The variability processing and analysis of the Gaia mission

We present the variability processing and analysis that is foreseen for the Gaia mission within Coordination Unit 7 (CU7) of the Gaia Data Processing and Analysis Consortium (DPAC). A top level description of the tasks is given.Comment: 4 pages, 1 figure. To be published in the proceedings of the GREAT-ITN conference "The Milky Way Unravelled by Gaia: GREAT Science from the Gaia Data Releases", 1-5 December 2014, University of Barcelona, Spain, EAS Publications Series, eds Nicholas Walton, Francesca Figueras, and Caroline Soubira

The usefulness of contrast-enhanced sonography in the differential diagnostic of adrenal tumors

Introduction: The occurrence of gland tumors causes significant clinical problem. Non hormone-secreting tumors provide the most complicated diagnostic difficulties. The application of contrast-enhanced sonography could improve the vessels visualization and point out characteristic features of benign and malignant changes. The authors believe that this new method make possible the differential adrenal tumor diagnostic process more precise and increase the specificity of ultrasonography in the recognition of benign and malignant tumors. The aim of this study was to define the usefulness of contrasting agent Levovist in differential diagnostics of adrenal tumors and its influence on sensitivity and specificity of ultrasound examination and to establish patients qualification criteria for surgical procedures. Material and methods: Ultrasound examinations were made with the use of digital devise by GE Voluson 740, probe 4–6 mHz with Doppler options and volumetric probe 3D according to the following protocol: 26 patients with recognized adrenal tumor were qualified for the examination. Patients in the first stage of tumor vascularization had Doppler examination with color (CD) and power Doppler (PD). Three-dimensional ultrasonography was used to improve visualization of vascularization. In the final phase of the examination the patients were administrated of Levovist in the recommended by the producer dose: 2,5 g in the concentration of 400 mg/l.Results: 26 cases of adrenal gland tumours were subjected to analysis. In standard ultrasonographic examination focal changes in 25 patients were hipoechogenic focuses and in one case the focus was hyperechogenic. Heterogeneity of focuses was observed in 16 cases. In Doppler examination with color (CD) and power Doppler (PD) vascular blood flow was revealed within 12. After using contrasting agent Levovist vascular blood flow was achieved in 4 additional cases, which constituted 61%. Conclusions: 1. 3D ultrasound could be useful in cases of big adrenal tumors - over 3 cm diameter after application of ultrasound contrast agents. 2. The use of Levovist in Doppler examination improves the visualization of tumor vascularization. However, it is impossible to differentiate benign from malignant tumors unequivocally.Wstęp: Guzy nadnerczy ze względu na ich częstość są istotnym problemem klinicznym. Największych trudności diagnostycznych przysparzają guzy nieczynne hormonalnie. Zastosowanie środków kontrastujących może poprawić wizualizcję naczyń i tym samym wyróżnić cechy charakterystyczne dla guzów łagodnych i złośliwych. W nowej metodzie autorzy niniejszej pracy upatrywali możliwość dokładniejszej diagnostyki guzów nadnerczy oraz poprawę swoistości badania ultrasonograficznego w rozpoznawaniu zmian łagodnych i złośliwych. Celem prezentowanej pracy było określenie przydatności środka kontrastującego Levovist w diagnostyce różnicowej guzów nadnerczy, ocena jego wpływu na czułość i swoistość badania USG oraz wyznaczenie kryteriów pozwalających na kwalifikację chorych do zabiegu operacyjnego. Materiał i metody: Badania ultrasonograficzne wykonano aparatem cyfrowym firmy GE Voluson 740, sondą szerokopasmową 4–6 mHz z opcjami doplerowskimi i sondą wolumetryczną 3D według następującego protokołu: 1. klasyczne badanie ultrasonograficzne; 2. badanie z opcjami doplerowskimi: color Doppler i Power Doppler; 3. badanie sondą trójwymiarową 3D; 4. badanie z użyciem środka kontrastującego Levovist. W końcowej fazie badania podawano dożylnie Levovist w dawce zalecanej przez producenta 2,5 g w stężeniu 400 mg/l.Wyniki: Analizie poddano 26 przypadków guzów nadnerczy. W standardowym badaniu ultrasonograficznym zmiany ogniskowe u 25 pacjentów były ogniskami hipoechogennymi, w 1 przypadku ognisko było hiperechogenne. Niejednorodność ognisk obserwowano w 16 przypadkach. W badaniu doplerowskim kodowanym kolorem i doplerem mocy uwidoczniono przepływ naczyniowy w obrębie 12 guzów (46%). Po podaniu środka kontrastującego Levovist uzyskano przepływ naczyniowy w 4 dodatkowych przypadkach, co stanowiło 61%. Wnioski: 1. Zastosowanie ultrasonograficznych środków kontrastujących wspomagane obrazowaniem naczyniowym 3D może przynieść rezultaty w wybranych przypadkach dużych guzów nadnerczy o średnicy powyżej 3,0 cm. 2. Badanie doplerowskie z użyciem Levovistu poprawia wizualizację naczyń w guzie nowotworowym, nie pozwala jednak na jednoznaczne różnicowanie zmian złośliwych i łagodnych

Circulating Oxidized Low-Density Lipoproteins and Antibodies against Oxidized Low-Density Lipoproteins as Potential Biomarkers of Colorectal Cancer

Introduction. The aim of the study was evaluation of the diagnostic utility of serum oxidized low-density lipoproteins (oxLDL), antibodies against oxLDLs (o-LAB), and CEA as risk markers of colorectal cancer (CRC). Material and Methods. The serum levels of study factors were measured in 73 patients with CRC and in 35 healthy controls who were gender- and BMI-matched to the study group. Concentrations of oxLDL, o-LAB, and CEA were detected in ELISA tests. Serum lipids, lipoproteins, and glucose levels were also coestimated. Results. Age and o-LAB were significant factors of CRC presence, but results of logistic regression analysis showed that both were weak predictors of CRC risk. Concentration of o-LAB was significantly higher in colon cancer than in rectal cancer, especially when the cancer was located in the right section of colon. Serum CEA levels were significantly elevated in the advanced stage of disease, primary tumor progression, angiolymphatic invasion, and presence of distant metastasis. Conclusions. Obtained results have demonstrated that oxLDL and o-LAB were not satisfactory risk markers of CRC. Although significant relation between o-LAB level and CRC is observed, it may be rather the result of individual differences in the host immune responses against cancer

A comparative study of four significance measures for periodicity detection in astronomical surveys

We study the problem of periodicity detection in massive data sets of photometric or radial velocity time series, as presented by ESA's Gaia mission. Periodicity detection hinges on the estimation of the false alarm probability of the extremum of the periodogram of the time series. We consider the problem of its estimation with two main issues in mind. First, for a given number of observations and signal-to-noise ratio, the rate of correct periodicity detections should be constant for all realized cadences of observations regardless of the observational time patterns, in order to avoid sky biases that are difficult to assess. Secondly, the computational loads should be kept feasible even for millions of time series. Using the Gaia case, we compare the FM method of Paltani and Schwarzenberg-Czerny, the Baluev method and the GEV method of Süveges, as well as a method for the direct estimation of a threshold. Three methods involve some unknown parameters, which are obtained by fitting a regression-type predictive model using easily obtainable covariates derived from observational time series. We conclude that the GEV and the Baluev methods both provide good solutions to the issues posed by a large-scale processing. The first of these yields the best scientific quality at the price of some moderately costly pre-processing. When this pre-processing is impossible for some reason (e.g. the computational costs are prohibitive or good regression models cannot be constructed), the Baluev method provides a computationally inexpensive alternative with slight biases in regions where time samplings exhibit strong aliase

Pulsating star research and the Gaia revolution

In this article we present an overview of the ESA Gaia mission and of the unprecedented impact that Gaia will have on the field of variable star research. We summarise the contents and impact of the first Gaia data release on the description of variability phenomena, with particular emphasis on pulsating star research. The Tycho-Gaia astrometric solution, although limited to 2.1 million stars, has been used in many studies related to pulsating stars. Furthermore a set of 3,194 Cepheids and RR Lyrae stars with their times series have been released. Finally we present the plans for the ongoing study of variable phenomena with Gaia and highlight some of the possible impacts of the second data release on variable, and specifically, pulsating stars.Comment: 12 pages, 4 figures, proceedings for the 22nd Los Alamos Stellar Pulsation Conference Series Meeting "Wide field variability surveys: a 21st-century perspective", held in San Pedro de Atacama, Chile, Nov. 28 - Dec. 2, 201

The Detection of Transiting Exoplanets by Gaia

Context: The space telescope Gaia is dedicated mainly to performing high-precision astrometry, but also spectroscopy and epoch photometry which can be used to study various types of photometric variability. One such variability type is exoplanetary transits. The photometric data accumulated so far have finally matured enough to allow the detection of some exoplanets. Aims: In order to fully exploit the scientific potential of Gaia, we search its photometric data for the signatures of exoplanetary transits. Methods: The search relies on a version of the Box-Least-Square (BLS) method, applied to a set of stars prioritized by machine-learning classification methods. An independent photometric validation was obtained using the public full-frame images of TESS. In order to validate the first two candidates, radial-velocity follow-up observations were performed using the spectrograph PEPSI of the Large Binocular Telescope (LBT). Results: The radial-velocity measurements confirm that two of the candidates are indeed hot Jupiters. Thus, they are the first exoplanets detected by Gaia - Gaia-1b and Gaia-2b. Conclusions: Gaia-1b and Gaia-2b demonstrate that the approach presented in this paper is indeed effective. This approach will be used to assemble a set of additional exoplanet candidates, to be released in Gaia third data release, ensuring better fulfillment of the exoplanet detection potential of Gaia.Comment: Accepted for publication in A&A, 8 pages, 8 figure

Gaia Data Release 3: The first Gaia catalogue of variable AGN

One of the novelties of the Gaia-DR3 with respect to the previous data releases is the publication of the multiband light curves of about 1 million AGN. The goal of this work was the creation of a catalogue of variable AGN, whose selection was based on Gaia data only. We first present the implementation of the methods to estimate the variability parameters into a specific object study module for AGN. Then we describe the selection procedure that led to the definition of the high-purity variable AGN sample and analyse the properties of the selected sources. We started from a sample of millions of sources, which were identified as AGN candidates by 11 different classifiers based on variability processing. Because the focus was on the variability properties, we first defined some pre-requisites in terms of number of data points and mandatory variability parameters. Then a series of filters was applied using only Gaia data and the Gaia Celestial Reference Frame 3 (Gaia-CRF3) sample as a reference.The resulting Gaia AGN variable sample, named GLEAN, contains about 872000 objects, more than 21000 of which are new identifications. We checked the presence of contaminants by cross-matching the selected sources with a variety of galaxies and stellar catalogues. The completeness of GLEAN with respect to the variable AGN in the last Sloan Digital Sky Survey quasar catalogue is about 47%, while that based on the variable AGN of the Gaia-CRF3 sample is around 51%. From both a comparison with other AGN catalogues and an investigation of possible contaminants, we conclude that purity can be expected to be above 95%. Multiwavelength properties of these sources are investigated. In particular, we estimate that about 4% of them are radio-loud. We finally explore the possibility to evaluate the time lags between the flux variations of the multiple images of strongly lensed quasars, and show one case.Comment: 19 pages, 31 figures, 2 table. This paper is part of Gaia Data Release 3 (DR3). In press for A&