DISCOVERY OF A YOUNG PLANETARY MASS COMPANION TO THE NEARBY M DWARF VHS J125601.92-125723.9

In a search for common proper motion companions using the VISTA Hemisphere Survey and 2MASS catalogs we have identified a very red (J-Ks=2.47 mag) late-L dwarf companion of a previously unrecognized M dwarf VHS J125601.92-125723.9, located at a projected angular separation of 8.06"+/-0.03". From low-resolution optical and near-IR spectroscopy we classified the primary and the companion as an M7.5+/-0.5 and L7+/-1.5, respectively. The primary shows weaker alkali lines than field dwarfs of similar spectral type, but still consistent with either a high-gravity dwarf or a younger object of hundreds of millions of years. The secondary shows spectral features characteristic for low surface gravity objects at ages below several hundred Myr, like the triangular shape of the H-band continuum and alkali lines weaker than in field dwarfs of the same spectral type. The absence of lithium in the atmosphere of the primary and the likely membership to the Local Association allowed us to constrain the age of the system to the range of 150-300 Myr. We report a measurement of the trigonometric parallax pi=78.8+/-6.4 mas, which translates into a distance of 12.7+/-1.0 pc; the pair thus has a projected physical separation of 102+/-9 AU. We derived the Lbol of the components and compared them with theoretical evolutionary models to estimate the masses and effective temperatures. For the primary, we determined log(Lbol/LSun)=-3.14+/-0.10, and a mass of 73 (+20,-15} MJup at the boundary between stars and brown dwarfs and Teff of 2620+/-140 K. For the companion we obtained log(Lbol/LSun)=-5.05+/-0.22 and a mass of 11.2 (+9.7,-1.8) MJup placing it near the deuterium-burning mass limit. The effective temperature derived from evolutionary models is 880 (+140,-110) K, about 400-700 K cooler than expected for field late-L dwarfs.

[1]  James Liebert,et al.  Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field , 2006, astro-ph/0609648.

[2]  Michael C. Liu,et al.  THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, , 2012, 1201.2465.

[3]  B. Macintosh,et al.  Direct Imaging of Multiple Planets Orbiting the Star HR 8799 , 2008, Science.

[4]  A. A. Henden,et al.  Astrometry and photometry for cool dwarfs and brown dwarfs , 2002 .

[5]  J. Graham,et al.  Lithium in Brown Dwarf Candidates: The Mass and Age of the Faintest Pleiades Stars , 1996 .

[6]  G. Montagnier,et al.  The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits. II. Survey description, results, and performances , 2014, 1405.1560.

[7]  I. McLean,et al.  Identifying Young Brown Dwarfs Using Gravity-Sensitive Spectral Features , 2003, astro-ph/0309634.

[8]  P. Rojo,et al.  A library of near-infrared integral field spectra of young M–L dwarfs , 2013, 1306.3709.

[9]  F. Allard,et al.  Deuterium Burning in Substellar Objects , 2000 .

[10]  et al,et al.  Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: The Effects of Temperature, Clouds, and Gravity , 2004, astro-ph/0402451.

[11]  D. Mouillet,et al.  Giant Planet Companion to 2MASSW J1207334-393254 , 2005 .

[12]  C. Marois,et al.  The highest resolution near infrared spectrum of the imaged planetary mass companion 2M1207 b , 2010 .

[13]  K. Luhman,et al.  DISCOVERY OF A BINARY BROWN DWARF AT 2 pc FROM THE SUN , 2013, 1303.2401.

[14]  Discovery of Two T Dwarf Companions with the Spitzer Space Telescope , 2006, astro-ph/0609464.

[15]  J. Bochanski,et al.  THE BROWN DWARF KINEMATICS PROJECT. II. DETAILS ON NINE WIDE COMMON PROPER MOTION VERY LOW MASS COMPANIONS TO NEARBY STARS, , 2009, 0911.1363.

[16]  David R. Soderblom,et al.  Calculating Galactic Space Velocities and Their Uncertainties, with an Application to the Ursa Major Group , 1987 .

[17]  George H. Rieke,et al.  Gravity Indicators in the Near-Infrared Spectra of Brown Dwarfs , 2003, astro-ph/0305147.

[18]  Adam J. Burgasser,et al.  The NIRSPEC Brown Dwarf Spectroscopic Survey. I. Low-Resolution Near-Infrared Spectra , 2003, astro-ph/0309257.

[19]  M. Z. Zapatero Osorio,et al.  NEW ISOLATED PLANETARY-MASS OBJECTS AND THE STELLAR AND SUBSTELLAR MASS FUNCTION OF THE σ ORIONIS CLUSTER , 2012, 1205.4950.

[20]  R. F. Jameson,et al.  The ages of L dwarfs , 2008, 0801.2915.

[21]  D. Lafrenière,et al.  SIMP J2154−1055: A NEW LOW-GRAVITY L4β BROWN DWARF CANDIDATE MEMBER OF THE ARGUS ASSOCIATION , 2014, 1407.5344.

[22]  B. Macintosh,et al.  CLOUDS AND CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HR8799b , 2011, 1103.3895.

[23]  I. Reid,et al.  SpeX SPECTROSCOPY OF UNRESOLVED VERY LOW MASS BINARIES. I. IDENTIFICATION OF 17 CANDIDATE BINARIES STRADDLING THE L DWARF/T DWARF TRANSITION , 2009, 0912.3808.

[24]  C. A. Grady,et al.  DIRECT IMAGING OF A COLD JOVIAN EXOPLANET IN ORBIT AROUND THE SUN-LIKE STAR GJ 504 , 2013, 1307.2886.

[25]  Bernd Freytag,et al.  Solar Chemical Abundances Determined with a CO5BOLD 3D Model Atmosphere , 2010, 1003.1190.

[26]  Michael C. Liu,et al.  A NEAR-INFRARED SPECTROSCOPIC STUDY OF YOUNG FIELD ULTRACOOL DWARFS , 2013, 1305.4418.

[27]  F. Bouchy,et al.  The HARPS search for southern extra-solar planets - XXXI. The M-dwarf sample , 2011, 1111.5019.

[28]  James P. Emerson,et al.  VISTA data flow system: pipeline processing for WFCAM and VISTA , 2004, SPIE Astronomical Telescopes + Instrumentation.

[29]  G. Basri,et al.  A VOLUME-LIMITED SAMPLE OF 63 M7–M9.5 DWARFS. II. ACTIVITY, MAGNETISM, AND THE FADE OF THE ROTATION-DOMINATED DYNAMO , 2009, 0912.4259.

[30]  J. Jenkins,et al.  Spectroscopic signatures of youth in low-mass kinematic candidates of young moving groups , 2014, 1402.3479.

[31]  F. V. Leeuwen.  Validation of the new Hipparcos reduction , 2007, 0708.1752.

[32]  M. Osorio,et al.  Spectroscopic follow-up of L- and T-type proper-motion member candidates in the Pleiades , 2014, 1410.2383.

[33]  H. L. Johnson,et al.  Astronomical Measurements in the Infrared , 1966 .

[34]  Arlo U. Landolt,et al.  UBVRI Photometric Standard Stars in the Magnitude Range 11 , 1992 .

[35]  L. Bildsten,et al.  Light Element Depletion in Contracting Brown Dwarfs and Pre-Main-Sequence Stars , 1997, astro-ph/9711099.

[36]  K. Luhman,et al.  The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs , 2012, 1208.5800.

[37]  C. Bailer-Jones,et al.  Pleiades low-mass brown dwarfs: the cluster L dwarf sequence , 2006, astro-ph/0608255.

[38]  M. Osorio,et al.  Brown Dwarfs in the Pleiades Cluster Confirmed by the Lithium Test , 1996, astro-ph/9607002.

[39]  J. Kirkpatrick,et al.  Keck Spectra of Pleiades Brown Dwarf Candidates and a Precise Determination of the Lithium Depletion Edge in the Pleiades , 1998, astro-ph/9804005.

[40]  Arlo U. Landolt,et al.  UBVRI PHOTOMETRIC STANDARD STARS AROUND THE CELESTIAL EQUATOR: UPDATES AND ADDITIONS , 2009, 0904.0638.

[41]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[42]  M. Skrutskie,et al.  The Coolest Isolated M Dwarf and Other 2MASS Discoveries , 1997 .

[43]  Durham,et al.  WIDE COOL AND ULTRACOOL COMPANIONS TO NEARBY STARS FROM Pan-STARRS 1 , 2014, 1407.2938.

[44]  Peredur M. Williams,et al.  Archiving multi-epoch data and the discovery of variables in the near-infrared , 2009, 0905.3073.

[45]  M. Shara,et al.  THE BROWN DWARF KINEMATICS PROJECT I. PROPER MOTIONS AND TANGENTIAL VELOCITIES FOR A LARGE SAMPLE OF LATE-TYPE M, L, AND T DWARFS , 2008, 0809.3008.

[46]  Martin G. Cohen,et al.  THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE): MISSION DESCRIPTION AND INITIAL ON-ORBIT PERFORMANCE , 2010, 1008.0031.

[47]  K. Cruz,et al.  2MASS J035523.37+113343.7: A YOUNG, DUSTY, NEARBY, ISOLATED BROWN DWARF RESEMBLING A GIANT EXOPLANET , 2012, The Astronomical journal.

[48]  A Search for Very Low Mass Stars and Brown Dwarfs in the Young σ Orionis Cluster , 1999, astro-ph/9903217.

[49]  D. Saumon,et al.  The Evolution of L and T Dwarfs in Color-Magnitude Diagrams , 2008, 0808.2611.

[50]  A VLBI resolution of the Pleiades distance controversy , 2014, Science.

[51]  M. Shara,et al.  THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS , 2012, 1203.5543.

[52]  Todd J. Henry,et al.  A Standard Stellar Spectral Sequence in the Red/Near-Infrared: Classes K5 to M9 , 1991 .

[53]  Suzanne L. Hawley,et al.  Brown Dwarfs in the Hyades and Beyond? , 1998, astro-ph/9811347.

[54]  Bruce Macintosh,et al.  THE YOUNG PLANET-MASS OBJECT 2M1207b: A COOL, CLOUDY, AND METHANE-POOR ATMOSPHERE , 2011, 1106.1201.

[55]  K. Poppenhaeger,et al.  Multi-wavelength observations of Proxima Centauri , 2011, 1109.1130.

[56]  W. Kausch,et al.  Molecfit: A general tool for telluric absorption correction - II. Quantitative evaluation on ESO-VLT/X-Shooterspectra , 2015, 1501.07265.

[57]  James Liebert,et al.  Meeting the Cool Neighbors. V. A 2MASS-Selected Sample of Ultracool Dwarfs , 2003, astro-ph/0307429.

[58]  A. Burgasser,et al.  YOUNG L DWARFS IDENTIFIED IN THE FIELD: A PRELIMINARY LOW-GRAVITY, OPTICAL SPECTRAL SEQUENCE FROM L0 TO L5 , 2008, 0812.0364.

[59]  G. Marcy,et al.  Precise Radial Velocities of 2046 Nearby FGKM Stars and 131 Standards , 2012, 1207.6212.

[60]  R. Rebolo,et al.  Search for free-floating planetary-mass objects in the Pleiades , 2014, 1407.2849.

[61]  R. Griffin.  Accurate Wavelengths of Stellar and Telluric Absorption Lines Near λ7000Å , 1973 .

[62]  P. H. Hauschildt,et al.  Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458 , 2003 .

[63]  Saurav Dhital,et al.  THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 7 SPECTROSCOPIC M DWARF CATALOG. I. DATA , 2011, 1101.1082.

[64]  Gavin Dalton,et al.  The Visible & Infrared Survey Telescope for Astronomy , 2004 .

[65]  Germano R. Quast,et al.  Young Nearby Loose Associations , 2008, 0808.3362.

[66]  Laird M. Close,et al.  EVIDENCE AGAINST AN EDGE-ON DISK AROUND THE EXTRASOLAR PLANET, 2MASS 1207 b AND A NEW THICK-CLOUD EXPLANATION FOR ITS UNDERLUMINOSITY,, , 2011, 1103.1880.

[67]  W. D. Vacca,et al.  THE INFRARED TELESCOPE FACILITY (IRTF) SPECTRAL LIBRARY: COOL STARS , 2009, 0909.0818.

[68]  C. Bailer-Jones,et al.  THE SUBSTELLAR POPULATION OF σ ORIONIS: A DEEP WIDE SURVEY , 2011, 1109.1210.

[69]  M. Osorio,et al.  Near-infrared low-resolution spectroscopy of Pleiades L-type brown dwarfs , 2010, 1005.3249.

[70]  Ben Zuckerman,et al.  Young Stars Near the Sun , 2004 .

[71]  R. J. Wainscoat,et al.  THE EXTREMELY RED, YOUNG L DWARF PSO J318.5338−22.8603: A FREE-FLOATING PLANETARY-MASS ANALOG TO DIRECTLY IMAGED YOUNG GAS-GIANT PLANETS , 2013, 1310.0457.

[72]  Evgenya L. Shkolnik,et al.  PLANETS AROUND LOW-MASS STARS. III. A YOUNG DUSTY L DWARF COMPANION AT THE DEUTERIUM-BURNING LIMIT, , 2013, 1307.2237.

[73]  John T. Rayner,et al.  An Infrared Spectroscopic Sequence of M, L, and T Dwarfs , 2004, astro-ph/0412313.

[74]  David Lafreniere,et al.  DISCOVERY OF A WIDE PLANETARY-MASS COMPANION TO THE YOUNG M3 STAR GU PSC , 2014, 1405.2932.

[75]  N. Deacon,et al.  Southern infrared proper motion survey. II. A sample of low mass stars with μ ≥ 0.1''/ yr , 2007, astro-ph/0702692.

[76]  Luis J. Goicoechea,et al.  Highlights of Spanish Astrophysics V , 2001 .

[77]  W. M. Wood-Vasey,et al.  THE NINTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY: FIRST SPECTROSCOPIC DATA FROM THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY , 2012, 1207.7137.

[78]  Tiffany Meshkat,et al.  HD 106906 b: A PLANETARY-MASS COMPANION OUTSIDE A MASSIVE DEBRIS DISK , 2013, 1312.1265.

[79]  D. A. Golimowski,et al.  L' AND M' Photometry Of Ultracool Dwarfs , 2004 .

[80]  R. Rebolo,et al.  A New Pleiades Member at the Lithium Substellar Boundary , 1998, physics/9803026.

[81]  B. Macintosh,et al.  Images of a fourth planet orbiting HR 8799 , 2010, Nature.

[82]  W. Freudling,et al.  Automated data reduction workflows for astronomy , 2013, 1311.5411.

[83]  F. Allard,et al.  Evolutionary Models for Very Low-Mass Stars and Brown Dwarfs with Dusty Atmospheres , 2000 .

[84]  Barbara E. McArthur,et al.  Confirmation of Errors in Hipparcos Parallaxes from Hubble Space Telescope Fine Guidance Sensor Astrometry of the Pleiades , 2004, astro-ph/0412093.

[85]  Patrick J. Lowrance,et al.  Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574 , 2005 .

[86]  W. Kausch,et al.  Molecfit: A general tool for telluric absorption correction - I. Method and application to ESO instruments , 2015, 1501.07239.

[87]  Laird M. Close,et al.  THE GEMINI NICI PLANET-FINDING CAMPAIGN: DISCOVERY OF A SUBSTELLAR L DWARF COMPANION TO THE NEARBY YOUNG M DWARF CD−35 2722 , 2011, 1101.2893.

[88]  D. A. Golimowski,et al.  Preliminary Parallaxes of 40 L and T Dwarfs from the US Naval Observatory Infrared Astrometry Program , 2004 .

[89]  M. Osorio,et al.  Trigonometric parallaxes of young field L dwarfs , 2014, 1406.1345.

[90]  P. H. Hauschildt,et al.  Spectral Energy Distributions for Disk and Halo M Dwarfs , 2000, astro-ph/0001100.

[91]  R. Paul Butler,et al.  Radial Velocities for 889 Late-Type Stars , 2001, astro-ph/0112477.

[92]  Young Brown Dwarfs as Giant Exoplanet Analogs , 2013, Proceedings of the International Astronomical Union.

[93]  I. A. Steele,et al.  Finding benchmark brown dwarfs to probe the substellar initial mass function as a function of time , 2006 .

[94]  Meeting the Cool Neighbors. X. Ultracool Dwarfs from the 2MASS All-Sky Data Release , 2008 .

[95]  O. Eggen.  The kinematics of young disk population supercluster members , 1992 .

[96]  Paul Clark,et al.  The VISTA infrared camera , 2006, SPIE Astronomical Telescopes + Instrumentation.

[97]  James Liebert,et al.  M dwarf spectra from 0.6 to 1.5 micron - A spectral sequence, model atmosphere fitting, and the temperature scale , 1993 .

[98]  J. Kirkpatrick,et al.  The companion to gliese 569 , 1990 .