New Analysis Indicates No Thermal Inversion in the Atmosphere of HD 209458b

An important focus of exoplanet research is the determination of the atmospheric temperature structure of strongly irradiated gas giant planets, or hot Jupiters. HD 209458b is the prototypical exoplanet for atmospheric thermal inversions, but this assertion does not take into account recently obtained data or newer data reduction techniques. We re-examine this claim by investigating all publicly available Spitzer Space Telescope secondary-eclipse photometric data of HD 209458b and performing a self-consistent analysis. We employ data reduction techniques that minimize stellar centroid variations, apply sophisticated models to known Spitzer systematics, and account for time-correlated noise in the data. We derive new secondary-eclipse depths of 0.119 +/- 0.007%, 0.123 +/- 0.006%, 0.134 +/- 0.035%, and 0.215 +/- 0.008% in the 3.6, 4.5, 5.8, and 8.0 micron bandpasses, respectively. We feed these results into a Bayesian atmospheric retrieval analysis and determine that it is unnecessary to invoke a thermal inversion to explain our secondary-eclipse depths. The data are well-fitted by a temperature model that decreases monotonically between pressure levels of 1 and 0.01 bars. We conclude that there is no evidence for a thermal inversion in the atmosphere of HD 209458b.Comment: 8 pages, 5 figures; accepted for publication in Ap

A Search for Water in the Atmosphere of HAT-P-26b Using LDSS-3C

The characterization of a physically-diverse set of transiting exoplanets is an important and necessary step towards establishing the physical properties linked to the production of obscuring clouds or hazes. It is those planets with identifiable spectroscopic features that can most effectively enhance our understanding of atmospheric chemistry and metallicity. The newly-commissioned LDSS-3C instrument on Magellan provides enhanced sensitivity and suppressed fringing in the red optical, thus advancing the search for the spectroscopic signature of water in exoplanetary atmospheres from the ground. Using data acquired by LDSS-3C and the Spitzer Space Telescope, we search for evidence of water vapor in the transmission spectrum of the Neptune-mass planet HAT-P-26b. Our measured spectrum is best explained by the presence of water vapor, a lack of potassium, and either a high-metallicity, cloud-free atmosphere or a solar-metallicity atmosphere with a cloud deck at ~10 mbar. The emergence of multi-scale-height spectral features in our data suggests that future observations at higher precision could break this degeneracy and reveal the planet's atmospheric chemical abundances. We also update HAT-P-26b's transit ephemeris, t_0 = 2455304.65218(25) BJD_TDB, and orbital period, p = 4.2345023(7) days.Comment: 9 pages, 8 figures, Accepted for publication in Ap

Thermal Emission and Albedo Spectra of Super Earths with Flat Transmission Spectra

Planets larger than Earth and smaller than Neptune are some of the most numerous in the galaxy, but observational efforts to understand this population have proved challenging because optically thick clouds or hazes at high altitudes obscure molecular features (Kreidberg et al. 2014b). We present models of super Earths that include thick clouds and hazes and predict their transmission, thermal emission, and reflected light spectra. Very thick, lofted clouds of salts or sulfides in high metallicity (1000x solar) atmospheres create featureless transmission spectra in the near-infrared. Photochemical hazes with a range of particle sizes also create featureless transmission spectra at lower metallicities. Cloudy thermal emission spectra have muted features more like blackbodies, and hazy thermal emission spectra have emission features caused by an inversion layer at altitudes where the haze forms. Close analysis of reflected light from warm (~400-800 K) planets can distinguish cloudy spectra, which have moderate albedos (0.05-0.20), from hazy models, which are very dark (0.0-0.03). Reflected light spectra of cold planets (~200 K) accessible to a space-based visible light coronagraph will have high albedos and large molecular features that will allow them to be more easily characterized than the warmer transiting planets. We suggest a number of complementary observations to characterize this population of planets, including transmission spectra of hot (>1000 K) targets, thermal emission spectra of warm targets using the James Webb Space Telescope (JWST), high spectral resolution (R~10^5) observations of cloudy targets, and reflected light spectral observations of directly-imaged cold targets. Despite the dearth of features observed in super Earth transmission spectra to date, different observations will provide rich diagnostics of their atmospheres.Comment: 23 pages, 23 figures. Revised for publication in The Astrophysical Journa

Forward and Inverse Modeling of the Emission and Transmission Spectrum of GJ 436b: Investigating Metal Enrichment, Tidal Heating, and Clouds

The Neptune-mass GJ 436b is one of the most-studied transiting exoplanets with repeated measurements of both its thermal emission and transmission spectra. We build on previous studies to answer outstanding questions about this planet, including its potentially high metallicity and tidal heating of its interior. We present new observations of GJ 436b's thermal emission at 3.6 and 4.5 micron, which reduce uncertainties in estimates of GJ 436b's flux at those wavelengths and demonstrate consistency between Spitzer observations spanning more than 7 years. We analyze the Spitzer thermal emission photometry and Hubble WFC3 transmission spectrum in tandem. We use a powerful dual-pronged modeling approach, comparing these data to both self-consistent and retrieval models. We vary the metallicity, intrinsic luminosity from tidal heating, disequilibrium chemistry, and heat redistribution. We also study the effect of clouds and photochemical hazes on the spectra, but do not find strong evidence for either. The self-consistent and retrieval modeling combine to suggest that GJ 436b has a high atmospheric metallicity, with best fits at or above several hundred times solar metallicity, tidal heating warming its interior with best-fit intrinsic effective effective temperatures around 300--350 K, and disequilibrium chemistry. High metal-enrichments (>600x solar) can only occur from the accretion of rocky, rather than icy, material. Assuming Tint~300--350 K, we find that Q'~2x10^5--10^6, larger than Neptune's Q', and implying a long tidal circularization timescale for the planet's orbit. We suggest that Neptune-mass planets may be a more diverse class than previously imagined, with metal-enhancements potentially spanning several orders of magnitude, to perhaps over 1000x solar metallicity. High fidelity observations with instruments like JWST will be critical for characterizing this diversity.Comment: 15 pages, 18 figures. Revised for publication in Ap

Catastrophic thinking about pain: A critical appraisal highlighting the importance of the social context and balance

Numerous research studies have shown that endorsing a catastrophic interpretation about pain is associated with deleterious outcomes, such as higher levels of distress, pain intensity and disability for the person in pain. The fear-avoidance model has been found to be useful in explaining these associations by stressing that heightened feelings of distress and behaviour aimed at reducing or avoiding pain might be adaptive in an acute pain context but can become maladaptive when the pain becomes chronic. Pain is rarely a private event and the communal coping model underscores that the heightened pain expression in people endorsing catastrophic thoughts about pain could have a social, communicative function of eliciting empathic responses in others. However, these models are not all-encompassing. In particular, neither of the models takes into account the growing evidence indicating that catastrophic thinking in observers can also impact their emotional experience and behaviour in response to the other’s pain. Moreover, the context of multiple goals in which pain and pain behaviour occurs is largely ignored in both models. In this article we present an integrative perspective on catastrophic thinking that takes into account the social system and interplay between different goals people in pain and observers might pursue (e.g., school/work performance, leisure, social engagement). Specifically, this integrative perspective stresses the importance of considering the bidirectional influence between catastrophic thoughts in the person experiencing pain and observers. Furthermore, the importance of balance between pain-relief and other important goals as well as in the level of catastrophic thoughts in understanding the maladaptive influence of catastrophic thinking will be underlined. Clinical implications and future research directions of this integrated perspective are discussed

Brown Dwarf Retrievals on FIRE!: Atmospheric Constraints and Lessons Learned from High Signal-to-Noise Medium Resolution Spectroscopy of a T9 Dwarf

Brown dwarf spectra offer vital testbeds for our understanding of the chemical and physical processes that sculpt substellar atmospheres. Recently, atmospheric retrieval approaches have been applied to a number of low-resolution (R~100) spectra of brown dwarfs, yielding constraints on the abundances of chemical species and temperature structures of these atmospheres. Medium-resolution (R~1e3) spectra of brown dwarfs offer significant additional insight, as molecular features are more easily disentangled from one another and the thermal structure of the upper atmosphere is more readily probed. We present results from a GPU-based retrieval analysis of a high signal-to-noise, medium-resolution (R~6000) FIRE spectrum from 0.85-2.5 microns of a T9 dwarf. At 60x higher spectral resolution than previous brown dwarf retrievals, a number of novel challenges arise. We examine the strong effect of different opacity sources on our retrieved constraints, in particular for CH4. Furthermore, we find that flaws in the data such as errors from order stitching can greatly bias our results. We compare these results to those obtained for a R~100 spectrum of the same object, revealing how constraints on atmospheric abundances and temperatures improve by an order of magnitude or more (depending on the species) with increased spectral resolution. In particular, we precisely constrain the abundance of H2S, which is undetectable at lower spectral resolution. While these medium-resolution retrievals offer the potential of precise, stellar-like constraints on atmospheric abundances (~0.02 dex), our retrieved radius is unphysically small (R~0.50 R$_{Jup}$), indicating lingering shortcomings with our modeling framework. This work is an initial investigation into brown dwarf retrievals at medium spectral resolution, offering guidance for future ground-based studies and JWST observations of substellar objects.Comment: 28 pages, 28 figures, 4 tables. Accepted to Ap