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"Ragozzine, Darin"

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Barclay, T., Rowe, J., Lissauer, J., Huber, D., Fressin, F., Howell, S., Bryson, S., Chaplin, W., Desert, J.-M., Lopez, E., Marcy, G., Mullally, F., Ragozzine, D., Torres, G., Adams, E., Agol, E., Barrado, D., Basu, S., Bedding, T., … Thompson, S. (2013). A sub-Mercury-sized exoplanet. Nature, 494(7438), 452–454. https://doi.org/10/f4n77f

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. © 2013 Macmillan Publishers Limited. All rights reserved.

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Steffen, J. H., Fabrycky, D. C., Ford, E. B., Carter, J. A., Désert, J.-M., Fressin, F., Holman, M. J., Lissauer, J. J., Moorhead, A. V., Rowe, J. F., Ragozzine, D., Welsh, W. F., Batalha, N. M., Borucki, W. J., Buchhave, L. A., Bryson, S., Caldwell, D. A., Charbonneau, D., Ciardi, D. R., … Cleve, J. V. (2012). Transit timing observations from kepler: III. confirmation of 4 multiple planet systems by a fourier-domain study of anti-correlated transit timing variations. Monthly Notices of the Royal Astronomical Society, 421(3), 2342–2354. https://doi.org/10.1111/j.1365-2966.2012.20467.x

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. © 2012 Fermi Research Alliance LLC, Contractor for the U.S. Dept of Energy Monthly Notices of the Royal Astronomical Society © 2012 RAS.

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Ford, E. B., Fabrycky, D. C., Steffen, J. H., Carter, J. A., Fressin, F., Holman, M. J., Lissauer, J. J., Moorhead, A. V., Morehead, R. C., Ragozzine, D., Rowe, J. F., Welsh, W. F., Allen, C., Batalha, N. M., Borucki, W. J., Bryson, S. T., Buchhave, L. A., Burke, C. J., Caldwell, D. A., … Wohler, B. (2012). Transit timing observations from kepler. II. confirmation of two multiplanet systems via a non-parametric correlation analysis. The Astrophysical Journal, 750(2), 113. https://doi.org/10.1088/0004-637x/750/2/113

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. © 2012. The American Astronomical Society. All rights reserved.

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Cochran, W. D., Fabrycky, D. C., Torres, G., Fressin, F., Désert, J.-M., Ragozzine, D., Sasselov, D., Fortney, J. J., Rowe, J. F., Brugamyer, E., Bryson, S. T., Carter, J. A., Ciardi, D. R., Howell, S. B., Steffen, J. H., Borucki, W. J., Koch, D. G., Winn, J. N., Welsh, W. F., … Batalha, N. M. (2011). Kepler-18b, c, and d: a system of three planets confirmed by transit timing variations, light curve validation, warm-spitzer photometry, and radial velocity measurements*. Astrophysical Journal Supplement Series, 197(1), 7-null. https://doi.org/10.1088/0067-0049/197/1/7

We report the detection of three transiting planets around a Sun-like star, which we designate Kepler-18. The transit signals were detected in photometric data from the Kepler satellite, and were confirmed to arise from planets using a combination of large transit-timing variations (TTVs), radial velocity variations, Warm-Spitzer observations, and statistical analysis of false-positive probabilities. The Kepler-18 star has a mass of 0.97 M ⊙, a radius of 1.1 R ⊙, an effective temperature of 5345K, and an iron abundance of [Fe/H] = +0.19. The planets have orbital periods of approximately 3.5, 7.6, and 14.9 days. The innermost planet "b" is a "super-Earth" with a mass of 6.9 ± 3.4 M ⊕, a radius of 2.00 ± 0.10 R ⊕, and a mean density of 4.9 ± 2.4gcm3. The two outer planets "c" and "d" are both low-density Neptune-mass planets. Kepler-18c has a mass of 17.3 ± 1.9 M ⊕, a radius of 5.49 ± 0.26 R ⊕, and a mean density of 0.59 0.07gcm 3, while Kepler-18d has a mass of 16.4 ± 1.4 M ⊕, a radius of 6.98 ± 0.33 R ⊕ and a mean density of 0.27 ± 0.03gcm3. Kepler-18c and Kepler-18d have orbital periods near a 2:1 mean-motion resonance, leading to large and readily detected TTVs. © 2011. The American Astronomical Society. All rights reserved.

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Borucki, W. J., Koch, D. G., Basri, G., Batalha, N. M., Brown, T. M., Bryson, S. T., Caldwell, D. A., Christensen-Dalsgaard, J., Cochran, W. D., DeVore, E., Dunham, E. W., Gautier, T. N., Geary, J. C., Gilliland, R. L., Gould, A., Howell, S. B., Jenkins, J. M., Latham, D. W., Lissauer, J. J., … Still, M. (2011). Characteristics of planetary candidates observed by Kepler II : Analysis of the first four months of data. The Astrophysical Journal, 736(1), 19. https://doi.org/10.1088/0004-637x/736/1/19

On 2011 February 1 the Kepler mission released data for 156,453 stars observed from the beginning of the science observations on 2009 May 2 through September 16. There are 1235 planetary candidates with transit-like signatures detected in this period. These are associated with 997 host stars. Distributions of the characteristics of the planetary candidates are separated into five class sizes: 68 candidates of approximately Earth-size (Rp < 1.25 R⊕), 288 super-Earth-size (1.25 R⊕ ≤ R p < 2 R⊕), 662 Neptune-size (2 R ⊕ ≤ Rp < 6 R⊕), 165 Jupiter-size (6 R⊕ ≤ Rp < 15 R ⊕), and 19 up to twice the size of Jupiter (15 R ⊕ ≤ Rp < 22 R⊕). In the temperature range appropriate for the habitable zone, 54 candidates are found with sizes ranging from Earth-size to larger than that of Jupiter. Six are less than twice the size of the Earth. Over 74% of the planetary candidates are smaller than Neptune. The observed number versus size distribution of planetary candidates increases to a peak at two to three times the Earth-size and then declines inversely proportional to the area of the candidate. Our current best estimates of the intrinsic frequencies of planetary candidates, after correcting for geometric and sensitivity biases, are 5% for Earth-size candidates, 8% for super-Earth-size candidates, 18% for Neptune-size candidates, 2% for Jupiter-size candidates, and 0.1% for very large candidates; a total of 0.34 candidates per star. Multi-candidate, transiting systems are frequent; 17% of the host stars have multi-candidate systems, and 34% of all the candidates are part of multi-candidate systems. © 2011. The American Astronomical Society. All rights reserved.

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