J/AJ/133/2258ivo://CDS.VizieR/J/AJ/133/2258doi:10.26093/cds/vizier.51332258CDSSchmidt S.J.Cruz K.L.Bongiorno B.J.Liebert J.Reid I.N.2017-06-02T08:37:17Z2007-10-25T09:47:42ZCDS support team

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

cds-question@unistra.frdwarf-starslate-type-starsline-intensitiesWe present the activity and kinematics of a representative volume-limited (20pc) sample of 152 late-M and L dwarfs (M7-L8) photometrically selected from the Two Micron All Sky Survey (2MASS). Using new proper-motion measurements and spectrophotometric distance estimates, we calculate tangential velocities. The sample has a mean tangential velocity of <V_tan_>=31.5km/s, a velocity dispersion of {sigma}_tan_=20.7km/s, and a maximum tangential velocity of V_tan_=138.8km/s. These kinematic results are in excellent agreement with previous studies of ultracool dwarfs in the local solar neighborhood. H{alpha} emission, an indicator of chromospheric activity, was detected in 63 of 81 late-M dwarfs and in 16 of 69 L dwarfs examined. We find a lack of correlation between activity strength, measured by log(FH{alpha}/Fbol), and V_tan_, although velocity distributions suggest that the active dwarfs in our sample are slightly younger than the inactive dwarfs. Consistent with previous studies of activity in ultracool dwarfs, we find that the fraction of H-emitting objects per spectral type peaks at spectral type M7 and declines through mid-L dwarfs. Activity strength is similarly correlated with spectral type for types later than M7. Eleven dwarfs out of 150 show evidence of variability, ranging from small fluctuations to large flare events. We estimate a flare cycle of 5% for late-M dwarfs and 2% for L dwarfs. Observations of strong, variable activity on the L1 dwarf 2MASS J10224821+5825453 and an amazing flare event on the M7 dwarf 2MASS J1028404-143843 are discussed.2007AJ....133.2258Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/133/2258CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/241 : 2MASS Catalog Intermediate Data Release (IPAC/UMass, 2000)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)J/AJ/123/2806 : Nearby stars in the NLTT catalogue (Reid+, 2002)J/AJ/123/2822 : Photometry of southern NLTT stars (Reid+, 2002)J/AJ/123/2828 : Spectroscopy of northern NLTT stars (Cruz+, 2002)J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)J/AJ/126/2449 : Nearby ultracool dwarfs in galactic plane (Reid+, 2003)J/AJ/126/3007 : Spectroscopy of faint red NLTT dwarfs (Reid+, 2003)J/AJ/128/463 : A preliminary 20pc census from the NLTT catalogue (Reid+, 2004)J/AJ/133/439 : Luminosity function of M7-L8 ultracool dwarfs (Cruz+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/133/2258https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/133/2258http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/133/2258https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/133/2258https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/133/2258http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/133/2258GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/133/2258/table12 (Kinematics and H{alpha} emission data for the 2MUPM Sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/133/2258/table12?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/133/2258/table12?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/133/2258/table12?GETtext/xml+votable180.050000true1.145-40.7350.0055555555555555566/116 221 399 586 2202 2502 2784 2978 4116 4262 4436 4719 4739 4768 4775 4813 5264 6047 6328 6382 6408 6613 6783 7220 7440 7533 7709 7985 8348 8381 8402 8794 8808 8972 9146 9479 9779 10332 10676 10753 10850 11292 11336 11453 11596 11639 11719 11856 12063 12466 13559 13678 14858 14908 14910 15085 16502 16609 17075 17530 17985 18032 18060 18266 18683 18726 19525 19615 19680 19763 19857 19895 20713 21209 22535 22687 22739 22759 22950 23010 23144 23471 24590 24716 24897 25310 25314 25411 25558 25818 26282 26300 27019 27058 27383 27469 28006 28316 28346 30061 31009 31268 31296 31534 32643 32650 33334 33767 34289 34535 34622 34660 34780 34893 34961 35020 35327 35451 35499 35685 35902 35923 36602 36640 36845 38322 39140 39482 40313 40332 40738 40882 40941 41984 43475 43966 44143 44226 44456 44518 44603 44807 45023 45175 45238 45834 46138 47192 48957 49036 49139https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/133/2258?format=asciiOpticaldefaultJ/AJ/133/2258/table12Kinematics and H{alpha} emission data for the 2MUPM SamplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint2MASSJThe 2MASS Designation (HHMMSSss+DDMMSSs)meta.id;meta.maincharf_2MASSJ[ac] Flag on binarity (G1)meta.codecharUCD? The Ultra Cool Dwarf numbermeta.idintnullableONameOther Namemeta.idcharSpTypeMK Spectral typesrc.spTypecharDist? Distancepcpos.distance;pos.heliocentricfloatnullablee_Dist? Uncertainty in Distpcstat.errorfloatnullablemu? Proper motionarcsec/yrpos.pmfloatnullablee_mu? Uncertainty in muarcsec/yrstat.errorfloatnullablen_mu[b] Origin of the proper motion (2)meta.notecharPA? Position angledegpos.posAngfloatnullablee_PA? Uncertainty in PAdegstat.errorfloatnullableVtan? Tangential velocitykm/sphys.veloc.transversefloatnullablee_Vtan? Uncertainty in VTankm/sstat.errorfloatnullabler_SpType? Reference for SpType, in refs.dat filemeta.ref;pos.frameintnullabler_plxParallax reference, in refs.dat file (3)meta.ref;pos.framecharKmagThe K band magnitudemagphot.mag;em.IR.KfloatmbolThe bolometric magnitudemagphot.mag.bolfloatFbolThe bolometric fluxmW.m**-2phot.flux.boldoublel_EWLimit flag on EWmeta.code.error;spect.line.eqWidthcharEW? The H{alpha} equivalent width0.1nmspect.line.eqWidth;em.line.HalphafloatnullableFHa? The H{alpha} fluxmW.m**-2phot.flux;em.line.HalphadoublenullablelogFHa/Fbol? H{alpha} flux to bolometric fluxphot.flux.bolfloatnullableObs.DateUT date of observationtime.epoch;obsnullabler_Spect? Spectra reference, in refs.dat (2)meta.ref;pos.frameintnullable_RAPosition, from 2MASS name (right ascension part)degpos.eq.ra;meta.main_DEPosition, from 2MASS name (declination part)degpos.eq.dec;meta.mainJ/AJ/133/2258/refsReferencesComCommentsmeta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRefReference numbermeta.id;meta.mainintBibCodeBibCodemeta.bib.bibcodecharAutAuthor's namemeta.bib.authorchar