Probing the Stellar Surface of HD 209458 from Multicolor Transit Observations

Multicolor photometric observations of a planetary transit in the system HD 209458 are analyzed. The observations, made in the Stromgren photometric system, allowed a recalculation of the basic physical properties of the star-planet system. This includes derivation of linear limb-darkening values of HD 209458, which is the first time that a limb-darkening sequence has observationally been determined for a star other than the Sun. As the derived physical properties depend on assumptions that are currently known with limited precision only, scaling relations between derived parameters and assumptions are given. The observed limb-darkening is in good agreement with theoretical predictions from evolutionary stellar models combined with ATLAS model atmospheres, verifying these models for the temperature (Teff ~ 6000K), surface gravity (log g ~ 4.3) and mass (~ 1.2 Msol) of HD 209458.Comment: 16 pages, 8 figures, uses elsart.cls, accepted for New Astronom

Non-grey dimming events of KIC 8462852 from GTC spectrophotometry

We report ground-based spectrophotometry of KIC 8462852, during its first dimming events since the end of the Kepler mission. The dimmings show a clear colour-signature, and are deeper in visual blue wavelengths than in red ones. The flux loss' wavelength dependency can be described with an \AA ngstr\"om absorption coefficient of $2.19\pm0.45$, which is compatible with absorption by optically thin dust with particle sizes on the order of 0.0015 to 0.15 $\mu$m. These particles would be smaller than is required to be resistant against blow-out by radiation pressure when close to the star. During occultation events, these particles must be replenished on time-scales of days. If dust is indeed the source of KIC 8462852's dimming events, deeper dimming events should show more neutral colours, as is expected from optically thick absorbers.Comment: 5 pages, accepted for A&A letter

Internationalization and Financial Federalism: The United States and Germany at the Crossroads?

In this article, the authors examine some effects of economic internationalization on state structures, especially in regard to the distribution of power and authority within federalist systems. Using an institutional rational choice model, they analyze changes in financial regulation and market structures in Germany and the United States. The focus is on the financial realm because of its high degree of internationalization and because, in both countries, financial markets and regulation have historically exhibited federalist traits. The findings indicate that internationalization has led to significant convergence in financial market structures and regulation across the two countries and that in each case this convergence has been accompanied by centralization of financial regulatory authority. Although both the German type of cooperative federalism and the U.S. model of competitive federalism proved to be vulnerable to the growing international pressures, the two countries took different paths of change that reflected differences in domestic institutions. Thus, the authors conclude that convergence is, and will likely remain, of a limited nature

A Prototype for the PASS Permanent All Sky Survey

A prototype system for the Permanent All Sky Survey (PASS) project is presented. PASS is a continuous photometric survey of the entire celestial sphere with a high temporal resolution. Its major objectives are the detection of all giant-planet transits (with periods up to some weeks) across stars up to mag 10.5, and to deliver continuously photometry that is useful for the study of any variable stars. The prototype is based on CCD cameras with short focal length optics on a fixed mount. A small dome to house it at Teide Observatory, Tenerife, is currently being constructed. A placement at the antarctic Dome C is also being considered. The prototype will be used for a feasibility study of PASS, to define the best observing strategies, and to perform a detailed characterization of the capabilities and scope of the survey. Afterwards, a first partial sky surveying will be started with it. That first survey may be able to detect transiting planets during its first few hundred hours of operation. It will also deliver a data set around which software modules dealing with the various scientific objectives of PASS will be developed. The PASS project is still in its early phase and teams interested in specific scientific objectives, in providing technical expertise, or in participating with own observations are invited to collaborate.Comment: Accepted for Astronomische Nachrichten (special issue for 3rd Potsdam Thinkshop 'Robotic Astronomy' in July 2004). 4 pages, 4 fig

A cool starspot or a second transiting planet in the TrES-1 system?

We investigate the origin of a flux increase found during a transit of TrES-1, observed with the HST. This feature in the HST light curve cannot be attributed to noise and is supposedly a dark area on the stellar surface of the host star eclipsed by TrES-1 during its transit. We investigate the likeliness of two possible hypothesis for its origin: A starspot or a second transiting planet. We made use of several transit observations of TrES-1 from space with the HST and from ground with the IAC-80 telescope. On the basis of these observations we did a statistical study of flux variations in each of the observed events, to investigate if similar flux increases are present in other parts of the data set. The HST observation presents a single clear flux rise during a transit whereas the ground observations led to the detection of two such events but with low significance. In the case of having observed a starspot in the HST data, assuming a central impact between the spot and TrES-1, we would obtain a lower limit for the spot radius of 42000 km. For this radius the spot temperature would be 4690 K, 560 K lower then the stellar surface of 5250 K. For a putative second transiting planet we can set a lower limit for its radius at 0.37 R$_J$ and for periods of less than 10.5 days, we can set an upper limit at 0.72 R$_J$. Assuming a conventional interpretation, then this HST observation constitutes the detection of a starspot. Alternatively, this flux rise might also be caused by an additional transiting planet. The true nature of the origin can be revealed if a wavelength dependency of the flux rise can be shown or discarded with a higher certainty. Additionally, the presence of a second planet can also be detected by radial velocity measurements.Comment: 8 pages, 6 figures, accepted for publication in A&

Catena: Collaboration, Cohesion and Continuity in Design Thinking and Making

In the interests of enhanced collaborative methods of design thinking, design communication, representation and rapid ideation, this article examines how a series of related activities and events, ‘catenated’ together, or forming a ‘catena’1 of design thinking, could create a clearer, more meaningful and more efficient portfolio of work for a beginning design studio. Drawing inspiration upon the operative verbs found in the work of sculptor Richard Serra,2 and using the artefacts from such activities to create generative design products and iterations across a semester schedule, this paper chronicles a series of active in-class collaborations over the course of a semester that allowed a cohort of students to connect a series of design projects together, rather than experience a series of unconnected learning objectives as was typical. References to learning theories including Jerome Bruner’s spiral curriculum and David Kolb’s theory of experiential learning3 informed the inquiry. Student feedback and reflection informed the areas of success and areas of improvement

Cost-effectiveness of etanercept in patients with severe ankylosing spondylitis in Germany

Objectives. To estimate the cost-effectiveness of etanercept (ETN) plus usual care (including NSAIDs) compared with usual care alone (including NSAIDs) in patients with severe AS in Germany. Methods. A mathematical model previously applied to the UK was adapted using resource use and cost data (for 2007) from the national database of the German Collaborative Arthritis Centres. Social health insurance (SHI) and societal perspectives were analysed. Assumptions on initial response and changes in health-related quality of life were based on Phase III randomized controlled trials. Initial treatment response according to British Society for Rheumatology guidelines were assumed as a conservative estimate in the German context. Long-term disease progression was based on the available literature. Incremental cost-effectiveness ratios (ICERs) were expressed as euros/quality-adjusted life year (QALY), for a cohort of 1000 patients over 25 years. Sensitivity analyses explored uncertainty in results. Results. In the base case, ETN plus usual care (including NSAIDs) yielded 1475 more QALYs at an additional cost of €80 827 668 (SHI) or €32 657 590 (societal) leading to an ICER of €54 815/QALY and €22 147/QALY, respectively. Over a shorter time horizon of 10 years, the ICERs were €59 006 and €29 815 for SHI and societal viewpoints, respectively. Assumptions having the largest impact on results included withdrawal rates from ETN, quality of life, disease costs and initial response. Conclusions. Cost-effectiveness for ETN in patients with severe AS in Germany differs according to the cost perspective. Study estimates were higher than in the UK but comparable with reported cost-effectiveness of anti-TNF treatments in patients with RA in German

TRUFAS, a wavelet based algorithm for the rapid detection of planetary transits

Aims: We describe a fast, robust and automatic detection algorithm, TRUFAS, and apply it to data that are being expected from the CoRoT mission. Methods: The procedure proposed for the detection of planetary transits in light curves works in two steps: 1) a continuous wavelet transformation of the detrended light curve with posterior selection of the optimum scale for transit detection, and 2) a period search in that selected wavelet transformation. The detrending of the light curves are based on Fourier filtering or a discrete wavelet transformation. TRUFAS requires the presence of at least 3 transit events in the data. Results: The proposed algorithm is shown to identify reliably and quickly the transits that had been included in a standard set of 999 light curves that simulate CoRoT data. Variations in the pre-processing of the light curves and in the selection of the scale of the wavelet transform have only little effect on TRUFAS' results. Conclusions: TRUFAS is a robust and quick transit detection algorithm, especially well suited for the analysis of very large volumes of data from space or ground-based experiments, with long enough durations for the target-planets to produce multiple transit events.Comment: 9 pages, 10 figures, accepted by A&