Spectral library of age-benchmark low-mass stars and brown dwarfs

Abstract

In the past years, some extremely red brown dwarfs were found. They were believed to have low surface gravity, but many of their spectral characteristics were similar to those of high surface gravity brown dwarfs, showing that youth (or low surface gravity) spectral characteristics are poorly understood. We aim to test surface gravity indicators in late-M and early-L brown dwarf spectra using data obtained with the X-shooter spectrograph at the Very Large Telescope. We selected a benchmark sample of brown dwarfs members of Chamaeleon\,I ($\sim$2 Myr), Upper Scorpius (5$-$10~Myr), Pleiades (132$\pm$27 Myr), and Praesepe (590$-$790 Myr) with well-constrained ages, and similar metallicities. We provided a consistent spectral classification of the sample in the optical and in the near-infrared. We measured the equivalent widths of their alkali lines, finding that they have a moderate correlation with age, especially for objects with spectral types M8 and later. We used spectral indices defined in the literature to estimate surface gravity, finding that their gravity assignment is accurate for 75\% of our sample. We investigated the correlation between red colours and age, finding that after $\sim$10~Myr, the colour does not change significantly for our sample {with spectral types M6.0-L3.0}. In this case, red colours might be associated with circumstellar disks, {ring structures, extinction, or viewing angle}. Finally, we calculated the {bolometric luminosity}, {and $J$ and $K$ bolometric corrections} for our sample. We found that six objects are overluminous compared to other members of the same association. Those objects are also flagged as binary candidates by the $Gaia$ survey.

Accepted for publication in MNRAS. The spectra will be available in the publisher version of this paper and in GitHub: <https://github.com/elenamanjavacas/spectral_libraries>

References in corpus (28)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• The 0.8-14.5 micron Spectra of Mid-L to Mid-T Dwarfs: Diagnostics of Effective Temperature, Grain Sedimentation, Gas Transport, and Surface Gravity
• Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5
• The Stellar Population of the Chamaeleon I Star-Forming Region
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• Characterizing Young Brown Dwarfs using Low Resolution Near-IR Spectra
• Mapping the Shores of the Brown Dwarf Desert I.: Upper Scorpius
• The Age and Age Spread of the Praesepe and Hyades Clusters: a Consistent, ~800 Myr Picture from Rotating Stellar Models
• An ALMA Survey of CO isotopologue emission from Protoplanetary Disks in Chamaeleon I
• A Large-Area Search for Low-Mass Objects in Upper Scorpius II: Age and Mass Distributions
• New brown dwarfs in Upper Sco using UKIDSS Galactic Cluster Survey science verification data
• The Viewing Geometry of Brown Dwarfs Influences Their Observed Colours and Variability Properties
• The effect of rotation on the abundances of the chemical elements of the A-type stars in the Praesepe cluster
• Measuring tiny mass accretion rates onto young brown dwarfs
• New Low-Mass Stars and Brown Dwarfs with Disks in the Chamaeleon I Star-Forming Region
• The Seven Sisters DANCe. I. Empirical isochrones, Luminosity and Mass Functions of the Pleiades cluster
• An ALMA Continuum Survey of Circumstellar Disks in the Upper Scorpius OB Association
• WISEP J004701.06+680352.1: An intermediate surface gravity, dusty brown dwarf in the AB Dor Moving Group
• Pleiades low-mass brown dwarfs: the cluster L dwarf sequence
• Exploring the Role of Sub-micron Sized Dust Grains in the Atmospheres of Red L0 - L6 Dwarfs
• The optical+infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association
• Planets Around Low-Mass Stars (PALMS). VI. Discovery of a Remarkably Red Planetary-Mass Companion to the AB Dor Moving Group Candidate 2MASS J22362452+4751425
• The Gaia-ESO Survey: metallicity of the Chamaeleon I star forming region
• Age spreads and the temperature dependence of age estimates in Upper Sco
• Spectral library of age-benchmark low-mass stars and brown dwarfs
• Spectral energy distribution simulations of a possible ring structure around the young, red brown dwarf G196-3B

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• Synergies of THESEUS with the large facilities of the 2030s and guest observer opportunities
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