10,465 research outputs found
The PHOENIX Exoplanet Retrieval Algorithm and Using H Opacity as a Probe in Ultra-hot Jupiters
Atmospheric retrievals are now a standard tool to analyze observations of
exoplanet atmospheres. This data-driven approach quantitatively compares
atmospheric models to observations in order to estimate atmospheric properties
and their uncertainties. In this paper, we introduce a new retrieval package,
the PHOENIX Exoplanet Retrieval Analysis (PETRA). PETRA places the PHOENIX
atmosphere model in a retrieval framework, allowing us to combine the strengths
of a well-tested and widely-used atmosphere model with the advantages of
retrieval algorithms. We validate PETRA by retrieving on simulated data for
which the true atmospheric state is known. We also show that PETRA can
successfully reproduce results from previously published retrievals of WASP-43b
and HD 209458b. For the WASP-43b results, we show the effect that different
line lists and line profile treatments have on the retrieved atmospheric
properties. Lastly, we describe a novel technique for retrieving the
temperature structure and density in ultra-hot Jupiters using H
opacity, allowing us to probe atmospheres devoid of most molecular features
with JWST.Comment: 17 pages, 18 figures. Accepted for publication in A
Introduction: Ain’t It Evil to Live Backwards? : A Hip Hop Perspective of Religion
Historically, Black religion has been the cornerstone of the African experience in America. Due to the peculiar institution” of slavery and the ways this institutional residue still affect the lives of slave descendants, Hip Hop provides a forum to simultaneously acknowledge similarities and highlight differences. What scholars of religion and Hip Hop studies have revealed are the ways in which the effectiveness and our very understanding of “religion” changes when we bring Hip Hop in to the mix
Growth and the expression of alternative life cycles in the salamander \u3ci\u3eAmbystoma talpoideum\u3c/i\u3e (Caudata: Ambystomatidae)
Complex life cycles (CLCs) contain larval and adult phases that are morphologically and ecologically distinct. Simple life cycles (SLCs) have evolved from CLCs repeatedly in a wide variety of lineages but the processes that may underlie the transition have rarely been identified or investigated experimentally. We examined the influence of larval growth rate on the facultative expression of alternative life cycles (metamorphosis or maturation as gill-bearing adults [= paedomorphosis]) in the salamander Ambystoma talpoideum. We manipulated growth rates by altering the amount of food individuals received throughout larval development. The expression of alternative life cycles in A. talpoideum is influenced by growth via food levels, but the same growth rates at different points in the larval period elicit different responses. Individuals were more likely to metamorphose (i.e. express a CLC) when food levels and growth rates were high later in development and more likely to mature without metamorphosing (SLC) when growth rates were comparatively low during the same point in development. Growth rates at particular points in development, rather than overall larval growth rate, may be an important proximate factor in salamander life-cycle evolution
The Influence of Host Star Spectral Type on Ultra-Hot Jupiter Atmospheres
Ultra-hot Jupiters are the most highly irradiated gas giant planets, with
equilibrium temperatures from 2000 to over 4000 K. Ultra-hot Jupiters are
amenable to characterization due to their high temperatures, inflated radii,
and short periods, but their atmospheres are atypical for planets in that the
photosphere possesses large concentrations of atoms and ions relative to
molecules. Here we evaluate how the atmospheres of these planets respond to
irradiation by stars of different spectral type. We find that ultra-hot
Jupiters exhibit temperature inversions that are sensitive to the spectral type
of the host star. The slope and temperature range across the inversion both
increase as the host star effective temperature increases due to enhanced
absorption at short wavelengths and low pressures. The steep temperature
inversions in ultra-hot Jupiters around hot stars result in increased thermal
dissociation and ionization compared to similar planets around cooler stars.
The resulting increase in H opacity leads to a transit spectrum that has
muted absorption features. The emission spectrum, however, exhibits a large
contrast in brightness temperature, a signature that will be detectable with
both secondary eclipse observations and high-dispersion spectroscopy. We also
find that the departures from local thermodynamic equilibrium in the stellar
atmosphere can affect the degree of heating caused by atomic metals in the
planet's upper atmosphere. Additionally, we further quantify the significance
of heating by different opacity sources in ultra-hot Jupiter atmospheres.Comment: 13 pages, 9 figures, 2 tables. Accepted for publication in Ap
Astronomical, physical, and meteorological parameters for planetary atmospheres
A newly compiled table of astronomical, physical, and meteorological parameters for planetary atmospheres is presented. Formulae and explanatory notes for their application and a complete listing of sources are also given
Extremely Irradiated Hot Jupiters: Non-Oxide Inversions, H- Opacity, and Thermal Dissociation of Molecules
Extremely irradiated hot Jupiters, exoplanets reaching dayside temperatures
2000 K, stretch our understanding of planetary atmospheres and the models
we use to interpret observations. While these objects are planets in every
other sense, their atmospheres reach temperatures at low pressures comparable
only to stellar atmospheres. In order to understand our \textit{a priori}
theoretical expectations for the nature of these objects, we self-consistently
model a number of extreme hot Jupiter scenarios with the PHOENIX model
atmosphere code. PHOENIX is well-tested on objects from cool brown dwarfs to
expanding supernovae shells and its expansive opacity database from the UV to
far-IR make PHOENIX well-suited for understanding extremely irradiated hot
Jupiters. We find several fundamental differences between hot Jupiters at
temperatures 2500 K and their cooler counterparts. First, absorption by
atomic metals like Fe and Mg, molecules including SiO and metal hydrides, and
continuous opacity sources like H all combined with the short-wavelength
output of early-type host stars result in strong thermal inversions, without
the need for TiO or VO. Second, many molecular species, including HO, TiO,
and VO are thermally dissociated at pressures probed by eclipse observations,
biasing retrieval algorithms that assume uniform vertical abundances. We
discuss other interesting properties of these objects, as well as future
prospects and predictions for observing and characterizing this unique class of
astrophysical object, including the first self-consistent model of the hottest
known jovian planet, KELT-9b.Comment: 23 pages, 16 figures, 1 table. Submitted to Ap
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