Transient detection and classification

I provide an incomplete inventory of the astronomical variability that will be found by next‐generation time‐domain astronomical surveys. These phenomena span the distance range from near‐Earth satellites to the farthest Gamma Ray Bursts. The surveys that detect these transients will issue alerts to the greater astronomical community; this decision process must be extremely robust to avoid a slew of “false” alerts, and to maintain the community's trust in the surveys. I review the functionality required of both the surveys and the telescope networks that will be following them up, and the role of VOEvents in this process. Finally, I offer some ideas about object and event classification, which will be explored more thoroughly by other articles in these proceedings. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Olivine or impact melt: Nature of the “Orange” material on Vesta from Dawn

NASA’s Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types: (a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), (b) lobate patches with well-defined edges (nicknamed “pumpkin patches”), and (c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed “Leslie feature” first identified by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130–157) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Several possible options for the composition of the orange material are investigated including, cumulate eucrite layer exposed during impact, metal delivered by impactor, olivine–orthopyroxene mixture and impact melt. Based on our analysis, the orange material on Vesta is unlikely to be metal or olivine (originally proposed by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130–157)). Analysis of the elemental composition of Oppia ejecta blanket with GRaND suggests that its orange material has ∼25% cumulate eucrite component in a howarditic mixture, whereas two other craters with orange material in their ejecta, Octavia and Arruntia, show no sign of cumulate eucrites. Morphology and topography of the orange material in Oppia and Octavia ejecta and orange patches suggests an impact melt origin. A majority of the orange patches appear to be related to the formation of the Rheasilvia basin. Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt.     

Changes and variation in the discharge regime of the Upper Suriname River Basin and its relationship with the tropical Pacific and Atlantic SST anomalies

Long‐term changes and variability in river flows in the tropical Upper Suriname River Basin in Suriname (2–6°N, 54–58°W) are analysed, including the relation to sea surface temperatures (SSTs) in the tropical Atlantic and Pacific Ocean. To analyse variability, lag correlation and statistical properties of the data series are used. Long‐term changes are analysed using parametric and non‐parametric statistical techniques. The analyses are performed for the period 1952–1985. The results show that both river discharge series at Semoisie and Pokigron are non‐stationary and have a negative trend. The negative rainfall trend in the centre of Suriname may be responsible for the negative trend in the annual river discharges in the basin. The highest correlation (Pearson's coefficient c) is obtained when the Tropical North Atlantic (TNA) SSTs lags the monthly discharges at Pokigron by 3–4 months (c = 0·7) and when the Tropical South Atlantic (TSA) SSTs lags the discharges by 4 months (c = ? 0·7). It also follows that the high (low) monthly flows, from April–August (September–March) are associated with increasing (decreasing) SSTs in the TNA and with decreasing (increasing) SSTs in the TSA. The results also reveal that years with low (high) discharges are more related to warmer (colder) SSTs during the year in the TNA region and a southward displacement of the Inter‐Tropical Convergence Zone (ITCZ). However, the Pacific El Niño (La Niña) events may also be responsible for low (high) flow years in this basin. Copyright © 2007 John Wiley & Sons, Ltd.     

Atlas of North Sea surface temperatures. Weekly and monthly means for the period 1969 to 1993

Ocean Dynamics - Der vorliegende Atlas enthält statistische Bearbeitungen der seit dem Jahr 1969 wöchentlich analysierten Oberflächentemperaturkarten des Bundesamtes für...     

The merging/AGN connection: a case for 3D spectroscopy

We discuss an ongoing study of the connection between galaxy merging/interaction and AGN activity, based on integral field spectroscopy. We focus on the search for AGN ionization in the central regions of mergers, previously not classified as AGNs. We present here the science case, the current status of the project, and plans for future observations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transformation of global spherical harmonic models of the gravity field to a local adjusted spherical cap harmonic model

The new global gravity models represented by global spherical harmonics like EGM2008 require a high degree and order in their coefficients to resolve the gravity field in local areas; therefore, there are interests to represent the regional or local field by less parameters and to develop a parameter transformation from the global model to a local kind of spherical harmonic model. The authors use local spherical cap harmonics for the regional gravity potential representation related to a local pole and a local spherical coordinate system. This allows to model regional gravity potential with less parameters and less memory requirements in computation and storage. From different kinds of representations of spherical cap harmonics, we have selected the so-called adjusted spherical cap harmonics (ASCH). This is the most appropriate for the presented mathematical model of deriving its coefficients from global gravity models. In that way, the global gravity models can fully be exploited and mapped to regional ASCH, in particular with respect to the computation of regional geoid models with improved solution.     

Flood Forecasting and Flood Warning in the Firth of Clyde, UK

Coastal flooding has caused significant damage to a number of communities around the Firth of Clyde in south-west Scotland, UK. The Firth of Clyde is an enclosed embayment affected by storm surge generated in the Northern Atlantic and propagated through the Irish Channel. In recent years, the worst flooding occurred on 5th January 1991 with the estimated damage of approximately £7M. On average, some £0.5M damage is caused each year by coastal flooding. With the latest climate change predictions suggesting increased storm activity and the expected increase in mean sea levels, these damages are likely to increase. In line with the expansion of flood warning provision in Scotland, the Scottish Environment Protection Agency (SEPA) has developed a flood warning system to provide local authorities and emergency services with up to 24 h warning of coastal flooding within the Firth of Clyde and River Clyde Estuary up to Glasgow City Centre. The Firth of Clyde flood warning system consists of linked 1-D and 2-D mathematical models of the Firth of Clyde and Clyde Estuary, and other software tools for data processing, viewing and generating warning messages. The general methodology adopted in its implementation was developed following extensive consultation with the relevant authorities, including local councils and police. The warning system was launched in October 1999 and has performed well during four winter flood seasons. The system currently makes forecasts four times a day and is the only operational coastal flood warning system in Scotland.This paper summarises the development of the warning system, gives a review of its operation since its launch in 1999 and discusses future developments in flood warning in Scotland.