61 research outputs found

    Archiving multi-epoch data and the discovery of variables in the near infrared

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    We present a description of the design and usage of a new synoptic pipeline and database model for time series photometry in the VISTA Data Flow System (VDFS). All UKIRT-WFCAM data and most of the VISTA main survey data will be processed and archived by the VDFS. Much of these data are multi-epoch, useful for finding moving and variable objects. Our new database design allows the users to easily find rare objects of these types amongst the huge volume of data being produced by modern survey telescopes. Its effectiveness is demonstrated through examples using Data Release 5 of the UKIDSS Deep Extragalactic Survey (DXS) and the WFCAM standard star data. The synoptic pipeline provides additional quality control and calibration to these data in the process of generating accurate light-curves. We find that 0.6+-0.1% of stars and 2.3+-0.6% of galaxies in the UKIDSS-DXS with K<15 mag are variable with amplitudes \Delta K>0.015 magComment: 30 pages, 31 figures, MNRAS, in press Minor changes from previous version due to refereeing and proof-readin

    Is there a caustic crossing in the lensed quasar Q2237+0305 observational data record?

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    We re-investigate the gravitationally lensed system Q2237+0305 data record to quantify the probability of having a caustic crossing in the A component. Several works assume that this is the case, but no quantitative analysis is available in the literature. We combine the datasets from the OGLE and GLITP collaborations to accurately trace the prominent event in the lightcurve for the A component of the system. Then the observed event is compared with synthetic light curves derived from trajectories in magnification maps. These maps are generated using a ray-tracing technique. We take more than 10^9 trajectories and test a wide range of different physical properties of the lensing galaxy and the source quasar (lens transverse velocity, microlens mass, source intensity profile and source size). We found that around 75% of our good trajectories (i.e. that are consistent with the observations) are caustic crossings. In addition, a high transverse velocity exceeding 300 km/s, a microlens mass of about 0.1 M_sun and a small standard accretion disk is the best parameter combination. The results justify the interpretation of the OGLE-GLITP event in Q2237+0305A as a caustic crossing. Moreover, the physical properties of the lens and source are in very good agreement with previous works. We also remark that a standard accretion disk is prefered to those simpler approaches, and that the former should be used in subsequent simulations.Comment: 5 pages, 3 figures, 3 tables, to appear in MNRA

    Do the dominant plant species impact the substrate and vegetation composition of post-coal mining spoil heaps?

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    This is an accepted manuscript of an article published by Elsevier in Ecological Engineering on 03/12/2019, available online: https://doi.org/10.1016/j.ecoleng.2019.105685 The accepted version of the publication may differ from the final published version�� 2019 Dominant species influence both species and functional composition of the vegetation as well as soil properties of the substrate. However, knowledge about the role played by dominant species in the process of shaping their habitat within post-industrial ecosystems is still limited. We aimed to assess the impact of four dominant species (Calamagrostis epigejos, Daucus carota, Poa compressa and Tussilago farfara) on soil abiotic and biotic properties, and to detect differences in species and functional composition of the vegetation types studied. We hypothesized that (1) dominant species of higher mean biomass cause lower aboveground biodiversity and (2) dominant species of higher mean biomass have a higher impact than the others on soil properties. We measured soil chemistry (TOC, N, P, K, Na, Mg content, EC, pH and enzyme activities) as well as biomass, species diversity and functional diversity of vegetation on 15 study plots (28.3 m2) for each species studied. The DCA analysis revealed a clear distinction between the patches dominated by studied species. Vegetation patches dominated by Calamagrostis epigejos were correlated with amount of biomass, canopy height CWM and specific leaf CWM. Patches dominated by Daucus carota were related to the light requirements (EIV-L), Total Organic Carbon (TOC) and K content. The vegetation patches dominated by Poa compressa were related to dehydrogenase activity, higher Mg content and species richness of the vegetation patches. The highest TOC content was recorded for T. farfara substrates, and the lowest for C. epigejos substrates. The content of potassium does not differ statistically significantly in the substrates from sites dominated by D. carota and P. compressa. The highest values of Mg content were recorded for D. carota and were statistically different from Poa compressa sites, while the higher phosphorus content (statistically significantly different) was recorded for patches dominated by T. farfara and P. compressa. Despite our assumptions, the species with the highest mean biomass (Calamagrostis epigejos) did not cause lower species or functional diversity. In contrast, Tussilago farfara has the highest impact on postindustrial site habitats on coal mine heaps, as extreme values of four soil substratum parameters were recorded on these plots. This species also decreased both species and functional diversity of vegetation. The knowledge about relationship existing between plants (aboveground vegetation) and soil organisms seems important in order to undertake suitable reclamation measures and to restore variety of functions as well as to create diverse vegetation based on native species.Published versio

    The Konkoly Blazhko Survey: Is light-curve modulation a common property of RRab stars?

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    A systematic survey to establish the true incidence rate of the Blazhko modulation among short-period, fundamental-mode, Galactic field RR Lyrae stars has been accomplished. The Konkoly Blazhko Survey (KBS) was initiated in 2004. Since then more than 750 nights of observation have been devoted to this project. A sample of 30 RRab stars was extensively observed, and light-curve modulation was detected in 14 cases. The 47% occurrence rate of the modulation is much larger than any previous estimate. The significant increase of the detected incidence rate is mostly due to the discovery of small-amplitude modulation. Half of the Blazhko variables in our sample show modulation with so small amplitude that definitely have been missed in the previous surveys. We have found that the modulation can be very unstable in some cases, e.g. RY Com showed regular modulation only during one part of the observations while during two seasons it had stable light curve with abrupt, small changes in the pulsation amplitude. This type of light-curve variability is also hard to detect in other Survey's data. The larger frequency of the light-curve modulation of RRab stars makes it even more important to find the still lacking explanation of the Blazhko phenomenon. The validity of the [Fe/H](P,phi_{31}) relation using the mean light curves of Blazhko variables is checked in our sample. We have found that the formula gives accurate result for small-modulation-amplitude Blazhko stars, and this is also the case for large-modulation-amplitude stars if the light curve has complete phase coverage. However, if the data of large-modulation-amplitude Blazhko stars are not extended enough (e.g. < 500 data points from < 15 nights), the formula may give false result due to the distorted shape of the mean light curve used.Comment: Accepted for publication in MNRAS, 14 pages, 7 Figure

    A near-infrared survey of Miras and the distance to the Galactic Centre

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    We report the results of a near-infrared survey for long-period variables in a field of view of 20 arcmin by 30 arcmin towards the Galactic Centre (GC). We have detected 1364 variables, of which 348 are identified with those reported in Glass et al. (2001). We present a catalogue and photometric measurements for the detected variables and discuss their nature. We also establish a method for the simultaneous estimation of distances and extinctions using the period-luminosity relations for the JHKs bands. Our method is applicable to Miras with periods in the range 100--350 d and mean magnitudes available in two or more filter bands. While J-band means are often unavailable for our objects because of the large extinction, we estimated distances and extinctions for 143 Miras whose H- and Ks-band mean magnitudes are obtained. We find that most are located at the same distance to within our accuracy. Assuming that the barycentre of these Miras corresponds to the GC, we estimate its distance modulus to be 14.58+-0.02(stat.)+-0.11(syst.) mag, corresponding to 8.24+-0.08(stat.)+-0.42(syst.) kpc. We have assumed the distance modulus to the LMC to be 18.45 mag, and the uncertainty in this quantity is included in the systematic error above. We also discuss the large and highly variable extinction. Its value ranges from 1.5 mag to larger than 4 mag in A(Ks) except towards the thicker dark nebulae and it varies in a complicated way with the line of sight. We have identified mid-infrared counterparts in the Spitzer/IRAC catalogue of Ramirez et al. (2008) for most of our variables and find that they follow rather narrow period-luminosity relations in the 3.6 to 8.0 micrometre wavelength range.Comment: Accepted for publication in MNRAS, 22 pages (28 tables, 11 figures). Figure 7 and tables 6, 7 and 9 will be published in full online onl

    Catálogo de autoridades da Rede BIM (DPHDM): Estudo de caso no tratamento de registros de pontos de acesso

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    Identificar possíveis problemas na alimentação da base de autoridades de assuntos da Rede BIM através da utilização do software Pergamum, e contribuir para padronização de seus pontos de acesso. A partir da revisão da literatura proposta, considera a importância da recuperação da informação para sua disseminação e ainda faz um breve levantamento dos padrões internacionais utilizados para esse fim. A metodologia utilizada envolveu a análise da base, limitada à letra “c” do alfabeto, e se propôs a detectar possíveis inconsistências existentes. Os principais problemas encontrados foram: falhas de grafia, falhas de entrada de cabeçalhos e duplicidade de assuntos. Os resultados práticos para a Rede BIM são: agilização dos serviços de catalogação e referência da Rede BIM, maior controle bibliográfico e facilidade na recuperação de itens nas pesquisas dos usuários. O Estudo de caso se propõe a contribuir com esclarecimentos quanto a equívocos cometidos, de forma a auxiliar na padronização e documentação do processo de alimentação da base de autoridades de assuntos pelos bibliotecários das 45 organizações militares, possibilitando benefícios aos serviços de catalogação e referência e finalmente, propiciando um atendimento mais prático e ágil ao usuário da Rede BIM

    Impact of clinical phenotypes on management and outcomes in European atrial fibrillation patients: a report from the ESC-EHRA EURObservational Research Programme in AF (EORP-AF) General Long-Term Registry

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    Background: Epidemiological studies in atrial fibrillation (AF) illustrate that clinical complexity increase the risk of major adverse outcomes. We aimed to describe European AF patients\u2019 clinical phenotypes and analyse the differential clinical course. Methods: We performed a hierarchical cluster analysis based on Ward\u2019s Method and Squared Euclidean Distance using 22 clinical binary variables, identifying the optimal number of clusters. We investigated differences in clinical management, use of healthcare resources and outcomes in a cohort of European AF patients from a Europe-wide observational registry. Results: A total of 9363 were available for this analysis. We identified three clusters: Cluster 1 (n = 3634; 38.8%) characterized by older patients and prevalent non-cardiac comorbidities; Cluster 2 (n = 2774; 29.6%) characterized by younger patients with low prevalence of comorbidities; Cluster 3 (n = 2955;31.6%) characterized by patients\u2019 prevalent cardiovascular risk factors/comorbidities. Over a mean follow-up of 22.5 months, Cluster 3 had the highest rate of cardiovascular events, all-cause death, and the composite outcome (combining the previous two) compared to Cluster 1 and Cluster 2 (all P &lt;.001). An adjusted Cox regression showed that compared to Cluster 2, Cluster 3 (hazard ratio (HR) 2.87, 95% confidence interval (CI) 2.27\u20133.62; HR 3.42, 95%CI 2.72\u20134.31; HR 2.79, 95%CI 2.32\u20133.35), and Cluster 1 (HR 1.88, 95%CI 1.48\u20132.38; HR 2.50, 95%CI 1.98\u20133.15; HR 2.09, 95%CI 1.74\u20132.51) reported a higher risk for the three outcomes respectively. Conclusions: In European AF patients, three main clusters were identified, differentiated by differential presence of comorbidities. Both non-cardiac and cardiac comorbidities clusters were found to be associated with an increased risk of major adverse outcomes

    Measurement of the nuclear modification factor for muons from charm and bottom hadrons in Pb+Pb collisions at 5.02 TeV with the ATLAS detector

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    Heavy-flavour hadron production provides information about the transport properties and microscopic structure of the quark-gluon plasma created in ultra-relativistic heavy-ion collisions. A measurement of the muons from semileptonic decays of charm and bottom hadrons produced in Pb+Pb and pp collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV with the ATLAS detector at the Large Hadron Collider is presented. The Pb+Pb data were collected in 2015 and 2018 with sampled integrated luminosities of 208 mu b(-1) and 38 mu b(-1), respectively, and pp data with a sampled integrated luminosity of 1.17 pb(-1) were collected in 2017. Muons from heavy-flavour semileptonic decays are separated from the light-flavour hadronic background using the momentum imbalance between the inner detector and muon spectrometer measurements, and muons originating from charm and bottom decays are further separated via the muon track's transverse impact parameter. Differential yields in Pb+Pb collisions and differential cross sections in pp collisions for such muons are measured as a function of muon transverse momentum from 4 GeV to 30 GeV in the absolute pseudorapidity interval vertical bar eta vertical bar &lt; 2. Nuclear modification factors for charm and bottom muons are presented as a function of muon transverse momentum in intervals of Pb+Pb collision centrality. The bottom muon results are the most precise measurement of b quark nuclear modification at low transverse momentum where reconstruction of B hadrons is challenging. The measured nuclear modification factors quantify a significant suppression of the yields of muons from decays of charm and bottom hadrons, with stronger effects for muons from charm hadron decays

    A search for an unexpected asymmetry in the production of e+μ− and e−μ+ pairs in proton-proton collisions recorded by the ATLAS detector at root s = 13 TeV

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    This search, a type not previously performed at ATLAS, uses a comparison of the production cross sections for e(+)mu(-) and e(-)mu(+) pairs to constrain physics processes beyond the Standard Model. It uses 139 fb(-1) of proton-proton collision data recorded at root s = 13 TeV at the LHC. Targeting sources of new physics which prefer final states containing e(+)mu(-) and e(-)mu(+), the search contains two broad signal regions which are used to provide model-independent constraints on the ratio of cross sections at the 2% level. The search also has two special selections targeting supersymmetric models and leptoquark signatures. Observations using one of these selections are able to exclude, at 95% confidence level, singly produced smuons with masses up to 640 GeV in a model in which the only other light sparticle is a neutralino when the R-parity-violating coupling lambda(23)(1)' is close to unity. Observations using the other selection exclude scalar leptoquarks with masses below 1880 GeV when g(1R)(eu) = g(1R)(mu c) = 1, at 95% confidence level. The limit on the coupling reduces to g(1R)(eu) = g(1R)(mu c) = 0.46 for a mass of 1420 GeV
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