Search for Rayleigh scattering in the atmosphere of GJ1214b

We investigate the atmosphere of GJ1214b, a transiting super-Earth planet with a low mean density, by measuring its transit depth as a function of wavelength in the blue optical portion of the spectrum. It is thought that this planet is either a mini-Neptune, consisting of a rocky core with a thick, hydrogen-rich atmosphere, or a planet with a composition dominated by water. Most observations favor a water-dominated atmosphere with a small scale-height, however, some observations indicate that GJ1214b could have an extended atmosphere with a cloud layer muting the molecular features. In an atmosphere with a large scale-height, Rayleigh scattering at blue wavelengths is likely to cause a measurable increase in the apparent size of the planet towards the blue. We observed the transit of GJ1214b in the B-band with the FOcal Reducing Spectrograph (FORS) at the Very Large Telescope (VLT) and in the g-band with both ACAM on the William Hershel Telescope (WHT) and the Wide Field Camera (WFC) at the Isaac Newton Telescope (INT). We find a planet-to-star radius ratio in the B-band of 0.1162+/-0.0017, and in the g-band 0.1180+/-0.0009 and 0.1174+/-0.0017 for the WHT & INT observations respectively. These optical data do not show significant deviations from previous measurements at longer wavelengths. In fact, a flat transmission spectrum across all wavelengths best describes the combined observations. When atmospheric models are considered a small scale-height water-dominated model fits the data best.Comment: Accepted for publication in Ap

A quantitative assessment of methane cycling in Hikurangi Margin sediments (New Zealand) using geophysical imaging and biogeochemical modeling

Takahe seep, located on the Opouawe Bank, Hikurangi Margin, is characterized by a well-defined subsurface seismic chimney structure ca. 80,500 m2 in area. Sub-seafloor geophysical data based on acoustic anomaly layers indicated the presence of gas hydrate and free gas layers within the chimney structure. Reaction-transport modeling was applied to porewater data from 11 gravity cores to constrain methane turnover rates and benthic methane fluxes in the upper 10 m. Model results show that methane dynamics were highly variable due to transport and dissolution of ascending gas. The dissolution of gas (up to 3761 mmol m−2 yr−1) dwarfed the rate of methanogenesis within the simulated sediment column (2.6 mmol m−2 yr−1). Dissolved methane is mainly consumed by anaerobic oxidation of methane (AOM) at the base of the sulfate reduction zone and trapped by methane hydrate formation below it, with maximum rates in the central part of the chimney (946 and 2420 mmol m−2 yr−1, respectively). A seep-wide methane budget was constrained by combining the biogeochemical model results with geophysical data and led to estimates of AOM rates, gas hydrate formation and benthic dissolved methane fluxes of 3.68 × 104 mol yr−1, 73.85 × 104 mol yr−1and 1.19 × 104 mol yr−1, respectively. A much larger flux of methane probably escapes in gaseous form through focused bubble vents. The approach of linking geochemical model results with spatial geophysical data put forward here can be applied elsewhere to improve benthic methane turnover rates from limited single spot measurements to larger spatial scales

Cohorts and neighbors: Urban-rural conflict along the age gradient

The 2021 German Federal Election saw an increasing variation in voting behavior between both age groups and geographic groups. This paper brings these developments together and argues that the urban-rural divide is much bigger among younger than among older voters. We combine data from the German Longitudinal Election Study with original survey data and introduce the number of freelance artists at the ZIP code level as a new measure of urbanity. Using this data, we show that the urban-rural age divide concerns cultural attitudes as well as the propensity to vote. While the Greens mainly attract young voters in cities, the AfD performed well among young rural voters, particularly in Eastern Germany. At the same time, the differences between the young and the old are larger in cities than in the countryside. These results suggest that the importance of the urban-rural divide is likely to increase in future elections

From Austerity to Expansion? Consolidation, Budget Surpluses, and the Decline of Fiscal Capacity

In the wake of the financial crisis, most developed countries have entered a period of prolonged budgetary austerity. While the success of austerity programs is still unclear, it is also an open question what success would mean for activist government in the long run. This paper rejects the progressive belief that successful fiscal consolidation will lead to a strengthening of fiscal capacity, arguing that consolidations transform the political context in which fiscal policy is made. By analyzing the evolution of public expenditure in six countries with sustained budget surpluses, it shows that while surpluses were mostly achieved through expenditure cuts, they were predominantly used for cutting taxes. While fiscal crises abated, their collateral damage to public expenditure remained. This result is further elaborated by a case study of the Swedish budget surplus. The paper concludes that consolidations can create a specific type of fiscal regime and thus have long-term consequences for the fiscal capacity of the state.Angesichts der Schuldenprobleme in vielen entwickelten Ländern befinden sich die meisten von ihnen in einer Phase lang anhaltender Austerität. Und während noch völlig unklar ist, ob die Sparprogramme Erfolg haben, werden sie immer wieder mit dem Versprechen verbunden, erfolgreiche Konsolidierungen würden zu einer Wiedergewinnung staatlicher Handlungsfähigkeit führen. Diese Studie verwirft diese „progressive Konsolidierungsthese“ auf Basis einer theoretischen und empirischen Analyse. Ihr Argument lautet, dass Haushaltskonsolidierungen den Kontext, in dem Fiskalpolitik gemacht wird, dauerhaft verändern. Zwar erhöhen sie fiskalische Spielräume, zugleich aber schränken sie politische Spielräume ein. Anhand von sechs Ländern mit dauerhaften Haushaltsüberschüssen wird gezeigt, dass diese Überschüsse durch Ausgabenkürzungen erzielt, aber für Steuersenkungen verwendet wurden. Die Kollateralschäden der Konsolidierung blieben über Jahre in den Budgets sichtbar. Dieses Ergebnis wird von einer Fallstudie zu den schwedischen Haushaltsüberschüssen bestätigt. Das Fazit der Untersuchung ist, dass Konsolidierungen zu einem Wechsel des fiskalischen Regimes führen können, wodurch die staatliche Handlungsfähigkeit langfristig beschränkt wird. Überschüsse sind insofern nicht Ausdruck wachsender Gestaltungsfreiheit, sondern schrumpfender Ambitionen des Staates.1 Introduction 2 The argument 3 Research design and case selection 4 Comparative results 5 The Swedish case up close 6 Conclusion Appendix 1 Appendix 2 Appendix 3 Reference

Nonlinear wavefront reconstruction with convolutional neural networks for Fourier-based wavefront sensors

Fourier-based wavefront sensors, such as the Pyramid Wavefront Sensor (PWFS), are the current preference for high contrast imaging due to their high sensitivity. However, these wavefront sensors have intrinsic nonlinearities that constrain the range where conventional linear reconstruction methods can be used to accurately estimate the incoming wavefront aberrations. We propose to use Convolutional Neural Networks (CNNs) for the nonlinear reconstruction of the wavefront sensor measurements. It is demonstrated that a CNN can be used to accurately reconstruct the nonlinearities in both simulations and a lab implementation. We show that solely using a CNN for the reconstruction leads to suboptimal closed loop performance under simulated atmospheric turbulence. However, it is demonstrated that using a CNN to estimate the nonlinear error term on top of a linear model results in an improved effective dynamic range of a simulated adaptive optics system. The larger effective dynamic range results in a higher Strehl ratio under conditions where the nonlinear error is relevant. This will allow the current and future generation of large astronomical telescopes to work in a wider range of atmospheric conditions and therefore reduce costly downtime of such facilities.Comment: 14 pages, 7 figure