Showing papers by "Geoffrey W. Marcy published in 2012"
San Jose State University1, Ames Research Center2, Las Cumbres Observatory Global Telescope Network3, Harvard University4, University of California, Berkeley5, University of Florida6, Pennsylvania State University7, Georgia State University8, NASA Exoplanet Science Institute9, California Institute of Technology10, Carnegie Institution for Science11, University of Copenhagen12, Aarhus University13, University of Texas at Austin14, Massachusetts Institute of Technology15, Search for extraterrestrial intelligence16, Lawrence Hall of Science17, University of Hertfordshire18, Villanova University19, Fermilab20, Princeton University21, San Diego State University22
TL;DR: In this paper, the authors used the noise-weighted robust averaging of multi-quarter photo-center offsets derived from difference image analysis, which identifies likely background eclipsing binaries.
Abstract: New transiting planet candidates are identified in sixteen months (May 2009 - September 2010) of data from the Kepler spacecraft. Nearly five thousand periodic transit-like signals are vetted against astrophysical and instrumental false positives yielding 1,091 viable new planet candidates, bringing the total count up to over 2,300. Improved vetting metrics are employed, contributing to higher catalog reliability. Most notable is the noise-weighted robust averaging of multi-quarter photo-center offsets derived from difference image analysis which identifies likely background eclipsing binaries. Twenty-two months of photometry are used for the purpose of characterizing each of the new candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are tabulated as well as the products of light curve modeling: reduced radius (Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest fractional increases are seen for the smallest planet candidates (197% for candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and those at longer orbital periods (123% for candidates outside of 50-day orbits versus 85% for candidates inside of 50-day orbits). The gains are larger than expected from increasing the observing window from thirteen months (Quarter 1-- Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the benefit of continued development of pipeline analysis software. The fraction of all host stars with multiple candidates has grown from 17% to 20%, and the paucity of short-period giant planets in multiple systems is still evident. The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the Habitable Zone are forthcoming if, indeed, such planets are abundant.
1,162 citations
University of California, Berkeley1, Ames Research Center2, San Jose State University3, Lowell Observatory4, Jet Propulsion Laboratory5, University of Texas at Austin6, Harvard University7, Las Cumbres Observatory Global Telescope Network8, Space Telescope Science Institute9, Niels Bohr Institute10, Aarhus University11, National Center for Atmospheric Research12, NASA Exoplanet Science Institute13, Massachusetts Institute of Technology14, Fermilab15, University of California, Santa Cruz16, Yale University17, University of Florida18, California Institute of Technology19, University of California, Santa Barbara20, University of Hertfordshire21, San Diego State University22, Carnegie Institution for Science23, Lawrence Hall of Science24, Villanova University25
TL;DR: In this paper, the authors report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars.
Abstract: We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars. These results are based on the 1235 planets (formally "planet candidates") from the Kepler mission that include a nearly complete set of detected planets as small as 2 R_⊕. For each of the 156,000 target stars, we assess the detectability of planets as a function of planet radius, R_p, and orbital period, P, using a measure of the detection efficiency for each star. We also correct for the geometric probability of transit, R_*/a. We consider first Kepler target stars within the "solar subset" having T_eff = 4100-6100 K, log g = 4.0-4.9, and Kepler magnitude K_p 2 R_⊕ we measure an occurrence of less than 0.001 planets per star. For all planets with orbital periods less than 50 days, we measure occurrence of 0.130 ± 0.008, 0.023 ± 0.003, and 0.013 ± 0.002 planets per star for planets with radii 2-4, 4-8, and 8-32 R_⊕, in agreement with Doppler surveys. We fit occurrence as a function of P to a power-law model with an exponential cutoff below a critical period P_0. For smaller planets, P_0 has larger values, suggesting that the "parking distance" for migrating planets moves outward with decreasing planet size. We also measured planet occurrence over a broader stellar T_eff range of 3600-7100 K, spanning M0 to F2 dwarfs. Over this range, the occurrence of 2-4 R_⊕ planets in the Kepler field increases with decreasing T_eff, with these small planets being seven times more abundant around cool stars (3600-4100 K) than the hottest stars in our sample (6600-7100 K).
1,159 citations
University of Copenhagen1, Harvard University2, Lund University3, Ames Research Center4, San Jose State University5, University of Texas at Austin6, California Institute of Technology7, University of Florida8, Space Telescope Science Institute9, University of California, Berkeley10, Bowling Green State University11, University of Hertfordshire12, Rensselaer Polytechnic Institute13, University of California, Santa Barbara14, Las Cumbres Observatory Global Telescope Network15
TL;DR: Spectroscopic metallicities of the host stars of 226 small exoplanet candidates discovered by NASA's Kepler mission are reported, finding that planets with radii less than four Earth radii form around host stars with a wide range of metallicities (but on average a metallicity close to that of the Sun), whereas large planets preferentially form around stars with higher metallicities.
Abstract: The abundance of heavy elements (metallicity) in the photospheres of stars similar to the Sun provides a 'fossil' record of the chemical composition of the initial protoplanetary disk. Metal-rich stars are much more likely to harbour gas giant planets(1-4), supporting the model that planets form by accumulation of dust and ice particles(5). Recent ground-based surveys suggest that this correlation is weakened for Neptunian-sized planets(4,6-9). However, how the relationship between size and metallicity extends into the regime of terrestrial-sized exoplanets is unknown. Here we report spectroscopic metallicities of the host stars of 226 small exoplanet candidates discovered by NASA's Kepler mission(10), including objects that are comparable in size to the terrestrial planets in the Solar System. We find that planets with radii less than four Earth radii form around host stars with a wide range of metallicities (but on average a metallicity close to that of the Sun), whereas large planets preferentially form around stars with higher metallicities. This observation suggests that terrestrial planets may be widespread in the disk of the Galaxy, with no special requirement of enhanced metallicity for their formation.
743 citations
TL;DR: In this article, the Rossiter-McLaughlin effect was used to show that the obliquities of stars with close-in giant planets were initially nearly random, and that the low-obliquity that are often observed are a consequence of star-planet tidal interactions.
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.
658 citations
San Diego State University1, Harvard University2, University of California, Santa Cruz3, University of Florida4, Ames Research Center5, Villanova University6, Georgia State University7, Massachusetts Institute of Technology8, Search for extraterrestrial intelligence9, San Jose State University10, Katholieke Universiteit Leuven11, University of Texas at Austin12, Niels Bohr Institute13, University of Copenhagen14, NASA Exoplanet Science Institute15, Jet Propulsion Laboratory16, Space Telescope Science Institute17, University of California, Berkeley18, Tel Aviv University19, Las Cumbres Observatory Global Telescope Network20, University of California, Santa Barbara21, Fermilab22
TL;DR: The observed rate of circumbinary planets in this sample implies that more than ∼1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.
Abstract: Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated the existence of a ‘circumbinary planet’ orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289 days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun’s mass) every 131 days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.
520 citations
San Diego State University1, Harvard University2, University of California, Santa Cruz3, University of Texas at Austin4, University of Florida5, University of Hawaii at Manoa6, Tel Aviv University7, Massachusetts Institute of Technology8, University of Washington9, University of Copenhagen10, Search for extraterrestrial intelligence11, University of California, Berkeley12, Ames Research Center13, Las Cumbres Observatory Global Telescope Network14, University of California, Santa Barbara15, California Institute of Technology16, Carnegie Institution for Science17
TL;DR: The detection of Kepler-47 establishes that close binary stars can host complete planetary systems, and reveals two small planets orbiting a pair of two low-mass stars.
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.
406 citations
TL;DR: In this paper, the authors present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically associated transiting planets.
Abstract: We present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically associated transiting planets. Binary stars provide the primary source of false positives among Kepler planet candidates, implying that false positives should be nearly randomly distributed among Kepler targets. In contrast, true transiting planets would appear clustered around a smaller number of Kepler targets if detectable planets tend to come in systems and/or if the orbital planes of planets encircling the same star are correlated. There are more than one hundred times as many Kepler planet candidates in multi-candidate systems as would be predicted from a random distribution of candidates, implying that the vast majority are true planets. Most of these multis are multiple-planet systems orbiting the Kepler target star, but there are likely cases where (1) the planetary system orbits a fainter star, and the planets are thus significantly larger than has been estimated, or (2) the planets orbit different stars within a binary/multiple star system. We use the low overall false-positive rate among Kepler multis, together with analysis of Kepler spacecraft and ground-based data, to validate the closely packed Kepler-33 planetary system, which orbits a star that has evolved somewhat off of the main sequence. Kepler-33 hosts five transiting planets, with periods ranging from 5.67 to 41 days.
366 citations
Ames Research Center1, San Jose State University2, Search for extraterrestrial intelligence3, Harvard University4, Aarhus University5, National Center for Atmospheric Research6, University of Texas at Austin7, California Institute of Technology8, Space Telescope Science Institute9, University of California, Berkeley10, Carnegie Institution for Science11, Max Planck Society12, University of Florida13, University of California, Santa Cruz14, Fermilab15, University of Copenhagen16, Massachusetts Institute of Technology17, Yale University18, Southern Connecticut State University19, Marshall Space Flight Center20, Villanova University21, Las Cumbres Observatory Global Telescope Network22, San Diego State University23, University of Birmingham24, Iowa State University25, University of Sydney26, University of Amsterdam27, Centre National D'Etudes Spatiales28
TL;DR: A search of the time-series photometry from NASA's Kepler spacecraft reveals a transiting planet candidate orbiting the 11th magnitude G5 dwarf KIC 10593626 with a period of 290 days as discussed by the authors.
Abstract: A search of the time-series photometry from NASA's Kepler spacecraft reveals a transiting planet candidate orbiting the 11th magnitude G5 dwarf KIC 10593626 with a period of 290 days. The characteristics of the host star are well constrained by high-resolution spectroscopy combined with an asteroseismic analysis of the Kepler photometry, leading to an estimated mass and radius of 0.970 ± 0.060 M ☉ and 0.979 ± 0.020 R ☉. The depth of 492 ± 10 ppm for the three observed transits yields a radius of 2.38 ± 0.13 Re for the planet. The system passes a battery of tests for false positives, including reconnaissance spectroscopy, high-resolution imaging, and centroid motion. A full BLENDER analysis provides further validation of the planet interpretation by showing that contamination of the target by an eclipsing system would rarely mimic the observed shape of the transits. The final validation of the planet is provided by 16 radial velocities (RVs) obtained with the High Resolution Echelle Spectrometer on Keck I over a one-year span. Although the velocities do not lead to a reliable orbit and mass determination, they are able to constrain the mass to a 3σ upper limit of 124 M ⊕, safely in the regime of planetary masses, thus earning the designation Kepler-22b. The radiative equilibrium temperature is 262 K for a planet in Kepler-22b's orbit. Although there is no evidence that Kepler-22b is a rocky planet, it is the first confirmed planet with a measured radius to orbit in the habitable zone of any star other than the Sun.
298 citations
TL;DR: In this article, the authors compare the properties of the star KOI 961 and Barnard's Star, a nearby, well-characterized mid-M dwarf, and find that they are similar effective temperatures and metallicities.
Abstract: We present the characterization of the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets, originally discovered by the Kepler Mission. We proceed by comparing KOI 961 to Barnard's Star, a nearby, well-characterized mid-M dwarf. By comparing colors, optical and near-infrared spectra, we find remarkable agreement between the two, implying similar effective temperatures and metallicities. Both are metal-poor compared to the Solar neighborhood, have low projected rotational velocity, high absolute radial velocity, large proper motion and no quiescent H-alpha emission--all of which is consistent with being old M dwarfs. We combine empirical measurements of Barnard's Star and expectations from evolutionary isochrones to estimate KOI 961's mass (0.13 ± 0.05 M_⊙), radius (0.17 ± 0.04 R_⊙) and luminosity (2.40 x 10^(-3.0 ± 0.3) L_⊙). We calculate KOI 961's distance (38.7 ± 6.3 pc) and space motions, which, like Barnard's Star, are consistent with a high scale-height population in the Milky Way. We perform an independent multi-transit fit to the public Kepler light curve and significantly revise the transit parameters for the three planets. We calculate the false-positive probability for each planet-candidate, and find a less than 1% chance that any one of the transiting signals is due to a background or hierarchical eclipsing binary, validating the planetary nature of the transits. The best-fitting radii for all three planets are less than 1 Re_⊕, with KOI 961.03 being Mars-sized (Rp = 0.57 ± 0.18 R_⊕), and they represent some of the smallest exoplanets detected to date.
281 citations
University of California, Santa Cruz1, University of Florida2, Fermilab3, Search for extraterrestrial intelligence4, Ames Research Center5, Harvard University6, San Jose State University7, University of Copenhagen8, University of Texas at Austin9, San Francisco State University10, Yale University11, University of Hertfordshire12, University of California, Berkeley13, Tel Aviv University14, Las Cumbres Observatory Global Telescope Network15, University of California, Santa Barbara16
TL;DR: In this article, the authors present four sets of light curves from the Kepler spacecraft, each of which shows multiple planets transiting the same star, and report dynamical fits to the transit times, yielding possible values for the planets' masses and eccentricities.
Abstract: Eighty planetary systems of two or more planets are known to orbit stars other than the Sun. For most, the data can be sufficiently explained by non-interacting Keplerian orbits, so the dynamical interactions of these systems have not been observed. Here we present four sets of light curves from the Kepler spacecraft, each which of shows multiple planets transiting the same star. Departure of the timing of these transits from strict periodicity indicates that the planets are perturbing each other: the observed timing variations match the forcing frequency of the other planet. This confirms that these objects are in the same system. Next we limit their masses to the planetary regime by requiring the system remain stable for astronomical timescales. Finally, we report dynamical fits to the transit times, yielding possible values for the planets' masses and eccentricities. As the timespan of timing data increases, dynamical fits may allow detailed constraints on the systems' architectures, even in cases for which high-precision Doppler follow-up is impractical.
TL;DR: An analysis of transits of planets over starspots on the Sun-like star Kepler-30 is reported, and it is shown that the orbits of its three planets are aligned with the stellar equator, similar to that of the Solar System, and contrasts with the isolated hot Jupiters.
Abstract: In our Solar System, the Sun's equator and the planets' orbital planes are almost in alignment. This probably reflects the way they formed, from a single spinning disk of gas. Many exoplanet systems do not display this arrangement, however, and isolated 'hot Jupiters' are often misaligned and even have a retrograde orbit. This paper reports an exoplanet system that features alignments similar to those in the Solar System. Analysis of planetary transits across starspots on the Sun-like star Kepler-30 shows that the orbits of its three planets are aligned with the stellar equator. These findings support the suggestion that high orbital tilts (obliquities) are confined to systems that have experienced dynamic interactions of the type that produce hot Jupiters and potentially rule out stardisk misalignments as a cause.
TL;DR: In this paper, the authors present the characterization of the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets, originally discovered by the Kepler Mission.
Abstract: We present the characterization of the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets, originally discovered by the Kepler Mission. We proceed by comparing KOI 961 to Barnard's Star, a nearby, well-characterized mid-M dwarf. By comparing colors, optical and near-infrared spectra, we find remarkable agreement between the two, implying similar effective temperatures and metallicities. Both are metal-poor compared to the Solar neighborhood, have low projected rotational velocity, high absolute radial velocity, large proper motion and no quiescent H-alpha emission--all of which is consistent with being old M dwarfs. We combine empirical measurements of Barnard's Star and expectations from evolutionary isochrones to estimate KOI 961's mass (0.13 +/- 0.05 Msun), radius (0.17 +/- 0.04 Rsun) and luminosity (2.40 x 10^(-3.0 +/- 0.3) Lsun). We calculate KOI 961's distance (38.7 +/- 6.3 pc) and space motions, which, like Barnard's Star, are consistent with a high scale-height population in the Milky Way. We perform an independent multi-transit fit to the public Kepler light curve and significantly revise the transit parameters for the three planets. We calculate the false-positive probability for each planet-candidate, and find a less than 1% chance that any one of the transiting signals is due to a background or hierarchical eclipsing binary, validating the planetary nature of the transits. The best-fitting radii for all three planets are less than 1 Rearth, with KOI 961.03 being Mars-sized (Rp = 0.57 +/- 0.18 Rearth), and they represent some of the smallest exoplanets detected to date.
TL;DR: In this paper, the authors present four sets of lightcurves from the Kepler spacecraft, which each show multiple planets transiting the same star, and report dynamical fits to the transit times, yielding possible values for the planets' masses and eccentricities.
Abstract: Eighty planetary systems of two or more planets are known to orbit stars other than the Sun. For most, the data can be sufficiently explained by non-interacting Keplerian orbits, so the dynamical interactions of these systems have not been observed. Here we present 4 sets of lightcurves from the Kepler spacecraft, which each show multiple planets transiting the same star. Departure of the timing of these transits from strict periodicity indicates the planets are perturbing each other: the observed timing variations match the forcing frequency of the other planet. This confirms that these objects are in the same system. Next we limit their masses to the planetary regime by requiring the system remain stable for astronomical timescales. Finally, we report dynamical fits to the transit times, yielding possible values for the planets' masses and eccentricities. As the timespan of timing data increases, dynamical fits may allow detailed constraints on the systems' architectures, even in cases for which high-precision Doppler follow-up is impractical.
TL;DR: A statistical method is applied to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star.
Abstract: Since the discovery of the first extrasolar giant planets around Sun-like stars, evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered has a radius 1.42 times that of the Earth’s radius (R_⊕ plus), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R_⊕) and the other smaller than the Earth (0.87R_⊕), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star. Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate. The outer planet could have developed a thick water vapour atmosphere.
TL;DR: In this article, the authors reported the confirmation and characterization of a transiting gas giant planet orbiting the M dwarf KOI-254 every 2.455239 days, which was originally discovered by the Kepler mission.
Abstract: We report the confirmation and characterization of a transiting gas giant planet orbiting the M dwarf KOI-254 every 2.455239 days, which was originally discovered by the Kepler mission. We use radial velocity measurements, adaptive optics imaging, and near-infrared spectroscopy to confirm the planetary nature of the transit events. KOI-254 b is the first hot Jupiter discovered around an M-type dwarf star. We also present a new model-independent method of using broadband photometry to estimate the mass and metallicity of an M dwarf without relying on a direct distance measurement. Included in this methodology is a new photometric metallicity calibration based on J – K colors. We use this technique to measure the physical properties of KOI-254 and its planet. We measure a planet mass of M_P = 0.505 M_(Jup), radius R_P = 0.96 R_(Jup), and semimajor axis a = 0.030 AU, based on our measured stellar mass M_* = 0.59 M_☉ and radius R_* = 0.55 R_☉. We also find that the host star is metal-rich, which is consistent with the sample of M-type stars known to harbor giant planets.
Fermilab1, University of California, Santa Cruz2, University of Florida3, Harvard University4, Ames Research Center5, Search for extraterrestrial intelligence6, California Institute of Technology7, San Diego State University8, University of California, Santa Barbara9, University of Texas at Austin10, Space Telescope Science Institute11, Southern Connecticut State University12, University of California, Berkeley13, University of Hertfordshire14, San Jose State University15, Las Cumbres Observatory Global Telescope Network16
TL;DR: In this paper, a Fourier-domain analysis of the deviations in the transit times from a constant period that result from dynamical interactions within the system is presented, which is used to confirm the planetary nature of objects in systems with multiple transiting exoplanet candidates.
Abstract: We present a method to confirm the planetary nature of objects in systems with multiple transiting exoplanet candidates. This method involves a Fourier-domain analysis of the deviations in the transit times from a constant period that result from dynamical interactions within the system. The combination of observed anticorrelations in the transit times and mass constraints from dynamical stability allow us to claim the discovery of four planetary systems, Kepler-25, Kepler-26, Kepler-27 and Kepler-28, containing eight planets and one additional planet candidate.
Fermilab1, University of California, Santa Cruz2, University of Florida3, Harvard University4, Ames Research Center5, Search for extraterrestrial intelligence6, California Institute of Technology7, San Diego State University8, University of California, Berkeley9, University of Texas at Austin10, Space Telescope Science Institute11, Southern Connecticut State University12, University of Hertfordshire13, San Jose State University14, Las Cumbres Observatory Global Telescope Network15
TL;DR: In this article, a Fourier-Domain analysis of the deviations in the transit times from a constant period that result from dynamical interactions within the system is presented, which is used to confirm the planetary nature of objects in systems with multiple transiting exoplanet candidates.
Abstract: We present a method to confirm the planetary nature of objects in systems with multiple transiting exoplanet candidates. This method involves a Fourier-Domain analysis of the deviations in the transit times from a constant period that result from dynamical interactions within the system. The combination of observed anti-correlations in the transit times and mass constraints from dynamical stability allow us to claim the discovery of four planetary systems Kepler-25, Kepler-26, Kepler-27, and Kepler-28, containing eight planets and one additional planet candidate.
California Institute of Technology1, Harvard University2, Ames Research Center3, University of California, Berkeley4, Massachusetts Institute of Technology5, University of Copenhagen6, University of California, Santa Cruz7, University of Florida8, Pennsylvania State University9, Princeton University10, University of Texas at Austin11, Yale University12, Southern Connecticut State University13, San Jose State University14
TL;DR: The discovery of the Kepler-20 planetary system was first identified through the detection of five distinct periodic transit signals in the Kepler light curve of the host star 2MASSJ19104752+4220194 as discussed by the authors.
Abstract: We present the discovery of the Kepler-20 planetary system, which we initially identified through the detection of five distinct periodic transit signals in the Kepler light curve of the host star 2MASSJ19104752+4220194. We find a stellar effective temperature T_(eff)=5455±100K, a metallicity of [Fe/H]=0.01±0.04, and a surface gravity of log(g)=4.4±0.1. Combined with an estimate of the stellar density from the transit light curves we deduce a stellar mass of M_*=0.912±0.034 M_⊙ and a stellar radius of R_*=0.944^(+0.060)_(-0.095) R_⊙. For three of the transit signals, our results strongly disfavor the possibility that these result from astrophysical false positives. We conclude that the planetary scenario is more likely than that of an astrophysical false positive by a factor of 2 x 10^5 (Kepler-20b), 1 x 10^5 (Kepler-20c), and 1.1 x 10^3 (Kepler-20d), sufficient to validate these objects as planetary companions. For Kepler-20c and Kepler-20d, the blend scenario is independently disfavored by the achromaticity of the transit: From Spitzer data gathered at 4.5µm, we infer a ratio of the planetary to stellar radii of 0.075±0.015 (Kepler-20c) and 0.065±0.011 (Kepler-20d), consistent with each of the depths measured in the Kepler optical bandpass. We determine the orbital periods and physical radii of the three confirmed planets to be 3.70d and 1.91^(+0.12)_(-0.21) R_⊕ for Kepler-20b, 10.85 d and 3.07^(+0.20)_(-0.31) R_⊕ for Kepelr-20c, and 77.61 d and 2.75^(+0.17)_(-0.30) R_⊕ for Kepler-20d. From multi-epoch radial velocities, we determine the masses of Kepler-20b and Kepler-20c to be 8.7±2.2 M_⊕ and 16.1±3.5 M_⊕, respectively, and we place an upper limit on the mass of Kepler-20d of 20.1 M_⊕ (2 σ).
Association of Universities for Research in Astronomy1, Ames Research Center2, Search for extraterrestrial intelligence3, Harvard University4, University of California, Berkeley5, NASA Exoplanet Science Institute6, University of Birmingham7, National Center for Atmospheric Research8, University of Porto9, University of Paris10, Yale University11, Spanish National Research Council12, University of La Laguna13, Space Telescope Science Institute14, Canadian Space Agency15, University of Sydney16, Aarhus University17, Paris Diderot University18, University of Vienna19, University of Wrocław20, Queen Mary University of London21, California Institute of Technology22, University of Copenhagen23, Southern Connecticut State University24, San Jose State University25, Lowell Observatory26, University of Washington27, University of Arizona28, University of Toulouse29, Pierre-and-Marie-Curie University30
TL;DR: In this article, the authors present Kepler observations of the bright (V = 8.3), oscillating star HD 179070, which reveal that the star is orbited every 2.8 days by a small, 1.6 R Earth object.
Abstract: We present Kepler observations of the bright (V = 8.3), oscillating star HD 179070. The observations show transit-like events which reveal that the star is orbited every 2.8 days by a small, 1.6 R Earth object. Seismic studies of HD 179070 using short cadence Kepler observations show that HD 179070 has a frequency-power spectrum consistent with solar-like oscillations that are acoustic p-modes. Asteroseismic analysis provides robust values for the mass and radius of HD 179070, 1.34 ± 0.06 M ☉ and 1.86 ± 0.04 R ☉, respectively, as well as yielding an age of 2.84 ± 0.34 Gyr for this F5 subgiant. Together with ground-based follow-up observations, analysis of the Kepler light curves and image data, and blend scenario models, we conservatively show at the >99.7% confidence level (3σ) that the transit event is caused by a 1.64 ± 0.04 R Earth exoplanet in a 2.785755 ± 0.000032 day orbit. The exoplanet is only 0.04 AU away from the star and our spectroscopic observations provide an upper limit to its mass of ~10 M Earth (2σ). HD 179070 is the brightest exoplanet host star yet discovered by Kepler.
TL;DR: In this paper, the authors used jointly fitted Doppler and astrometric models to calculate the three-dimensional orbit and dynamical mass of the companion of the G0V star HR7672B.
Abstract: The companion to the G0V star HR7672 directly imaged by Liu et al. has moved measurably along its orbit since the discovery epoch, making it possible to determine its dynamical properties. Originally targeted with adaptive optics because it showed a long-term radial velocity (RV) acceleration (trend), we have monitored this star with precise Doppler measurements and have now established a 24 year time baseline. The RV variations show significant curvature (change in the acceleration) including an inflection point. We have also obtained a recent image of HR7672B with NIRC2 at Keck. The astrometry also shows curvature. In this paper, we use jointly fitted Doppler and astrometric models to calculate the three-dimensional orbit and dynamical mass of the companion. The mass of the host star is determined using a direct radius measurement from CHARA interferometry in combination with high-resolution spectroscopic modeling. We find that HR7672B has a highly eccentric, e = 0.50^(+0.01)_(–0.01), near edge-on, i = 97.3^(+0.4)_(–0.5) deg, orbit with semimajor axis, ɑ = 18.3^(+0.4)_(–0.5) AU. The mass of the companion is m = 68.7^(+2.4)_(–3.1) M_J . HR7672B thus resides near the substellar boundary, just below the hydrogen-fusing limit. These measurements of the companion mass are independent of its brightness and spectrum and establish HR7672B as a rare and precious "benchmark" brown dwarf with a well-determined mass, age, and metallicity essential for testing theoretical evolutionary models and synthetic spectral models. Indeed, we find that such models under-predict its luminosity by a factor of ≈2. HR 7672B is presently the only L, T, or Y dwarf known to produce an RV trend around a solar-type star.
California Institute of Technology1, Pennsylvania State University2, Las Cumbres Observatory Global Telescope Network3, University of California, Berkeley4, Ames Research Center5, University of Washington6, University of Toronto7, Lawrence Berkeley National Laboratory8, Weizmann Institute of Science9, Tel Aviv University10, University of Tokyo11
TL;DR: In this article, the authors reported observations of a possible young transiting planet orbiting a previously known weak-lined T-Tauri star in the 7-10 Myr old Orion-OB1a/25-Ori region.
Abstract: We report observations of a possible young transiting planet orbiting a previously known weak-lined T-Tauri star in the 7–10 Myr old Orion-OB1a/25-Ori region. The candidate was found as part of the Palomar Transient Factory (PTF) Orion project. It has a photometric transit period of 0.448413 ± 0.000040 days, and appears in both 2009 and 2010 PTF data. Follow-up low-precision radial velocity (RV) observations and adaptive optics imaging suggest that the star is not an eclipsing binary, and that it is unlikely that a background source is blended with the target and mimicking the observed transit. RV observations with the Hobby–Eberly and Keck telescopes yield an RV that has the same period as the photometric event, but is offset in phase from the transit center by ≈ − 0.22 periods. The amplitude (half range) of the RV variations is 2.4 km s^(−1) and is comparable with the expected RV amplitude that stellar spots could induce. The RV curve is likely dominated by stellar spot modulation and provides an upper limit to the projected companion mass of M_psin i_(orb) ≾4.8 ± 1.2 M_(Jup); when combined with the orbital inclination, i_(orb), of the candidate planet from modeling of the transit light curve, we find an upper limit on the mass of the planetary candidate of M_p ≾5.5 ± 1.4 M_(Jup). This limit implies that the planet is orbiting close to, if not inside, its Roche limiting orbital radius, so that it may be undergoing active mass loss and evaporation.
University of California, Santa Cruz1, Fermilab2, Harvard University3, Ames Research Center4, University of Florida5, Search for extraterrestrial intelligence6, San Diego State University7, San Jose State University8, University of Copenhagen9, University of Texas at Austin10, Yale University11, California Institute of Technology12, Space Telescope Science Institute13, Southern Connecticut State University14, University of California, Berkeley15, University of Hertfordshire16, Las Cumbres Observatory Global Telescope Network17, University of California, Santa Barbara18
TL;DR: In this paper, a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability is presented. But the method is not suitable for the detection of all the transiting candidates.
Abstract: We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies is in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the TTVs of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple-planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.
TL;DR: In this paper, the probable RSG progenitor of the Type II-Plateau (II-P) supernova (SN) 2012aw in the nearby (10.0 Mpc) spiral galaxy Messier 95 (M95; NGC 3351) was identified in both Hubble Space Telescope images of the host galaxy and near-infrared ground-based images, obtained 6-12 yr prior to the SN.
Abstract: We report on the direct detection and characterization of the probable red supergiant (RSG) 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 ≈ 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 ≈ 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 RSG progenitor had an initial mass 15 ≲ M_(ini)(M_☉) < 20. Interpolating by eye between the available tracks, we surmise that the star had initial mass ~17-18 M_☉. 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 (AV = 0.24 mag with R_V = 3.1).
TL;DR: The TRENDS (TaRgetting bENchmark-objects with Doppler Spectroscopy) imaging survey as mentioned in this paper was designed to directly detect and study the companions responsible for accelerating their host star.
Abstract: We present initial results from a new high-contrast imaging program dedicated to stars that exhibit long-term Doppler radial velocity accelerations (or "trends"). The goal of the TRENDS (TaRgetting bENchmark-objects with Doppler Spectroscopy) imaging survey is to directly detect and study the companions responsible for accelerating their host star. In this first paper of the series, we report the discovery of low-mass stellar companions orbiting HD 53665, HD 68017, and HD 71881 using NIRC2 adaptive optics (AO) observations at Keck. Follow-up imaging demonstrates association through common proper motion. These comoving companions have red colors with estimated spectral types of K7-M0, M5, and M3-M4, respectively. We determine a firm lower limit to their mass from Doppler and astrometric measurements. In the near future, it will be possible to construct three-dimensional orbits and calculate the dynamical mass of HD 68017 B and possibly HD 71881 B. We already detect astrometric orbital motion of HD 68017 B, which has a projected separation of 13.0 AU. Each companion is amenable to AO-assisted direct spectroscopy. Further, each companion orbits a solar-type star, making it possible to infer metallicity and age from the primary. Such benchmark objects are essential for testing theoretical models of cool dwarf atmospheres.
TL;DR: In this paper, 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, was made with the nearly 8 years of radial velocity followup at the Hobby-Eberly Telescope and Keck Observatory, including observations made as part of the Transit Ephemeris Refinement and Monitoring Survey effort to provide precise ephemerides to long-period planets for transit follow-up.
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 Msin i of ~3.4 M_(Jup). 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 effort to provide precise ephemerides to long-period planets for transit follow-up. With a total of 137 radial velocity observations covering almost 8 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 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 the »10σ level, and exclude any transit with an impact parameter b > 0.951 at greater than 5σ. We present the BOOTTRAN package for calculating Keplerian orbital parameter uncertainties via bootstrapping. We made a comparison and found consistency between our orbital fit parameters calculated by the RVLIN package and error bars by BOOTTRAN with those produced by a Bayesian analysis using MCMC.
TL;DR: In this article, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 ± 0.000019 days, transit epoch T_c = 2455176.
Abstract: We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 ± 0.000019 days, transit epoch T_c = 2455176.85173 ± 0.00047 (BJD—barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time, UTC), and transit duration 0.1174 ± 0.0017 days. The host star has a mass of 1.01 ± 0.03 M_☉, radius of 0.96^(+0.05)_(– 0.04) R_☉, effective temperature 5500 ± 80 K, and metallicity [Fe/H] = +0.31 ± 0.08. The planetary companion has a mass of 0.567 ± 0.022 M_J and radius of 1.190^(+0.081)_(–0.056) R_J yielding a mean density of 0.42 ± 0.07 g cm^(–3).
TL;DR: In this paper, the authors reported the detection of three new exoplanets from Keck Observatory, including HD 163607, a metal-rich G5V star with a planet in an orbital period of 282.4 ± 3.8 days and an eccentricity of 0.26 ± 0.14.
Abstract: We report the detection of three new exoplanets from Keck Observatory. HD 163607 is a metal-rich G5IV star with two planets. The inner planet has an observed orbital period of 75.29 ± 0.02 days, a semi-amplitude of 51.1 ± 1.4 m s^(–1), an eccentricity of 0.73 ± 0.02, and a derived minimum mass of MP sin i = 0.77 ± 0.02 M_(Jup). This is the largest eccentricity of any known planet in a multi-planet system. The argument of periastron passage is 78.7 ± 2°0; consequently, the planet's closest approach to its parent star is very near the line of sight, leading to a relatively high transit probability of 8%. The outer planet has an orbital period of 3.60 ± 0.02 years, an orbital eccentricity of 0.12 ± 0.06, and a semi-amplitude of 40.4 ± 1.3 m s^(–1). The minimum mass is MP sin i = 2.29 ± 0.16 M _(Jup). HD 164509 is a metal-rich G5V star with a planet in an orbital period of 282.4 ± 3.8 days and an eccentricity of 0.26 ± 0.14. The semi-amplitude of 14.2 ± 2.7 m s^(–1) implies a minimum mass of 0.48 ± 0.09 M_(Jup). The radial velocities (RVs) of HD 164509 also exhibit a residual linear trend of –5.1 ± 0.7 m s–1 year–1, indicating the presence of an additional longer period companion in the system. Photometric observations demonstrate that HD 163607 and HD 164509 are constant in brightness to submillimagnitude levels on their RV periods. This provides strong support for planetary reflex motion as the cause of the RV variations.
TL;DR: The transiting exoearth robust reduction algorithm (TERRA) as discussed by the authors identifies and removes instrumental noise modes by finding common trends in a large ensemble of light curves drawn from the entire Kepler field of view.
Abstract: We present the transiting exoearth robust reduction algorithm (TERRA)—a novel framework for identifying and removing instrumental noise in Kepler photometry. We identify instrumental noise modes by finding common trends in a large ensemble of light curves drawn from the entire Kepler field of view. Strategically, these noise modes can be optimized to reveal transits having a specified range of timescales. For Kepler target stars of low photometric noise, TERRA produces ensemble-calibrated photometry having 33 ppm rms scatter in 12 hr bins, rendering individual transits of Earth-size planets around Sun-like stars detectable as ~3σ signals.
TL;DR: Doppler observations from Keck Observatory have revealed a triple-planet system orbiting the nearby K4V star HIP 57274 as discussed by the authors, which adds to the number of super-Earth mass planets with M sin i < 12 M-circle plus that have been detected with Doppler surveys.
Abstract: Doppler observations from Keck Observatory have revealed a triple-planet system orbiting the nearby K4V star, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with M sin i = 11.6 M-circle plus (0.036 M-Jup), an orbital period of 8.135 +/- 0.004 days, and slightly eccentric orbit e = 0.19 +/- 0.1. We calculate a transit probability of 6.5% for the inner planet. The second planet has M sin i = 0.4 M-Jup with an orbital period of 32.0 +/- 0.02 days in a nearly circular orbit (e = 0.05 +/- 0.03). The third planet has M sin i = 0.53 M-Jup with an orbital period of 432 +/- 8 days (1.18 years) and an eccentricity e = 0.23 +/- 0.03. This discovery adds to the number of super-Earth mass planets with M sin i < 12 M-circle plus that have been detected with Doppler surveys. We find that 56% +/- 18% of super-Earths are members of multi-planet systems. This is certainly a lower limit because of observational detectability limits, yet significantly higher than the fraction of Jupiter mass exoplanets, 20% +/- 8%, that are members of Doppler-detected, multi-planet systems.