New photometry and astrometry of the isolated neutron star RX J0720-3125 using recent VLT/FORS observations

Since the first optical detection of RXJ0720.4-3125 various observations have been performed to determine astrometric and photometric data. We present the first detection of the isolated neutron star in the V Bessel filter to study the spectral energy distribution and derive a new astrometric position. At ESO Paranal we obtained very deep images with FORS 1 (three hours exposure time) of RXJ0720.4-3125 in V Bessel filter in January 2008. We derive the visual magnitude by standard star aperture photometry.Using sophisticated resampling software we correct the images for field distortions. Then we derive an updated position and proper motion value by comparing its position with FORS 1 observations of December 2000. We calculate a visual magnitude of V = 26.81 +- 0.09mag, which is seven times in excess of what is expected from X-ray data, but consistent with the extant U, B and R data. Over about a seven year epoch difference we measured a proper motion of mu = 105.1 +- 7.4mas/yr towards theta = 296.951 deg +- 0.0063 deg (NW), consistent with previous data.Comment: 7 pages, 9 figure

X-ray stellar population of the LMC

In the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive stars, or X-ray binaries are best revealed in X-rays. However, previously available X-ray observatories often provided only crude information on individual objects in the Magellanic Clouds. The advent of the highly efficient X-ray facilities XMM-Newton and Chandra has now dramatically increased the sensitivity and the spatial resolution available to X-ray astronomers, thus enabling a fairly easy determination of the properties of individual sources in the LMC.Comment: Invited review at IAUS 256 "The Magellanic system: stars, gas and galaxies" (July 2008, Keele, UK); proceedings edited by J. Th. van Loon and J. M. Oliveira; 10 pages, 1 figure (in jpg

ROSAT HRI catalogue of X-ray sources in the LMC region

All 543 pointed observations of the ROSAT High Resolution Imager (HRI) with exposure times higher than 50 sec in a field of 10 deg x 10 deg covering the Large Magellanic Cloud (LMC) were analyzed. A catalogue was produced containing 397 X-ray sources with their properties measured by the HRI. The list was cross-correlated with the ROSAT Position Sensitive Propotional Counter (PSPC) source catalogue presented by Haberl & Pietsch (1999), the SIMBAD data base, and the TYCHO catalogue. 138 HRI sources are contained in the PSPC catalogue. The spatial resolution of the HRI was higher than that of the PSPC and the source position could be determined with errors mostly smaller than 15 arcsec which are dominated by systematic attitude errors. 94 HRI sources were identified with known objects based on their positional coincidence and X-ray properties. The catalogue contains 39 foreground stars, 24 supernova remnants (SNRs), five supersoft sources (SSSs), nine X-ray binaries (XBs), and nine AGN well known from literature. Another eight sources were identified with known candidates for these source classes. Additional 21 HRI sources are suggested in the present work as candidates for SNR, X-ray binary in the LMC, or background AGN because of their extent, hardness ratios, X-ray to optical flux ratio, or flux variability.Comment: 22 pages, 8 figures, 4 table

XMM-Newton observations of the Small Magellanic Cloud: X-ray outburst of the 6.85 s pulsar XTE J0103-728

A bright X-ray transient was seen during an XMM-Newton observation in the direction of the Small Magellanic Cloud (SMC) in October 2006. The EPIC data allow us to accurately locate the source and to investigate its temporal and spectral behaviour. X-ray spectra covering 0.2-10 keV and pulse profiles in different energy bands were extracted from the EPIC data. The detection of 6.85 s pulsations in the EPIC-PN data unambiguously identifies the transient with XTE J0103-728, discovered as 6.85 s pulsar by RXTE. The X-ray light curve during the XMM-Newton observation shows flaring activity of the source with intensity changes by a factor of two within 10 minutes. Modelling of pulse-phase averaged spectra with a simple absorbed power-law indicates systematic residuals which can be accounted for by a second emission component. For models implying blackbody emission, thermal plasma emission or emission from the accretion disk (disk-blackbody), the latter yields physically sensible parameters. The photon index of the power-law of ~0.4 indicates a relatively hard spectrum. The 0.2-10 keV luminosity was 2x10^{37} with a contribution of ~3% from the disk-blackbody component. A likely origin for the excess emission is reprocessing of hard X-rays from the neutron star by optically thick material near the inner edge of an accretion disk. From a timing analysis we determine the pulse period to 6.85401(1) s indicating an average spin-down of ~0.0017 s per year since the discovery of XTE J0103-728 in May 2003. The X-ray properties and the identification with a Be star confirm XTE J0103-728 as Be/X-ray binary transient in the SMC.Comment: 5 pages, 4 figures, submitted to A&A on 21 Dec. 200

Adaptive FEM with coarse initial mesh guarantees optimal convergence rates for compactly perturbed elliptic problems

We prove that for compactly perturbed elliptic problems, where the corresponding bilinear form satisfies a Garding inequality, adaptive mesh-refinement is capable of overcoming the preasymptotic behavior and eventually leads to convergence with optimal algebraic rates. As an important consequence of our analysis, one does not have to deal with the a-priori assumption that the underlying meshes are sufficiently fine. Hence, the overall conclusion of our results is that adaptivity has stabilizing effects and can overcome possibly pessimistic restrictions on the meshes. In particular, our analysis covers adaptive mesh-refinement for the finite element discretization of the Helmholtz equation from where our interest originated

Indicators of sustainable land use: Concepts for the analysis of society-nature interrelations and implications for sustainable development

Session: Environmental Management, Sustainability and Development Sustainable development aims at shaping the socio-economic behavior towards nature in ways that guarantee the preservation of the life-supporting natural systems for future generations. Moreover, it seeks to achieve some kind of ?global justice" with respect to the distribution of natural resources. Steps towards sustainability require fundamental changes in the prevailing production and consumption patterns and lifestyles in the industrial centers of the world. These changes will be influenced by framework conditions set by economic and environmental policy. Indicators may help to understand and describe developments too complex to be grasped as a whole. They make phenomena or trends visible and may be seen as "empirical models of reality". Indicators can support economic and environmental policy by contributing to a simplification and quantification of complex environmental problems. The proposed contribution will analyze the "empirical models" indicator systems put forward recently, e.g. by the World Resources Institute and Eurostat and the "ecological footprint / sustainable process index" concept of Wackernagel, Rees and Narodoslawsky. It will then propose a model which relies on two concepts for the interaction of societies with their natural environment: 1 / Socio-economic metabolism, i.e. the material and energy flows between socio-economic systems and their natural environment. 2 / The colonization of nature, i.e. the conundrum of deliberate interventions into natural systems aimed at their "improvement" with respect to socio-economic goals. These concepts are used to develop "pressure indicators", i.e. indicators which describe socio-economic processes which are highly likely to have environmentally detrimental consequences. These pressure indicators may be used to analyze if current socio-economic trends are directed towards sustainable development. These environmental indicators can be linked to economic actors (economic sectors or activities) as well as to economic indicators, such as the system of national accounts (SNA). They may thus support economic and environmental policy making. Together with "state indicators" which describe socio-economic as well as natural "stocks" (e.g. biodiversity, environmental quality, material infrastructure etc.) and so-called "response indicators" which trace policy measures aimed at alleviating environmental problems, pressure indicators can be used to develop comprehensive systems of sustainability indicators. The proposed contribution will focus on the regional / spatial aspects of such indicator systems. It will draw from the on-going research project "Colonizing Landscapes - Indicators of Sustainable Land Use" in the framework of the Austrian research program "Sustainable Development of Cultural Landscapes". Keywords: Indicators, land use, sustainability, pressures on the environment, economic activities, physical economy, colonization of nature, socio-economic metabolism