50 research outputs found

    New challenges in lake and river monitoring

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    Freshwater ecosystems are highly dynamic and change on time-scales that range from a few hours to several months. The development of models that simulate these processes is often hampered by the lack of sufficient data to parameterize the processes and validate the models. In this article, I review some of the challenges posed by this lack of information and suggest ways in which they can be met by using automatic monitoring systems. One of these studies is the project tempQsim (EVK1-CT2002-00112) funded by the European Commission. In this project, detailed field and model analyses have been performed at eight catchment study sites in south and south-east Europe. A number of perceptual models for the study sites have been established, and results are being used to improve selected catchment models and provide a more adequate description of pollution dynamics. Results from the extensive field studies and model tests are now being used to derive recommendations for more tailored monitoring concepts in highly dynamic, but ‘data scarce’ environments, such as are frequently found in Mediterranean river basins. The author includes implications of the EU Water Framework Directive on monitoring methods

    New challenges in lake and river monitoring

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    Today, the problems posed by the shortage of water and continuingpollution demand more effective ways of monitoring and managing ourlakes and rivers. In Europe, the statutory requirements of the WaterFramework Directive (WFD) make further demands on our collectiveexpertise and require a sound understanding of the processes that regulatethe dynamics of aquatic systems. Freshwater ecosystems are highlydynamic and change on time-scales that range from a few hours to severalmonths. The development of models that simulate these processes is oftenhampered by the lack of sufficient data to parameterize the processes andvalidate the models. In this article, I review some of the challenges posedby this lack of information and suggest ways in which they can be met byusing automatic monitoring systems of the kind described by Rouen et al.(2005, this volume). The examples are drawn from recent modellingstudies in semi-arid regions. One of these studies is the project tempQsim(EVK1-CT2002-00112) funded by the European Commission. In thisproject, detailed field and model analyses have been performed at eightcatchment study sites in south and south-east Europe. A number ofperceptual models for the study sites have been established, and results arebeing used to improve selected catchment models and provide a moreadequate description of pollution dynamics (e.g. Tournoud et al. 2004,Tzoraki et al. 2004). Results from the extensive field studies and modeltests are now being used to derive recommendations for more tailoredmonitoring concepts in highly dynamic, but ‘data scarce’ environments,such as are frequently found in Mediterranean river basins

    The one that got away: a unique eclipse in the young brown dwarf Roque 12

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    We report the discovery of a deep, singular eclipse of the bona fide brown dwarf Roque 12, a substellar member of the Pleiades. The eclipse was 0.6mag deep, lasted 1.3h, and was observed with two telescopes simultaneously in October 2002. No further eclipse was recorded, despite continuous monitoring with Kepler/K2 over 70d in 2015. There is tentative (2σ) evidence for radial velocity variations of 5km/s, over timescales of three months. The best explanation for the eclipse is the presence of a companion on an eccentric orbit. The observations constrain the eccentricity to e>0.5, the period to P>70d, and the mass of the companion to to ~0.001-0.04Msol. In principle it is also possible that the eclipse is caused by circum-sub-stellar material. Future data releases by Gaia and later LSST as well as improved radial velocity constraints may be able to unambiguously confirm the presence of the companion which would turn this system into one of the very few known eclipsing binary brown dwarfs with known age

    A survey for variable young stars with small telescopes: III. Warm spots on the active star V1598Cyg

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    Magnetic spots on low-mass stars can be traced and characterised using multi-band photometric light curves. Here we analyse an extensive data set for one active star, V1598Cyg, a known variable K dwarf which is either pre-main sequence and/or in a close binary system. Our light curve contains 2854 photometric data points, mostly in V, Rc, Ic, but also in U, B and Hα, with a total baseline of about 4yr, obtained with small telescopes as part of the HOYS project. We find that V1598Cyg is a very fast rotator with a period of 0.8246 days and varying amplitudes in all filters, best explained as a signature of strong magnetic activity and spots. We fit the photometric amplitudes in V, Rc, Ic and use them to estimate spot properties, using a grid-based method that is also propagating uncertainties. We verify the method on a partial data set with high cadence and all five broad-band filters. The method yields spot temperatures and fractional spot coverage with typical uncertainties of 100K and 3-4%, respectively. V1598Cyg consistently exhibits spots that are a few hundred degrees warmer than the photosphere, most likely indicating that the light curve is dominated by chromospheric plage. The spot activity varies over our observing baseline, with a typical time scale of 0.5-1yr, which we interpret as the typical spot lifetime. Combining our light curve with archival data, we find a six year cycle in the average brightness, that is probably a sign of a magnetic activity cycle

    Shifting limitations in crop production in Ethiopia

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    Water vulnerability assessment framework

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    The present deliverable report is related to Task 1.4 of the MADFORWATER project. The aim of the current report is double: (1) To define a framework for the development and assessment of integrated water & land management strategies (IWLMS) at basin level. This will be subsequently implemented in WP5 and WP6 of the MADFORWATER project. (2) To assess water security on a scale lower than the national level (as it was done in Task 1.2 of the MADFORWATER project) in order to provide a better understanding of the current water management practices and water vulnerabilities of the MADFORWATER selected basins: Souss-Massa basin in Morocco, Cap-Bon and Miliane basin in Tunisia, and the North-Eastern Nile Delta sub-basin in Egypt. It became apparent, during the execution of the MADFORWATER project, the need to handle a stronger consistency of indicators and information across different scales. In this view, Deliverable 1.4 focused on a systematic analysis to understand how the impact of potential local measures in the field of wastewater reuse could be assessed at different scales. Results were then used to derivate the assessment framework accordingly

    Stakeholder consultation workshops

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    This deliverable is relative to Task 7.3 - Stakeholder advisory board periodic consultation workshops, and summarises the main activities developed during those workshops and the most relevant outcomes, in the framework of the MADFORWATER project

    The near-infrared excitation of the HH211 protostellar outflow

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    The protostellar outflow HH211 is of considerable interest since it is extremely young and highly collimated. Here, we explore the outflow through imaging and spectroscopy in the near-infrared to determine if there are further diagnostic signatures of youth. We confirm the detection of a near-infrared continuum of unknown origin. We propose that it is emitted by the driving millimeter source, escapes the core through tunnels, and illuminates features aligning the outflow. Narrow-band flux measurements of these features contain an unusually large amount of continuum emission. [Fe II] emission has been detected and is restricted to isolated condensations. However, the characteristics of vibrational excitation of molecular hydrogen resemble those of older molecular outflows. We attempt to model the ordered structure of the western outflow as a series of shocks, finding that bow shocks with J-type dissociative apices and C-type flanks are consistent. Moreover, essentially the same conditions are predicted for all three bows except for a systematic reduction in speed and density with distance from the driving source. We find increased K-band extinctions in the bright regions as high as 2.9 magnitudes and suggest that the bow shocks become visible where the outflow impacts on dense clumps of cloud material. We propose that the outflow is carved out by episodes of pulsating jets. The jets, driven by central explosive events, are responsible for excavating a central tunnel through which radiation temporarily penetrates.Comment: 12 pages, 9 figure

    A survey for variable young stars with small telescopes: V - Analysis of TXOri, V505Ori, and V510Ori, the HST ULLYSES targets in the σOri cluster

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    Investigations of the formation of young stellar objects (YSOs) and planets require the detailed analysis of individual sources as well as statistical analysis of a larger number of objects. The Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) project provides such a unique opportunity by establishing a UV spectroscopic library of young high- and low-mass stars in the local universe. Here we analyse optical photometry of the three ULLYSES targets (TX Ori, V505 Ori, V510 Ori) and other YSOs in the σ Ori cluster taken at the time of the HST observations to provide a reference for those spectra. We identify three populations of YSOs along the line of sight to σ Ori, separated in parallax and proper motion space. The ULLYSES targets show typical YSO behaviour with pronounced variability and mass accretion rates of the order of 10−8 M⊙/yr. Optical colours do not agree with standard interstellar reddening and suggest a significant contribution of scattered light. They are also amongst the most variable and strongest accretors in the cluster. V505 Ori shows variability with a seven day period, indicating an inner disk warp at the co-rotation radius. Uncovering the exact nature of the ULLYSES targets will require improved detailed modelling of the HST spectra in the context of the available photometry, including scattered light contributions as well as non-standard reddening

    Molecular outflows in the young open cluster IC348

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    We present a wide-field survey of the young open cluster IC348 for molecular H2 outflows. Outflow activity is only found at its south-western limit, where a new subcluster of embedded sources is in an early phase of its formation. If the IC348 cluster had been built up by such subclusters forming at different times, this could explain the large age-spread that Herbig (1998) found for the IC348 member stars. In addition to several compact groups of H2 knots, our survey reveals a large north-south oriented outflow, and we identify the newly discovered far-infrared and mm-object IC348MMS as its source. New deep images in the 1-0 S(1) line of molecular hydrogen trace the HH211 jet and counterjet as highly-collimated chains of knots, resembling the interferometric CO and SiO jets. This jet system appears rotated counter-clockwise by about 3 degrees with respect to the prominent H2 bow shocks. Furthermore, we resolve HH211-mm as a double point-like source in the mm-continuum.Comment: 10 pages, 9 figures, accepted for publication in Ap
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