574
• BANYAN. VII. A New Population of Young Substellar Candidate Members of Nearby Moving Groups from the BASS Survey
• Characterizing Young Brown Dwarfs using Low Resolution Near-IR Spectra
• Mapping the Shores of the Brown Dwarf Desert I.: Upper Scorpius
• The Spectroscopically Determined Substellar Mass Function of the Orion Nebula Cluster
• Spectroscopy of New Substellar Candidates in the Pleiades: Towards a Spectral Sequence for Young Brown Dwarfs
• A Search for Very Low-mass Stars and Brown Dwarfs in the Young sigma Orionis Cluster
• Near-Infrared Spectral Classification of late-M and L Dwarfs
• A Neptune-sized transiting planet closely orbiting a 5-10-million-year-old star
• New Low-Mass Members of the Taurus Star-Forming Region
• Identifying Young Brown Dwarfs Using Gravity-Sensitive Spectral Features
• Zodiacal Exoplanets in Time (ZEIT) III: A short-period planet orbiting a pre-main-sequence star in the Upper Scorpius OB Association
• Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92-125723.9
• Colors and Kinematics of L Dwarfs From the Sloan Digital Sky Survey
• Gravity Indicators in the Near-Infrared Spectra of Brown Dwarfs
• A library of near-infrared integral field spectra of young M-L dwarfs
• BANYAN. III. Radial velocity, Rotation and X-ray emission of low-mass star candidates in nearby young kinematic groups
• The Substellar Mass Function in sigma Orionis
• The Directly Imaged Planet around the Young Solar Analog 1RXS J160929.1-210524: Confirmation of Common Proper Motion, Temperature and Mass
• New isolated planetary mass objects and the stellar and substellar mass function of the sigma Orionis cluster
• A Survey for Low-mass Stars and Brown Dwarfs in the Upper-Scorpius OB Association
• A Large-Area Search for Low Mass Objects in Upper Scorpius I: The Photometric Campaign and New Brown Dwarfs
• A Methane Isolated Planetary Mass Object in Orion
• A Large-Area Search for Low-Mass Objects in Upper Scorpius II: Age and Mass Distributions
• A Census of Young Stars and Brown Dwarfs in IC 348 and NGC 1333
• New Members of the Scorpius Centaurus Complex and Ages of its sub-regions
• Discovery of a Planetary-mass Companion to a Brown Dwarf in Taurus
• Advances in exoplanet science from Kepler
• Four Brown Dwarfs in the Taurus Star-Forming Region
• A Surprising Reversal of Temperatures in the Brown-Dwarf Eclipsing Binary 2MASS J05352184-0546085
• The White Dwarfs within 20 Parsecs of the Sun: Kinematics and Statistics
• Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association
• Spectroscopy of Very Low Mass Stars and Brown Dwarfs in the Lambda Orionis Star Forming Region. I. Enlarging the census down to the planetary mass domain in Collinder 69
• New brown dwarfs in Upper Sco using UKIDSS Galactic Cluster Survey science verification data
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• A Survey for New Members of the Taurus Star-Forming Region with the Sloan Digital Sky Survey
• Measuring tiny mass accretion rates onto young brown dwarfs
• Spectroscopic identification of DENIS-selected brown dwarf candidates in the Upper Scorpius OB association
• The NIRSPEC Brown Dwarf Spectroscopic Survey II: High-Resolution J-Band Spectra of M, L and T Dwarfs
• Disks around Brown Dwarfs in the Sigma Orionis Cluster
• Accretion and Dynamical Interactions in Small-N Star-Forming Clusters: I. N=5 case
• Substellar Objects in Nearby Young Clusters (SONYC) VI: The planetary-mass domain of NGC1333
• The substellar mass function in sigma Orionis. II. Optical, near-infrared and IRAC/Spitzer photometry of young cluster brown dwarfs and planetary-mass objects
• NICS-TNG low-resolution 0.85-2.45um spectra of L-Dwarfs: a near-infrared spectral classification scheme for faint dwarfs
• Discovery of a ~23 Mjup Brown Dwarf Orbiting ~700 AU from the Massive Star HIP 78530 in Upper Scorpius
• Optical spectroscopy of isolated planetary mass objects in the sigma Orionis cluster
• Multiple Carbon monoxide Snow-lines in Disks Sculpted by Radial Drift
• Spectroscopy of brown dwarf candidates in IC 348 and the determination of its substellar IMF down to planetary masses
• Spectroscopy of new brown dwarf members of rho Ophiuchi and an updated initial mass function
• Infrared Spectroscopy and Analysis of Brown Dwarf and Planetary Mass Objects in the Orion Nebula Cluster
• Substellar Objects in Nearby Young Clusters (SONYC) IV: A census of very low mass objects in NGC1333
• Substellar Objects in Nearby Young Clusters (SONYC): The bottom of the Initial Mass Function in NGC1333
• Keck NIRC Observations of Planetary-mass Candidate Members in the sigma Orionis Open Cluster
• Spectroscopy of Very Low Mass Stars and Brown Dwarfs in the Lambda Orionis Star Forming Region
• K-Band Spectra and Narrowband Photometry of DENIS Field Brown Dwarfs
• Candidate free-floating super-Jupiters in the young sigma Orionis open cluster
• Multi-fibre optical spectroscopy of low-mass stars and brown dwarfs in Upper Sco
• Search for free-floating planetary-mass objects in the Pleiades
• An Enhanced Spectroscopic Census of the Orion Nebula Cluster
• SPITZER: Accretion in Low Mass Stars and Brown Dwarfs in the Lambda Orionis Cluster
• Self-consistent evolution of accreting low-mass stars and brown dwarfs
• A census of very-low-mass stars and brown dwarfs in the sigma Orionis cluster
• Surface Gravities for 228 M, L, and T Dwarfs in the NIRSPEC Brown Dwarf Spectroscopic Survey
• Substellar Objects in Nearby Young Clusters (SONYC) V: New brown dwarfs in rho Ophiuchi
• J-Band Infrared Spectroscopy of a Sample of Brown Dwarfs Using Nirspec on Keck II
• Astrometric and photometric initial mass functions from the UKIDSS Galactic Clusters Survey: IV Upper Sco
• Trigonometric parallaxes of young field L dwarfs
• Young T-Dwarf Candidates in IC 348
• A Pan-STARRS + UKIDSS Search for Young, Wide Planetary-Mass Companions in Upper Scorpius
• Dynamical Masses of Young Stars I: Discordant Model Ages of Upper Scorpius
• S Ori 70: Just a Foreground Field Brown Dwarf?
• Proper motions of field L and T dwarfs
• New members in the Upper Sco association from the UKIDSS Early Data Release
• The low-mass population of the Rho Ophiuchi molecular cloud
• Substellar Objects in Nearby Young Clusters (SONYC) IX: The planetary-mass domain of Chamaeleon-I and updated mass function in Lupus-3
• Oph 1622-2405: Not a Planetary-Mass Binary
• A Correlation Between Circumstellar Disks and Rotation in the Upper Scorpius OB Association
• New constraints on the formation and settling of dust in the atmospheres of young M and L dwarfs
• A Young Planetary-Mass Object in the rho Oph Cloud Core
• The substellar population of Sigma Orionis: A deep wide survey
• New constraints on the membership of the T dwarf S Ori 70 in the sigma Orionis cluster
• Substellar Objects in Nearby Young Clusters (SONYC) VIII: Substellar population in Lupus 3
• Deep Near-Infrared Imaging of the rho Oph Cloud Core: Clues to the Origin of the Lowest-Mass Brown Dwarfs
• A Keck LGS AO Search for Brown Dwarf and Planetary Mass Companions to Upper Scorpius Brown Dwarfs
• Spectroscopic estimate of surface gravity for a planetary member in the Sigma Ori cluster
• Substellar Objects in Nearby Young Clusters (SONYC) II: The Brown Dwarf Population of Rho Ophiuchi
• HD144548: A young triply eclipsing system in the Upper Scorpius OB association
• A Search for L/T Transition Dwarfs With Pan-STARRS1 and WISE. III. Young L Dwarf Discoveries and Proper Motion Catalogs in Taurus and Scorpius-Centaurus
• Near Infrared Spectroscopy of Young Brown Dwarfs in Upper Scorpius
• Age spreads and the temperature dependence of age estimates in Upper Sco
• Search and characterization of T-type planetary mass candidates in the sigma Orionis cluster
• An eclipsing double-line spectroscopic binary at the stellar/substellar boundary in the Upper Scorpius OB association
• Probing the Upper Scorpius mass function in the planetary-mass regime
• New brown dwarfs in the south part of the Upper Scorpius Association
• A new free-floating planet in the Upper Scorpius association
• Testing the fragmentation limit in the Upper Sco association
• Spectral energy distribution simulations of a possible ring structure around the young, red brown dwarf G196-3B
• Searching for planetary-mass T-dwarfs in the core of Serpens
• Characterization of the known T type dwarfs towards the Sigma Orionis cluster
• Spitzer Spectroscopy of the Circumprimary Disk in the Binary Brown Dwarf 2MASS J04414489+2301513
• Discovery of Young Methane Dwarfs in the Rho Ophiuchi L 1688 Dark Cloud
• Multi-Object and Long-Slit Spectroscopy of Very Low Mass Brown Dwarfs in Orion Nebular Cluster

Cited by in corpus (39)

• Refining the Census of the Upper Scorpius Association with Gaia
• A rich population of free-floating planets in the Upper Scorpius young stellar association
• A Survey for New Members of Taurus from Stellar to Planetary Masses
• The GJ 504 system revisited. Combining interferometric, radial velocity, and high contrast imaging data
• New Young Stars and Brown Dwarfs in the Upper Scorpius Association
• A medium-resolution spectrum of the exoplanet HIP 65426 b
• A WISE Survey of Circumstellar disks in the Upper Scorpius Association
• The B-Star Exoplanet Abundance Study: a co-moving 16-25 Mjup companion to the young binary system HIP 79098
• A new take on the low-mass brown dwarf companions on wide-orbits in Upper-Scorpius
• EMIR, the near-infrared camera and multi-object spectrograph for the GTC
• A Novel Survey for Young Substellar Objects with the W-band Filter. I. Filter Design and New Discoveries in Ophiuchus and Perseus
• The origin of free-floating planets
• Youth analysis of near infrared spectra of young low-mass stars and brown dwarfs
• Infrared Spectroscopy of free-floating planet candidates in Upper Scorpius and Ophiuchus
• Spectral library of age-benchmark low-mass stars and brown dwarfs
• Redder than Red: Discovery of an Exceptionally Red L/T Transition Dwarf
• Improved infrared photometry and a preliminary parallax measurement for the extremely cold brown dwarf CWISEP J144606.62$-$231717.8
• Euclid: Early Release Observations -- A glance at free-floating new-born planets in the sigma Orionis cluster
• Exploring the planetary-mass population in the Upper Scorpius association
• USco1621 B and USco1556 B: Two wide companions at the deuterium-burning mass limit in Upper Scorpius
• Disks around young planetary-mass objects: Ultradeep Spitzer imaging of NGC1333
• Measurement of the angular momenta of pre-main-sequence stars: early evolution of slow and fast rotators and empirical constraints on spin-down torque mechanisms
• New Candidates for Planetary-mass Brown Dwarfs in IC 348
• Strong H$\alpha$ emission in the young planetary mass companion 2MASS J0249-0557 c
• ALMA observations of the early stages of substellar formation in the Lupus 1 and 3 molecular clouds
• Euclid Quick Data Release (Q1) -- Spectroscopic search, classification and analysis of ultracool dwarfs in the Deep Fields
• Spectral characterization of young LT dwarfs
• Confirming the least massive members of the Pleiades star cluster
• X-SHYNE: X-Shooter spectra of young exoplanet analogs II. Presentation and analysis of the full library
• Spectroscopy of Candidate Members of the Sco-Cen Complex
• A Novel Survey for Young Substellar Objects with the W-band filter III: Searching for very low mass brown dwarfs in Serpens South and Serpens Core
• SEDBYS: A python-based SED Builder for Young Stars
• Search for the sub-stellar lithium depletion boundary in the open star cluster Coma Berenices
• Fast Photometric Variability of Very Low Mass Stars in IC 348: Detection of Superflare in an M-dwarf
• The substellar population in Corona Australis
• Low-mass and sub-stellar eclipsing binaries in stellar clusters
• ExoplaNeT accRetion mOnitoring sPectroscopic surveY (ENTROPY) - II. Time series of Balmer line profiles of Delorme 1(AB)b
• Disk fraction among free-floating planetary-mass objects in Upper Scorpius
• Two close binaries across the hydrogen-burning limit in the Praesepe open cluster