A Spitzer Five-Band Analysis of the Jupiter-Sized Planet TrES-1

With an equilibrium temperature of 1200 K, TrES-1 is one of the coolest hot Jupiters observed by {\Spitzer}. It was also the first planet discovered by any transit survey and one of the first exoplanets from which thermal emission was directly observed. We analyzed all {\Spitzer} eclipse and transit data for TrES-1 and obtained its eclipse depths and brightness temperatures in the 3.6 {\micron} (0.083 % {\pm} 0.024 %, 1270 {\pm} 110 K), 4.5 {\micron} (0.094 % {\pm} 0.024 %, 1126 {\pm} 90 K), 5.8 {\micron} (0.162 % {\pm} 0.042 %, 1205 {\pm} 130 K), 8.0 {\micron} (0.213 % {\pm} 0.042 %, 1190 {\pm} 130 K), and 16 {\micron} (0.33 % {\pm} 0.12 %, 1270 {\pm} 310 K) bands. The eclipse depths can be explained, within 1$\sigma$ errors, by a standard atmospheric model with solar abundance composition in chemical equilibrium, with or without a thermal inversion. The combined analysis of the transit, eclipse, and radial-velocity ephemerides gives an eccentricity $e = 0.033^{+0.015}_{-0.031}$, consistent with a circular orbit. Since TrES-1's eclipses have low signal-to-noise ratios, we implemented optimal photometry and differential-evolution Markov-chain Monte Carlo (MCMC) algorithms in our Photometry for Orbits, Eclipses, and Transits (POET) pipeline. Benefits include higher photometric precision and \sim10 times faster MCMC convergence, with better exploration of the phase space and no manual parameter tuning.Comment: 17 pages, Accepted for publication in Ap

Resolution Study for Three-dimensional Supernova Simulations with the Prometheus-Vertex Code

We present a carefully designed, systematic study of the angular resolution dependence of simulations with the Prometheus-Vertex neutrino-hydrodynamics code. Employing a simplified neutrino heating-cooling scheme in the Prometheus hydrodynamics module allows us to sample the angular resolution between 4 degrees and 0.5 degrees. With a newly-implemented static mesh refinement (SMR) technique on the Yin-Yang grid, the angular coordinates can be refined in concentric shells, compensating for the diverging structure of the spherical grid. In contrast to previous studies with Prometheus and other codes, we find that higher angular resolution and therefore lower numerical viscosity provides more favorable explosion conditions and faster shock expansion. We discuss the possible reasons for the discrepant results. The overall dynamics seem to converge at a resolution of about 1 degree. Applying the SMR setup to marginally exploding progenitors is disadvantageous for the shock expansion, however, because kinetic energy of downflows is dissipated to internal energy at resolution interfaces, leading to a loss of turbulent pressure support and a steeper temperature gradient. We also present a way to estimate the numerical viscosity on grounds of the measured turbulent kinetic-energy spectrum, leading to smaller values that are better compatible with the flow behavior witnessed in our simulations than results following calculations in previous literature. Interestingly, the numerical Reynolds numbers in the turbulent, neutrino-heated postshock layer (some 10 to several 100) are in the ballpark of expected neutrino-drag effects on the relevant length scales in the turbulent postshock layer. We provide a formal derivation and quantitative assessment of the neutrino drag terms in an appendix.Comment: 37 pages, 14 figures, 4 tables; revised version with neutrino drag discussion extended for numerical evaluation; accepted by Ap

Monte Carlo Quasi-Heatbath by approximate inversion

When sampling the distribution P(phi) ~ exp(-|A phi|^2), a global heatbath normally proceeds by solving the linear system A phi = eta, where eta is a normal Gaussian vector, exactly. This paper shows how to preserve the distribution P(phi) while solving the linear system with arbitrarily low accuracy. Generalizations are presented.Comment: 10 pages, 1 figure; typos corrected, reference added; version to appear in Phys. Rev.

The mid-infrared spectrum of the transiting exoplanet HD 209458b

We report the spectroscopic detection of mid-infrared emission from the transiting exoplanet HD 209458b. Using archive data taken with the Spitzer/IRS instrument, we have determined the spectrum of HD 209458b between 7.46 and 15.25 microns. We have used two independent methods to determine the planet spectrum, one differential in wavelength and one absolute, and find the results are in good agreement. Over much of this spectral range, the planet spectrum is consistent with featureless thermal emission. Between 7.5 and 8.5 microns, we find evidence for an unidentified spectral feature. If this spectral modulation is due to absorption, it implies that the dayside vertical temperature profile of the planetary atmosphere is not entirely isothermal. Using the IRS data, we have determined the broad-band eclipse depth to be 0.00315 +/- 0.000315, implying significant redistribution of heat from the dayside to the nightside. This work required development of improved methods for Spitzer/IRS data calibration that increase the achievable absolute calibration precision and dynamic range for observations of bright point sources.Comment: 35 pages, 12 figures, revised version accepted by the Astrophysical Journa