The dynamical architecture and habitable zones of the quintuplet planetary system 55 Cancri

We perform numerical simulations to study the secular orbital evolution and dynamical structure of the quintuplet planetary system 55 Cancri with the self-consistent orbital solutions by Fischer and coworkers. In the simulations, we show that this system can be stable for at least 108 yr. In addition, we extensively investigate the planetary configuration of four outer companions with one terrestrial planet in the wide region of 0.790AU 〈 a 〈 5.900AU to examine the existence of potential asteroid structure and Habitable Zones （HZs）. We show that there are unstable regions for orbits about 4：1, 3：1 and 5：2 mean motion resonances （MMRs） of the outermost planet in the system, and several stable orbits can remain at 3：2 and 1：1 MMRs, which resembles the asteroid belt in the solar system. From a dynamical viewpoint, proper HZ candidates for the existence of more potential terrestrial planets reside in the wide area between 1.0 AU and 2.3 AU with relatively low eccentricities.     

Detailed visual observations and modelling of the 1998 Leonid shower

We present a detailed activity profile for the 1998 Leonid shower from visual observations. The shower displayed at least two distinct components – a broad component peaking between 2344 and 2350, and two narrower filaments near 23521 and 23533 probably of younger origin based on modelling results. This dual-peaked structure in the flux profile has peak fluxes to a limiting magnitude of +6.5 of 0.03 Leonid km⁻² h⁻¹. The distribution of particles also changes dramatically across the stream in 1998, with large meteoroids dominating the early peak and smaller meteoroids relatively more abundant near the time of the nodal passage of the comet. Detailed comparison of the observed activity with models in 1998 shows that the early component comes from material ejected between 500 and 1000 yr ago. Our modelling results suggest that the later dual peaks are caused by high- β meteoroids with large ejection velocities released during the 1932 and 1965 passages of Comet 55P/Tempel–Tuttle.     

Spectroscopy of globular cluster candidates in the Sculptor group galaxies NGC 253 and 55

We have obtained spectra for 103 published globular cluster candidates in the Sculptor group galaxies NGC 253 and 55. On the basis of radial velocities and digitized plate images, 14 globular clusters are identified in NGC 253 and one probable globular cluster is identified in NGC 55. The majority of the objects in the sample appear to be background galaxies. We have obtained and analysed COSMOS plate scans of NGC 253 and 55 and use these along with the spectroscopically identified clusters to define new samples of globular cluster candidates in the two galaxies which should have reduced contamination.     

A freshwater species wintering in a brackish environment: Habitat selection and diet of Slavonian grebes in the southern Baltic Sea

After the breeding season, Slavonian grebes (Podiceps auritus) leave their freshwater breeding habitats and migrate to wintering grounds in marine or brackish waters. The most important wintering area in northwestern Europe is located in the southern Baltic Sea, with the largest concentrations in the offshore area of the Pommeranian Bight. Analysis of ship-based surveys revealed that the habitat selection of Slavonian grebes in this brackish area is significantly influenced by water depth and bottom sediment type. The grebes prefer shallow waters of 4–14 m depth and occur only over sandy sediments. While the diving depths of endothermic animals is limited due to energetic constraints and thermoregulation, sediment type is regarded to be a proxy for food choice. The diet of Slavonian grebes in the Pomeranian Bight consists mainly of demersal gobies (Gobiidae) that frequently occur over sandy bottom substrates.     

The dynamical architecture and habitable zones of the quintuplet planetary system 55 Cancri

We perform numerical simulations to study the secular orbital evolution and dynamical structure of the quintuplet planetary system 55 Cancri with the self-consistent orbital solutions by Fischer and coworkers. In the simulations, we show that this sys-tem can be stable for at least 108 yr. In addition, we extensively investigate the planetary configuration of four outer companions with one terrestrial planet in the wide region of 0.790 AU ≤ a ≤ 5.900 AU to examine the existence of potential asteroid structure and Habitable Zones (HZs). We show that there are unstable regions for orbits about 4:1, 3:1 and 5:2 mean motion resonances (MMRs) of the outermost planet in the system, and sev-eral stable orbits can remain at 3:2 and 1:1 MMRs, which resembles the asteroid belt in the solar system. From a dynamical viewpoint, proper HZ candidates for the existence of more potential terrestrial planets reside in the wide area between 1.0 AU and 2.3 AU with relatively low eccentricities.     

Speckle observations with PISCO in Merate: IV. Astrometric measurements of visual binaries in 2005

We present relative astrometric measurements of visual binaries made during the second semester of 2005, with the speckle camera PISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long term program is to improve the accuracy of the orbits and determine the masses of the components. We performed 130 new observations of 120 objects, with most of the angular separations in the range 0″.1–4″, and with an average accuracy of 0″.01. Most of the position angles could be determined without the usual 180. ambiguity with the application of triple‐correlation techniques, and their mean error is 0°8. We have found a possible new triple system: ADS 11077. The measurements of the closest binaries were made with a new data reduction procedure, based on model fitting of the background of the auto‐correlations. As this procedure proved to be very efficient, we have re‐processed the old observations of close binaries made with PISCO in Merate since 2004. We thus improved 20 measurements already published and obtained 7 new measurements for observations that were previously reported as “unresolved”. We finally present revised orbits for ADS 684, MCA 55Aac (in the Beta 1 Cyg–Albireo multiple system) and ADS 14783 for which the previously published orbits led to large residuals with our measurements and for which the new observations made since their computation allowed a significant improvement of those old orbits. The sum of the masses that we derived for those systems are consistent with the spectral type of the stars and the dynamic parallaxes are in good agreement with the parallaxes measured by Hipparcos. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Evaluating next-generation intensity–duration–frequency curves for design flood estimates in the snow-dominated western United States

Civil infrastructure such as culverts and bridges are commonly designed using precipitation-based intensity–duration–frequency (PREC-IDF) curves, which assume that the occurrence of precipitation is in the form of rainfall and immediately available for the rainfall-runoff process. In snow-dominated regions, where most winter precipitation occurs as snow that melts during spring to early summer, the use of standard PREC-IDF curves may lead to substantial underestimation of design floods and high failure risk of infrastructure. In this context, we developed next-generation IDF (NG-IDF) curves that characterize the actual water reaching the land surface (i.e., rainfall plus snowmelt) to enhance standard infrastructure design in snow-dominated regions. This study evaluates the performance of NG-IDF curves coupled with U.S. Department of Agriculture Technical Release 55 hydrologic model in estimating design floods for 246 snowy locations in different hydroclimate regimes of the western United States. Design flood estimates from a well-validated continuous simulation using a physics-based hydrologic model, the Distributed Hydrology Soil Vegetation Model (DHSVM), were used as the performance benchmark. Compared with the benchmark estimates, the standard PREC-IDF curves led to substantial errors in design flood estimates, while the NG-IDF curves significantly reduced these errors. For example, the averaged error in the 50-year design flood estimates over the 246 locations was reduced from 31% with the use of PREC-IDF curves to 12% with the use of NG-IDF curves. Despite the different model structures, the single-event NG-IDF approach versus the continuous simulation DHSVM did not exhibit statistically significant differences in 91% of the 246 locations for the 50-year design flood estimates. This indicates a satisfactory performance of NG-IDF curves to estimate design flow under the conditions tested in the snow-dominated western United States. This article also presents technical suggestions and the limitations of infrastructure design using NG-IDF curves for regulatory agencies and practicing engineers.     

Ruprecht 55: an OB association at the edge of our Galaxy

We present new spectroscopy in the optical range and 21-cm H  i data covering the Ruprecht 55 (Ru 55) field in the Puppis window where several authors have proposed the existence of one (or two) clusters.
We have determined new MK spectral types for about 50 stars in the region, finding 43 OB-type stars among them. LS 985 was found to be an O9 V + O9.5 III binary and it is the earliest type of star in our observed sample.
We have identified a stellar OB association (Ru 55), which is most likely related to a depletion detected in our H  i data, as: (i) they are located at the same distance (6 kpc), within observational errors; (ii) both have similar radial velocities (∼67 km s⁻¹); (iii) current OB stars could have provided the energy needed to blow the cavity; (iv) the dynamical time-scale for the hole buildup matches the age estimated for the earliest OB stars; and (v) LS 985 might be responsible for ionizing the H  i cavity inner walls close to it.     

Observations of interplanetary meteoroids with TIRA

The Tracking and Imaging RAdar (TIRA) at the Research Establishment for Applied Science (FGAN) was used in the L-band (1.33 GHz) to observe the Leonid shower in 1999. The radar beam was pointed directly into the radiant in the constellation Leo to receive “head echoes” from meteoroids when they ablate in the atmosphere at altitudes around 100 km. Two hundred and eighty-seven meteors were observed during 21 h in the early hours of November 17 and 18, 1999. The individual velocities, radiants and rough heliocentric orbits are calculated. Criteria are derived from optically observed Leonids which are then applied to decide whether an echo was created by a Leonid or a background meteoroid. However, in most cases the accuracy in the observational data is not good enough to allow for a clear distinction. Only for 100 meteors the velocity errors were less than 10 km/s. Out of those, 71 could be excluded on a 3σ level to be a Leonid (95 are excluded on a 1σ level). This confirms the theory that the Leonids have dominantly sizes of optical meteoroids with no significant extension in the lower mass range. Therefore, the risk of meteoroid impacts on spacecraft does not increase considerably during a Leonid storm. Background measurements 9 days after the Leonids maximum were taken in 2001 which corroborated the overall results obtained in 1999.