J/A+A/686/A37ivo://CDS.VizieR/J/A+A/686/A37doi:10.26093/cds/vizier.36860037CDSPiscarreta L.Muzic K.Almendros-Abad V.Scholz A.2025-02-24T20:00:53Z2024-10-02T10:29:23ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frlate-type-starsspectroscopyinfrared-astronomyJWST and next-generation facilities are expected to uncover populations of free-floating objects below the deuterium-burning limit in a number of young clusters and star-forming regions. These young planetary-mass brown dwarfs have spectral types L and T; they are shaped by molecular absorption and modified by their low gravity, which makes them distinct from field objects. We aim to provide a detailed characterization of near-infrared spectra for young LT brown dwarfs, including robust spectral typing, calibrating spectral indices, identifying possible binaries, and selecting suitable spectral standards. We processed and analyzed archival spectra from VLT/X-shooter for a sample of 56 dwarfs with ages between 10 and 600Myr and spectral types between late-M and mid-T. We re-determine spectral types by comparing them with a set of literature templates and assess a large range of spectral indices, calibrated using a specifically designed literature sample. We are able to identify 15 spectral indices that are useful for spectral typing for specific spectral ranges discussed here and provide the scaling relations with spectral types. Moreover, we also identify 6 spectral indices which can be used to separate young L dwarfs from the field ones. The equivalent-widths of the alkali lines show a correlation with age, increasing towards the objects with higher surface gravity. From our sample, we confirm 3 that are likely to be binaries by their anomalous spectra that appear to be better fitted by a combination of spectral types. Finally, we identify 12 objects as preliminary near-infrared spectral standards for young LT dwarfs. This paper presents a significant step toward understanding the spectral sequence and properties of young L and T dwarfs. The relations and standards provided here will be useful for future spectroscopic work on young brown dwarfs and giant planets.2024A&A...686A..37Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/686/A37CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/686/A37https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/686/A37http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/686/A37https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/686/A37https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/686/A37http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/686/A37GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/686/A37/sources (List of sources)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/686/A37/sources?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/686/A37/sources?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/686/A37/sources?GETtext/xml+votable180.050000true241.5262083-23.58702780.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/686/A375/11088 6/463 466 4720 4725 17729 18166 18281 18594 19761 19763 19783 20996 23471 23718 24581 25097 25170 25335 25838 27074 31411 33166 33377 33667 34400 34434 34535 34645 34818 34824 34866 35202 35387 35630 36237 42990 43475 44357-44362 44364 46094 46671 48349https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/686/A37?format=asciiInfrareddefaultJ/A+A/686/A37/sourcesList of sourcesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[2/63] Source IDmeta.idintNameSource namemeta.id;meta.maincharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainRegionRegion to which each source belongsobs.fieldcharE_SpType? Upper bound uncertainty on the SpTypestat.error;stat.maxfloatnullablee_SpType? Lower bound uncertainty on the SpTypestat.error;src.spTypefloatnullableTempSetSet of templates used for the SpType derivationinstr.setupcharAv? Visual extinctionmagphys.absorptionfloatnullableSpTypeSpectral typesrc.spTypecharspShow the spectrummeta.ref.urlcharFileNameSpectrum file name in subdirectory fitsmeta.id;meta.fitschar