Here is the second part of the listing.

2005

This paper on the atmospheric dynamics of HD 209458b suggests the existence of a superrotating jet:

Dynamic Meteorology at the Photosphere of HD 209458b

Curtis S. Cooper, Adam P. Showman

We calculate the meteorology of the close-in transiting extrasolar planet HD 209458b using a global, three-dimensional atmospheric circulation model. Dynamics are driven by perpetual irradiation of one hemisphere of this tidally locked planet. The simulation predicts global temperature contrasts of ~500 K at the photosphere and the development of a steady superrotating jet. The jet extends from the equator to mid-latitudes and from the top model layer at 1 mbar down to 10 bars at the base of the heated region. Wind velocities near the equator exceed 4 km/s at 300 mbar. The hottest regions of the atmosphere are blown downstream from the substellar point by 60 degrees of longitude. We predict from these results a factor of ~2 ratio between the maximum and minimum observed radiation from the planet over a full orbital period, with peak infrared emission preceding the time of the secondary eclipse by ~14 hours.

The first and second direct detections of photons emitted by an exoplanetary atmosphere:

Detection of Thermal Emission from an Extrasolar Planet

David Charbonneau, Lori E. Allen, S. Thomas Megeath, Guillermo Torres, Roi Alonso, Timothy M. Brown, Ronald L. Gilliland, David W. Latham, Georgi Mandushev, Francis T. O'Donovan, Alessandro Sozzetti

We present Spitzer Space Telescope infrared photometric time series of the transiting extrasolar planet system TrES-1. The data span a predicted time of secondary eclipse, corresponding to the passage of the planet behind the star. In both bands of our observations, we detect a flux decrement with a timing, amplitude, and duration as predicted by published parameters of the system. This signal represents the first direct detection of (i.e. the observation of photons emitted by) a planet orbiting another star. The observed eclipse depths (in units of relative flux) are 0.00066 +/- 0.00013 at 4.5um and 0.00225 +/- 0.00036 at 8.0um. These estimates provide the first observational constraints on models of the thermal emission of hot Jupiters. Assuming that the planet emits as a blackbody, we estimate an effective temperature of Tp=1060 +/- 50 K. Under the additional assumptions that the planet is in thermal equilibrium with the radiation from the star and emits isotropically, we find a Bond albedo of A = 0.31 +/- 0.14. This would imply that the planet absorbs the majority of stellar radiation incident upon it, a conclusion of significant impact to atmospheric models of these objects. We compare our data to a previously-published model of the planetary thermal emission, which predicts prominent spectral features in our observational bands due to water and carbon monoxide. Based on the time of secondary eclipse, we present an upper limit on the orbital eccentricity that is sufficiently small that we conclude that tidal dissipation is unlikely to provide a significant source of energy interior to the planet.

Infrared radiation from an extrasolar planet

Drake Deming, Sara Seager, L. Jeremy Richardson, Joseph Harrington

A class of extrasolar giant planets - the so-called `hot Jupiters' - orbit within 0.05 AU of their primary stars. These planets should be hot and so emit detectable infrared radiation. The planet HD 209458b is an ideal candidate for the detection and characterization of this infrared light because it is eclipsed by the star. This planet has an anomalously large radius (1.35 times that of Jupiter), which may be the result of ongoing tidal dissipation, but this explanation requires a non-zero orbital eccentricity (~0.03), maintained by interaction with a hypothetical second planet. Here we report detection of infrared (24 micron) radiation from HD 209458b, by observing the decrement in flux during secondary eclipse, when the planet passes behind the star. The planet's 24 micron flux is 55 +/- 10 micro-Jy (1 sigma), with a brightness temperature of 1130 +/- 150 Kelvins, confirming the predicted heating by stellar irradiation. The secondary eclipse occurs at the midpoint between transits of the planet in front of the star (to within +/- 7 min, 1 sigma), which means that a dynamically significant orbital eccentricity is unlikely.

And their first theoretical analyses:

Theoretical Interpretation of the Measurements of the Secondary Eclipses of TrES-1 and HD209458b

A. Burrows, I. Hubeny, D. Sudarsky

We calculate the planet-star flux-density ratios as a function of wavelength from 0.5 microns to 25 microns for the transiting extrasolar giant planets TrES-1 and HD209458b and compare them with the recent Spitzer/IRAC-MIPS secondary eclipse data in the 4.5, 8.0, and 24 micron bands. With only three data points and generic calibration issues, detailed conclusions are difficult, but inferences regarding atmospheric composition, temperature, and global circulation can be made. Our models reproduce the observations reasonably well, but not perfectly, and we speculate on the theoretical consequences of variations around our baseline models. One preliminary conclusion is that we may be seeing in the data indications that the day side of a close-in extrasolar giant planet is brighter in the mid-infrared than its night side, unlike Jupiter and Saturn. This correspondence will be further tested when the data anticipated in other Spitzer bands are acquired, and we make predictions for what those data may show.

Comparative Planetary Atmospheres: Models of TrES-1 and HD209458b

J.J. Fortney, M.S. Marley, K. Lodders, D. Saumon, R. Freedman

We present new self-consistent atmosphere models for transiting planets TrES-1 and HD209458b. The planets were recently observed with the Spitzer Space Telescope in bands centered on 4.5 and 8.0 um, for TrES-1, and 24 um, for HD209458b. We find that standard solar metallicity models fit the observations for HD209458b. For TrES-1, which has an Teff ~300K cooler, we find that models with a metallicity 3-5 times enhanced over solar abundances can match the 1-sigma error bar at 4.5 um and 2-sigma at 8.0 um. Models with solar abundances that included energy deposition into the stratosphere give fluxes that fall within the 2-sigma error bars in both bands. The best-fit models for both planets assume that reradiation of absorbed stellar flux occurs over the entire planet. For all models of both planets we predict planet/star flux ratios in other Spitzer bandpasses.

Discussion of a newly recognized general issue with transmission spectra:

The Effect of Condensates on the Characterization of Transiting Planet Atmospheres with Transmission Spectroscopy

Jonathan J. Fortney

Through a simple physical argument we show that the slant optical depth through the atmosphere of a "hot Jupiter" planet is 35-90 times greater than the normal optical depth. This not unexpected result has direct consequences for the method of transmission spectroscopy for characterizing the atmospheres of transiting giant planets. The atmospheres of these planets likely contain minor condensates and hazes which at normal viewing geometry have negligible optical depth, but at slant viewing geometry have appreciable optical depth that can obscure absorption features of gaseous atmospheric species. We identify several possible condensates. We predict that this is a general masking mechanism for all planets, not just for HD 209458b, and will lead to weaker than expected or undetected absorption features. Constraints on an atmosphere from transmission spectroscopy are not the same as constraints on an atmosphere at normal viewing geometry.

A first look at atmospheric transmission spectra of Earthlike planets around M dwarfs:

Biosignatures from Earth-Like Planets Around M Dwarfs

Antigona Segura, James F. Kasting, Victoria Meadows, Martin Cohen, John Scalo, David Crisp, Rebecca A.H. Butler, Giovana Tinetti

Coupled one-dimensional photochemical-climate calculations have been performed for hypothetical Earth-like planets around M dwarfs. Visible, near-infrared and thermal-infrared synthetic spectra of these planets were generated to determine which biosignature gases might be observed by a future, space-based telescope. Our star sample included two observed active M dwarfs, AD Leo and GJ 643, and three quiescent model stars. The spectral distribution of these stars in the ultraviolet generates a different photochemistry on these planets. As a result, the biogenic gases CH4, N2O, and CH3Cl have substantially longer lifetimes and higher mixing ratios than on Earth, making them potentially observable by space-based telescopes. On the active M-star planets, an ozone layer similar to Earth's was developed that resulted in a spectroscopic signature comparable to the terrestrial one. The simultaneous detection of O2 (or O3) and a reduced gas in a planet's atmosphere has been suggested as strong evidence for life. Planets circling M stars may be good locations to search for such evidence.

2006

Carbon chemistry of HD 209458b's upper atmosphere:

Dynamics and Disequilibrium Carbon Chemistry in HD 209458b's Atmosphere

Curtis S. Cooper, Adam P. Showman

Chemical equilibrium considerations suggest that, assuming solar elemental abundances, carbon on HD 209458b is sequestered primarily as carbon monoxide (CO) and methane (CH4). The relative mole fractions of CO(g) and CH4(g) in chemical equilibrium are expected to vary greatly according to variations in local temperature and pressure. We show, however, that in the p = 1--1000 mbar range, chemical equilibrium does not hold. To explore disequilibrium effects, we couple the chemical kinetics of CO and CH4 to a three-dimensional numerical model of HD 209458b's atmospheric circulation. These simulations show that vigorous dynamics caused by uneven heating of this tidally locked planet homogenize the CO and CH4 concentrations at p < 1 bar, even in the presence of lateral temperature variations of ~500--1000 K. In the 1--1000 mbar pressure range, we find that over 98% of the carbon is in CO. This is true even in cool regions where CH4 is much more stable thermodynamically. Our work shows furthermore that planets 300--500 K cooler than HD 209458b can also have abundant CO in their upper layers due to disequilibrium effects. We demonstrate several interesting observational consequences of these results.

The first accurate general model of hot Jupiter infrared light curves:

Theory for the Secondary Eclipse Fluxes, Spectra, Atmospheres, and Light Curves of Transiting Extrasolar Giant Planets

A. Burrows, D. Sudarsky, I. Hubeny

We have created a general methodology for calculating the wavelength-dependent light curves of close-in extrasolar giant planets (EGPs) as they traverse their orbits. Focussing on the transiting EGPs HD189733b, TrES-1, and HD209458b, we calculate planet/star flux ratios during secondary eclipse and compare them with the Spitzer data points obtained so far in the mid-infrared. We introduce a simple parametrization for the redistribution of heat to the planet's nightside, derive constraints on this parameter (Pn), and provide a general set of predictions for planet/star contrast ratios as a function of wavelength, model, and phase. Moreover, we calculate average dayside and nightside atmospheric temperature/pressure profiles for each transiting planet/Pn pair with which existing and anticipated Spitzer data can be used to probe the atmospheric thermal structure of severely irradiated EGPs. We find that the baseline models do a good job of fitting the current secondary eclipse dataset, but that the Spitzer error bars are not yet small enough to discriminate cleanly between all the various possibilities.

A closer look at atmospheric opacities:

Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres

Christopher M. Sharp, Adam Burrows

We present a comprehensive description of the theory and practice of opacity calculations from the infrared to the ultraviolet needed to generate models of the atmospheres of brown dwarfs and extrasolar giant planets. Methods for using existing line lists and spectroscopic databases in disparate formats are presented and plots of the resulting absorptive opacities versus wavelength for the most important molecules and atoms at representative temperature/pressure points are provided. Electronic, ro-vibrational, bound-free, bound-bound, free-free, and collision-induced transitions and monochromatic opacities are derived, discussed, and analyzed. The species addressed include the alkali metals, iron, heavy metal oxides, metal hydrides, H2, H2O, $CH4, CO, NH3, H2S, PH3, and representative grains.

A more detailed atmospheric dynamical model:

Atmospheric Circulation of Close-In Extrasolar Giant Planets: I. Global, Barotropic, Adiabatic Simulations

James Y-K. Cho, Kristen Menou, Brad Hansen, Sara Seager

We present results from a set of over 300 pseudospectral simulations of atmospheric circulation on extrasolar giant planets with circular orbits. The simulations are of high enough resolution (up to 341 total and sectoral modes) to resolve small-scale eddies and waves, required for reasonable physical accuracy. In this work, we focus on the global circulation pattern that emerges in a shallow, ``equivalent-barotropic'', turbulent atmosphere on both tidally synchronized and unsynchronized planets. A full exploration of the large physical and numerical parameter-space is performed to identify robust features of the circulation. The model is validated with Solar System giant planets. For extrasolar giant planets with physical parameters similar to HD 209458 b --a presumably synchronized extrasolar giant planet representative in many dynamical respects-- the circulation is characterized by the following features: 1) a coherent polar vortex that revolves around the pole in each hemisphere; 2) a low number--typically two or three--of slowly-varying, broad zonal (east-west) jets that form when the maximum jet speed is comparable to, or somewhat stronger than, those observed on the planets in the Solar System; and, 3) motion-associated temperature field, whose detectability and variability depend on the strength of the net heating rate and the global root mean square wind speed in the atmosphere. In many ways, the global circulation is Earth-like, rather than Jupiter-like. However, if extrasolar giant planets rotate faster and are not close-in (therefore not synchronized), their circulations become more Jupiter-like.

Another, more detailed model of HD 209458b's IR light curve:

The Influence of Atmospheric Dynamics on the Infrared Spectra and Light Curves of Hot Jupiters

J. J. Fortney, C. S. Cooper, A. P. Showman, M. S. Marley, R. S. Freedman

We explore the infrared spectrum of a three-dimensional dynamical model of planet HD209458b as a function of orbital phase. The dynamical model predicts day-side atmospheric pressure-temperature profiles that are much more isothermal at pressures less than 1 bar than one-dimensional radiative-convective models have found. The resulting day-side thermal spectra are very similar to a blackbody, and only weak water absorption features are seen at short wavelengths. The dayside emission is consequently in significantly better agreement with ground-based and space-based secondary eclipse data than any previous models, which predict strong flux peaks and deep absorption features. At other orbital phases, absorption due to carbon monoxide and methane is also predicted. We compute the spectra under two treatments of atmospheric chemistry: one uses the predictions of equilibrium chemistry, and the other uses non-equilibrium chemistry, which ties the timescales of methane and carbon monoxide chemistry to dynamical timescales. As a function of orbital phase, we predict planet-to-star flux ratios for standard infrared bands and all Spitzer Space Telescope bands. In Spitzer bands, we predict 2-fold to 15-fold variation in planetary flux as a function of orbital phase with equilibrium chemistry, and 2-fold to 4-fold variation with non-equilibrium chemistry. Variation is generally more pronounced in bands from 3-10 $\mu$m than at longer wavelengths. The orbital phase of maximum thermal emission in infrared bands is 15--45 orbital degrees before the time of secondary eclipse. Changes in flux as a function of orbital phase for HD209458b should be observable with Spitzer, given the previously acheived observational error bars.

The most detailed model yet of the spectra of Earthlike planets:

Spectral Evolution of an Earth-Like Planet

L. Kaltenegger, W.A. Traub, K.W. Jucks

We have developed a characterization of the geological evolution of the Earths atmosphere and surface in order to model the observable spectra of an Earth-like planet through its geological history. These calculations are designed to guide the interpretation of an observed spectrum of such a planet by future instruments that will characterize exoplanets. Our models focus on spectral features that either imply habitability or are required for habitability. These features are generated by H2O, CO2, CH4, O2, O3, N2O, and vegetation-like surface albedos. We chose six geological epochs to characterize. These epochs exhibit a wide range in abundance for these molecules, ranging from a CO2 rich early atmosphere, to a CO2/CH4-rich atmosphere around 2 billion years ago to a present-day atmosphere. We analyzed the spectra to quantify the strength of each important spectral feature in both the visible and thermal infrared spectral regions, and the resolutions required to unambiguously observe the features for each epoch. We find a wide range of spectral resolutions required for observing the different features. For example, H2O and O3 can be observed with relatively low resolution, while O2 and N2O require higher resolution. We also find that the inclusion of clouds in our models significantly affects both the strengths and resolutions required to observe all spectral features.

More theory on the variety of spectra of Earthlike exoplanets:

The Response of Atmospheric Chemistry on Earthlike Planets around F, G and K Stars to Small Variations in Orbital Distance

John Lee Grenfell, Barbara Stracke, Philip von Paris, Beate Patzer, Ruth Titz, Antigona Segura, Heike Rauer

One of the prime goals of future investigations of extrasolar planets is to search for life as we know it. The Earth's biosphere is adapted to current conditions. How would the atmospheric chemistry of the Earth respond if we moved it to different orbital distances or changed its host star? This question is central to astrobiology and aids our understanding of how the atmospheres of terrestrial planets develop. To help address this question, we have performed a sensitivity study using a coupled radiative-convective photochemical column model to calculate changes in atmospheric chemistry on a planet having Earth's atmospheric composition, which we subjected to small changes in orbital position, of the order of 5-10 per cent for a solar-type G2V, F2V, and K2V star. We then applied a chemical source-sink analysis to the biomarkers in order to understand how chemical processes affect biomarker concentrations. We start with the composition of the present Earth, since this is the only example we know for which a spectrum of biomarker molecules has been measured. We then investigate the response of the biomarkers to changes in the input stellar flux. Computing the thermal profile for atmospheres rich in H2 O, CO2 and CH4 is however a major challenge for current radiative schemes, due, among other things, to lacking spectroscopic data. Therefore, as a first step, we employ a more moderate approach, by investigating small shifts in planet-star distance and assuming an earthlike biosphere. To calculate this shift we assumed a criteria for complex life based on the Earth, i.e. the earthlike planetary surface temperature varied between zero to thirty degrees Centigrade which led to a narrow HZ width of (0.94-1.08)

More on IR transmission spectra:

Infrared Transmission Spectra for Extrasolar Giant Planets

G. Tinetti, M. C. Liang, A. Vidal-Madjar, D. Ehrenreich, A. Lecavelier des Etangs, Y. Yung

Among the hot Jupiters that transit their parent stars known to date, the two best candidates to be observed with transmission spectroscopy in the mid-infrared (MIR) are HD189733b and HD209458b, due to their combined characteristics of planetary density, orbital parameters and parent star distance and brightness. Here we simulate transmission spectra of these two planets during their primary eclipse in the MIR, and we present sensitivity studies of the spectra to the changes of atmospheric thermal properties, molecular abundances and C/O ratios. Our model predicts that the dominant species absorbing in the MIR on hot Jupiters are water vapor and carbon monoxide, and their relative abundances are determined by the C/O ratio. Since the temperature profile plays a secondary role in the transmission spectra of hot Jupiters compared to molecular abundances, future primary eclipse observations in the MIR of those objects might give an insight on EGP atmospheric chemistry. We find here that the absorption features caused by water vapor and carbon monoxide in a cloud-free atmosphere, are deep enough to be observable by the present and future generation of space-based observatories, such as Spitzer Space Telescope and James Webb Space Telescope. We discuss our results in light of the capabilities of these telescopes.

Part 3 to follow.

Bill

Here is the third part of the listing.

2007

Detection of silicate clouds on HD 209458b:

A Spectrum of an Extrasolar Planet

L. Jeremy Richardson, Drake Deming, Karen Horning, Sara Seager, Joseph Harrington

Of the over 200 known extrasolar planets, 14 exhibit transits in front of their parent stars as seen from Earth. Spectroscopic observations of the transiting planets can probe the physical conditions of their atmospheres. One such technique can be used to derive the planetary spectrum by subtracting the stellar spectrum measured during eclipse (planet hidden behind star) from the combined-light spectrum measured outside eclipse (star + planet). Although several attempts have been made from Earth-based observatories, no spectrum has yet been measured for any of the established extrasolar planets. Here we report a measurement of the infrared spectrum (7.5--13.2 micron) of the transiting extrasolar planet HD209458b. Our observations reveal a hot thermal continuum for the planetary spectrum, with approximately constant ratio to the stellar flux over this wavelength range. Superposed on this continuum is a broad emission peak centered near 9.65 micron that we attribute to emission by silicate clouds. We also find a narrow, unidentified emission feature at 7.78 micron. Models of these ``hot Jupiter'' planets predict a flux peak near 10 micron, where thermal emission from the deep atmosphere emerges relatively unimpeded by water absorption, but models dominated by water fit the observed spectrum poorly.

More theory on Earthlike exoplanets orbiting M dwarfs:

Biomarker Response to Galactic Cosmic Ray-Induced NOx and the Methane Greenhouse Effect in the Atmosphere of an Earthlike Planet Orbiting an M-Dwarf Star

John Lee Grenfell, Jean-Mathias Griessmeier, Beate Patzer, Heike Rauer, Antigona Segura, Anja Stadelmann, Barbara Stracke, Ruth Titz, Philip von Paris

Planets orbiting in the habitable zone (HZ) of M-Dwarf stars are subject to high levels of galactic cosmic rays (GCRs) which produce nitrogen oxides in earthlike atmospheres. We investigate to what extent this NOx may modify biomarker compounds such as ozone (O3) and nitrous oxide (N2O), as well as related compounds such as water (H2O) (essential for life) and methane (CH4) (which has both abiotic and biotic sources) . Our model results suggest that such signals are robust, changing in the M-star world atmospheric column by up to 20% due to the GCR NOx effects compared to an M-star run without GCR effects and can therefore survive at least the effects of galactic cosmic rays. We have not however investigated stellar cosmic rays here. CH4 levels are about 10 times higher than on the Earth related to a lowering in hydroxyl (OH) in response to changes in UV. The increase is less than reported in previous studies. This difference arose partly because we used different biogenic input. For example, we employed 23% lower CH4 fluxes compared to those studies. Unlike on the Earth, relatively modest changes in these fluxes can lead to larger changes in the concentrations of biomarker and related species on the M-star world. We calculate a CH4 greenhouse heating effect of up to 4K. O3 photochemistry in terms of the smog mechanism and the catalytic loss cycles on the M-star world differs considerably compared with the Earth.

Another important paper of hot Jupiter hydrodynamics:

Observational Consequences of Hydrodynamic Flows on Hot Jupiters

Jonathan Langton, Gregory Laughlin

We use a grid-based shallow water model to simulate the atmospheric dynamics of the transiting hot Jupiter HD 209458b. Under the usual assumption that the planet is in synchronous rotation with zero obliquity, a steady state is reached with a well-localized cold spot centered 76 degrees east of the antistellar point. This represents a departure from predictions made by previous simulations in the literature that used the shallow water formalism; we find that the disagreement is explained by the factor of 30 shorter radiative timescale used in our model. We also examine the case that the planet is in Cassini state 2, in which the expected obliquity is ~90 degrees. Under these circumstances, a periodic equilibrium is reached, with the temperature slightly leading the solar forcing. Using these temperature distributions, we calculate disk-integrated bolometric infrared light curves from the planet. The light curves for the two models are surprisingly similar, despite large differences in temperature patterns in the two cases. In the zero-obliquity case, the intensity at the minimum is 66% of the maximum intensity, with the minimum occuring 72 degrees ahead of transit. In the high-obliquity case, the minimum occurs 54 degrees ahead of transit, with an intensity of 58% of the maximum.

Detection of water absorption features in the spectrum of HD 209458b:

Identification of Absorption Features in an Extrasolar Planet Atmosphere

T. S. Barman

Abstract: Water absorption is identified in the atmosphere of HD209458b by comparing models for the planet's transmitted spectrum to recent, multi-wavelength, eclipse-depth measurements (from 0.3 to 1 microns) published by Knutson et al. (2007). A cloud-free model which includes solar abundances, rainout of condensates, and photoionization of sodium and potassium is in good agreement with the entire set of eclipse-depth measurements from the ultraviolet to near-infrared. Constraints are placed on condensate removal by gravitational settling, the bulk metallicity, and the redistribution of absorbed stellar flux. Comparisons are also made to the Charbonneau et al. (2002) sodium measurements.

First evidence of a thermal inversion and a stratosphere on HD 209458b:

The 3.6-8.0 Micron Broadband Emission Spectrum of HD 209458b: Evidence for an Atmospheric Temperature Inversion

Heather A. Knutson, David Charbonneau, Lori E. Allen, Adam Burrows, S. Thomas Megeath

We estimate the strength of the bandpass-integrated thermal emission from the extrasolar planet HD 209458b at 3.6, 4.5, 5.8, and 8.0 microns using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We observe a single secondary eclipse simultaneously in all four bandpasses and find relative eclipse depths of 0.00094 +/- 0.00009, 0.00213 +/- 0.00015, 0.00301 +/- 0.00043, and 0.00240 +/- 0.00026, respectively. These eclipse depths reveal that the shape of the inferred emission spectrum for the planet differs significantly from the predictions of standard atmosphere models; instead the most plausible explanation would require the presence of an inversion layer high in the atmosphere leading to significant water emission in the 4.5 and 5.8 micron bandpasses. This is the first clear indication of such a temperature inversion in the atmosphere of a hot Jupiter, as previous observations of other planets appeared to be in reasonably good agreement with the predictions of models without such an inversion layer.

Theoretical Spectral Models of the Planet HD 209458b with a Thermal Inversion and Water Emission Bands

Adam Burrows, Ivan Hubeny, Jano Budaj, Heather Knutson, David Charbonneau

We find that a theoretical fit to all the HD 209458b data at secondary eclipse requires that the dayside atmosphere of HD 209458b have a thermal inversion and a stratosphere. This inversion is caused by the capture of optical stellar flux by an absorber of uncertain origin that resides at altitude. One consequence of stratospheric heating and temperature inversion is the flipping of water absorption features into emission features from the near- to the mid-infrared and we see evidence of such a water emission feature in the recent HD 209458b IRAC data of Knutson et al. In addition, an upper-atmosphere optical absorber may help explain both the weaker-than-expected Na D feature seen in transit and the fact that the transit radius at 24 um is smaller than the corresponding radius in the optical. Moreover, it may be a factor in why HD 209458b's optical transit radius is as large as it is. We speculate on the nature of this absorber and the planets whose atmospheres may, or may not, be affected by its presence.

Very important paper on the classification of hot Jupiters:

A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres

Jonathan J. Fortney, Katharina Lodders, Mark S. Marley, Richard S. Freedman

We highlight the importance of gaseous TiO and VO opacity on the highly irradiated close-in giant planets. The atmospheres of these planets naturally fall into two classes that are somewhat analogous to the M- and L-type dwarfs. Those that are warm enough to have appreciable opacity due to TiO and VO gases we term the ``pM Class'' planets, and those that are cooler we term ``pL Class'' planets. We calculate model atmospheres for these planets, including pressure-temperature profiles, spectra, and characteristic radiative time constants. We show that pM Class planets have hot stratospheres ~2000K and appear ``anomalously'' bright in the mid infrared secondary eclipse, as was recently found for planets HD 149026b and HD 209458b. This class of planets absorbs incident flux and emits thermal flux from high in their atmospheres. Consequently, they will have large day/night temperature contrasts and negligible phase shifts between orbital phase and thermal emission light curves, because radiative timescales are much shorter than possible dynamical timescales. The pL Class planets absorb incident flux deeper in the atmosphere where atmospheric dynamics will more readily redistribute absorbed energy. This will lead to cooler day sides, warmer night sides, and larger phase shifts in thermal emission light curves. Around a Sun-like primary this boundary occurs at 0.04-0.05 AU. The eccentric transiting planets HD 147506b and HD 17156b alternate between the classes. Thermal emission in the optical from pM Class planets is significant red-ward of 400 nm, making these planets attractive targets for optical detection. The difference in the observed day/night contrast between ups Andromeda b (pM Class) and HD 189733b (pL Class) is naturally explained in this scenario.

Part 3b to follow.

Bill

Here is the fourth part of the listing.

Early work on mapping the spatial variation of upper atmospheric temperatures of several hot Jupiters:

Mapping the Atmospheres of Hot Jupiters

H. A. Knutson

We present the results of recent observations of phase-dependent variations in brightness designed to characterize the atmospheres of hot Jupiters. In particular, we focus on recent observations of the transiting planet HD 189733b at 8 micron using the Spitzer Space Telescope, which allow us to determine the efficiency of the day-night circulation on this planet and estimate the longitudinal positions of hot and cold regions in the atmosphere. We discuss the implications of these observations in the context of two other successful detections of more sparsely-sampled phase variations for the non-transiting systems upsilon And b and HD 179949b, which imply a potential diversity in the properties of the atmospheres of hot Jupiters. Lastly, we highlight several upcoming Spitzer observations that will extend this sample to additional wavelengths and more transiting systems in the near future.

More complex hydrodynamical simulations:

Hydrodynamic Simulations of Unevenly Irradiated Jovian Planets

Jonathan Langton, Gregory Laughlin

We employ a two-dimensional grid-based hydrodynamic model to simulate upper atmospheric dynamics on extrasolar giant planets. Our model is well-suited to simulate the dynamics of the atmospheres of planets with high orbital eccentricity that are subject to widely-varying irradiation conditions. We identify six such planets, with eccentricities between e=0.28 and e=0.93 and semimajor axes ranging from a=0.0508 A.U. to a=0.432 A.U., as particularly interesting objects for study. For each of these planets, we determine the temperature profile and resulting infrared light curves in the 8-um Spitzer bands. Especially notable are the results for HD 80606b, which has the largest eccentricity (e=0.9321) of any known planet, and HAT-P-2b, which transits its parent star, so that its physical properties are well-constrained. Despite the variety of orbital parameters, the atmospheric dynamics of these eccentric planets display a number of interesting common properties. In all cases, the atmospheric response is primarily driven by the intense irradiation at periastron. The resulting expansion of heated air produces high-velocity turbulent flow, including long-lived circumpolar vortices. Additionally, a superrotating acoustic front develops on some planets; the strength of this disturbance depends on both the eccentricity and the temperature gradient resulting from uneven heating. The specifics of the resulting infrared light curves depend strongly on the orbital geometry. We show, however, that the variations on HD 80606 b and HAT-P-2b should be readily detectable at 4.5 and 8 um using the Spitzer Space Telescope. Indeed, these two objects present the most attractive observational targets of all known high-e exoplanets.

More work on exoplanetary cloud formation:

Cloud formation in giant planets

Christiane Helling

We calculate the formation of dust clouds in atmospheres of giant gas-planets. The chemical structure and the evolution of the grain size distribution in the dust cloud layer is discussed based on a consistent treatment of seed formation, growth/evaporation and gravitational settling. Future developments are shortly addressed.

First detection in polarized scattered light:

First detection of polarized scattered light from an exoplanetary atmosphere

S.V. Berdyugina, A.V. Berdyugin, D.M. Fluri, V. Piirola

We report the first direct detection of an exoplanet in polarized scattered light. The transiting planet HD189733b is one of the very hot Jupiters with shortest periods and, thus, smallest orbits, which makes them ideal candidates for polarimetric detections. We obtained polarimetric measurements of HD189733 in the B band well distributed over the orbital period and detected two polarization maxima near planetary elongations with the peak amplitude of $\sim2\cdot10^{-4}$. Assuming Rayleigh scattering, we estimated the effective size of the scattering atmosphere (Lambert sphere) to be 1.5$\pm$0.2 $R_{\rm J}$, which is 30% larger than the radius of the opaque body previously inferred from transits. If the scattering matter fills the planetary Roche lobe, the lower limit of the geometrical albedo can be estimated as 0.14. The phase dependence of polarization indicates that the planetary orbit is oriented almost in the north-south direction with the longitude of the ascending node Omega=(16degr or 196degr) +- 8degr. We obtain independent estimates of the orbit inclination i=98degr +- 8degr and eccentricity e=0.0 (with the uncertainty of 0.05) which are in excellent agreement with values determined previously from transits and radial velocities. Our findings clearly demonstrate the power of polarimetry and open a new dimension in exploring exoplanetary atmospheres even for systems without transits.

Detection of atmospheric haze on HD 189733b:

Detection of atmospheric haze on an extrasolar planet: The 0.55 - 1.05 micron transmission spectrum of HD189733b with the Hubble Space Telescope

F. Pont, H. Knutson, R. L. Gilliland, C. Moutou, D. Charbonneau

The nearby transiting planet HD 189733b was observed during three transits with the ACS camera of the Hubble Space Telescope in spectroscopic mode. The resulting time series of 675 spectra covers the 550-1050 nm range, with a resolution element of ~8 nm, at extremely high accuracy (signal-to-noise ratio up to 10,000 in 50 nm intervals in each individual spectrum). Using these data, we disentangle the effects of limb darkening, measurement systematics, and spots on the surface of the host star, to calculate the wavelength dependence of the effective transit radius to an accuracy of ~50 km. This constitutes the ``transmission spectrum'' of the planetary atmosphere. It indicates at each wavelength at what height the planetary atmosphere becomes opaque to the grazing stellar light during the transit. In this wavelength range, strong features due to sodium, potassium and water are predicted by atmosphere models for a planet like HD 189733b, but they can be hidden by broad absorption from clouds or hazes higher up in the atmosphere.

We observed an almost featureless transmission spectrum between 550 and 1050 nm, with no indication of the expected sodium or potassium atomic absorption features. Comparison of our results with the transit radius observed in the near and mid-infrared (2-8 microns), and the slope of the spectrum, suggest the presence of a haze of sub-micron particles in the upper atmosphere of the planet.

Bill

I do appreciate what you're doing. Do you intend to keep this updated as new papers come out?

This is a fascinating area of research to be sure, and you're clearly taking a lot of time and trouble ferreting out this info Mongo, but I think this thread is in danger of turning into a bit of a blog. Might be better just to post the links with one or two sentences summarising the paper than reproducing as much as you are.

Not being ungrateful, just concerned that with a deluge of discoveries about to it hit us it would be impossible and impractical to keep this up without turning over a large chunk of UMSF to the thread.

I believe that you are right. In most cases, the title contains sufficient information to tell a prospective reader if they would be interested in that paper. If a paper contains important information not mentioned in the title, then I will add a short comment.

2008

On the Absorption and Redistribution of Energy in Irradiated Planets

Atmospheric Circulation of Hot Jupiters: Three-dimensional circulation models of HD 209458b and HD 189733b with Simplified Forcing

On the Presence of Water and Global Circulation in the Transiting Planet HD 189733b

HST/STIS Optical Transit Transmission Spectra of the hot-Jupiter HD209458b

The following paper presents the first temperature-pressure profile for HD 209458b between 0.001 and 50 mbar, extending from below the base of the stratosphere to the lower thermosphere:

Determining atmospheric conditions at the terminator of the hot-Jupiter HD209458b

Optical Albedo Theory of Strongly-Irradiated Giant Planets: The Case of HD 209458b

HD 75289Ab revisited - Searching for starlight reflected from a hot Jupiter

The following paper reports the first determination of the pressure-altitude (as well as temperature) profile for HD 209458b:

Rayleigh scattering by H2 in the extrasolar planet HD209458b

Thermal Emission of Exoplanet XO-1b

A time-dependent radiative model for the atmosphere of the eccentric transiting planets

The following paper was a breakthrough in explaining the unexpectedly low albedos of the measured exoplanets:

Reflected light from 3D exoplanetary atmospheres and simulation of HD 209458b

Cloudy Atmosphere of the Extra-solar Planet HD189733b : A Possible Explanation of the Detected B-band Polarization

The Atmospheric Signatures of Super-Earths: How to Distinguish Between Hydrogen-Rich and Hydrogen-Poor Atmospheres

Ranges of Atmospheric Mass and Composition of Super Earth Exoplanets

A New Atmospheric Model for HD 189733 b

Atmospheric composition and structure of HD209458b

Atmospheric Circulation of Hot Jupiters: A Shallow Three-Dimensional Model

Atmospheric circulation of hot Jupiters: Coupled radiative-dynamical general circulation model simulations of HD 189733b and HD 209458b

Cryptic photosynthesis, Extrasolar planetary oxygen without a surface biological signature

Detection of a Temperature Inversion in the Broadband Infrared Emission Spectrum of TrES-4

The following paper contains important cautions against earlier, physically incomplete circulation models:

Thermodynamics of atmospheric circulation on hot Jupiters

The following paper discusses a circulation model for HD 17156b, a highly eccentric (e=0.67), relatively long-period (21.2 days) exoplanet with a 27-fold range of stellar irradiation, resulting in a very dynamic atmosphere:

The Upper Atmosphere of HD17156b

Molecular Signatures in the Near Infrared Dayside Spectrum of HD 189733b

Anisotropic winds from close-in extra-solar planets

2009

Thermosphere and exosphere of Hot-Jupiters

Can TiO Explain Thermal Inversions in the Upper Atmospheres of Irradiated Giant Planets?

Search for Carbon Monoxide in the atmosphere of the Transiting Exoplanet HD189733b

HD 80606b is the most eccentric (e=0.9336), longest-period (111.4 days) transiting exoplant known, with an 828-fold stellar irradiation range. The following paper presents a model of its atmosphere (direct link to the pdf):

A Direct Observation of Rapid Heating of an Extrasolar Planet

Bill

Do you mind if I make a (modified) copy of this list and post it on the Extrasolar Visions II forum?

Go right ahead.