Further constraints on the optical transmission spectrum of HAT-P-1b

We report on novel observations of HAT-P-1 aimed at constraining the optical transmission spectrum of the atmosphere of its transiting Hot-Jupiter exoplanet. Ground-based differential spectrophotometry was performed over two transit windows using the DOLORES spectrograph at the Telescopio Nazionale Galileo (TNG). Our measurements imply an average planet to star radius ratio equal to $\rm R_p/R_{\star}$=(0.1159$\pm$0.0005). This result is consistent with the value obtained from recent near infrared measurements of this object but differs from previously reported optical measurements being lower by around 4.4 exoplanet scale heights. Analyzing the data over 5 different spectral bins 600\AA$\,$ wide we observed a single peaked spectrum (3.7 $\rm\sigma$ level) with a blue cut-off corresponding to the blue edge of the broad absorption wing of sodium and an increased absorption in the region in between 6180-7400\AA. We also infer that the width of the broad absorption wings due to alkali metals is likely narrower than the one implied by solar abundance clear atmospheric models. We interpret the result as evidence that HAT-P-1b has a partially clear atmosphere at optical wavelengths with a more modest contribution from an optical absorber than previously reported.Comment: Accepted by Ap

The GTC exoplanet transit spectroscopy survey. VII. An optical transmission spectrum of WASP-48b

We obtained long-slit optical spectroscopy of one transit of WASP-48b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) spectrograph at the 10.4 m Gran Telescopio Canarias (GTC). We integrated the spectrum of WASP-48 and one reference star in several channels with different wavelength ranges, creating numerous color light curves of the transit. We fit analytic transit curves to the data taking into account the systematic effects present in the time series in an effort to measure the change of the planet-to-star radius ratio ($R_p/R_s$) across wavelength. After removing the transit model and systematic trends to the curves we reached precisions between 261 ppm and 455-755 ppm for the white and spectroscopic light curves, respectively. We obtained $R_p/R_s$ uncertainty values between $0.8 \times 10^{-3}$ and $1.5\times 10^{-3}$ for all the curves analyzed in this work. The measured transit depth for the curves made by integrating the wavelength range between 530 nm and 905 nm is in agreement with previous studies. We report a relatively flat transmission spectrum for WASP-48b with no statistical significant detection of atmospheric species, although the theoretical models that fit the data more closely include of TiO and VO.Comment: 8 pages, 8 figures. Accepted for publication in Astronomy and Astrophysic

Critical light scattering in liquids

We compare theoretical results for the characteristic frequency of the Rayleigh peak calculated in one-loop order within the field theoretical method of the renormalization group theory with experiments and other theoretical results. Our expressions describe the non-asymptotic crossover in temperature, density and wave vector. In addition we discuss the frequency dependent shear viscosity evaluated within the same model and compare our theoretical results with recent experiments in microgravity.Comment: 17 pages, 12 figure

Multicritical behaviour in magnetic fluids

The phases of a magnetic fluid in an external field are considered. As model systems we take an ideal (hard core) gas with Ising interaction and a van der Waals gas with additional Heisenberg interaction. In mean field approximation various phases and critical points are identified. For appropriate values of the ratio of the magnetic to the non-magnetic interactions there exist multicritical points like tricritical points and critical end points. For the ideal Ising fluid we calculate the line of wing critical points analytically and prove classical tricritical behaviour. In the van der Waals case wing critical points and the gas-liquid critical point may coexist. The corresponding phase diagrams in (p, t, h)-space are shown.Для моделей ідеального (тверді кульки) газу із взаємодією Ізінга та газу Ван дер Ваальса із взаємодією типу Гайзенберга досліджуються фази магнітного флюїду у зовнішньому полі. У наближенні середнього поля ідентифіковані різні фази та критичні точки. Показано, що для певних значень відношення констант магнітної та немагнітної взаємодій існують мультикритичні точки типу трикритичних і критичних кінцевих точок. Для моделі ідеального ізінгівського флюїду аналітично розраховано бокові лінії критичних точок та знайдено класичну трикритичну поведінку. У випадку моделі Ван дер Ваальса бокові критичні лінії та критична точка можуть співіснувати. Наведені відповідні фазові діаграми у змінних (p, t, h)

Implicit STEM ability beliefs predict secondary school students’ STEM self-efficacy beliefs and their intention to opt for a STEM field career

Despite the widely-accepted view that low self-efficacy beliefs negatively influence students’ intention to opt for a STEM field oriented study or career path, it remains unclear how to effectively stimulate these beliefs in students who do seem to have the ability and motivation to opt for a STEM career. A suggestion from previous literature is that students’ implicit beliefs about the malleability of their learning ability can have a major impact on their self-efficacy beliefs, and, importantly, that these implicit beliefs are malleable themselves. Even though this relation between implicit beliefs, self-efficacy, and STEM field aspirations has been suggested multiple times, there is no empirical evidence to support this claim. The goal of the current study was to examine whether implicit beliefs about the malleability of STEM ability are associated with secondary school students’ intention to opt for a STEM field bachelor’s degree, using a Structural Equation Modelling approach. Furthermore, we examined the mediating role of STEM-oriented self-efficacy beliefs on the relationship between implicit ability beliefs and STEM intention. We used a Likert-type questionnaire, consisting of subscales to measure ability beliefs, self-efficacy, and intention to opt for a STEM degree of secondary school students in their fifth grade (n = 483). Results showed that there is a positive relation between implicit STEM ability beliefs and the intention to opt for a STEM field bachelor degree, and that this relation is partly mediated by self-efficacy beliefs. Incremental STEM ability beliefs predicted positive self-efficacy beliefs and increased STEM intention. These findings provide a foundation for a novel approach to stimulate and motivate students for the STEM field, namely by stimulating incremental beliefs about their STEM ability

Fluctuations and criticality (dedicated to Reinhard Folk on his 60th birthday)

It is our pleasure and honour to present a collection of papers dedicated to Reinhard Folk on the occasion of his 60th birthday. With this Festschrift, colleagues and friends of the jubilee pay tribute to his long lasting and fruitful work in the field of condensed matter physics

Effect of structural defects on anomalous ultrasound propagation in solids during second-order phase transitions

The effect of structural defects on the critical ultrasound attenuation and ultrasound velocity dispersion in Ising-like three-dimensional systems is studied. A field-theoretical description of the dynamic effects of acoustic-wave propagation in solids during phase transitions is performed with allowance for both fluctuation and relaxation attenuation mechanisms. The temperature and frequency dependences of the scaling functions of the attenuation coefficient and the ultrasound velocity dispersion are calculated in a two-loop approximation for pure and structurally disordered systems, and their asymptotic behavior in hydrodynamic and critical regions is separated. As compared to a pure system, the presence of structural defects in it is shown to cause a stronger increase in the sound attenuation coefficient and the sound velocity dispersion even in the hydrodynamic region as the critical temperature is reached. As compared to pure analogs, structurally disordered systems should exhibit stronger temperature and frequency dependences of the acoustic characteristics in the critical region.Comment: 7 RevTeX pages, 4 figure