THE TRENDS HIGH-CONTRAST IMAGING SURVEY. V. DISCOVERY OF AN OLD AND COLD BENCHMARK T-DWARF ORBITING THE NEARBY G-STAR HD 19467

The nearby Sun-like star HD 19467 shows a subtle radial velocity (RV) acceleration of –1.37 ± 0.09 m s^(–1) yr^(–1) over a 16.9 yr time baseline (an RV trend), hinting at the existence of a distant orbiting companion. We have obtained high-contrast images of the star using NIRC2 at Keck Observatory and report the direct detection of the body that causes the acceleration. The companion, HD 19467 B, is ΔK_s = 12.57 ± 0.09 mag fainter than its parent star (contrast ratio of 9.4 × 10^(–6)), has blue colors J – K_s = –0.36 ± 0.14 (J – H = –0.29 ± 0.15), and is separated by ρ = 1."± 0."004 (51.1 ± 1.0 AU). Follow-up astrometric measurements obtained over a 1.1 yr time baseline demonstrate physical association through common parallactic and proper motion. We calculate a firm lower-limit of m ⩾ 51.9^(+3.6)_(-4.3)M_J for the companion mass from orbital dynamics using a combination of Doppler observations and imaging. We estimate a model-dependent mass of m=56.7^(+4.6)_(-7.2)M_(Jup) from a gyrochronological age of 4.3^(+1.0)_(-1.2) Gyr. Isochronal analysis suggests a much older age of 9 ± 1 Gyr, which corresponds to a mass of m = 67.4^(+0.9)_(-1.5)M_J. HD 19467 B's measured colors and absolute magnitude are consistent with a late T dwarf [≈T5-T7]. We may infer a low metallicity of [Fe/H] =–0.15 ± 0.04 for the companion from its G3V parent star. HD 19467 B is the first directly imaged benchmark T dwarf found orbiting a Sun-like star with a measured RV acceleration.

[1]  Jason T. Wright,et al.  Five New Extrasolar Planets , 2005 .

[2]  L. Hillenbrand,et al.  Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics , 2008, 0807.1686.

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

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

[5]  Jr.,et al.  A New High Contrast Imaging Program at Palomar Observatory , 2010, 1012.0008.

[6]  R. P. Butler,et al.  PRECISION RADIAL VELOCITIES WITH AN IODINE ABSORPTION CELL , 1992 .

[7]  M. Tamura,et al.  MID-INFRARED PHOTOMETRY OF COLD BROWN DWARFS: DIVERSITY IN AGE, MASS, AND METALLICITY , 2010, 1001.0762.

[8]  Jason T. Wright,et al.  THE TRENDS HIGH-CONTRAST IMAGING SURVEY. II. DIRECT DETECTION OF THE HD 8375 TERTIARY , 2012, 1210.7374.

[9]  O. Schnurr,et al.  An overlooked brown dwarf neighbour (T7.5 at d ~ 5 pc) of the Sun and two additional T dwarfs at about 10 pc , 2013, 1307.2722.

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

[11]  J. Valenti,et al.  Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs , 2005 .

[12]  Jason T. Wright,et al.  Chromospheric Ca II Emission in Nearby F, G, K, and M Stars , 2004, astro-ph/0402582.

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

[14]  Michael C. Cushing,et al.  THE DISCOVERY OF Y DWARFS USING DATA FROM THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE) , 2011, 1108.4678.

[15]  J. Valenti,et al.  Spectroscopy Made Easy: A New Tool for Fitting Observations with Synthetic Spectra , 1996 .

[16]  Howard Isaacson,et al.  THE DYNAMICAL MASS AND THREE-DIMENSIONAL ORBIT OF HR7672B: A BENCHMARK BROWN DWARF WITH HIGH ECCENTRICITY , 2011, 1112.1725.

[17]  Mukremin Kilic,et al.  THE TRENDS HIGH-CONTRAST IMAGING SURVEY. III. A FAINT WHITE DWARF COMPANION ORBITING HD 114174 , 2013 .

[18]  G. Torres.  Substellar Companion Masses from Minimal Radial Velocity or Astrometric Information: a Monte Carlo Approach , 1999 .

[19]  Michael C. Liu,et al.  RETIRED A STARS AND THEIR COMPANIONS. III. COMPARING THE MASS–PERIOD DISTRIBUTIONS OF PLANETS AROUND A-TYPE STARS AND SUN-LIKE STARS , 2009, 0912.0518.

[20]  Terry Jones,et al.  FIRST LIGHT LBT AO IMAGES OF HR 8799 bcde AT 1.6 AND 3.3 μm: NEW DISCREPANCIES BETWEEN YOUNG PLANETS AND OLD BROWN DWARFS , 2012, 1203.2615.

[21]  C. A. Grady,et al.  NEAR-INFRARED MULTI-BAND PHOTOMETRY OF THE SUBSTELLAR COMPANION GJ 758 B , 2010, 1011.5505.

[22]  R. Paul Butler,et al.  Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L Dwarf Companion to the Nearby Solar Analog HR 7672 , 2002 .

[23]  Jessica R. Lu,et al.  Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole with Stellar Orbits , 2008, 0808.2870.

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

[25]  Z. Li,et al.  BRIGHTEST SATELLITE GALAXY ALIGNMENT OF SLOAN DIGITAL SKY SURVEY GALAXY GROUPS , 2013 .

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

[27]  Michael C. Liu,et al.  DISCOVERY OF A HIGHLY UNEQUAL-MASS BINARY T DWARF WITH KECK LASER GUIDE STAR ADAPTIVE OPTICS: A COEVALITY TEST OF SUBSTELLAR THEORETICAL MODELS AND EFFECTIVE TEMPERATURES , 2010, 1008.2200.

[28]  Howard Isaacson,et al.  CHROMOSPHERIC ACTIVITY AND JITTER MEASUREMENTS FOR 2630 STARS ON THE CALIFORNIA PLANET SEARCH , 2010, 1009.2301.

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

[30]  J. Wright,et al.  Radial velocity jitter in stars from the california and carnegie planet search at keck observatory , 2005 .

[31]  John Asher Johnson,et al.  ESTIMATES OF THE PLANET YIELD FROM GROUND-BASED HIGH-CONTRAST IMAGING OBSERVATIONS AS A FUNCTION OF STELLAR MASS , 2011, 1103.4910.

[32]  S. Barnes.  Accepted for publication in The Astrophysical Journal Ages for illustrative field stars using gyrochronology: viability, limitations and errors , 2022 .

[33]  J. Crepp,et al.  THE TRENDS HIGH-CONTRAST IMAGING SURVEY. I. THREE BENCHMARK M DWARFS ORBITING SOLAR-TYPE STARS , 2012, 1210.3000.

[34]  D. S. Acton,et al.  First Light Adaptive Optics Images from the Keck II Telescope: A New Era of High Angular Resolution Imagery , 2000 .

[35]  Jason T. Wright,et al.  THE CALIFORNIA PLANET SURVEY. I. FOUR NEW GIANT EXOPLANETS , 2010, 1003.3488.

[36]  M. Couture,et al.  HIRES: the high-resolution echelle spectrometer on the Keck 10-m Telescope , 1994, Astronomical Telescopes and Instrumentation.

[37]  Etienne Artigau,et al.  CFBDSIR J1458+1013B: A VERY COLD (>T10) BROWN DWARF IN A BINARY SYSTEM,, , 2011, 1103.0014.

[38]  Malcolm Smith,et al.  The Gemini Planet Imager: integration and status , 2012, Other Conferences.

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

[40]  Bruce A. Macintosh,et al.  Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere , 2013, Science.

[41]  Emilio Molina,et al.  Summary and Discussion , 2014 .

[42]  P. Baudoz,et al.  Hokupa'a-gemini discovery of two ultracool companions to the young star hd 130948 , 2002 .