182 research outputs found
Exoplanet Transmission Spectroscopy using KMOS
KMOS (K-Band Multi Object Spectrograph) is a novel integral field
spectrograph installed in the VLT's ANTU unit. The instrument offers an ability
to observe 24 2.8"2.8" sub-fields positionable within a 7.2' patrol
field, each sub-field producing a spectrum with a 1414-pixel spatial
resolution. The main science drivers for KMOS are the study of galaxies, star
formation, and molecular clouds, but its ability to simultaneously measure
spectra of multiple stars makes KMOS an interesting instrument for exoplanet
atmosphere characterization via transmission spectroscopy. We set to test
whether transmission spectroscopy is practical with KMOS, and what are the
conditions required to achieve the photometric precision needed, based on
observations of a partial transit of WASP-19b, and full transits of GJ 1214b
and HD 209458b. Our analysis uses the simultaneously observed comparison stars
to reduce the effects from instrumental and atmospheric sources, and Gaussian
processes to model the residual systematics. We show that KMOS can, in theory,
deliver the photometric precision required for transmission spectroscopy.
However, this is shown to require a) pre-imaging to ensure accurate centering
and b) a very stable night with optimal observing conditions (seeing
0.8"). Combining these two factors with the need to observe several
transits, each with a sufficient out-of-transit baseline (and with the fact
that similar or better precision can be reached with telescopes and instruments
with smaller pressure,) we conclude that transmission spectroscopy is not the
optimal science case to take advantage of the abilities offered by KMOS and
VLT.Comment: 11 pages, accepted to MNRA
A uniform analysis of HD209458b Spitzer/IRAC lightcurves with Gaussian process models
We present an analysis of Spitzer/IRAC primary transit and secondary eclipse
lightcurves measured for HD209458b, using Gaussian process models to
marginalise over the intrapixel sensitivity variations in the 3.6 micron and
4.5 micron channels and the ramp effect in the 5.8 micron and 8.0 micron
channels. The main advantage of this approach is that we can account for a
broad range of degeneracies between the planet signal and systematics without
actually having to specify a deterministic functional form for the latter. Our
results do not confirm a previous claim of water absorption in transmission.
Instead, our results are more consistent with a featureless transmission
spectrum, possibly due to a cloud deck obscuring molecular absorption bands.
For the emission data, our values are not consistent with the thermal inversion
in the dayside atmosphere that was originally inferred from these data.
Instead, we agree with another re-analysis of these same data, which concluded
a non-inverted atmosphere provides a better fit. We find that a solar-abundance
clear-atmosphere model without a thermal inversion underpredicts the measured
emission in the 4.5 micron channel, which may suggest the atmosphere is
depleted in carbon monoxide. An acceptable fit to the emission data can be
achieved by assuming that the planet radiates as an isothermal blackbody with a
temperature of K.Comment: 18 pages, 5 figures, 6 tables. Accepted by MNRA
Tools for evaluating and monitoring effectiveness of urban landscape water conservation interventions and programs
Our research objective was to investigate ways to evaluate landscape water use to help cities more effectively direct water conservation programs to locations with capacity to conserve. Research was conducted in connection with a landscape irrigation evaluation delivered through a city-sponsored Water Check Program. Research efforts led to development of several assessment and monitoring tools including: Landscape Irrigation Ratio (LIR), Participant Outcome Evaluation Tool, and Program Evaluation Tool. We utilized these tools to identify locations with capacity to conserve water applied to landscapes, compare water use before and after the water check, and evaluate Water Check Program effectiveness. We found the LIR approach successfully distinguished residential locations efficiently or acceptably using water applied to landscapes from ones with use considered inefficient or excessive. In analyzing change in participantsâ water use and eliminating explanations other than the water check, we found factors influencing landscape water use tend to be highly contextualized and the intervention itself needed to be analyzed. The majority of participants who adopted the water check recommendations successfully reduced their landscape water use, but results indicate water check programs can be designed for greater effectiveness by accommodating participantsâ differing knowledge and skill levels. We argue that the tools we developed provide the water conservation field with a needed set of common assessment methods. We conclude that landscape water checks have the potential to provide people with the information and problem-solving skills necessary to maintain residential landscapes using appropriate amounts of water if they are well designed, delivered, and monitored
The Very Low Albedo of WASP-12b From Spectral Eclipse Observations with
We present an optical eclipse observation of the hot Jupiter WASP-12b using
the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope.
These spectra allow us to place an upper limit of (97.5%
confidence level) on the planet's white light geometric albedo across 290--570
nm. Using six wavelength bins across the same wavelength range also produces
stringent limits on the geometric albedo for all bins. However, our
uncertainties in eclipse depth are 40% greater than the Poisson limit and
may be limited by the intrinsic variability of the Sun-like host star --- the
solar luminosity is known to vary at the level on a timescale of
minutes. We use our eclipse depth limits to test two previously suggested
atmospheric models for this planet: Mie scattering from an aluminum-oxide haze
or cloud-free Rayleigh scattering. Our stringent nondetection rules out both
models and is consistent with thermal emission plus weak Rayleigh scattering
from atomic hydrogen and helium. Our results are in stark contrast with those
for the much cooler HD 189733b, the only other hot Jupiter with spectrally
resolved reflected light observations; those data showed an increase in albedo
with decreasing wavelength. The fact that the first two exoplanets with optical
albedo spectra exhibit significant differences demonstrates the importance of
spectrally resolved reflected light observations and highlights the great
diversity among hot Jupiters.Comment: 8 pages, 4 figures, 1 table, published in ApJL, in pres
Estimating landscape irrigated areas and potential water conservation at the rural-urban interface using remote sensing and GIS
Research goals were to analyze patterns of urban landscape water use, assess landscape water conservation potential, and identify locations with capacity to conserve. Methodological contributions involved acquiring airborne multispectral digital images over two urban cities which were processed, classified, and imported into a GIS environment where landscaped area were extracted and combined with property and water billing data and local evapotranspiration rates to calculate landscape irrigation applications exceeding estimated water needs. Additional analyses were conducted to compare classified aerial images to ground-measured landscaped areas, landscaped areas to total parcel size, water use on residential and commercial properties, and turf areas under tress when they were leafed out and bare. Results verified the accuracy and value of this approach for municipal water management, showed more commercial properties applied water in excess of estimated needs compared to residential ones, and that small percentages of users accounted for most of the excess irrigatio
The Deep Blue Color of HD 189733b: Albedo Measurements with Hubble Space Telescope/Space Telescope Imaging Spectrograph at Visible Wavelengths
We present a secondary eclipse observation for the hot Jupiter HD 189733b across the wavelength range 290-570 nm made using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. We measure geometric albedos of A_g = 0.40 ± 0.12 across 290-450 nm and A_g < 0.12 across 450-570 nm at 1Ï confidence. The albedo decrease toward longer wavelengths is also apparent when using six wavelength bins over the same wavelength range. This can be interpreted as evidence for optically thick reflective clouds on the dayside hemisphere with sodium absorption suppressing the scattered light signal beyond ~450 nm. Our best-fit albedo values imply that HD 189733b would appear a deep blue color at visible wavelengths
Past, present and future challenges in health care priority setting:findings from an international expert survey
Purpose
Current conditions have intensified the need for health systems to engage in the difficult task of priority setting. As the search for a âmagic bulletâ is replaced by an appreciation for the interplay between evidence, interests, culture, and outcomes, progress in relation to these dimensions requires assessment of achievements to date and identification of areas where knowledge and practice require attention most urgently. The paper aims to discuss these issues.
Design/methodology/approach
An international survey was administered to experts in the area of priority setting. The survey consisted of open-ended questions focusing on notable achievements, policy and practice challenges, and areas for future research in the discipline of priority setting. It was administered online between February and March of 2015.
Findings
âDecision-making frameworksâ and âEngagementâ were the two most frequently mentioned notable achievements. âPriority setting in practiceâ and âAwareness and educationâ were the two most frequently mentioned policy and practical challenges. âPriority setting in practiceâ and âEngagementâ were the two most frequently mentioned areas in need of future research.
Research limitations/implications
Sampling bias toward more developed countries. Future study could use findings to create a more concise version to distribute more broadly.
Practical implications
Globally, these findings could be used as a platform for discussion and decision making related to policy, practice, and research in this area.
Originality/value
Whilst this study reaffirmed the continued importance of many longstanding themes in the priority setting literature, it is possible to also discern clear shifts in emphasis as the discipline progresses in response to new challenges.
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