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Geary, John

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Geary, John
Author's Publications: search.filters.isAuthorOfPublication.4b006cb6-7303-47ab-ac4c-384c5665cc25

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    Kepler-20: A Sun-like Star with Three Sub-Neptune Exoplanets and Two Earth-size Candidates
    (IOP Publishing, 2012) Gautier, Thomas N.; Charbonneau, David; Rowe, Jason F.; Marcy, Geoffrey W.; Isaacson, Howard; Torres, Guillermo; Fressin, Francois; Rogers, Leslie A.; Désert, Jean-Michel; Buchhave, Lars A.; Latham, David; Quinn, Samuel N.; Ciardi, David R.; Fabrycky, Daniel C.; Ford, Eric B.; Gilliland, Ronald L.; Walkowicz, Lucianne M.; Bryson, Stephen T.; Cochran, William D.; Endl, Michael; Fischer, Debra A.; Howell, Steve B.; Horch, Elliott P.; Barclay, Thomas; Batalha, Natalie; Borucki, William J.; Christiansen, Jessie L.; Geary, John; Henze, Christopher E.; Holman, Matthew; Ibrahim, Khadeejah; Jenkins, Jon M.; Kinemuchi, Karen; Koch, David G.; Lissauer, Jack J.; Sanderfer, Dwight T.; Sasselov, Dimitar; Seager, Sara; Silverio, Kathryn; Smith, Jeffrey C.; Still, Martin; Stumpe, Martin C.; Tenenbaum, Peter; Van Cleve, Jeffrey
    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 2MASS J19104752+4220194. From high-resolution spectroscopy of the star, we find a stellar effective temperature T eff = 5455 ± 100 K, a metallicity of [Fe/H] = 0.01 ± 0.04, and a surface gravity of log g = 4.4 ± 0.1. We combine these estimates with an estimate of the stellar density derived from the transit light curves to deduce a stellar mass of M sstarf = 0.912 ± 0.034 M ☉ and a stellar radius of R sstarf = 0.944+0.060 –0.095 R ☉. For three of the transit signals, we demonstrate that our results strongly disfavor the possibility that these result from astrophysical false positives. We accomplish this by first identifying the subset of stellar blends that reproduce the precise shape of the light curve and then using the constraints on the presence of additional stars from high angular resolution imaging, photometric colors, and the absence of a secondary component in our spectroscopic observations. We conclude that the planetary scenario is more likely than that of an astrophysical false positive by a factor of 2 × 105 (Kepler-20b), 1 × 105 (Kepler-20c), and 1.1 × 103 (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 4.5 μm, 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 3.70 days and 1.91+0.12 –0.21 R ⊕ for Kepler-20b, 10.85 days and 3.07+0.20 –0.31 R ⊕ for Kepler-20c, and 77.61 days 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 ⊕ (2σ).
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    A sub-Mercury-sized exoplanet
    (Springer Nature, 2013) Barclay, Thomas; Rowe, Jason F.; Lissauer, Jack J.; Huber, Daniel; Fressin, François; Howell, Steve B.; Bryson, Stephen T.; Chaplin, William J.; Désert, Jean-Michel; Lopez, Eric D.; Marcy, Geoffrey W.; Mullally, Fergal; Ragozzine, Darin; Torres, Guillermo; Adams, Elisabeth R.; Agol, Eric; Barrado, David; Basu, Sarbani; Bedding, Timothy R.; Buchhave, Lars A.; Charbonneau, David; Christiansen, Jessie L.; Christensen-Dalsgaard, Jørgen; Ciardi, David; Cochran, William D.; Dupree, Andrea K.; Elsworth, Yvonne; Everett, Mark; Fischer, Debra A.; Ford, Eric B.; Fortney, Jonathan J.; Geary, John; Haas, Michael R.; Handberg, Rasmus; Hekker, Saskia; Henze, Christopher E.; Horch, Elliott; Howard, Andrew W.; Hunter, Roger C.; Isaacson, Howard; Jenkins, Jon M.; Karoff, Christoffer; Kawaler, Steven D.; Kjeldsen, Hans; Klaus, Todd C.; Latham, David; Li, Jie; Lillo-Box, Jorge; Lund, Mikkel N.; Lundkvist, Mia; Metcalfe, Travis S.; Miglio, Andrea; Morris, Robert L.; Quintana, Elisa V.; Stello, Dennis; Smith, Jeffrey C.; Still, Martin; Thompson, Susan E.
    Since the discovery of the first exoplanets1, 2, it has been known that other planetary systems can look quite unlike our own3. Until fairly recently, we have been able to probe only the upper range of the planet size distribution4, 5, and, since last year, to detect planets that are the size of Earth6 or somewhat smaller7. 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 Mercury8. 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.
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    PISCO: the Parallel Imager for Southern Cosmology Observations
    (Society of Photo-optical Instrumentation Engineers, 2014) Stalder, Brian; Stark, Antony; Amato, Stephen; Geary, John; Shectman, Stephen A.; Stubbs, Christopher; Szentgyorgyi, Andrew
    We present the design and lab performance of the Parallel Imager for Southern Cosmology Observations (PISCO), a photometer for the 6.5 m diameter Magellan telescopes that produces gl, rl, il, and zl band images simulta- neously within a 9 arcminute field of view. This design provides efficient follow-up observations of faint sources, particularly galaxy clusters and supernovae. Simultaneous imaging speeds the observing cadence by at a factor of ~ 3 (including optical losses) compared to other photometric imagers. Also, the determination of color (flux ratio between bands) is relatively immune to time variations in gray opacity due to clouds, so observations can proceed in less than optimal conditions. First light is expected in September 2014.