Solving the m-mixing problem for the three-dimensional time-dependent Schr\"{o}dinger equation by rotations: application to strong-field ionization of H2+

We present a very efficient technique for solving the three-dimensional time-dependent Schrodinger equation. Our method is applicable to a wide range of problems where a fullly three-dimensional solution is required, i.e., to cases where no symmetries exist that reduce the dimensionally of the problem. Examples include arbitrarily oriented molecules in external fields and atoms interacting with elliptically polarized light. We demonstrate that even in such cases, the three-dimensional problem can be decomposed exactly into two two-dimensional problems at the cost of introducing a trivial rotation transformation. We supplement the theoretical framework with numerical results on strong-field ionization of arbitrarily oriented H2+ molecules.Comment: 5 pages, 4 figure

First Light of Engineered Diffusers at the Nordic Optical Telescope Reveal Time Variability in the Optical Eclipse Depth of WASP-12b

We present the characterization of two engineered diffusers mounted on the 2.5 meter Nordic Optical Telescope, located at Roque de Los Muchachos, Spain. To assess the reliability and the efficiency of the diffusers, we carried out several test observations of two photometric standard stars, along with observations of one primary transit observation of TrES-3b in the red (R-band), one of CoRoT-1b in the blue (B-band), and three secondary eclipses of WASP-12b in V-band. The achieved photometric precision is in all cases within the sub-millimagnitude level for exposures between 25 and 180 seconds. Along a detailed analysis of the functionality of the diffusers, we add a new transit depth measurement in the blue (B-band) to the already observed transmission spectrum of CoRoT-1b, disfavouring a Rayleigh slope. We also report variability of the eclipse depth of WASP-12b in the V-band. For the WASP-12b secondary eclipses, we observe a secondary-depth deviation of about 5-sigma, and a difference of 6-sigma and 2.5-sigma when compared to the values reported by other authors in similar wavelength range determined from Hubble Space Telescope data. We further speculate about the potential physical processes or causes responsible for this observed variabilityComment: 11 pages, 9 figure

NEAR-SURFACE EFFECTS IN MODELLING OSCILLATIONS OF ETA BOO

Following the report of solar-like oscillations in the G0 V star eta Boo (Kjeldsen et al. 1995, AJ 109, 1313), a first attempt to model the observed frequencies was made by Christensen-Dalsgaard et al. (1995, ApJ Letters, in press). This attempt succeeded in reproducing the observed frequency separations, although there remained a difference of about 10 microHz between observed and computed frequencies. In those models, the near-surface region of the star was treated rather crudely. Here we consider more sophisticated models that include non-local mixing-length theory, turbulent pressure and nonadiabatic oscillations.Comment: uuencoded and compressed Postscript (2 pages, including figure); To appear in Proceedings of IAU Colloquium 155, "Astrophysical Applications of Stellar Pulsation", Cape Town, South Afric

Influence of molecular symmetry on strong-field ionization: Studies on ethylene, benzene, fluorobenzene, and chlorofluorobenzene

Using the molecular strong-field approximation we consider the effects of molecular symmetry on the ionization of molecules by a strong, linearly polarized laser pulse. Electron angular distributions and total ionization yields are calculated as a function of the relative orientation between the molecule and the laser polarization. Our studies focus on ethylene (C$_2$H$_4$), benzene (C$_6$H$_6$), fluorobenzene (C$_6$H$_5$F), and ortho chlorofluorobenzene (1,2 C$_6$H$_4$ClF), the molecules representing four different point groups. The results are compared with experiments, when available, and with the molecular tunneling theory appropriately extended to non-linear polyatomic molecules. Our investigations show that the orientational dependence of ionization yields is primarily determined by the nodal surface structure of the molecular orbitals.Comment: 13 pages, 10 figures. Submitted to Physical Review

The Octave (Birmingham - Sheffield Hallam) automated pipeline for extracting oscillation parameters of solar-like main-sequence stars

The number of main-sequence stars for which we can observe solar-like oscillations is expected to increase considerably with the short-cadence high-precision photometric observations from the NASA Kepler satellite. Because of this increase in number of stars, automated tools are needed to analyse these data in a reasonable amount of time. In the framework of the asteroFLAG consortium, we present an automated pipeline which extracts frequencies and other parameters of solar-like oscillations in main-sequence and subgiant stars. The pipeline uses only the timeseries data as input and does not require any other input information. Tests on 353 artificial stars reveal that we can obtain accurate frequencies and oscillation parameters for about three quarters of the stars. We conclude that our methods are well suited for the analysis of main-sequence stars, which show mainly p-mode oscillations.Comment: accepted by MNRA

Identity, abundance and reactivation kinetics of thermophilic fermentative endospores in cold marine sediment and seawater

Cold marine sediments harbor endospores of fermentative and sulfate-reducing, thermophilic bacteria. These dormant populations of endospores are believed to accumulate in the seabed via passive dispersal by ocean currents followed by sedimentation from the water column. However, the magnitude of this process is poorly understood because the endospores present in seawater were so far not identified, and only the abundance of thermophilic sulfate-reducing endospores in the seabed has been quantified. We investigated the distribution of thermophilic fermentative endospores (TFEs) in water column and sediment of Aarhus Bay, Denmark, to test the role of suspended dispersal and determine the rate of endospore deposition and the endospore abundance in the sediment. We furthermore aimed to determine the time course of reactivation of the germinating TFEs. TFEs were induced to germinate and grow by incubating pasteurized sediment and water samples anaerobically at 50 degrees C. We observed a sudden release of the endospore component dipicolinic acid immediately upon incubation suggesting fast endospore reactivation in response to heating. Volatile fatty acids (VFAs) and H-2 began to accumulate exponentially after 3.5 h of incubation showing that reactivation was followed by a short phase of outgrowth before germinated cells began to divide. Thermophilic fermenters were mainly present in the sediment as endospores because the rate of VFA accumulation was identical in pasteurized and non-pasteurized samples. Germinating TFEs were identified taxonomically by reverse transcription, PCR amplification and sequencing of 16S rRNA. The water column and sediment shared the same phylotypes, thereby confirming the potential for seawater dispersal. The abundance of TFEs was estimated by most probable number enumeration, rates of VFA production, and released amounts of dipicolinic acid during germination. The surface sediment contained similar to 105-106 inducible TFEs cm(-3). TFEs thus outnumber thermophilic sulfate-reducing endospores by an order of magnitude. The abundance of cultivable TFEs decreased exponentially with sediment depth with a half-life of 350 years. We estimate that 6 X 109 anaerobic thermophilic endospores are deposited on the seafloor per m2 per year in Aarhus Bay, and that these thermophiles represent >10% of the total endospore community in the surface sediment

An investigation of site-similarity approaches to generalisation of a rainfall–runoff model

This paper investigates a new approach to spatial generalisation of rainfall–runoff model parameters – site-similarity with pooling groups – for use in flood frequency estimation at ungauged sites using continuous simulation. The method is developed for the generalisation of a simple conceptual model, the Probability Distributed Model, with four parameters which require specific estimation. The study is based on a relatively large sample of catchments in Great Britain. Various options are investigated within the approach. In the final version, the pooling group comprises the 10 calibrated catchments closest, in catchment property space, to the target site, where the catchment properties used to define the space differ for each parameter of the model. An analysis that, explicitly, takes account of calibration uncertainty as a source of error enables the uncertainty associated with generalised parameter values to be reduced, justifiably. The approach uses calibration uncertainty estimated through jack-knifing and employs a weighting scheme within pooling groups that uses weights which vary both with distance in the catchment property space and with the calibration uncertainty. Models using generalised values from this approach perform relatively well compared with direct calibration. Although performance appears to be better in some areas of the country than others, there are no obvious relationships between catchment properties and performance

The open cluster NGC 6520 and the nearby dark molecular cloud Barnard 86

Wide field BVI photometry and $^{12}$CO(1$\to$0) observations are presen ted in the region of the open cluster NGC 6520 and the dark molecular cloud Barnard~86. From the analysis of the optical data we find that the cluster is rather compact, with a radius of 1.0$\pm$0.5 arcmin, smaller than previous estimates. The cluster age is 150$\pm$50 Myr and the reddening E$_{B-V}$=0.42$\pm$0.10. The distance from the Sun is estimated to be 1900$\pm$100 pc, and it is larger than previous estimates. We finally derive basic properties of the dark nebula Barnard 86 on the assumption that it lies at the same distance of the cluster.Comment: 21 pages, 8 eps figures (a few degraded in resolution), accepted for publication in the Astronomical Journa