The X-ray spectrum of NGC 7213 and the Seyfert–LINER connection

We present an XMM–Newton observation of the Seyfert–LINER (low-ionization nuclear emission-line region) galaxy NGC 7213. The RGS soft X-ray spectrum is well fitted with a power law plus soft X-ray collisionally ionized thermal plasma  ( kT = 0.18^+0.03_−0.01 keV)  . We confirm the presence of Fe  i , Fe  xxv and Fe  xxvi Kα emission in the EPIC spectrum and set tighter constraints on their equivalent widths of  82⁺¹⁰₋₁₃, 24⁺⁹₋₁₁  and 24⁺¹⁰₋₁₃ eV, respectively. We compare the observed properties together with the inferred mass accretion rate of NGC 7213 with those of other Seyfert and LINER galaxies. We find that NGC 7213 has intermediate X-ray spectral properties lying between those of the weak active galactic nucleus found in the LINER M81 and higher-luminosity Seyfert galaxies. There appears to be a continuous sequence of X-ray properties from the Galactic Centre through LINER galaxies to Seyferts, probably determined by the amount of material available for accretion in the central regions.     

The distribution of absorption in AGN detected in the XMM–Newton observations of the CDFS

We have used very deep XMM–Newton observations of the Chandra Deep Field -South to examine the spectral properties of the faint active galactic nucleus (AGN) population. Crucially, redshift measurements are available for 84 per cent (259/309) of the XMM–Newton sample. We have calculated the absorption and intrinsic luminosities of the sample using an extensive Monte Carlo technique incorporating the specifics of the XMM–Newton observations. 23 sources are found to have substantial absorption and intrinsic X-ray luminosities greater than 10⁴⁴ erg s⁻¹, putting them in the 'type-2' QSO regime. We compare the redshift, luminosity and absorption distributions of our sample to the predictions of a range of AGN population models. In contrast to recent findings from ultradeep Chandra surveys, we find that there is little evidence that the absorption distribution is dependent on either redshift or intrinsic X-ray luminosity. The pattern of absorption in our sample is best reproduced by models in which ∼75 per cent of the AGN population is heavily absorbed at all luminosities and redshifts.     

A concept for a superconducting tunnelling junction based spectrograph

We describe a multi-order spectrograph concept suitable for 8-m class telescopes, using the intrinsic spectral resolution of superconducting tunnelling junction detectors to sort the spectral orders. The spectrograph works at low orders, 1–5 or 1–6, and provides spectral coverage with a resolving power of   R ≃ 8000  from the atmospheric cut-off at 320 nm to the long-wavelength end of the infrared H or K band at 1800 nm or 2400 nm. We calculate that the spectrograph would provide substantial throughput and wavelength coverage, together with high time resolution and sufficient dynamic range. The concept uses currently available technology, or technologies with short development horizons, restricting the spatial sampling to two linear arrays; however, an upgrade path to provide more spatial sampling is identified. All of the other challenging aspects of the concept – the cryogenics, thermal baffling and magnetic field biasing – are identified as being feasible.     

A statistical study of gamma-ray burst afterglows measured by the Swift Ultraviolet Optical Telescope

We present the first statistical analysis of 27 Ultraviolet Optical Telescope (UVOT) optical/ultraviolet light curves of gamma-ray burst (GRB) afterglows. We have found, through analysis of the light curves in the observer's frame, that a significant fraction rise in the first 500 s after the GRB trigger, all light curves decay after 500 s, typically as a power law with a relatively narrow distribution of decay indices, and the brightest optical afterglows tend to decay the quickest. We find that the rise could be either produced physically by the start of the forward shock, when the jet begins to plough into the external medium, or geometrically where an off-axis observer sees a rising light curve as an increasing amount of emission enters the observers line of sight, which occurs as the jet slows. We find that at 99.8 per cent confidence, there is a correlation, in the observed frame, between the apparent magnitude of the light curves at 400 s and the rate of decay after 500 s. However, in the rest frame, a Spearman rank test shows only a weak correlation of low statistical significance between luminosity and decay rate. A correlation should be expected if the afterglows were produced by off-axis jets, suggesting that the jet is viewed from within the half-opening angle θ or within a core of a uniform energy density  θ_c  . We also produced logarithmic luminosity distributions for three rest-frame epochs. We find no evidence for bimodality in any of the distributions. Finally, we compare our sample of UVOT light curves with the X-ray Telescope (XRT) light-curve canonical model. The range in decay indices seen in UVOT light curves at any epoch is most similar to the range in decay of the shallow decay segment of the XRT canonical model. However, in the XRT canonical model, there is no indication of the rising behaviour observed in the UVOT light curves.     

57-second oscillations in Nova Centauri 1986 (V842 Cen)

High-speed photometry in 2008 shows that the light curve of V842 Cen possesses a coherent modulation at 56.825 s, with sidebands at 56.598 and 57.054 s. These have appeared since this nova remnant was observed in 2000 and 2002. We deduce that the dominant signal is the rotation period of the white dwarf primary and the sidebands are caused by reprocessing from a surface moving with an orbital period of 3.94 h. Thus, V842 Cen is an intermediate polar (IP) of the DQ Herculis subclass, is the fastest rotating white dwarf among the IPs and is the third fastest known in a cataclysmic variable. As in other IPs, we see no dwarf nova oscillations, but there are often quasi-periodic oscillations in the range 350–1500 s. There is a strong brightness modulation with a period of 3.78 h, which we attribute to negative superhumps, and there is an even stronger signal at 2.886 h which is of unknown origin but is probably a further example of that seen in GW Lib and some other systems. We used the Swift satellite to observe V842 Cen in the ultraviolet and in X-rays, although no periodic modulation was detected in the short observations. The X-ray luminosity of this object appears to be much lower than that of other IPs in which the accretion region is directly visible.     

The geological sources of Hg contamination in Kejimkujik National Park,Nova Scotia,Canada: a GIS approach

Recent studies have shown that mercury (Hg) levels in many fish from remote lakes exceed the recommended guidelines for human consumption. Most of these studies conclude that the source of contamination lies in the atmosphere. Kejimkujik National Park (KNP), Nova Scotia, Canada, is considered to be a pristine ecosystem in which fish and loon Hg levels are anomalously high. Studies in the park have shown that atmospheric Hg concentrations may not be high enough to account for the Hg levels in the biota, indicating that the park may be an unusual system in terms of Hg distribution and migration. In an attempt to summarise and synthesise the numerous Hg data sets which have been produced in the park over the last 5-10 years, a geographic information systems (GIS) approach was used to create a common database using the watersheds in the park as the common parameter. By using a GIS database, new relationships and correlations are established and the spatial distribution of Hg levels is more readily evaluated and quantified. The results indicate that geological sources of Hg, arising from biotite-rich granite rocks, may play a larger role in the contamination of the park than previously thought.     

‘Bringing government to the people’: women, local governance and community participation in South Africa

This paper considers the ongoing political transformations in South Africa in the context of debates about good governance and participatory democracy. It first appraises the current transformations of local government in South Africa, focusing specifically on relationships between gender equality and citizenship on the one hand, and local government policy, legislation, and community participation on the other, and then explores meanings of participation and how they inform approaches towards local socio-economic development. The findings of primary research conducted with civil society organisations and black women in communities in the Cape Town metropolitan area are explored through three interrelated themes. First, the model of structured participation that is central to South Africa’s democratic transformation is assessed from the perspective of black women. Second, cultures of alienation, both within local governance structures and amongst black women and the extent to which recent restructuring is combating or contributing to these are explored. Third, how participation policies are dealing with conflict within and between target groups are analysed, whether stakeholder group politics obliterate important differences in interests and whether alternative structures might be more effective in terms of women’s participation and empowerment. Finally, the findings are interpreted in relation to theoretical concepts of good governance and participatory democracy, and the potential and problems of realising South Africa’s transformation process toward developmental local government are assessed.