Understanding WASP-12b

The orbital period of the hot Jupiter WASP-12b is apparently changing. We study whether this reflects orbital decay due to tidal dissipation in the star, or apsidal precession of a slightly eccentric orbit. In the latter case, a third body or other perturbation would be needed to sustain the eccentricity against tidal dissipation in the planet itself. We have analyzed several such perturbative scenarios, but none is satisfactory. Most likely therefore, the orbit really is decaying. If this is due to a dynamical tide, then WASP-12 should be a subgiant without a convective core as Weinberg et al. (2017) have suggested. We have modeled the star with the MESA code. While no model fits all of the observational constraints, including the luminosity implied by the GAIA DR2 distance, main-sequence models are less discrepant than subgiant ones.Comment: 12 pages, 4 figure, submitted to MNRA

Observations of the D/H ratio in Methane in the atmosphere of Saturn's moon, Titan - where did the Saturnian system form?

The details of the Solar system's formation are still heavily debated. Questions remain about the formation locations of the giant planets, and the degree to which volatile material was mixed throughout the proto-planetary system. One diagnostic which offers great promise in helping to unravel the history of planet formation is the study of the level of deuteration in various Solar system bodies. For example, the D/H ratio of methane in the atmosphere of Titan can be used as a diagnostic of the initial conditions of the solar nebula within the region of giant planet formation, and can help us to determine where Titan (and, by extension, the Saturnian system) accreted its volatile material. The level of Titanian deuteration also has implications for both the sources and long term evolution of Titan's atmospheric composition. We present the results of observations taken in the 1.58 microns window using the NIFS spectrometer on the Gemini telescope, and model our data using the VSTAR line--by--line transfer model, which yields a D/H ratio for Titan's atmosphere of 143+/-16) x 10^{-6} [1]. We are currently in the process of modeling the Gemini high resolution GNIRS spectra using new sets of line parameters derived for methane in the region between 1.2-1.7 microns [2].Comment: 12 pages, 4 figures, Accepted for publication in proceedings of the Australian Space Science Conference 201

It\u27s the War Power, Again

Reviewing Fred I. Greenstein, Presidents and the Dissolution of the Union: Leadership Style from Polk to Lincoln; Stephen M. Griffin, Long Wars and the Constitution; Andrew J. Polsky, Elusive Victories: The American Presidency at War; and Mariah Zeisberg, War Powers: The Politics of Constitutional Authority

Empirical line lists and absorption cross sections for methane at high temperature

Hot methane is found in many "cool" sub-stellar astronomical sources including brown dwarfs and exoplanets, as well as in combustion environments on Earth. We report on the first high-resolution laboratory absorption spectra of hot methane at temperatures up to 1200 K. Our observations are compared to the latest theoretical spectral predictions and recent brown dwarf spectra. The expectation that millions of weak absorption lines combine to form a continuum, not seen at room temperature, is confirmed. Our high-resolution transmittance spectra account for both the emission and absorption of methane at elevated temperatures. From these spectra, we obtain an empirical line list and continuum that is able to account for the absorption of methane in high temperature environments at both high and low resolution. Great advances have recently been made in the theoretical prediction of hot methane, and our experimental measurements highlight the progress made and the problems that still remain.Comment: 9 pages, 5 figures and 3 tables. For associated online data see http://dx.doi.org/10.1088/0004-637X/813/1/1

Examining the broadband emission spectrum of WASP-19b: A new z band eclipse detection

WASP-19b is one of the most irradiated hot-Jupiters known. Its secondary eclipse is the deepest of all transiting planets, and has been measured in multiple optical and infrared bands. We obtained a z band eclipse observation, with measured depth of 0.080 +/- 0.029 %, using the 2m Faulkes Telescope South, that is consistent with the results of previous observations. We combine our measurement of the z band eclipse with previous observations to explore atmosphere models of WASP-19b that are consistent with the its broadband spectrum. We use the VSTAR radiative transfer code to examine the effect of varying pressure-temperature profiles and C/O abundance ratios on the emission spectrum of the planet. We find models with super-solar carbon enrichment best match the observations, consistent with previous model retrieval studies. We also include upper atmosphere haze as another dimension in the interpretation of exoplanet emission spectra, and find that particles <0.5 micron in size are unlikely to be present in WASP-19b.Comment: 10 pages, 8 figures, 2 tables, accepted for publication in Ap

In deciding how to exercise power via Executive Orders, US Presidents appeal to Congress only if it can be united

Recent months have seen Republican attacks on President Obama, accusing him of presiding over an ‘imperial presidency’, but to what extent do presidents actually operate completely outside of Congress’ powers? By looking at 5,000 executive orders issued by presidents over the last 80 years Jeremy D. Bailey and Brandon Rottinghaus find that when issuing these orders, presidents tend to appeal back to Congress when the majority party is strong, and act unilaterally when the majority is weak and divided