49,256 research outputs found
WRI's Governance Strategy, 2016-2020
Transparent, effective, accountable governance is critical to ensuring that development benefits people and the planet. The Governance Center of Excellence works with civil society, governments, development agencies, businesses, and other institutions to improve decision-making processes and legal frameworks. Our goal is to empower people and strengthen institutions to foster environmentally sound and socially equitable decision-making.In many countries, citizens and communities face social and environmental injustices that can leave them without a say in the development decisions that affect their lives and the resources they depend on.As a global leader on environmental governance, the Governance Center uses data and research to institutionalize fundamental democratic principles - such as transparency, participation, and accountability - into decision-making processes, policies, and legal frameworks. The Governance Center is divided into five practice areas—climate resilience, environmental democracy, energy governance, natural resource governance and urban governance— where our work is concentrated on six priority issues: climate, energy, food, forests, water, and cities
Pushing the precision limit of ground-based eclipse photometry
Until recently, it was considered by many that ground-based photometry could
not reach the high cadence sub-mmag regime because of the presence of the
atmosphere. Indeed, high frequency atmospheric noises (mainly scintillation)
limit the precision that high SNR photometry can reach within small time bins.
If one is ready to damage the sampling of his photometric time-series, binning
the data (or using longer exposures) allows to get better errors, but the
obtained precision will be finally limited by low frequency noises. To observe
several times the same planetary eclipse and to fold the photometry with the
orbital period is thus generally considered as the only option to get very well
sampled and precise eclipse light curve from the ground. Nevertheless, we show
here that reaching the sub-mmag sub-min regime for one eclipse is possible with
a ground-based instrument. This has important implications for transiting
planets characterization, secondary eclipses measurement and small planets
detection from the ground.Comment: Transiting Planets Proceeding IAU Symposium No.253, 2008. 7 pages, 4
figure
The DWARF project: Eclipsing binaries - precise clocks to discover exoplanets
We present a new observational campaign, DWARF, aimed at detection of
circumbinary extrasolar planets using the timing of the minima of low-mass
eclipsing binaries. The observations will be performed within an extensive
network of relatively small to medium-size telescopes with apertures of ~20-200
cm. The starting sample of the objects to be monitored contains (i) low-mass
eclipsing binaries with M and K components, (ii) short-period binaries with sdB
or sdO component, and (iii) post-common-envelope systems containing a WD, which
enable to determine minima with high precision. Since the amplitude of the
timing signal increases with the orbital period of an invisible third
component, the timescale of project is long, at least 5-10 years. The paper
gives simple formulas to estimate suitability of individual eclipsing binaries
for the circumbinary planet detection. Intrinsic variability of the binaries
(photospheric spots, flares, pulsation etc.) limiting the accuracy of the
minima timing is also discussed. The manuscript also describes the best
observing strategy and methods to detect cyclic timing variability in the
minima times indicating presence of circumbinary planets. First test
observation of the selected targets are presented.Comment: 12 pages, 2 figures, submitted to Astron. Nachrichte
Systematicity and surface similarity in the development of analogy
In split page format (number of pages: 45)Includes bibliographical reference
High-Cadence, High-Contrast Imaging for Exoplanet Mapping: Observations of the HR 8799 Planets with VLT/SPHERE Satellite Spot-Corrected Relative Photometry
Time-resolved photometry is an important new probe of the physics of
condensate clouds in extrasolar planets and brown dwarfs. Extreme adaptive
optics systems can directly image planets, but precise brightness measurements
are challenging. We present VLT/SPHERE high-contrast, time-resolved broad
H-band near-infrared photometry for four exoplanets in the HR 8799 system,
sampling changes from night to night over five nights with relatively short
integrations. The photospheres of these four planets are often modeled by
patchy clouds and may show large-amplitude rotational brightness modulations.
Our observations provide high-quality images of the system. We present a
detailed performance analysis of different data analysis approaches to
accurately measure the relative brightnesses of the four exoplanets. We explore
the information in satellite spots and demonstrate their use as a proxy for
image quality. While the brightness variations of the satellite spots are
strongly correlated, we also identify a second-order anti-correlation pattern
between the different spots. Our study finds that PCA-based KLIP reduction with
satellite spot-modulated artificial planet-injection based photometry (SMAP)
leads to a significant (~3x) gain in photometric accuracy over standard
aperture-based photometry and reaches 0.1 mag per point accuracy for our
dataset, the signal-to-noise of which is limited by small field rotation.
Relative planet-to-planet photometry can be compared be- tween nights, enabling
observations spanning multiple nights to probe variability. Recent high-quality
relative H-band photometry of the b-c planet pair agree to about 1%.Comment: Astrophysical Journal, in pres
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