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403 results on '"Walker, S. R."'

1. Discovery of WASP-113b and WASP-114b, two inflated hot-Jupiters with contrasting densities

Author

Barros, S. C. C., Brown, D. J. A., Hébrard, G., Chew, Y. Gómez Maqueo, Anderson, D. R., Boumis, P., Delrez, L., Hay, K. L., Lam, K. W. F., Llama, J., Lendl, M., McCormac, J., Skiff, B., Smalley, B, Turner, O, Vanhuysse, M., Armstrong, D. J., Boisse, I., Bouchy, F., Cameron, A. Collier, Faedi, F., Gillon, M., Hellier, C., Jehin, E., Liakos, A., Meaburn, J., Osborn, H. P., Pepe, F., Plauchu-Frayn, I., Pollacco, D., Queloz, D., Rey, J., Spake, J., Ségransan, D., Triaud, A. H. M., Udry, S., Walker, S. R., Watson, C. A., West, R. G., and Wheatley, P. J.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

We present the discovery and characterisation of the exoplanets WASP-113b and WASP-114b by the WASP survey, {\it SOPHIE} and {\it CORALIE}. The planetary nature of the systems was established by performing follow-up photometric and spectroscopic observations. The follow-up data were combined with the WASP-photometry and analysed with an MCMC code to obtain system parameters. The host stars WASP-113 and WASP-114 are very similar. They are both early G-type stars with an effective temperature of $\sim 5900\,$K, [Fe/H]$\sim 0.12$ and $T_{\rm eff}$ $\sim 4.1$dex. However, WASP-113 is older than WASP-114. Although the planetary companions have similar radii, WASP-114b is almost 4 times heavier than WASP-113b. WASP-113b has a mass of $0.48\,$ $\mathrm{M}_{\rm Jup}$ and an orbital period of $\sim 4.5\,$days; WASP-114b has a mass of $1.77\,$ $\mathrm{M}_{\rm Jup}$ and an orbital period of $\sim 1.5\,$days. Both planets have inflated radii, in particular WASP-113 with a radius anomaly of $\Re=0.35$. The high scale height of WASP-113b ($\sim 950$ km ) makes it a good target for follow-up atmospheric observations., Comment: 9 pages, 6 figures, 5 tables, accepted for publication in A&A

Published
2016
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2. K2-110 b - a massive mini-Neptune exoplanet

Author

Osborn, H. P., Santerne, A., Barros, S. C. C., Santos, N. C., Dumusque, X., Malavolta, L., Armstrong, D. J., Hojjatpanah, S., Demangeon, O., Adibekyan, V., Almenara, J. M., Barrado, D., Bayliss, D., Boisse, I., Bouchy, F., Brown, D. J. A., Cameron, A. C., Charbonneau, D., Deleuil, M., Mena, E. Delgado, Díaz, R. F., Hébrard, G., Kirk, J., King, G. W., Lam, K. W. F., Latham, D., Lillo-Box, J., Louden, T. M., Lovis, C., Marmier, M., McCormac, J., Molinari, E., Pollacco, D., Sousa, S. G., Udry, S., and Walker, S. R.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

We report the discovery of the exoplanet K2-110 b (previously EPIC212521166b) from K2 photometry orbiting in a 13.8637d period around an old, metal-poor K3 dwarf star. With a V-band magnitude of 11.9, K2-110 is particularly amenable to RV follow-up. A joint analysis of K2 photometry and high-precision RVs from 28 HARPS and HARPS-N spectra reveal it to have a radius of 2.6$\pm 0.1 R_{\oplus}$ and a mass of 16.7$\pm 3.2$~M$_{\oplus}$, hence a density of $5.2\pm1.2$ g.cm$^{-3}$, making it one of the most massive planets yet to be found with a sub-Neptune radius. When accounting for compression, the resulting Earth-like density is best fitted by a 0.2 M$_{\oplus}$ hydrogen atmosphere over an 16.5 M$_{\oplus}$ Earth-like interior, although the planet could also have significant water content. At 0.1~AU, even taking into account the old stellar age of $8 \pm 3$ Gyr, the planet is unlikely to have been significantly affected by EUV evaporation. However the planet likely disc-migrated to its current position making the lack of a thick H$_2$ atmosphere puzzling. This analysis has made K2-110 b one of the best-characterised mini-Neptunes with density constrained to less than 30%., Comment: Submitted to A&A, May 2016; Accepted April 2017

Published
2016
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3. Single Transit Candidates from K2: Detection and Period Estimation

Author

Osborn, H. P., Armstrong, D. J., Brown, D. J. A., McCormac, J., Doyle, A. P., Louden, T. M., Kirk, J., Spake, J. J., Lam, K. W. F., Walker, S. R., Faedi, F., and Pollacco, D. L.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Photometric surveys such as Kepler have the precision to identify exoplanet and eclipsing binary candidates from only a single transit. K2, with its 75d campaign duration, is ideally suited to detect significant numbers of single-eclipsing objects. Here we develop a Bayesian transit-fitting tool ("Namaste: An Mcmc Analysis of Single Transit Exoplanets") to extract orbital information from single transit events. We achieve favourable results testing this technique on known Kepler planets, and apply the technique to 7 candidates identified from a targeted search of K2 campaigns 1, 2 and 3. We find EPIC203311200 to host an excellent exoplanet candidate with a period, assuming zero eccentricity, of $540 ^{+410}_{-230}$ days and a radius of $0.51 \pm 0.05 R_{Jup}$. We also find six further transit candidates for which more follow-up is required to determine a planetary origin. Such a technique could be used in the future with TESS, PLATO and ground-based photometric surveys such as NGTS, potentially allowing the detection of planets in reach of confirmation by Gaia., Comment: Submitted to MNRAS on 25th November 2015. 15 Pages

Published
2015
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4. Photo-dynamical mass determination of the multi-planetary system K2-19

Author

Barros, S. C. C., Almenara, J. M., Demangeon, O., Tsantaki, M., Santerne, A., Armstrong, D. J., Barrado, D., Brown, D., Deleuil, M., Lillo-Box, J., Osborn, H., Pollacco, D., Abe, L., Andre, P., Bendjoya, P., Boisse, I., Bonomo, A. S., Bouchy, F., Bruno, G., Cerda, J. Rey, Courcol, B., Díaz, R. F., Hébrard, G., Kirk, J., Lachurié, J. C., Lam, K. W. F., Martinez, P., McCormac, J., Moutou, C., Rajpurohit, A., Rivet, J. -P., Spake, J., Suarez, O., Toublanc, D., and Walker, S. R.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

K2-19 is the second multi-planetary system discovered with K2 observations. The system is composed of two Neptune size planets close to the 3:2 mean-motion resonance. To better characterise the system we obtained two additional transit observations of K2-19b and five additional radial velocity observations. These were combined with K2 data and fitted simultaneously with the system dynamics (photo-dynamical model) which increases the precision of the transit time measurements. The higher transit time precision allows us to detect the chopping signal of the dynamic interaction of the planets that in turn permits to uniquely characterise the system. Although the reflex motion of the star was not detected, dynamic modelling of the system allowed us to derive planetary masses of $M_b= 44 \pm 12\, M_{\oplus}$ and $M_c = 15.9 \pm 7.0\, M_{\oplus}$ for the inner and the outer planets respectively, leading to densities close to Uranus. We also show that our method allows the derivation of mass ratios using only the 80 days of observations during the first campaign of K2., Comment: 10 pages, 7 figures, 2 tables, MNRAS accepted

Published
2015
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5. K2 Variable Catalogue: Variable Stars and Eclipsing Binaries in K2 Campaigns 1 and 0

Author

Armstrong, D. J., Kirk, J., Lam, K. W. F., McCormac, J., Walker, S. R., Brown, D. J. A., Osborn, H. P., Pollacco, D. L., and Spake, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We have created a catalogue of variable stars found from a search of the publicly available K2 mission data from Campaigns 1 and 0. This catalogue provides the identifiers of 8395 variable stars, including 199 candidate eclipsing binaries with periods up to 60d and 3871 periodic or quasi-periodic objects, with periods up to 20d for Campaign 1 and 15d for Campaign 0. Lightcurves are extracted and detrended from the available data. These are searched using a combination of algorithmic and human classification, leading to a classifier for each object as an eclipsing binary, sinusoidal periodic, quasi periodic, or aperiodic variable. The source of the variability is not identified, but could arise in the non-eclipsing binary cases from pulsation or stellar activity. Each object is cross-matched against variable star related guest observer proposals to the K2 mission, which specifies the variable type in some cases. The detrended lightcurves are also compared to lightcurves currently publicly available. The resulting catalogue is made available online via the MAST archive at https://archive.stsci.edu/prepds/k2varcat/, and gives the ID, type, period, semi-amplitude and range of the variation seen. We also make available the detrended lightcurves for each object., Comment: Accepted by A&A. 6 pages, 6 figures. Catalogue and lightcurves are available online via MAST at https://archive.stsci.edu/prepds/k2varcat/

Published
2015
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6. K2 Variable Catalogue I: A Catalogue of Variable Stars from K2 Field 0

Author

Armstrong, D. J., Osborn, H. P., Brown, D. J. A., Kirk, J., Lam, K. W. F., Pollacco, D. L., Spake, J., and Walker, S. R.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We have searched the K2 campaign 0 data for lightcurve variations associated with stellar variability. The results of this search are presented as a catalogue, giving the identifiers of nearly 2500 variable stars in the dataset. We list the detected range of the variation, periodicity if relevant and semi-amplitude. Lightcurves are classified into strictly periodic, quasi-periodic and aperiodic groups. We do not attempt to identify the source of variability, which may arise from pulsation or stellar activity. However, we cross match the objects against variable star related guest observer proposals, specifying the variable type in many cases. At present eclipsing binary stars are not included. Future releases will address each K2 field as it is made available, and may be improved to include more detailed catalogue information. Detrended object lightcurves are now available for download from the catalogue website., Comment: 3 pages, 2 figures. Provided for the community on arxiv only. The catalogue is available at http://deneb.astro.warwick.ac.uk/phrlbj/k2varcat/ . Catalogue now updated to provide plots and detrended object lightcurves for download

Published
2014

7. WASP-104b and WASP-106b: two transiting hot Jupiters in 1.75-day and 9.3-day orbits

Author

Smith, A. M. S., Anderson, D. R., Armstrong, D. J., Barros, S. C. C., Bonomo, A. S., Bouchy, F., Brown, D. J. A., Cameron, A. Collier, Delrez, L., Faedi, F., Gillon, M., Chew, Y. Gómez Maqueo, Hébrard, G., Jehin, E., Lendl, M., Louden, T. M., Maxted, P. F. L., Montagnier, G., Neveu-VanMalle, M., Osborn, H. P., Pepe, F., Pollacco, D., Queloz, D., Rostron, J. W., Segransan, D., Smalley, B., Triaud, A. H. M. J., Turner, O. D., Udry, S., Walker, S. R., West, R. G., and Wheatley, P. J.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

We report the discovery from the WASP survey of two exoplanetary systems, each consisting of a Jupiter-sized planet transiting an 11th magnitude (V) main-sequence star. WASP-104b orbits its star in 1.75 d, whereas WASP-106b has the fourth-longest orbital period of any planet discovered by means of transits observed from the ground, orbiting every 9.29 d. Each planet is more massive than Jupiter (WASP-104b has a mass of $1.27 \pm 0.05 \mathrm{M_{Jup}}$, while WASP-106b has a mass of $1.93 \pm 0.08 \mathrm{M_{Jup}}$). Both planets are just slightly larger than Jupiter, with radii of $1.14 \pm 0.04$ and $1.09 \pm 0.04 \mathrm{R_{Jup}}$ for WASP-104 and WASP-106 respectively. No significant orbital eccentricity is detected in either system, and while this is not surprising in the case of the short-period WASP-104b, it is interesting in the case of WASP-106b, because many otherwise similar planets are known to have eccentric orbits., Comment: 8 pages, 6 figures, 5 tables. Accepted for publication in A&A

Published
2014
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8. WASP-135b : A Highly Irradiated, Inflated Hot Jupiter Orbiting a G5V Star

Author

Spake, J. J., Brown, D. J. A., Doyle, A. P., Hébrard, G., McCormac, J., Armstrong, D. J., Pollacco, D., Chew, Y. Gómez Maqueo, Anderson, D. R., Barros, S. C. C., Bouchy, F., Boumis, P., Bruno, G., Cameron, A. Collier, Courcol, B., Davies, G. R., Faedi, F., Hellier, C., Kirk, J., Lam, K. W. F., Liakos, A., Louden, T., Maxted, P. F. L., Osborn, H. P., Palle, E., Arranz, J. Prieto, Udry, S., Walker, S. R., West, R. G., and Wheatley, P. J.

Published
2016

9. Meta‐analysis of individual‐patient data from EVAR‐1, DREAM, OVER and ACE trials comparing outcomes of endovascular or open repair for abdominal aortic aneurysm over 5 years

Author

Powell, J. T., Sweeting, M. J., Ulug, P., Blankensteijn, J. D., Lederle, F. A., Becquemin, J.‐P., Greenhalgh, R. M., Greenhalgh, R. M., Beard, J. D., Buxton, M. J., Brown, L. C., Harris, P. L., Powell, J. T., Rose, J. D. G., Russell, I. T., Sculpher, M. J., Thompson, S. G., Lilford, R.J., Bell, P. R. F., Greenhalgh, R. M., Whitaker, S.C., Poole‐Wilson, the late P.A., Ruckley, C. V., Campbell, W. B., Dean, M. R. E., Ruttley, M. S. T., Coles, E. C., Powell, J. T., Halliday, A., Gibbs, S. J., Brown, L. C., Epstein, D., Sculpher, M. J., Thompson, S. G., Hannon, R. J., Johnston, L., Bradbury, A. W., Henderson, M. J., Parvin, S. D., Shepherd, D. F. C., Greenhalgh, R. M., Mitchell, A. W., Edwards, P. R., Abbott, G. T., Higman, D. J., Vohra, A., Ashley, S., Robottom, C., Wyatt, M. G., Rose, J. D. G., Byrne, D., Edwards, R., Leiberman, D. P., McCarter, D. H., Taylor, P. R., Reidy, J. F., Wilkinson, A. R., Ettles, D. F., Clason, A. E., Leen, G. L. S., Wilson, N. V., Downes, M., Walker, S. R., Lavelle, J. M., Gough, M. J., McPherson, S., Scott, D. J. A., Kessell, D. O., Naylor, R., Sayers, R., Fishwick, N. G., Harris, P. L., Gould, D. A., Walker, M. G., Chalmers, N. C., Garnham, A., Collins, M. A., Beard, J. D., Gaines, P. A., Ashour, M. Y., Uberoi, R., Braithwaite, B., Whitaker, S. C., Davies, J. N., Travis, S., Hamilton, G., Platts, A., Shandall, A., Sullivan, B. A., Sobeh, M., Matson, M., Fox, A. D., Orme, R., Yusef, W., Doyle, T., Horrocks, M., Hardman, J., Blair, P. H. B., Ellis, P. K., Morris, G., Odurny, A., Vohra, R., Duddy, M., Thompson, M., Loosemore, T. M. L., Belli, A. M., Morgan, R., Adiseshiah, M., Brookes, J. A. S., McCollum, C. N., Ashleigh, R., Aukett, M., Baker, S., Barbe, E., Batson, N., Bell, J., Blundell, J., Boardley, D., Boyes, S., Brown, O., Bryce, J., Carmichael, M., Chance, T., Coleman, J., Cosgrove, C., Curran, G., Dennison, T., Devine, C., Dewhirst, N., Errington, B., Farrell, H., Fisher, C., Fulford, P., Gough, M., Graham, C., Hooper, R., Horne, G., Horrocks, L., Hughes, B., Hutchings, T., Ireland, M., Judge, C., Kelly, L., Kemp, J., Kite, A., Kivela, M., Lapworth, M., Lee, C., Linekar, L., Mahmood, A., March, L., Martin, J., Matharu, N., McGuigen, K., Morris‐Vincent, P., Murray, S., Murtagh, A., Owen, G., Ramoutar, V., Rippin, C., Rowley, J., Sinclair, J., Spencer, S., Taylor, V., Tomlinson, C., Ward, S., Wealleans, V., West, J., White, K., Williams, J., Wilson, L., Grobbee, D. E., Blankensteijn, J. D., Bak, A. A. A., Buth, J., Pattynama, P. M., Verhoeven, E. L. G., van Voorthuisen, A. E., Blankensteijn, J. D., Balm, R., Buth, J., Cuypers, P. W. M., Grobbee, D. E., Prinssen, M., van Sambeek, M. R. H. M., Verhoeven, E. L. G., Baas, A. F., Hunink, M. G., van Engelshoven, J. M., Jacobs, M. J. H. M., de Mol, B. A. J. M., van Bockel, J. H., Balm, R., Reekers, J., Tielbeek, X., Verhoeven, E. L. G., Wisselink, W., Boekema, N., Heuveling, L. M., Sikking, I., Prinssen, M., Balm, R., Blankensteijn, J. D., Buth, J., Cuypers, P. W. M., van Sambeek, M. R. H. M., Verhoeven, E. L. G., de Bruin, J. L., Baas, A. F., Blankensteijn, J. D., Prinssen, M., Buth, J., Tielbeek, A.V., Blankensteijn, J. D., Balm, R., Reekers, J. A., van Sambeek, M. R. H. M., Pattynama, P., Verhoeven, E. L. G., Prins, T., van der Ham, A. C., van der Velden, J. J. I. M., van Sterkenburg, S. M. M., ten Haken, G. B., Bruijninckx, C. M. A., van Overhagen, H., Tutein Nolthenius, R. P., Hendriksz, T. R., Teijink, J. A. W., Odink, H. F., de Smet, A. A. E. A., Vroegindeweij, D., van Loenhout, R. M. M., Rutten, M. J., Hamming, J. F., Lampmann, L. E. H., Bender, M. H. M., Pasmans, H., Vahl, A. C., de Vries, C., Mackaay, A. J. C., van Dortmont, L. M. C., van der Vliet, A. J., Schultze Kool, L. J., Boomsma, J. H. B., van Dop, H. R., de Mol van Otterloo, J. C. A., de Rooij, T. P. W., Smits, T. M., Yilmaz, E. N., Wisselink, W., van den Berg, F. G., Visser, M. J. T., van der Linden, E., Schurink, G. W. H., de Haan, M., Smeets, H. J., Stabel, P., van Elst, F., Poniewierski, J., Vermassen, F. E. G., Lederle, F. A., Freischlag, J. A., Kohler, T. R., Latts, E., Matsumura, J., Padberg, F. T., Jr, Kyriakides, T. C., Swanson, K. M., Guarino, P., Peduzzi, P., Antonelli, M., Cushing, C., Davis, E., Durant, L., Joyner, S., Kossack, the late A., Kyriakides, T. C., LeGwin, Mary, McBride, V., OʼConnor, T., Poulton, J., Stratton, the late S., Zellner, S., Snodgrass, A. J., Thornton, J., Swanson, K. M., Haakenson, C. M., Stroupe, K.T., Jonk, Y., Hallett, J. W., Hertzer, N., Towne, J., Katz, D. A., Karrison, T., Matts, J. P., Marottoli, R., Kasl, S., Mehta, R., Feldman, R., Farrell, W., Allore, H., Perry, E., Niederman, J., Randall, F., Zeman, M., Beckwith, the late D., OʼLeary, T. J., Huang, G. D., Latts, E., Bader, M., Ketteler, E. R., Kingsley, D. D., Marek, J. M., Massen, R. J., Matteson, B. D., Pitcher, J. D., Langsfeld, M., Corson, J. D., Goff, J. M., Jr, Kasirajan, K., Paap, C., Robertson, D. C., Salam, A., Veeraswamy, R., Milner, R., Kasirajan, K., Guidot, J., Lal, B. K., Busuttil, S. J., Lilly, M. P., Braganza, M., Ellis, K., Patterson, M. A., Jordan, W. D., Whitley, D., Taylor, S., Passman, M., Kerns, D., Inman, C., Poirier, J., Ebaugh, J., Raffetto, J., Chew, D., Lathi, S., Owens, C., Hickson, K., Dosluoglu, H. H., Eschberger, K., Kibbe, M. R., Baraniewski, H. M., Matsumura, J., Endo, M., Busman, A., Meadows, W., Evans, M., Giglia, J. S., El Sayed, H., Reed, A. B., Ruf, M., Ross, S., Jean‐Claude, J. M., Pinault, G., Kang, P., White, N., Eiseman, M., Jones, the late R., Timaran, C. H., Modrall, J. G., Welborn, M. B., III, Lopez, J., Nguyen, T., Chacko, J. K. Y., Granke, K., Vouyouka, A. G., Olgren, E., Chand, P., Allende, B., Ranella, M., Yales, C., Whitehill, T. A., Krupski, the late W. C., Nehler, M. R., Johnson, S. P., Jones, D. N., Strecker, P., Bhola, M. A., Shortell, C. K., Gray, J. L., Lawson, J. H., McCann, R., Sebastian, M.W., Kistler Tetterton, J., Blackwell, C., Prinzo, P. A., Lee, N., Padberg, F. T., Jr, Cerveira, J. J., Lal, B. K., Zickler, R. W., Hauck, K. A., Berceli, S. A., Lee, W. A., Ozaki, C. K., Nelson, P. R., Irwin, A. S., Baum, R., Aulivola, B., Rodriguez, H., Littooy, F. N., Greisler, H., OʼSullivan, M. T., Kougias, P., Lin, P. H., Bush, R. L., Guinn, G., Bechara, C., Cagiannos, C., Pisimisis, G., Barshes, N., Pillack, S., Guillory, B., Cikrit, D., Lalka, S. G., Lemmon, G., Nachreiner, R., Rusomaroff, M., OʼBrien, E., Cullen, J. J., Hoballah, J., Sharp, W. J., McCandless, J. L., Beach, V., Minion, D., Schwarcz, T. H., Kimbrough, J., Ashe, L., Rockich, A., Warner‐Carpenter, J., Moursi, M., Eidt, J. F., Brock, S., Bianchi, C., Bishop, V., Gordon, I. L., Fujitani, R., Kubaska, S. M., III, Behdad, M., Azadegan, R., Ma Agas, C., Zalecki, K., Hoch, J. R., Carr, S. C., Acher, C., Schwarze, M., Tefera, G., Mell, M., Dunlap, B., Rieder, J., Stuart, J. M., Weiman, D. S., Abul‐Khoudoud, O., Garrett, H. E., Walsh, S. M., Wilson, K. L., Seabrook, G. R., Cambria, R. A., Brown, K. R., Lewis, B. D., Framberg, S., Kallio, C., Barke, R. A., Santilli, S. M., dʼAudiffret, A. C., Oberle, N., Proebstle, C., Johnson, L. L., Jacobowitz, G. R., Cayne, N., Rockman, C., Adelman, M., Gagne, P., Nalbandian, M., Caropolo, L. J., Pipinos, I. I., Johanning, J., Lynch, T., DeSpiegelaere, H., Purviance, G., Zhou, W., Dalman, R., Lee, J. T., Safadi, B., Coogan, S. M., Wren, S. M., Bahmani, D. D., Maples, D., Thunen, S., Golden, M. A., Mitchell, M. E., Fairman, R., Reinhardt, S., Wilson, M. A., Tzeng, E., Muluk, S., Peterson, N. M., Foster, M., Edwards, J., Moneta, G. L., Landry, G., Taylor, L., Yeager, R., Cannady, E., Treiman, G., Hatton‐Ward, S., Salabsky, the late B., Kansal, N., Owens, E., Estes, M., Forbes, B. A., Sobotta, C., Rapp, J. H., Reilly, L. M., Perez, S. L., Yan, K., Sarkar, R., Dwyer, S. S., Perez, S., Chong, K., Kohler, T. R., Hatsukami, T. S., Glickerman, D. G., Sobel, M., Burdick, T. S., Pedersen, K., Cleary, P., Back, M., Bandyk, D., Johnson, B., Shames, M., Reinhard, R. L., Thomas, S. C., Hunter, G. C., Leon, L. R., Jr, Westerband, A., Guerra, R. J., Riveros, M., Mills, J. L., Sr, Hughes, J. D., Escalante, A. M., Psalms, S. B., Day, N. N., Macsata, R., Sidawy, A., Weiswasser, J., Arora, S., Jasper, B. J., Dardik, A., Gahtan, V., Muhs, B. E., Sumpio, B. E., Gusberg, R. J., Spector, M., Pollak, J., Aruny, J., Kelly, E. L., Wong, J., Vasilas, P., Joncas, C., Gelabert, H. A., DeVirgillio, C., Rigberg, D. A., Cole, L., Becquemin, J.‐P., Marzelle, J., Becquemin, J.‐P., Sapoval, M., Becquemin, J.‐P., Favre, J.‐P., Watelet, J., Lermusiaux, P., Sapoval, M., Lepage, E., Hemery, F., Dolbeau, G., Hawajry, N., Cunin, P., Harris, P., Stockx, L., Chatellier, G., Mialhe, C., Fiessinger, J.‐N., Pagny, L., Kobeiter, H., Boissier, C., Lacroix, P., Ledru, F., Pinot, J.‐J., Deux, J.‐F., Tzvetkov, B., Duvaldestin, P., Watelet, J., Jourdain, C., David, V., Enouf, D., Ady, N., Krimi, A., Boudjema, N., Jousset, Y., Enon, B., Blin, V., Picquet, J., LʼHoste, P., Thouveny, F., Borie, H., Kowarski, S., Pernes, J.‐M., Auguste, M., Becquemin, J.‐P., Desgranges, P., Allaire, E., Marzelle, J., Kobeiter, H., Meaulle, P.‐Y., Chaix, D., Juliae, P., Fabiani, J. N., Chevalier, P., Combes, M., Seguin, A., Belhomme, D., Sapoval, M., Baque, J., Pellerin, O., Favre, J. P., Barral, X., Veyret, C., Watelet, J., Peillon, C., Plissonier, D., Thomas, P., Clavier, E., Lermusiaux, P., Martinez, R., Bleuet, F., C, Dupreix, Verhoye, J. P., Langanay, T., Heautot, J. F., Koussa, M., Haulon, S., Halna, P., Destrieux, L., Lions, C., Wiloteaux, S., Beregi, J. P., Bergeron, P., Pinot, J.‐J., Patra, P., Costargent, A., Chaillou, P., DʼAlicourt, A., Goueffic, Y., Cheysson, E., Parrot, A., Garance, P., Demon, A., Tyazi, A., Pillet, J.‐C., Lescalie, F., Tilly, G., Steinmetz, E., Favier, C., Brenot, R., Krause, D., Cercueil, J. P., Vahdat, O., Sauer, M., Soula, P., Querian, A., Garcia, O., Levade, M., Colombier, D., Cardon, J.‐M., Joyeux, A., Borrelly, P., Dogas, G., Magnan, P.‐É., Branchereau, A., Bartoli, J.‐M., Hassen‐Khodja, R., Batt, M., Planchard, P.‐F., Bouillanne, P.‐J., Haudebourg, P., Bayne, J., Gouny, P., Badra, A., Braesco, J., Nonent, M., Lucas, A., Cardon, A., Kerdiles, Y., Rolland, Y., Kassab, M., Brillu, C., Goubault, F., Tailboux, L., Darrieux, H., Briand, O., Maillard, J.‐C., Varty, K., and Cousins, C.

Published
2017
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28. Experimental Studies of Turbulent Intensity around a Tidal Turbine Support Structure

Author

Walker, S. R., Cappietti, L., and Løvås, T

Abstract

Tidal stream energy is a low-carbon energy source. Tidal stream turbines operate in a turbulent environment, and the effect of the structure between the turbine and seabed on this environment is not fully understood. An experimental study using 1:72 scale models based on a commercial turbine design was carried out to study the support structure influence on turbulent intensity around the turbine blades. The study was conducted using the wave-current tank at the Laboratory of Maritime Engineering (LABIMA), University of Florence. A realistic flow environment (ambient turbulent intensity = 11%) was established. Turbulent intensity was measured upstream and downstream of a turbine mounted on two different support structures (one resembling a commercial design, the other the same with an additional vertical element), in order to quantify any variation in turbulence and performance between the support structures. Turbine drive power was used to calculate power generation. Acoustic Doppler velocimetry (ADV) was used to record and calculate upstream and downstream turbulent intensity. In otherwise identical conditions, performance variation of only 4% was observed between two support structures. Turbulent intensity at 1, 3 and 5 blade diameters, both upstream and downstream, showed variation up to 21% between the two cases. The additional turbulent structures generated by the additional element of the second support structure appears to cause this effect, and the upstream propagation of turbulent intensity is believed to be permitted by surface waves. This result is significant for the prediction of turbine array performance.

Published
2017

34. NGTS: Next Generation Transit Survey

Author

Smith, A. M. S., Cabrera, J., Csizmadia, S., Eigmueller, P., Erikson, A., Rauer, H., Titz-Weider, R., Watson, C., Gillen, E., Guenther, M. N., Hodgkin, S. T., Queloz, D, Jenkins, J. S., Soto, M. G., Bayliss, D., Bouchy, F., Chazelas, B., Metrailler, L., Neveu-VanMalle, M., Udry, S., Burleigh, M. R., Chaushev, A. P., Goad, M. R., Grange, A., Armstrong, D. J., Louden, T. M., McCormac, J., Osborn, H. P., Pollacco, D. L., Walker, S. R., West, R. G., and Wheatley, P. J.

Subjects
Extrasolare Planeten und Atmosphären, exoplanets, ​Transits, NGTS
Published
2016

35. K2-110 b: a massive mini-Neptune exoplanet

Author

Osborn, H. P., primary, Santerne, A., additional, Barros, S. C. C., additional, Santos, N. C., additional, Dumusque, X., additional, Malavolta, L., additional, Armstrong, D. J., additional, Hojjatpanah, S., additional, Demangeon, O., additional, Adibekyan, V., additional, Almenara, J.-M., additional, Barrado, D., additional, Bayliss, D., additional, Boisse, I., additional, Bouchy, F., additional, Brown, D. J. A., additional, Cameron, A. C., additional, Charbonneau, D., additional, Deleuil, M., additional, Delgado Mena, E., additional, Díaz, R. F., additional, Hébrard, G., additional, Kirk, J., additional, King, G. W., additional, Lam, K. W. F., additional, Latham, D., additional, Lillo-Box, J., additional, Louden, T. M., additional, Lovis, C., additional, Marmier, M., additional, McCormac, J., additional, Molinari, E., additional, Pepe, F., additional, Pollacco, D., additional, Sousa, S. G., additional, Udry, S., additional, and Walker, S. R., additional

Published
2017
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39. WASP-113b and WASP-114b, two inflated hot Jupiters with contrasting densities

Author

Barros, S. C. C., primary, Brown, D. J. A., additional, Hébrard, G., additional, Gómez Maqueo Chew, Y., additional, Anderson, D. R., additional, Boumis, P., additional, Delrez, L., additional, Hay, K. L., additional, Lam, K. W. F., additional, Llama, J., additional, Lendl, M., additional, McCormac, J., additional, Skiff, B., additional, Smalley, B., additional, Turner, O., additional, Vanhuysse, M., additional, Armstrong, D. J., additional, Boisse, I., additional, Bouchy, F., additional, Collier Cameron, A., additional, Faedi, F., additional, Gillon, M., additional, Hellier, C., additional, Jehin, E., additional, Liakos, A., additional, Meaburn, J., additional, Osborn, H. P., additional, Pepe, F., additional, Plauchu-Frayn, I., additional, Pollacco, D., additional, Queloz, D., additional, Rey, J., additional, Spake, J., additional, Ségransan, D., additional, Triaud, A. H. M., additional, Udry, S., additional, Walker, S. R., additional, Watson, C. A., additional, West, R. G., additional, and Wheatley, P. J., additional

Published
2016
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40. Single transit candidates from K2: detection and period estimation

Author

Osborn, H. P., primary, Armstrong, D. J., additional, Brown, D. J. A., additional, McCormac, J., additional, Doyle, A. P., additional, Louden, T. M., additional, Kirk, J., additional, Spake, J. J., additional, Lam, K. W. F., additional, Walker, S. R., additional, Faedi, F., additional, and Pollacco, D. L., additional

Published
2016
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41. Strategic tillage in no-till farming systems in Australia’s northern grains-growing regions: I. Drivers and implementation

Author

Dang, Y. P., Seymour, Nicole P., Walker, S. R., Bell, M. J., Freebairn, D. M., Dang, Y. P., Seymour, Nicole P., Walker, S. R., Bell, M. J., and Freebairn, D. M.

Abstract

Development of no-tillage (NT) farming has revolutionized agricultural systems by allowing growers to manage greater areas of land with reduced energy, labour and machinery inputs to control erosion, improve soil health and reduce greenhouse gas emission. However, NT farming systems have resulted in a build-up of herbicide-resistant weeds, an increased incidence of soil- and stubble-borne diseases and enrichment of nutrients and carbon near the soil surface. Consequently, there is an increased interest in the use of an occasional tillage (termed strategic tillage, ST) to address such emerging constraints in otherwise-NT farming systems. Decisions around ST uses will depend upon the specific issues present on the individual field or farm, and profitability and effectiveness of available options for management. This paper explores some of the issues with the implementation of ST in NT farming systems. The impact of contrasting soil properties, the timing of the tillage and the prevailing climate exert a strong influence on the success of ST. Decisions around timing of tillage are very complex and depend on the interactions between soil water content and the purpose for which the ST is intended. The soil needs to be at the right water content before executing any tillage, while the objective of the ST will influence the frequency and type of tillage implement used. The use of ST in long-term NT systems will depend on factors associated with system costs and profitability, soil health and environmental impacts. For many farmers maintaining farm profitability is a priority, so economic considerations are likely to be a primary factor dictating adoption. However, impacts on soil health and environment, especially the risk of erosion and the loss of soil carbon, will also influence a grower’s choice to adopt ST, as will the impact on soil moisture reserves in rainfed cropping systems.

Published
2015

42. Strategic tillage in no-till farming systems in Australia’s northern grains-growing regions: II. Implications for agronomy, soil and environment

Author

Dang, Y. P., Moody, P. W., Bell, M. J., Seymour, Nicole P., Dalal, R. C., Freebairn, D. M., Walker, S. R., Dang, Y. P., Moody, P. W., Bell, M. J., Seymour, Nicole P., Dalal, R. C., Freebairn, D. M., and Walker, S. R.

Abstract

In semi-arid sub-tropical areas, a number of studies concerning no-till (NT) farming systems have demonstrated advantages in economic, environmental and soil quality aspects over conventional tillage (CT). However, adoption of continuous NT has contributed to the build-up of herbicide resistant weed populations, increased incidence of soil- and stubble-borne diseases, and stratification of nutrients and organic carbon near the soil surface. Some farmers often resort to an occasional strategic tillage (ST) to manage these problems of NT systems. However, farmers who practice strict NT systems are concerned that even one-time tillage may undo positive soil condition benefits of NT farming systems. We reviewed the pros and cons of the use of occasional ST in NT farming systems. Impacts of occasional ST on agronomy, soil and environment are site-specific and depend on many interacting soil, climatic and management conditions. Most studies conducted in North America and Europe suggest that introducing occasional ST in continuous NT farming systems could improve productivity and profitability in the short term; however in the long-term, the impact is negligible or may be negative. The short term impacts immediately following occasional ST on soil and environment include reduced protective cover, soil loss by erosion, increased runoff, loss of C and water, and reduced microbial activity with little or no detrimental impact in the long-term. A potential negative effect immediately following ST would be reduced plant available water which may result in unreliability of crop sowing in variable seasons. The occurrence of rainfall between the ST and sowing or immediately after the sowing is necessary to replenish soil water lost from the seed zone. Timing of ST is likely to be critical and must be balanced with optimising soil water prior to seeding. The impact of occasional ST varies with the tillage implement used; for example, inversion tillage using mouldboard tillage resul

Published
2015

43. Introductory remarks

Author

Walker, S. R., Walker, S. R., editor, Asscher, A. W., editor, Walker, Stuart R, editor, and Asscher, A William, editor

Published
1987
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44. Abstracts of papers toxicological meeting

Author

Beynen, A. C., Meijer, G. W., Joosten, H. F. P., van Kolfschoten, A. A., Koëter, H. B. W. M., Leegwater, P. C., Hermens, J. L. M., Rauws, A. G., Lumley, C. E., Walker, S. R., Bodar, C. W. M., Voogt, P. A., Wijnne, H., v. d. Zee, A., Zandee, D. I., Boogaard, P. J., Mulder, G. J., Nagelkerke, J. F., Boot, J. H., van Holsteijn, C. W. M., Blaauboer, B. J., Bos, R. P., Theuws, J. L. G., Jongeneelen, F. J., Brouwer, E. J., de Wolff, F. A., Busker, Ruud W., Commandeur, J. N. M., Vermeulen, N. P. E., Coosen, R., Schenk, E., van Leeuwen, F. X. R., Vos, J. G., Peereboom-Stegeman, J. H. J. Copius, van Veen, H., Pertijs, J., Danse, L. H. J. C., de Jong, K., Speijers, G. J. A., de Kom, J. F. M., Edelbroek, P. M., de Jong, E. G., Maes, R. A. A., de Vries, H., van Henegouwen, G. M. J. Beyersbergen, Berkhuysen, M. H. J., Kalloe, P., de Zwaan, A., de Kock, W. Chr, den Besten, P. J., Dogterom, P., Dormans, J. A. M. A., Boere, A. J. F., van Bree, L., Rombout, P. J. A., Evelo, C. T. A., Fijneman, P. H. S., Henderson, P. Th., Goeptar, A. R., Haenen, G. R. M. M., Bast, A., Tai Tin Tsoi, J. N. L., Timmerman, H., Hageman, G., Hermans, R., Kleinjans, J., Herweijer, M. A., Bootsman, T. C., van der Meer, S. G., Planta, R. J., Kappers, Frederike I., Wondergem-van Eijk, Jacqueline A. A. M., Kelder, P. P., de Mol, N. J., Janssen, L. H. M., Kroese, E. D., van de Poll, M. L. M, Meerman, J. H. N., Lock, R. A. C., Verbost, P. M., Flik, G., Bonga, S. E. Wendelaar, Lusthof, K. J., Hennes, W. C., den Hartogh, R., Kietjens, I., Dornans, J., Rombout, P., Schoonderwoerd, S. A., Luijendijk, J. J., van Henegouwen, G. M. J. Beijersbergen, te Koppele, J. M., Coles, B., Ketterer, B., van Ginkel, M. F., van der Voet, G. B., van Pelt, F. N. A. M., olde Meierink, Y. J. M., Weterings, P. J. J. H, van Os, C. H., Verhagen, H., Schutte, B., Reynders, M. M. J., Blijham, G. H., ten Hoor, F., Kleinjans, J. C. S., Wetzer, A. M., Weetink, H., Rietveld, E. C, Seutter-Berlage, F., and van Henegouwen, Gerard M. J. Beijersbergen

Published
1987
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45. Photodynamical mass determination of the multiplanetary system K2-19

Author

Barros, S. C. C., primary, Almenara, J. M., additional, Demangeon, O., additional, Tsantaki, M., additional, Santerne, A., additional, Armstrong, D. J., additional, Barrado, D., additional, Brown, D., additional, Deleuil, M., additional, Lillo-Box, J., additional, Osborn, H., additional, Pollacco, D., additional, Abe, L., additional, Andre, P., additional, Bendjoya, P., additional, Boisse, I., additional, Bonomo, A. S., additional, Bouchy, F., additional, Bruno, G., additional, Cerda, J. Rey, additional, Courcol, B., additional, Díaz, R. F., additional, Hébrard, G., additional, Kirk, J., additional, Lachurié, J. C., additional, Lam, K. W. F., additional, Martinez, P., additional, McCormac, J., additional, Moutou, C., additional, Rajpurohit, A., additional, Rivet, J.-P., additional, Spake, J., additional, Suarez, O., additional, Toublanc, D., additional, and Walker, S. R., additional

Published
2015
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46. K2-19, The first K2 muti-planetary system showing TTVs

Author

Barros, S. C. C., primary, Almenara, J. M., additional, Demangeon, O., additional, Tsantaki, M., additional, Santerne, A., additional, Armstrong, D. J., additional, Barrado, D., additional, Brown, D., additional, Deleuil, M., additional, Lillo-Box, J., additional, Osborn, H., additional, Pollacco, D., additional, Abe, L., additional, Andre, P., additional, Bendjoya, P., additional, Boisse, I., additional, Bonomo, A. S., additional, Bouchy, F., additional, Bruno, G., additional, Cerda, J. Rey, additional, Courcol, B., additional, Díaz, R. F., additional, Hébrard, G., additional, Kirk, J., additional, Lachurié, J. C., additional, Lam, K. W. F., additional, Martinez, P., additional, McCormac, J., additional, Moutou, C., additional, Rajpurohit, A., additional, Rivet, J.-P., additional, Spake, J., additional, Suarez, O., additional, Toublanc, D., additional, and Walker, S. R., additional

Published
2015
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48. EVALUATION AND INTER-COMPARISON OF OPEN ROAD LINE SOURCE MODELS CURRENTLY IN USE IN THE NORDIC COUNTRIES

Author

Berger, J., Walker, S. -R, Denby, B., Berkowicz, R., Løfstrøm, P., Ketzel, M., Härkönen, J., Nikmo, J., and Ari Karppinen

Subjects
VDP::Mathematics and natural scienses: 400::Geosciences: 450::Meteorology: 453, VDP::Matematikk og naturvitenskap: 400::Geofag: 450::Meteorologi: 453, Line source, Highway, Gaussian, Traffic produced turbulence, Normalisation, Dispersion
Abstract

The aim of this study is to inter-compare and evaluate operational open road Gaussian line source models currently in use in the Nordic countries Norway, Denmark and Finland. By comparing the models and their results on different datasets, a more robust and objective assessment of model performance and applicability can be made. Four models, HIWAY2-AQ, OML-Highway, CAR-FM1 and WORM, are applied to datasets from three measurement campaigns from each of the mentioned countries. A more specific target is to determine the conditions under which the models perform well or poorly in order to focus attention on these aspects in future model development. The various models arc evaluated primarily with regard to wind speed, wind direction and atmospheric stability in order to identify problem areas. Generally, the correlation between model estimates and observations decreases when normalising with emissions, due to the significant positive correlation between observed concentrations and emissions. Furthermore, we found a reduction of bias when normalising the Norwegian and Danish data, caused by overestimation of the dispersion at lower emission values. This occurs because the initial dispersion is too large in all the models. For higher emissions at the Danish site, the relative bias was higher, compared with the relative bias at the Norwegian site, indicating the influence of traffic density and vehicle speed (which arc both largest at the Danish site) on traffic produced turbulence and model performance. OML-Highway, however, performs best in this regard due to its more advanced parameterisation of traffic produced turbulence based on production and decay of turbulent kinetic energy. With regard to horizontal profiles, RB for CAR-FMI increased as function of distance from the road, indicating that the Lagrangian time scales are too short.

Published
2008

50. WASP-104b and WASP-106b: two transiting hot Jupiters in 1.75-day and 9.3-day orbits

Author

Smith, A. M. S., primary, Anderson, D. R., additional, Armstrong, D. J., additional, Barros, S. C. C., additional, Bonomo, A. S., additional, Bouchy, F., additional, Brown, D. J. A., additional, Collier Cameron, A., additional, Delrez, L., additional, Faedi, F., additional, Gillon, M., additional, Gómez Maqueo Chew, Y., additional, Hébrard, G., additional, Jehin, E., additional, Lendl, M., additional, Louden, T. M., additional, Maxted, P. F. L., additional, Montagnier, G., additional, Neveu-VanMalle, M., additional, Osborn, H. P., additional, Pepe, F., additional, Pollacco, D., additional, Queloz, D., additional, Rostron, J. W., additional, Segransan, D., additional, Smalley, B., additional, Triaud, A. H. M. J., additional, Turner, O. D., additional, Udry, S., additional, Walker, S. R., additional, West, R. G., additional, and Wheatley, P. J., additional

Published
2014
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