Geoffrey W. Marcy

Publications (227)1005.45 Total impact

• Article: The TRENDS High-Contrast Imaging Survey. III. A Faint White Dwarf Companion Orbiting HD 114174

  Justin R. Crepp, John Asher Johnson, Andrew W. Howard, Geoffrey W. Marcy, Alexandros Gianninas, Mukremin Kilic, Jason T. Wright
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  ABSTRACT: The nearby Sun-like star HD 114174 exhibits a strong and persistent Doppler acceleration indicating the presence of an unseen distant companion. We have acquired high-contrast imaging observations of this star using NIRC2 at Keck and report the direct detection of the body responsible for causing the "trend". HD 114174 B has a projected separation of 692+/-9 mas (18.1 AU) and is 10.75+/-0.12 magnitudes (contrast of 5x10{-5}) fainter than its host in the K-band, requiring aggressive point-spread function subtraction to identify. Our astrometric time baseline of 1.4 years demonstrates physical association through common proper motion. We find that the companion has absolute magnitude, M_J=13.97+/-0.11, and colors, J-K= 0.12+/-0.16 mag. These characteristics are consistent with an ~T3 dwarf, initially leading us to believe that HD 114174 B was a substellar object. However, a dynamical analysis that combines radial velocity measurements with available imaging data indicates a minimum mass of m=0.260+/-0.010Msun. We conclude that HD 114174 B must be a white dwarf. Assuming a hydrogen-rich composition, atmospheric and evolutionary model fits yield an effective temperature Teff = 8160+/-4000 K, surface gravity log g=8.90+/-0.02, and cooling age of t_c 3.4 Gyr, which is consistent with the 4.7+/-2.4 Gyr host star isochronal age estimate. HD 114174 B is a benchmark object located only d=26.1 pc from the Sun. It may be studied at a level of detail comparable to Sirius and Procyon, and used to understand the link between the mass of white dwarf remnants with that of their progenitors.
  05/2013;
• Article: Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone.

  William J Borucki, Eric Agol, Francois Fressin, Lisa Kaltenegger, Jason Rowe, Howard Isaacson, Debra Fischer, Natalie Batalha, Jack J Lissauer, Geoffrey W Marcy, [......], Shawn Seader, Avi Shporer, Jason H Steffen, Martin Still, Peter Tenenbaum, Susan E Thompson, Guillermo Torres, Joseph D Twicken, William F Welsh, Joshua N Winn
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  ABSTRACT: We present the detection of five planets-Kepler-62b, c, d, e, and f-of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R⊕), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets (Kepler-62e and -62f) are super-Earth-size (1.25 < planet radius ≤ 2.0 R⊕) planets in the habitable zone (HZ) of their host star, receiving 1.2 ± 0.2 and 0.41 ± 0.05 times the solar flux at Earth's orbit (S⊙). Theoretical models of Kepler-62e and -62f for a stellar age of ~7 Gyr suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk.
  Science 04/2013; · 31.20 Impact Factor
• Article: A super-Earth-sized planet orbiting in or near the habitable zone around Sun-like star

  Thomas Barclay, Christopher J. Burke, Steve B. Howell, Jason F. Rowe, Daniel Huber, Howard Isaacson, Jon M. Jenkins, Rea Kolbl, Geoffrey W. Marcy, Elisa V. Quintana, [......], Michael R. Haas, Roger Hunter, Jack J. Lissauer, Fergal Mullally, Anima Sabale, Shawn E. Seader, Jeffrey C. Smith, Peter Tenenbaum, AKM Kamal Uddin, Susan E. Thompson
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  ABSTRACT: We present the discovery of a super-earth-sized planet in or near the habitable zone of a sun-like star. The host is Kepler-69, a 13.7 mag G4V-type star. We detect two periodic sets of transit signals in the three-year flux time series of Kepler-69, obtained with the Kepler spacecraft. Using the very high precision Kepler photometry, and follow-up observations, our confidence that these signals represent planetary transits is >99.1%. The inner planet, Kepler-69b, has a radius of 2.24+/-0.4 Rearth and orbits the host star every 13.7 days. The outer planet, Kepler-69c, is a super-Earth-size object with a radius of 1.7+/-0.3 Rearth and an orbital period of 242.5 days. Assuming an Earth-like Bond albedo, Kepler-69c has an equilibrium temperature of 299 +/- 19 K, which places the planet close to the habitable zone around the host star. This is the smallest planet found by Kepler to be orbiting in or near habitable zone of a Sun-like star and represents an important step on the path to finding the first true Earth analog.
  04/2013;
• Source

  Available from: Lauren Weiss

  Article: The Mass of KOI-94d and a Relation for Planet Radius, Mass, and Incident Flux

  Lauren M. Weiss, Geoffrey W. Marcy, Jason F. Rowe, Andrew W. Howard, Howard Isaacson, Jonathan J. Fortney, Neil Miller, Brice-Olivier Demory, Debra A. Fischer, Elisabeth R. Adams, Andrea K. Dupree, Steve B. Howell, Rea Kolbl, John Asher Johnson, Elliott P. Horch, Mark E. Everett, Daniel C. Fabrycky, Sara Seager
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  ABSTRACT: We measure the mass of a modestly irradiated giant planet, KOI-94d. We wish to determine whether this planet, which is in a 22-day orbit and receives 2700 times as much incident flux as Jupiter, is as dense as Jupiter or rarefied like inflated hot Jupiters. KOI-94 also hosts 3 smaller transiting planets, all of which were detected by the Kepler Mission. With 26 radial velocities of KOI-94 from the W. M. Keck Observatory and a simultaneous fit to the Kepler light curve, we measure the mass of the giant planet and determine that it is not inflated. Support for the planetary interpretation of the other three candidates comes from gravitational interactions through transit timing variations, the statistical robustness of multi-planet systems against false positives, and several lines of evidence that no other star resides within the photometric aperture. The radial velocity analyses of KOI-94b and KOI-94e offer marginal (>2\sigma) mass detections, whereas the observations of KOI-94c offer only an upper limit to its mass. Using the KOI-94 system and other planets with published values for both mass and radius (138 exoplanets total, including 35 with M < 150 Earth masses), we establish two fundamental planes for exoplanets that relate their mass, incident flux, and radius from a few Earth masses up to ten Jupiter masses. These equations can be used to predict the radius or mass of a planet.
  03/2013;
• Article: All Six Planets Known to Orbit Kepler-11 Have Low Densities

  Jack J. Lissauer, Daniel Jontof-Hutter, Jason F. Rowe, Daniel C. Fabrycky, Eric D. Lopez, Eric Agol, Geoffrey W. Marcy, Katherine M. Deck, Debra A. Fischer, Jonathan J. Fortney, Steve B. Howell, Howard Isaacson, Jon M. Jenkins, Rea Kolbl, Dimitar Sasselov, Donald R. Short, William F. Welsh
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  ABSTRACT: The Kepler-11 planetary system contains six transiting planets ranging in size from 1.8 to 4.2 times the radius of Earth. Five of these planets orbit in a tightly-packed configuration with periods between 10 and 47 days. We perform a dynamical analysis of the system based upon transit timing variations observed in more than three years of \ik photometric data. Stellar parameters are derived using a combination of spectral classification and constraints on the star's density derived from transit profiles together with planetary eccentricity vectors provided by our dynamical study. Combining masses of the planets relative to the star from our dynamical study and radii of the planets relative to the star from transit depths together with deduced stellar properties yields measurements of the radii of all six planets, masses of the five inner planets, and an upper bound to the mass of the outermost planet, whose orbital period is 118 days. We find mass-radius combinations for all six planets that imply that substantial fractions of their volumes are occupied by constituents that are less dense than rock. The Kepler-11 system contains the lowest mass exoplanets for which both mass and radius have been measured.
  03/2013;
• Article: A sub-Mercury-sized exoplanet.

  Thomas Barclay, Jason F Rowe, Jack J Lissauer, Daniel Huber, François Fressin, Steve B Howell, Stephen T Bryson, William J Chaplin, Jean-Michel Désert, Eric D Lopez, [......], Mikkel N Lund, Mia Lundkvist, Travis S Metcalfe, Andrea Miglio, Robert L Morris, Elisa V Quintana, Dennis Stello, Jeffrey C Smith, Martin Still, Susan E Thompson
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  ABSTRACT: Since the discovery of the first exoplanets, it has been known that other planetary systems can look quite unlike our own. Until fairly recently, we have been able to probe only the upper range of the planet size distribution, and, since last year, to detect planets that are the size of Earth or somewhat smaller. Hitherto, no planets have been found that are smaller than those we see in the Solar System. Here we report a planet significantly smaller than Mercury. This tiny planet is the innermost of three that orbit the Sun-like host star, which we have designated Kepler-37. Owing to its extremely small size, similar to that of the Moon, and highly irradiated surface, the planet, Kepler-37b, is probably rocky with no atmosphere or water, similar to Mercury.
  Nature 02/2013; 494(7438):452-4. · 36.28 Impact Factor
• Article: Orbital Phase Variations of the Eccentric Giant Planet HAT-P-2b

  Nikole K. Lewis, Heather A. Knutson, Adam P. Showman, Nicolas B. Cowan, Gregory Laughlin, Adam Burrows, Drake Deming, Justin R. Crepp, Kenneth J. Mighell, Eric Agol, [......], Debra A. Fischer, Jonathan J. Fortney, Joel D. Hartman, Sasha Hinkley, Andrew W. Howard, John Asher Johnson, Melodie Kao, Jonathan Langton, Geoffrey W. Marcy, Joshua N. Winn
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  ABSTRACT: We present the first secondary eclipse and phase curve observations for the highly eccentric hot Jupiter HAT-P-2b in the 3.6, 4.5, 5.8, and 8.0 \mu m bands of the Spitzer Space Telescope. The 3.6 and 4.5 \mu m data sets span an entire orbital period of HAT-P-2b, making them the longest continuous phase curve observations obtained to date and the first full-orbit observations of a planet with an eccentricity exceeding 0.2. We present an improved non-parametric method for removing the intrapixel sensitivity variations in Spitzer data at 3.6 and 4.5 \mu m that robustly maps position-dependent flux variations. We find that the peak in planetary flux occurs at 4.39+/-0.28, 5.84+/-0.39, and 4.68+/-0.37 hours after periapse passage with corresponding maxima in the planet/star flux ratio of 0.1138%+/-0.0089%, 0.1162%+/-0.0080%, and 0.1888%+/-0.0072% in the 3.6, 4.5, and 8.0 \mu m bands respectively. We compare our measured secondary eclipse depths to the predictions from a one-dimensional radiative transfer model, which suggests the possible presence of a transient day side inversion in HAT-P-2b's atmosphere near periapse. We also derive improved estimates for the system parameters, including its mass, radius, and orbital ephemeris. Our simultaneous fit to the transit, secondary eclipse, and radial velocity data allows us to determine the eccentricity and argument of periapse of HAT-P-2b's orbit with a greater precision than has been achieved for any other eccentric extrasolar planet. We also find evidence for a long-term linear trend in the radial velocity data. This trend suggests the presence of another substellar companion in the HAT-P-2 system, which could have caused HAT-P-2b to migrate inward to its present-day orbit via the Kozai mechanism.
  02/2013;
• Article: Low stellar obliquities in compact multiplanet systems

  Simon Albrecht, Joshua N. Winn, Geoffrey W. Marcy, Andrew W. Howard, Howard Isaacson, John A. Johnson
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  ABSTRACT: We measure the sky-projected stellar obliquities (\lambda) in the multiple-transiting planetary systems KOI-94 and Kepler-25, using the Rossiter-McLaughlin effect. In both cases the host stars are well-aligned with the orbital planes of the planets. For KOI-94 we find \lambda=-11+-11 deg, confirming a recent result by Hirano and coworkers. Kepler-25 was a more challenging case because the transit depth is unusually small (0.13 %). To obtain the obliquity it was necessary to use prior knowledge of the star's projected rotation rate, and apply two different analysis methods to independent wavelength regions of the spectra. The two methods gave consistent results, \lambda=7+-8 deg and -0.5+-5.7 deg. There are now a total of five obliquity measurements for host stars of systems of multiple transiting planets, all of which are consistent with spin-orbit alignment. This alignment is unlikely to be the result of tidal interactions, because of the relatively large orbital distances and low planetary masses in the systems. In this respect the multiplanet host stars differ from hot-Jupiter host stars, which commonly have large spin-orbit misalignments whenever tidal interactions are weak. In particular the weak-tide subset of hot-Jupiter hosts have obliquities consistent with an isotropic distribution (p=0.6), but the multiplanet hosts are incompatible with such a distribution (p~10^-6). This suggests that high obliquities are confined to hot-Jupiter systems, and provides further evidence that hot Jupiter formation involves processes that tilt the planetary orbit.
  02/2013;
• Source

  Available from: Howard T. Isaacson

  Article: Fundamental Properties of Kepler Planet-Candidate Host Stars using Asteroseismology

  Daniel Huber, William J. Chaplin, Jørgen Christensen-Dalsgaard, Ronald L. Gilliland, Hans Kjeldsen, Lars A. Buchhave, Debra A. Fischer, Jack J. Lissauer, Jason F. Rowe, Roberto Sanchis-Ojeda, [......], Thomas Barclay, Timothy R. Bedding, Christopher J. Burke, Jessie L. Christiansen, Yvonne P. Elsworth, Michael R. Haas, Steven D. Kawaler, Travis S. Metcalfe, Fergal Mullally, Susan E. Thompson
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  ABSTRACT: We have used asteroseismology to determine fundamental properties for 66 Kepler planet-candidate host stars, with typical uncertainties of 3% and 7% in radius and mass, respectively. The results include new asteroseismic solutions for four host stars with confirmed planets (Kepler-4, Kepler-14, Kepler-23 and Kepler-25) and increase the total number of Kepler host stars with asteroseismic solutions to 77. A comparison with stellar properties in the planet-candidate catalog by Batalha et al. shows that radii for subgiants and giants obtained from spectroscopic follow-up are systematically too low by up to a factor of 1.5, while the properties for unevolved stars are in good agreement. We furthermore apply asteroseismology to confirm that a large majority of cool main-sequence hosts are indeed dwarfs and not misclassified giants. Using the revised stellar properties, we recalculate the radii for 107 planet candidates in our sample, and comment on candidates for which the radii change from a previously giant-planet/brown-dwarf/stellar regime to a sub-Jupiter size, or vice versa. A comparison of stellar densities from asteroseismology with densities derived from transit models in Batalha et al. assuming circular orbits shows significant disagreement for more than half of the sample due to systematics in the modeled impact parameters, or due to planet candidates which may be in eccentric orbits. Finally, we investigate tentative correlations between host-star masses and planet candidate radii, orbital periods, and multiplicity, but caution that these results may be influenced by the small sample size and detection biases.
  02/2013;
• Article: Kepler-68: Three Planets, One With a Density Between That of Earth and Ice Giants

  Ronald L. Gilliland, Geoffrey W. Marcy, Jason F. Rowe, Leslie Rogers, Guillermo Torres, Francois Fressin, Eric D. Lopez, Lars A. Buchhave, Joergen Christensen-Dalsgaard, Jean-Michel Desert, [......], Mia Lundkvist, Andrea Miglio, David Charbonneau, Eric B. Ford, Jonathan J. Fortney, Michael R. Haas, Andrew W. Howard, Steve B. Howell, Darin Ragozzine, Susan E. Thompson
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  ABSTRACT: NASA's Kepler Mission has revealed two transiting planets orbiting Kepler-68. Follow-up Doppler measurements have established the mass of the innermost planet and revealed a third jovian-mass planet orbiting beyond the two transiting planets. Kepler-68b, in a 5.4 day orbit has mass 8.3 +/- 2.3 Earth, radius 2.31 +/- 0.07 Earth radii, and a density of 3.32 +/- 0.92 (cgs), giving Kepler-68b a density intermediate between that of the ice giants and Earth. Kepler-68c is Earth-sized with a radius of 0.953 Earth and transits on a 9.6 day orbit; validation of Kepler-68c posed unique challenges. Kepler-68d has an orbital period of 580 +/- 15 days and minimum mass of Msin(i) = 0.947 Jupiter. Power spectra of the Kepler photometry at 1-minute cadence exhibit a rich and strong set of asteroseismic pulsation modes enabling detailed analysis of the stellar interior. Spectroscopy of the star coupled with asteroseismic modeling of the multiple pulsation modes yield precise measurements of stellar properties, notably Teff = 5793 +/- 74 K, M = 1.079 +/- 0.051 Msun, R = 1.243 +/- 0.019 Rsun, and density 0.7903 +/- 0.0054 (cgs), all measured with fractional uncertainties of only a few percent. Models of Kepler-68b suggest it is likely composed of rock and water, or has a H and He envelope to yield its density of about 3 (cgs).
  02/2013;
• Article: A 1.1 to 1.9 GHz SETI Survey of the Kepler Field: I. A Search for Narrow-band Emission from Select Targets

  Andrew P. V. Siemion, Paul Demorest, Eric Korpela, Ron J. Maddalena, Dan Werthimer, Jeff Cobb, Andrew W. Howard, Glen Langston, Matt Lebofsky, Geoffrey W. Marcy, Jill Tarter
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  ABSTRACT: We present a targeted search for narrow-band (< 5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T_eq > 230 K, stars with 5 or more detected candidates or stars with a super-Earth (R_p < 3 R_earth) in a > 50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between Feb--Apr 2011 and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1-2 GHz at an equivalent isotropically radiated power (EIRP) of ~1.5 x 10^21 erg s^-1, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be < 10^-6 M_solar^-1. Here we describe our observations, data reduction procedures and results.
  02/2013;
• Source

  Available from: Benjamin J. Fulton

  Article: The Stellar Obliquity and the Long-period planet in the HAT-P-17 Exoplanetary System

  Benjamin J. Fulton, Andrew W. Howard, Joshua N. Winn, Simon Albrecht, Geoffrey W. Marcy, Justin R. Crepp, Gaspar A. Bakos, John Asher Johnson, Joel D. Hartman, Howard Isaacson, Heather A. Knutson, Ming Zhao
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  ABSTRACT: We present the measured projected obliquity -- the sky-projected angle between the stellar spin axis and orbital angular momentum -- of the inner planet of the HAT-P-17 multi-planet system. We measure the sky-projected obliquity of the star to be \lambda=19+/-15 degrees by modeling the Rossiter-McLaughlin (RM) effect in Keck/HIRES radial velocities (RVs). The anomalous RV time series shows an asymmetry relative to the midtransit time, ordinarily suggesting a nonzero obliquity -- but in this case at least part of the asymmetry may be due to the convective blueshift, increasing the uncertainty in the determination of \lambda. We employ the semi-analytical approach of Hirano et al. (2011) that includes the effects of macroturbulence, instrumental broadening, and convective blueshift to accurately model the anomaly in the net RV caused by the planet eclipsing part of the rotating star. Obliquity measurements are an important tool for testing theories of planet formation and migration. To date, the measured obliquities of ~50 Jovian planets span the full range, from prograde to retrograde, with planets orbiting cool stars preferentially showing alignment of stellar spins and planetary orbits. Our results are consistent with this pattern emerging from tidal interactions in the convective envelopes of cool stars and close-in planets. In addition, our 1.8 years of new RVs for this system show that the orbit of the outer planet is more poorly constrained than previously thought, with an orbital period now in the range of 10-36 years.
  01/2013;
• Source

  Available from: Sabine Reffert

  Article: Discovery of Planetary Systems With SIM

  Geoffrey W. Marcy, Paul R. Butler, Sabine Frink, Debra Fischer, Ben Oppenheimer, David G. Monet, Andreas Quirrenbach, Jeffrey D. Scargle
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  ABSTRACT: We are witnessing the birth of a new observational science: the discovery and characterization of extrasolar planetary systems. In the past five years, over 70 extrasolar planets have been discovered by precision Doppler surveys, most by members of this SIM team. We are using the data base of information gleaned from our Doppler survey to choose the best targets for a new SIM planet search. In the same way that our Doppler database now serves SIM, our team will return a reconnaissance database to focus Terresrial Planet Finder (TPF) into a more productive, e cient mission. Goals: 1. Detect terrestrial planets of 1-3 M(Earth) around stars closer than 8 pc. 2. Detect 3-20 M(Earth) planets around stars at a distance of 8-30 pc. 3. Determine absolute masses of Doppler-detected planets and search for additional planets 4. Determine the degree of coplanarity in known multiple systems 5. Reconnaissance for TPF.
  11/2012;
• Article: The Discovery of HD 37605c and a Dispositive Null Detection of Transits of HD 37605b

  Sharon Xuesong Wang, Jason T. Wright, William Cochran, Stephen R. Kane, Gregory W. Henry, Matthew J. Payne, Michael Endl, Phillip J. MacQueen, Jeff A. Valenti, Victoria Antoci, Diana Dragomir, Jaymie M. Matthews, Andrew W. Howard, Geoffrey W. Marcy, Howard Isaacson, Eric B. Ford, Suvrath Mahadevan, Kaspar von Braun
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  ABSTRACT: We report the radial-velocity discovery of a second planetary mass companion to the K0 V star HD 37605, which was already known to host an eccentric, P~55 days Jovian planet, HD 37605b. This second planet, HD 37605c, has a period of ~7.5 years with a low eccentricity and an Msini of ~3.4 MJup. Our discovery was made with the nearly 8 years of radial velocity follow-up at the Hobby-Eberly Telescope and Keck Observatory, including observations made as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS) effort to provide precise ephemerides to long-period planets for transit follow-up. With a total of 137 radial velocity observations covering almost eight years, we provide a good orbital solution of the HD 37605 system, and a precise transit ephemeris for HD 37605b. Our dynamic analysis reveals very minimal planet-planet interaction and an insignificant transit time variation. Using the predicted ephemeris, we performed a transit search for HD 37605b with the photometric data taken by the T12 0.8-m Automatic Photoelectric Telescope (APT) and the Microvariability and Oscillations of Stars (MOST) satellite. Though the APT photometry did not capture the transit window, it characterized the stellar activity of HD 37605, which is consistent of it being an old, inactive star, with a tentative rotation period of 57.67 days. The MOST photometry enabled us to report a dispositive null detection of a non-grazing transit for this planet. Within the predicted transit window, we exclude an edge-on predicted depth of 1.9% at >>10sigma, and exclude any transit with an impact parameter b>0.951 at greater than 5sigma. We present the BOOTTRAN package for calculating Keplerian orbital parameter uncertainties via bootstrapping. We found consistency between our orbital parameters calculated by the RVLIN package and error bars by BOOTTRAN with those produced by a Bayesian analysis using MCMC.
  10/2012;
• Article: Kepler-47: a transiting circumbinary multiplanet system.

  Jerome A Orosz, William F Welsh, Joshua A Carter, Daniel C Fabrycky, William D Cochran, Michael Endl, Eric B Ford, Nader Haghighipour, Phillip J MacQueen, Tsevi Mazeh, [......], Karen Kinemuchi, Ethan Kruse, Darin Ragozzine, Dimitar Sasselov, Martin Still, Peter Tenenbaum, Kamal Uddin, Joshua N Winn, David G Koch, William J Borucki
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  ABSTRACT: We report the detection of Kepler-47, a system consisting of two planets orbiting around an eclipsing pair of stars. The inner and outer planets have radii 3.0 and 4.6 times that of Earth, respectively. The binary star consists of a Sun-like star and a companion roughly one-third its size, orbiting each other every 7.45 days. With an orbital period of 49.5 days, 18 transits of the inner planet have been observed, allowing a detailed characterization of its orbit and those of the stars. The outer planet's orbital period is 303.2 days, and although the planet is not Earth-like, it resides within the classical "habitable zone," where liquid water could exist on an Earth-like planet. With its two known planets, Kepler-47 establishes that close binary stars can host complete planetary systems.
  Science 08/2012; 337(6101):1511-4. · 31.20 Impact Factor
• Article: Kepler-47: A Transiting Circumbinary Multi-Planet System

  Jerome A. Orosz, William F. Welsh, Joshua A. Carter, Daniel C. Fabrycky, William D. Cochran, Michael Endl, Eric B. Ford, Nader Haghighipour, Phillip J. MacQueen, Tsevi Mazeh, [......], Karen Kinemuchi, Ethan Kruse, Darin Ragozzine, Dimitar Sasselov, Martin Still, Peter Tenenbaum, Kamal Uddin, Joshua N. Winn, David G. Koch, William J. Borucki
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  ABSTRACT: We report the detection of Kepler-47, a system consisting of two planets orbiting around an eclipsing pair of stars. The inner and outer planets have radii 3.0 and 4.6 times that of the Earth, respectively. The binary star consists of a Sun-like star and a companion roughly one-third its size, orbiting each other every 7.45 days. With an orbital period of 49.5 days, eighteen transits of the inner planet have been observed, allowing a detailed characterization of its orbit and those of the stars. The outer planet's orbital period is 303.2 days, and although the planet is not Earth-like, it resides within the classical "habitable zone", where liquid water could exist on an Earth-like planet. With its two known planets, Kepler-47 establishes that close binary stars can host complete planetary systems.
  08/2012;
• Article: Precise Doppler Monitoring of Barnard's Star

  Jieun Choi, Chris McCarthy, Geoffrey W. Marcy, Andrew W. Howard, Debra A. Fischer, John A. Johnson, Howard Isaacson, Jason T. Wright
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  ABSTRACT: We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the second nearest star system to Earth, obtained from Lick and Keck Observatories during 25 years between 1987 and 2012. The early precision was 20 \ms{} but was 2 \ms{} during the last 8 years, constituting the most extensive and sensitive search for Doppler signatures of planets around this stellar neighbor. We carefully analyze the 136 Keck radial velocities spanning 8 years by first applying a periodogram analysis to search for nearly circular orbits. We find no significant periodic Doppler signals with amplitudes above $\sim$2 \ms{}, setting firm upper limits on the minimum mass (\msini) of any planets with orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for circular orbits, we determine that planetary companions to Barnard's Star with masses above 2 \mearth{} and periods below 10 days would have been detected. Planets with periods up to 2 years and masses above 10 \mearth{} (0.03 \mjup) are also ruled out. A similar analysis allowing for eccentric orbits yields comparable mass limits. The habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger, save for face-on orbits. Previous claims of planets around the star by van de Kamp are strongly refuted. The radial velocity of Barnard's Star increases with time at $4.515\pm0.002$ \msy{}, consistent with the predicted geometrical effect, secular acceleration, that exchanges transverse for radial components of velocity.
  08/2012;
• Article: Alignment of the stellar spin with the orbits of a three-planet system.

  Roberto Sanchis-Ojeda, Daniel C Fabrycky, Joshua N Winn, Thomas Barclay, Bruce D Clarke, Eric B Ford, Jonathan J Fortney, John C Geary, Matthew J Holman, Andrew W Howard, Jon M Jenkins, David Koch, Jack J Lissauer, Geoffrey W Marcy, Fergal Mullally, Darin Ragozzine, Shawn E Seader, Martin Still, Susan E Thompson
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  ABSTRACT: The Sun's equator and the planets' orbital planes are nearly aligned, which is presumably a consequence of their formation from a single spinning gaseous disk. For exoplanetary systems this well-aligned configuration is not guaranteed: dynamical interactions may tilt planetary orbits, or stars may be misaligned with the protoplanetary disk through chaotic accretion , magnetic interactions or torques from neighbouring stars. Indeed, isolated 'hot Jupiters' are often misaligned and even orbiting retrograde. Here we report an analysis of transits of planets over starspots on the Sun-like star Kepler-30 (ref. 8), and show that the orbits of its three planets are aligned with the stellar equator. Furthermore, the orbits are aligned with one another to within a few degrees. This configuration is similar to that of our Solar System, and contrasts with the isolated hot Jupiters. The orderly alignment seen in the Kepler-30 system suggests that high obliquities are confined to systems that experienced disruptive dynamical interactions. Should this be corroborated by observations of other coplanar multi-planet systems, then star-disk misalignments would be ruled out as the explanation for the high obliquities of hot Jupiters, and dynamical interactions would be implicated as the origin of hot Jupiters.
  Nature 07/2012; 487(7408):449-53. · 36.28 Impact Factor
• Article: The Red Supergiant Progenitor of Supernova 2012aw (PTF12bvh) in Messier 95

  Schuyler D. Van Dyk, S. Bradley Cenko, Dovi Poznanski, Iair Arcavi, Avishay Gal-Yam, Alexei V. Filippenko, Kathryn Silverio, Alan Stockton, Jean-Charles Cuillandre, Geoffrey W. Marcy, Andrew W. Howard, Howard Isaacson
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  ABSTRACT: We report on the direct detection and characterization of the probable red supergiant progenitor of the intermediate-luminosity Type II-Plateau (II-P) supernova (SN) 2012aw in the nearby (10.0 Mpc) spiral galaxy Messier 95 (M95; NGC 3351). We have identified the star in both Hubble Space Telescope images of the host galaxy, obtained 17-18 yr prior to the explosion, and near-infrared ground-based images, obtained 6-12 yr prior to the SN. The luminous supergiant showed evidence for substantial circumstellar dust, manifested as excess line-of-sight extinction. The effective total-to-selective ratio of extinction to the star was R'_V \approx 4.35, which is significantly different from that of diffuse interstellar dust (i.e., R_V=3.1), and the total extinction to the star was therefore, on average, A_V \approx 3.1 mag. We find that the observed spectral energy distribution for the progenitor star is consistent with an effective temperature of 3600 K (spectral type M3), and that the star therefore had a bolometric magnitude of -8.29. Through comparison with recent theoretical massive-star evolutionary tracks we can infer that the red supergiant progenitor had an initial mass 15 \lesssim M_{ini} (M_sun) < 20. Interpolating by eye between the available tracks, we surmise that the star had initial mass ~17-18 M_sun. The circumstellar dust around the progenitor must have been destroyed in the explosion, as the visual extinction to the SN is found to be low (A_V=0.24 mag with R_V=3.1).
  07/2012;
• Article: Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments

  Simon Albrecht, Joshua N. Winn, John A. Johnson, Andrew W. Howard, Geoffrey W. Marcy, R. Paul Butler, Pamela Arriagada, Jeffrey D. Crane, Stephen A. Shectman, Ian B. Thompson, Teruyuki Hirano, Gaspar Bakos, Joel D. Hartman
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  ABSTRACT: We provide evidence that the obliquities of stars with close-in giant planets were initially nearly random, and that the low obliquities that are often observed are a consequence of star-planet tidal interactions. The evidence is based on 14 new measurements of the Rossiter-McLaughlin effect (for the systems HAT-P-6, HAT-P-7, HAT-P-16, HAT-P-24, HAT-P-32, HAT-P-34, WASP-12, WASP-16, WASP-18, WASP-19, WASP-26, WASP-31, Gl 436, and Kepler-8), as well as a critical review of previous observations. The low-obliquity (well-aligned) systems are those for which the expected tidal timescale is short, and likewise the high-obliquity (misaligned and retrograde) systems are those for which the expected timescale is long. At face value, this finding indicates that the origin of hot Jupiters involves dynamical interactions like planet-planet interactions or the Kozai effect that tilt their orbits, rather than inspiraling due to interaction with a protoplanetary disk. We discuss the status of this hypothesis and the observations that are needed for a more definitive conclusion.
  06/2012;