THE NASA-UC-UH ETA-EARTH PROGRAM. IV. A LOW-MASS PLANET ORBITING AN M DWARF 3.6 PC FROM EARTH

We report the discovery of a low-mass planet orbiting Gl 15 A based on radial velocities from the Eta-Earth Survey using HIRES at Keck Observatory. Gl 15 Ab is a planet with minimum mass M sin i = 5.35 ± 0.75 M_⊕, orbital period P = 11.4433  ±  0.0016 days, and an orbit that is consistent with circular. We characterize the host star using a variety of techniques. Photometric observations at Fairborn Observatory show no evidence for rotational modulation of spots at the orbital period to a limit of ~0.1 mmag, thus supporting the existence of the planet. We detect a second RV signal with a period of 44 days that we attribute to rotational modulation of stellar surface features, as confirmed by optical photometry and the Ca ii H & K activity indicator. Using infrared spectroscopy from Palomar-TripleSpec, we measure an M2 V spectral type and a sub-solar metallicity ([M/H] = −0.22, [Fe/H] = −0.32). We measure a stellar radius of 0.3863 ± 0.0021 R_☉ based on interferometry from CHARA.

[1]  Caltech,et al.  THE GJ 436 SYSTEM: DIRECTLY DETERMINED ASTROPHYSICAL PARAMETERS OF AN M DWARF AND IMPLICATIONS FOR THE TRANSITING HOT NEPTUNE , 2012, 1202.0083.

[2]  S. Lippincott.  Parallax and orbital motion of the two nearby long period visual binaries Groombridge 34 and ADS 9090. , 1972 .

[3]  M. Barbieri,et al.  HD 17156b: A Transiting Planet with a 21.2 Day Period and an Eccentric Orbit , 2007, 0710.0898.

[4]  S. Leggett.  Infrared Colors of Low-Mass Stars , 1992 .

[5]  A. Pickles.  A Stellar Spectral Flux Library: 1150–25000 Å , 1998 .

[6]  Debra A. Fischer,et al.  A Bayesian Periodogram Finds Evidence for Three Planets in 47 Ursae Majoris , 2010, 1003.5549.

[7]  S. T. Ridgway,et al.  First Results from the CHARA Array. II. A Description of the Instrument , 2005 .

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

[9]  Gregory W. Henry.  Techniques for Automated High-Precision Photometry of Sun-like Stars , 1999 .

[10]  R. P. Butler,et al.  A Transiting “51 Peg-like” Planet , 2000, The Astrophysical journal.

[11]  John T. Rayner,et al.  Spextool: A Spectral Extraction Package for SpeX, a 0.8–5.5 Micron Cross‐Dispersed Spectrograph , 2004 .

[12]  J. Valenti,et al.  THE NASA-UC ETA-EARTH PROGRAM. III. A SUPER-EARTH ORBITING HD 97658 AND A NEPTUNE-MASS PLANET ORBITING Gl 785 , 2010, 1011.0414.

[13]  Andrew R. Liddle,et al.  How many cosmological parameters , 2004, astro-ph/0401198.

[14]  James P. Lloyd,et al.  METAL-RICH M-DWARF PLANET HOSTS: METALLICITIES WITH K-BAND SPECTRA , 2010, 1007.4593.

[15]  Jason T. Wright,et al.  RETIRED A STARS AND THEIR COMPANIONS. VII. 18 NEW JOVIAN PLANETS , 2011, 1108.4205.

[16]  Habitability of exoplanetary systems with planets observed in transit , 2010, 1006.0657.

[17]  H Germany,et al.  A Method of Correcting Near‐Infrared Spectra for Telluric Absorption , 2002, astro-ph/0211255.

[18]  W. K. Hastings,et al.  Monte Carlo Sampling Methods Using Markov Chains and Their Applications , 1970 .

[19]  Willie Soon,et al.  Photometric and Ca II H and K Spectroscopic Variations in Nearby Sun-like Stars with Planets. III. , 2000 .

[20]  F. Bouchy,et al.  The HARPS search for southern extra-solar planets: XVIII. An Earth-mass planet in the GJ 581 planetary system , 2009, 0906.2780.

[21]  Jean-Luc Margot,et al.  ARCHITECTURE OF PLANETARY SYSTEMS BASED ON KEPLER DATA: NUMBER OF PLANETS AND COPLANARITY , 2012, 1207.5250.

[22]  S. T. Ridgway,et al.  First Results from the CHARA Array. IV. The Interferometric Radii of Low-Mass Stars , 2006, astro-ph/0602105.

[23]  D. Queloz,et al.  The HARPS search for Earth-like planets in the habitable zone - I. Very low-mass planets around HD 20794, HD 85512, and HD 192310 , 2011, 1108.3447.

[24]  Donald Geman,et al.  Stochastic Relaxation, Gibbs Distributions, and the Bayesian Restoration of Images , 1984, IEEE Transactions on Pattern Analysis and Machine Intelligence.

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

[26]  Mercedes Lopez-Morales,et al.  55 CANCRI: STELLAR ASTROPHYSICAL PARAMETERS, A PLANET IN THE HABITABLE ZONE, AND IMPLICATIONS FOR THE RADIUS OF A TRANSITING SUPER-EARTH , 2011, 1106.1152.

[27]  H. L. Johnson.  Infrared Photometry of M-Dwarf Stars. , 1965 .

[28]  R. P. Butler,et al.  DETERMINING SPECTROMETER INSTRUMENTAL PROFILES USING FTS REFERENCE SPECTRA , 1995 .

[29]  D. Ciardi,et al.  Stellar diameters and temperatures - V. 11 newly characterized exoplanet host stars , 2013, 1312.1792.

[30]  Andrew W. Howard,et al.  Observed Properties of Extrasolar Planets , 2013, Science.

[31]  CHARACTERIZING THE COOL KOIs. II. THE M DWARF KOI-254 AND ITS HOT JUPITER* , 2011, 1112.0017.

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

[33]  A. Witt,et al.  Spectral classification and photometry of high proper motion stars. , 1967 .

[34]  Kaspar von Braun,et al.  DIRECTLY DETERMINED LINEAR RADII AND EFFECTIVE TEMPERATURES OF EXOPLANET HOST STARS , 2009, 0901.1206.

[35]  N. Lomb.  Least-squares frequency analysis of unequally spaced data , 1976 .

[36]  S. Terebey,et al.  10 Micron Search for Cool Companions of Nearby Stars , 1998 .

[37]  J. Valenti,et al.  THE NASA-UC ETA-EARTH PROGRAM. I. A SUPER-EARTH ORBITING HD 7924 , 2009, 0901.4394.

[38]  Gordon A. H. Walker,et al.  To appear in Astrophysical Journal Letters Evidence for a Long-period Planet Orbiting Epsilon Eridani 1 , 2000 .

[39]  Frantz Martinache,et al.  The performance of TripleSpec at Palomar , 2008, Astronomical Telescopes + Instrumentation.

[40]  James Howard,et al.  Mass producing an efficient NIR spectrograph , 2004, SPIE Astronomical Telescopes + Instrumentation.

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

[42]  R. P. Butler,et al.  ATTAINING DOPPLER PRECISION OF 3 M S-1 , 1996 .

[43]  A. Dotter,et al.  ACCURATE LOW-MASS STELLAR MODELS OF KOI-126 , 2011, 1109.2063.

[44]  G. Rieke,et al.  Far-Infrared Properties of M Dwarfs , 2007, 0707.0464.

[45]  K. Apps,et al.  ON THE METAL RICHNESS OF M DWARFS WITH PLANETS , 2009, 0904.3092.

[46]  R. Paul Butler,et al.  THE LICK-CARNEGIE EXOPLANET SURVEY: A URANUS-MASS FOURTH PLANET FOR GJ 876 IN AN EXTRASOLAR LAPLACE CONFIGURATION , 2010, 1006.4244.

[47]  Caltech,et al.  ASTROPHYSICAL PARAMETERS AND HABITABLE ZONE OF THE EXOPLANET HOSTING STAR GJ 581 , 2011, 1102.0237.

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

[49]  D. Queloz,et al.  The HARPS search for southern extra-solar planets. X. A m sin i = 11 M_â planet around the nearby spotted M dwarf GJ 674 , 2007, 0704.0270.

[50]  Suzanne L. Hawley,et al.  The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The Northern M Dwarfs -Bandstrengths and Kinematics , 1995 .

[51]  Terry D. Oswalt,et al.  The Future of Small Telescopes in the New Millennium , 2003 .

[52]  Eric B. Ford,et al.  Improving the Efficiency of Markov Chain Monte Carlo for Analyzing the Orbits of Extrasolar Planets , 2005, astro-ph/0512634.

[53]  E. Ford.  QUANTIFYING THE UNCERTAINTY IN THE ORBITS OF EXTRASOLAR PLANETS , 2003, astro-ph/0305441.

[54]  F. Allard,et al.  Models of very-low-mass stars, brown dwarfs and exoplanets , 2011, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[55]  Gordon A. H. Walker,et al.  Evidence for a Long-Period Planet Orbiting ϵ Eridani , 2000, astro-ph/0009423.

[56]  A Planetary Companion to a Nearby M4 Dwarf, Gliese 876* , 1998, astro-ph/9807307.

[57]  Models of Stars, Brown Dwarfs and Exoplanets , 2011 .

[58]  G. Henry,et al.  An Automated Search for Variability in Chromospherically Active Stars , 1995 .

[59]  J. Scargle.  Studies in astronomical time series analysis. II - Statistical aspects of spectral analysis of unevenly spaced data , 1982 .

[60]  Jon M. Jenkins,et al.  ARCHITECTURE AND DYNAMICS OF KEPLER'S CANDIDATE MULTIPLE TRANSITING PLANET SYSTEMS , 2011, 1102.0543.

[61]  R. P. Butler,et al.  A JUPITER-LIKE PLANET ORBITING THE NEARBY M DWARF GJ 832 , 2008, 0809.0172.

[62]  Philip A. Ianna,et al.  The Solar Neighborhood. XIII. Parallax Results from the CTIOPI 0.9 Meter Program: Stars with μ >= 1.0" yr -1 (MOTION Sample) , 2005 .

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

[64]  É. Houdebine.  Observation and modelling of main-sequence star chromospheres – XIV. Rotation of dM1 stars★ , 2010 .

[65]  William Wilson Morgan,et al.  Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas , 1953 .

[66]  Howard Isaacson,et al.  THE NASA-UC ETA-EARTH PROGRAM. II. A PLANET ORBITING HD 156668 WITH A MINIMUM MASS OF FOUR EARTH MASSES , 2010, 1003.3444.

[67]  S. Baliunas,et al.  No Planet for Hd 166435 , 2022 .

[68]  The N2K Consortium. II. A Transiting Hot Saturn around HD 149026 with a Large Dense Core , 2005, astro-ph/0507009.

[69]  D. Queloz,et al.  The HARPS search for southern extra-solar planets - XIV. Gl 176b, a super-Earth rather than a Neptune, and at a different period , 2008, 0809.0750.

[70]  James P. Lloyd,et al.  METALLICITY AND TEMPERATURE INDICATORS IN M DWARF K-BAND SPECTRA: TESTING NEW AND UPDATED CALIBRATIONS WITH OBSERVATIONS OF 133 SOLAR NEIGHBORHOOD M DWARFS , 2011, 1112.4567.

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

[72]  Paolo Conconi,et al.  Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series , 2012 .

[73]  B. Twarog.  The chemical evolution of the solar neighborhood. I. A bias-free reduction technique and data sample , 1980 .

[74]  Charles J. Lada,et al.  THE AGE, STELLAR CONTENT, AND STAR FORMATION TIMESCALE OF THE B59 DENSE CORE , 2010, 1007.2192.

[75]  M. R. Haas,et al.  PLANET OCCURRENCE WITHIN 0.25 AU OF SOLAR-TYPE STARS FROM KEPLER , 2011, 1103.2541.

[76]  Philip A. Ianna,et al.  The Solar Neighborhood. XVII. Parallax Results from the CTIOPI 0.9 m Program: 20 New Members of the RECONS 10 Parsec Sample , 2006, astro-ph/0608230.

[77]  Jeffrey C. Hall,et al.  THE ACTIVITY AND VARIABILITY OF THE SUN AND SUN-LIKE STARS. II. CONTEMPORANEOUS PHOTOMETRY AND SPECTROSCOPY OF BRIGHT SOLAR ANALOGS , 2009 .

[78]  Howard Isaacson,et al.  The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters , 2010, Science.

[79]  D. Queloz,et al.  Detection of transits of the nearby hot Neptune GJ 436 b , 2007, Astronomy & Astrophysics.

[80]  F. Bouchy,et al.  An Earth-mass planet orbiting α Centauri B , 2012, Nature.

[81]  A. Upgren.  Five-color photometry of nearby red dwarfs. II. , 1973 .

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

[83]  S. Saar,et al.  Searching for Planets in the Hyades. III. The Quest for Short-Period Planets , 2003, astro-ph/0312122.

[84]  A. Howard,et al.  EFFICIENT FITTING OF MULTIPLANET KEPLERIAN MODELS TO RADIAL VELOCITY AND ASTROMETRY DATA , 2009, 0904.3725.

[85]  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 .

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

[87]  Russel J. White,et al.  STELLAR DIAMETERS AND TEMPERATURES. II. MAIN-SEQUENCE K- AND M-STARS , 2012, 1208.2431.

[88]  M. Mermilliod,et al.  $uvby\beta$ photoelectric photometric catalogue , 1998 .

[89]  G. Henry,et al.  Starspot evolution, differential rotation, and magnetic cycles in the chromospherically active binaries lambda andromedae, sigma Geminorum, II Pegasi, and V711 Tauri , 1995 .

[90]  E. Olson,et al.  Four-color photometry of late-type stars. , 1974 .

[91]  Darko Jevremovic,et al.  The Dartmouth Stellar Evolution Database , 2008, 0804.4473.

[92]  B. Krauskopf,et al.  Proc of SPIE , 2003 .

[93]  A. M. Fowler,et al.  Demonstration of an algorithm for read-noise reduction in infrared arrays , 1990 .