University of St Andrews

About: University of St Andrews is a education organization based out in St Andrews, Fife, United Kingdom. It is known for research contribution in the topics: Population & Laser. The organization has 16260 authors who have published 43364 publications receiving 1636072 citations. The organization is also known as: St Andrews University & University of St. Andrews.

Transience of hot dust around sun-like stars

Abstract: In this paper a simple model for the steady state evolution of debris disks due to collisions is developed and confronted with the properties of the emerging population of seven Sun-like stars that have hot dust at 10 AU (η Corvi and HD 72905); one has three Neptune mass planets at <1 AU (HD 69830); all exhibit strong mid-IR silicate features. We consider the most likely origin for this transient dust to be a dynamical instability that scattered planetesimals inward from a more distant planetesimal belt in an event akin to the late heavy bombardment in our own system, the dust being released from such planetesimals in collisions and sublimation.

Marine Reserves as a Tool for Ecosystem-Based Management: The Potential Importance of Megafauna

Abstract: Marine predators attract significant attention in ocean conservation planning and are therefore often used politically to promote reserve designation. We discuss whether their ecology and life history can help provide a rigorous ecological foundation for marine reserve design. In general, we find that reserves can benefit marine megafauna, and that megafauna can help establish target areas and boundaries for ecosystem reserves. However, the spatial nature of the interplay between potential threats and predator life histories requires careful consideration for the establishment of effective reserves. Modeling tools such as demographic sensitivity analysis will aid in establishing protection for different life stages and distributional ranges. The need for pelagic marine reserves is becoming increasingly apparent, and it is in this venue that marine predators may be most effectively used as indicator species of underlying prey distribution and ecosystem processes.

Adsorption properties of HKUST-1 toward hydrogen and other small molecules monitored by IR

Abstract: Among microporous systems metal organic frameworks are considered promising materials for molecular adsorption. In this contribution infrared spectroscopy is successfully applied to highlight the positive role played by coordinatively unsaturated Cu2+ ions in HKUST-1, acting as specific interaction sites. A properly activated material, obtained after solvent removal, is characterized by a high fraction of coordinatively unsaturated Cu2+ ions acting as preferential adsorption sites that show specific activities towards some of the most common gaseous species (NO, CO2, CO, N2 and H2). From a temperature dependent IR study, it has been estimated that the H2 adsorption energy is as high as 10 kJ mol−1. A very complex spectral evolution has been observed upon lowering the temperature. A further peculiarity of this material is the fact that it promotes ortho–para conversion of the adsorbed H2 species.

A high C/O ratio and weak thermal inversion in the atmosphere of exoplanet WASP-12b

Abstract: The transiting 'hot Jupiter' WASP-12b orbits a star slightly hotter than the Sun in a circular orbit at a distance of only 0023 astronomical units (AU), making it one of the hottest exoplanets known An analysis of dayside multi-wavelength photometry of WASP-12b reveals a carbon-rich atmosphere abundant in carbon monoxide Compared with model predictions, the atmosphere is depleted in water vapour and enhanced in methane content by two orders of magnitude In addition, the absence of a strong thermal inversion or a prominent stratosphere challenges existing theories about the atmospheres of such exoplanets A primordial carbon-to-oxygen ratio (C/O) greater than 08 in an exoplanet causes a carbide-dominated interior, as opposed to the silicate-dominated composition found on Earth; the atmospheres also can differ from those in the Solar System The solar C/O is 054 This study reports an analysis of spectra from the transiting hot Jupiter WASP-12b that reveals that C/O>1 in its atmosphere, based upon the observed concentrations of the prominent molecules CO, CH4 and H2O The carbon-to-oxygen ratio (C/O) in a planet provides critical information about its primordial origins and subsequent evolution A primordial C/O greater than 08 causes a carbide-dominated interior, as opposed to the silicate-dominated composition found on Earth1; the atmosphere can also differ from those in the Solar System1,2 The solar C/O is 054 (ref 3) Here we report an analysis of dayside multi-wavelength photometry4,5 of the transiting hot-Jupiter WASP-12b (ref 6) that reveals C/O ≥ 1 in its atmosphere The atmosphere is abundant in CO It is depleted in water vapour and enhanced in methane, each by more than two orders of magnitude compared to a solar-abundance chemical-equilibrium model at the expected temperatures We also find that the extremely irradiated atmosphere (T > 2,500 K) of WASP-12b lacks a prominent thermal inversion (or stratosphere) and has very efficient day–night energy circulation The absence of a strong thermal inversion is in stark contrast to theoretical predictions for the most highly irradiated hot-Jupiter atmospheres7,8,9

Metals in the exosphere of the highly irradiated planet WASP-12b

Abstract: We present near-UV transmission spectroscopy of the highly irradiated transiting exoplanet WASP-12b, obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. The spectra cover three distinct wavelength ranges: NUVA (2539-2580 angstrom), NUVB (2655-2696 angstrom), and NUVC (2770-2811 angstrom). Three independent methods all reveal enhanced transit depths attributable to absorption by resonance lines of metals in the exosphere of WASP-12b. Light curves of total counts in the NUVA and NUVC wavelength ranges show a detection at a 2.5 sigma level. We detect extra absorption in the Mg II lambda lambda 2800 resonance line cores at the 2.8 sigma level. The NUVA, NUVB, and NUVC light curves imply effective radii of 2.69 +/- 0.24 R-J, 2.18 +/- 0.18 R-J, and 2.66 +/- 0.22 R-J respectively, suggesting the planet is surrounded by an absorbing cloud which overfills the Roche lobe. We detect enhanced transit depths at the wavelengths of resonance lines of neutral sodium, tin, and manganese, and at singly ionized ytterbium, scandium, manganese, aluminum, vanadium, and magnesium. We also find the statistically expected number of anomalous transit depths at wavelengths not associated with any known resonance line. Our data are limited by photon noise, but taken as a whole the results are strong evidence for an extended absorbing exosphere surrounding the planet. The NUVA data exhibit an early ingress, contrary to model expectations; we speculate this could be due to the presence of a disk of previously stripped material.