THE DIRECTLY IMAGED PLANET AROUND THE YOUNG SOLAR ANALOG 1RXS J160929.1 − 210524: CONFIRMATION OF COMMON PROPER MOTION, TEMPERATURE, AND MASS

Giant planets are usually thought to form within a few tens of AU of their host stars, and hence it came as a surprise when we found what appeared to be a planetary mass (~0.008 M ?) companion around the 5 Myr old solar mass star 1RXS?J160929.1 ? 210524 in the Upper Scorpius association. At the time, we took the object's membership in Upper Scorpius?established from near-infrared, H- and K-band spectroscopy?and its proximity (22 or 330?AU) to the primary as strong evidence for companionship, but could not verify their common proper motion. Here, we present follow-up astrometric measurements that confirm that the companion is indeed comoving with the primary star, which we interpret as evidence that it is a truly bound planetary mass companion. We also present new J-band spectroscopy and 3.0-3.8 ?m photometry of the companion. Based on a comparison with model spectra, these new measurements are consistent with the previous estimate of the companion effective temperature of 1800 ? 200?K. We present a new estimate of the companion mass based on evolution models and the calculated bolometric luminosity of the companion; we obtain a value of 0.008+0.003 ?0.002 M ?, again consistent with our previous result. Finally, we present angular differential imaging observations of the system allowing us to rule out additional planets in the system more massive than 1?M Jup, 2?M Jup, and 8?M Jup at projected separations larger than 3'' (~440?AU), 07 (~100?AU), and 035 (~50?AU), respectively. This companion is the least massive known to date at such a large orbital distance; it shows that objects in the planetary mass range exist at orbital separations of several hundred?AU, posing a serious challenge for current formation models.

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

[2]  R. Rebolo,et al.  Discovery of a Wide Companion near the Deuterium-burning Mass Limit in the Upper Scorpius Association , 2007, 0712.3482.

[3]  M. Wyatt,et al.  Evolution of Debris Disks , 2008 .

[4]  Klaus W. Hodapp,et al.  The Gemini Near‐Infrared Imager (NIRI) , 2003 .

[5]  David Lafreniere,et al.  HST/NICMOS DETECTION OF HR 8799 b IN 1998 , 2009, 0902.3247.

[6]  David Lafreniere,et al.  Direct Imaging and Spectroscopy of a Planetary-Mass Candidate Companion to a Young Solar Analog , 2008, 0809.1424.

[7]  Mark Clampin,et al.  A planetary system as the origin of structure in Fomalhaut's dust belt , 2005, Nature.

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

[9]  H. Bouy,et al.  Proper motions of cool and ultracool candidate members in the Upper Scorpius OB association , 2009, 0907.0149.

[10]  Royal Observatory of Edinburgh,et al.  Consistent Simulations of Substellar Atmospheres and Nonequilibrium Dust Cloud Formation , 2008, 0801.3733.

[11]  David R. Alexander,et al.  THE LIMITING EFFECTS OF DUST IN BROWN DWARF MODEL ATMOSPHERES , 2001 .

[12]  Weinberger,et al.  The Circumstellar Disk of HD 141569 Imaged with NICMOS. , 1999, The Astrophysical journal.

[13]  Boeing,et al.  The Solar-System-Scale Disk around AB Aurigae , 2008, 0803.3629.

[14]  Aaron C. Boley,et al.  Clumps in the outer disk by disk instability: Why they are initially gas giants and the legacy of disruption , 2009, 0909.4543.

[15]  Anthony G. A. Brown,et al.  Exploring the Full Stellar Population of the Upper Scorpius OB Association , 2002 .

[16]  Jack J. Lissauer,et al.  Formation of the Giant Planets by Concurrent Accretion of Solids and Gas , 1995 .

[17]  Justin R. Crepp,et al.  FORMATION, SURVIVAL, AND DETECTABILITY OF PLANETS BEYOND 100 AU , 2009, 0902.2779.

[18]  Volker Bromm,et al.  The formation of a star cluster: predicting the properties of stars and brown dwarfs , 2002, astro-ph/0212380.

[19]  Hiroyuki Mito,et al.  The IRSA 2MASS all-sky point source catalog , 2008 .

[20]  R. O. Gray,et al.  ABSOLUTE PHYSICAL CALIBRATION IN THE INFRARED , 2008, 0806.1910.

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

[22]  P. Padoan,et al.  The Stellar Initial Mass Function from Turbulent Fragmentation , 2000, astro-ph/0011465.

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

[24]  B. Oppenheimer,et al.  The Gemini Deep Planet Survey , 2007, 0705.4290.

[25]  Roman R. Rafikov.  Convective cooling and fragmentation of gravitationally unstable disks , 2007 .

[26]  B. Zuckerman,et al.  The minimum Jeans mass, brown dwarf companion IMF, and predictions for detection of Y-type dwarfs , 2008, 0811.0429.

[27]  Glen Herriot,et al.  Progress on Altair: the Gemini North adaptive optics system , 2000, Astronomical Telescopes and Instrumentation.

[28]  Subaru Telescope,et al.  DISCOVERY OF THE COLDEST IMAGED COMPANION OF A SUN-LIKE STAR , 2009, 0911.1127.

[29]  K. Menou,et al.  LONG-PERIOD EXOPLANETS FROM DYNAMICAL RELAXATION , 2008, 0811.1981.

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

[31]  University of Toronto,et al.  THE RUNTS OF THE LITTER: WHY PLANETS FORMED THROUGH GRAVITATIONAL INSTABILITY CAN ONLY BE FAILED BINARY STARS , 2009, 0909.2644.

[32]  Alan P. Boss,et al.  Giant Planet Formation by Gravitational Instability , 1997 .

[33]  Submillimeter Images of a Dusty Kuiper Belt around η Corvi , 2004, astro-ph/0411061.

[34]  Jena,et al.  Direct evidence of a sub-stellar companion around CT Chamaeleontis , 2008, 0809.2812.

[35]  K. Luhman,et al.  DISCOVERY OF A PLANETARY-MASS COMPANION TO A BROWN DWARF IN TAURUS , 2010, 1004.0539.

[36]  Miki Ishii,et al.  A Young Brown Dwarf Companion to DH Tauri , 2004 .

[37]  Mark Clampin,et al.  Optical Images of an Exosolar Planet 25 Light-Years from Earth , 2008, Science.

[38]  B. Macintosh,et al.  Angular Differential Imaging: A Powerful High-Contrast Imaging Technique , 2005, astro-ph/0512335.

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

[40]  F. Meru,et al.  Exploring the conditions required to form giant planets via gravitational instability in massive protoplanetary discs , 2010, 1004.3766.

[41]  Wm. A. Wheaton,et al.  2MASS All Sky Catalog of point sources. , 2003 .

[42]  Etienne Artigau,et al.  A New Algorithm for Point-Spread Function Subtraction in High-Contrast Imaging: A Demonstration with Angular Differential Imaging , 2007, astro-ph/0702697.

[43]  Jan Van Harmelen,et al.  Gemini near-infrared integral field spectrograph (NIFS) , 2003, SPIE Astronomical Telescopes + Instrumentation.

[44]  P. Hauschildt,et al.  Evidence for a co-moving sub-stellar companion of GQ Lup , 2005, astro-ph/0503691.

[45]  IPAC,et al.  A Candidate Substellar Companion to CD –33°7795 (TWA 5) , 1999 .

[46]  M. Skrutskie,et al.  Discovery of a Young Substellar Companion in Chamaeleon , 2006, astro-ph/0609187.

[47]  D. Mouillet,et al.  A companion to AB Pic at the planet/brown dwarf boundary , 2005, astro-ph/0504658.

[48]  B. Zuckerman,et al.  Submillimetre images of dusty debris around nearby stars , 1998, Nature.

[49]  Mullard Space Science Laboratory,et al.  A Dust Ring around epsilon Eridani: Analog to the Young Solar System , 1998, astro-ph/9808224.

[50]  A. Boss.  On the Formation of Gas Giant Planets on Wide Orbits , 2006, astro-ph/0601278.

[51]  R. F. Jameson,et al.  Near‐infrared cross‐dispersed spectroscopy of brown dwarf candidates in the Upper Sco association★ , 2007, 0711.1109.

[52]  Evidence for Mass-dependent Circumstellar Disk Evolution in the 5 Myr Old Upper Scorpius OB Association , 2006, astro-ph/0609372.

[53]  I. Reid,et al.  LP 261‐75/2MASSW J09510549+3558021: A Young, Wide M4.5/L6 Binary , 2006 .

[54]  Glenn Schneider,et al.  NICMOS Imaging of the HR 4796A Circumstellar Disk , 1999 .

[55]  F. Allard,et al.  The NextGen Model Atmosphere Grid for 3000 ≤ Teff ≤ 10,000 K , 1998, astro-ph/9807286.