19,179 research outputs found

    Verification of the Kepler Input Catalog from Asteroseismology of Solar-type Stars

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    We calculate precise stellar radii and surface gravities from the asteroseismic analysis of over 500 solar-type pulsating stars observed by the Kepler space telescope. These physical stellar properties are compared with those given in the Kepler Input Catalog (KIC), determined from ground-based multi-color photometry. For the stars in our sample, we find general agreement but we detect an average overestimation bias of 0.23 dex in the KIC determination of log (g) for stars with log (g)_KIC > 4.0 dex, and a resultant underestimation bias of up to 50% in the KIC radii estimates for stars with R_KIC < 2 R sun. Part of the difference may arise from selection bias in the asteroseismic sample; nevertheless, this result implies there may be fewer stars characterized in the KIC with R ~ 1 R sun than is suggested by the physical properties in the KIC. Furthermore, if the radius estimates are taken from the KIC for these affected stars and then used to calculate the size of transiting planets, a similar underestimation bias may be applied to the planetary radii.Comment: Published in The Astrophysical Journal Letter

    Cities and climate change: Strategic options for philanthropic support

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    Now, more than ever, cities are at the front lines of U.S. climate action. As national action stalls, there is still a daunting amount to be done in reducing human-generated climate emissions. Fortunately, this report comes in the wake of a groundswell of initiatives to engage on climate change by cities, countries, and states across the U.S. Several important and thorough reports on the types of mitigation actions cities can take have recently been released. We already have examples of cities taking significant leadership roles in reducing their own climate emissions, from New York and Boston to Austin, Boulder, and Los Angeles - yet U.S. climate emissions continue to rise, and cities have an outsized role to play. The purpose of this project is to review current U.S. city climate activities in order to identify areas where additional investment by foundations could help accelerate city action to reduce urban greenhouse gas emissions. The focus of the inquiry is on aggressive actions cities can take that significantly increase their “level of ambition” to achieve emissions reductions on an accelerated timetable. City strategies on climate adaptation are not encompassed in this project. [TRUNCATED

    Spatial land-use inventory, modeling, and projection/Denver metropolitan area, with inputs from existing maps, airphotos, and LANDSAT imagery

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    A landscape model was constructed with 34 land-use, physiographic, socioeconomic, and transportation maps. A simple Markov land-use trend model was constructed from observed rates of change and nonchange from photointerpreted 1963 and 1970 airphotos. Seven multivariate land-use projection models predicting 1970 spatial land-use changes achieved accuracies from 42 to 57 percent. A final modeling strategy was designed, which combines both Markov trend and multivariate spatial projection processes. Landsat-1 image preprocessing included geometric rectification/resampling, spectral-band, and band/insolation ratioing operations. A new, systematic grid-sampled point training-set approach proved to be useful when tested on the four orginal MSS bands, ten image bands and ratios, and all 48 image and map variables (less land use). Ten variable accuracy was raised over 15 percentage points from 38.4 to 53.9 percent, with the use of the 31 ancillary variables. A land-use classification map was produced with an optimal ten-channel subset of four image bands and six ancillary map variables. Point-by-point verification of 331,776 points against a 1972/1973 U.S. Geological Survey (UGSG) land-use map prepared with airphotos and the same classification scheme showed average first-, second-, and third-order accuracies of 76.3, 58.4, and 33.0 percent, respectively

    Hard X-ray imaging facility for space shuttle: A scientific and conceptual engineering study

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    A shuttle-accommodated instrument for imaging hard X-rays in the study of nonthermal particles and high temperature particles in various solar and cosmic phenomena was defined and its feasibility demonstrated. The imaging system configuration is described as well as the electronics, aspect systems, mechanical and thermal properties and the ground support equipment
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