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In this work we study 35 stellar clusters in the Small Magellanic Cloud (SMC) in order to provide their mean metallicities and ages. We also provide mean metallicities of the fields surrounding the clusters. We used Str\"omgren photometry obtained with the 4.1 m SOAR telescope and take advantage of $(b - y)$ and $m1$ colors for which there is a metallicity calibration presented in the literature. The spatial metallicity and age distributions of clusters across the SMC are investigated using the results obtained by Str\"omgren photometry. We confirm earlier observations that younger, more metal-rich star clusters are concentrated in the central regions of the galaxy, while older, more metal-poor clusters are located farther from the SMC center. We construct the age-metallicity relation for the studied clusters and find good agreement with theoretical models of chemical enrichment, and with other literature age and metallicity values for those clusters. We also provide the mean metallicities for old and young populations of the field stars surrounding the clusters, and find the latter to be in good agreement with recent studies of the SMC Cepheid population. Finally, the Str\"omgren photometry obtained for this study is made publicly available., Comment: 22 pages, 12 figures, 6 tables, Published in A&A

We present time-series photometry of 21 nearby Type II Cepheids in the near-infrared J, H and Ks passbands. We use this photometry, together with the Third Gaia Early Data Release parallaxes, to determine for the first time period-luminosity relations (PLRs) for Type II Cepheids from field representatives of these old pulsating stars in the near-infrared regime. We found PLRs to be very narrow for BL Herculis stars, which makes them candidates for precision distance indicators. We then use archival photometry and the most accurate distance obtained from eclipsing binaries to recalibrate PLRs for Type II Cepheids in the Large Magellanic Cloud (LMC). Slopes of our PLRs in the Milky Way and in the LMC differ by slightly more than 2{\sigma} and are in a good agreement with previous studies of the LMC, Galactic Bulge and Galactic Globular Clusters Type II Cepheids samples. We use PLRs of Milky Way Type II Cepheids to measure the distance to the LMC and we obtain a distance modulus of 18.540$\pm$0.026(stat.)$\pm$0.034(syst.)mag in the WJKs Wesenheit index. We also investigate the metallicity effect within our Milky Way sample and we find rather significant value of about -0.2mag/dex in each band meaning that more metal-rich Type II Cepheids are intrinsically brighter than their more metal-poor counterparts, in agreement with the value obtained from Type II Cepheids in Galactic Globular Clusters. The main source of systematic error on our Milky Way PLRs calibration and the LMC distance is the current uncertainty of the Gaia parallax zero point., Comment: Accepted for ApJ

European Research Council (ERC) 695099 National Science Centre, Poland UMO-2017/26/A/ST9/00446 UMO-2018/31/G/ST9/03050 Ministry of Science and Higher Education, Poland IdP II 2015 0002 64 DIR/WK/2018/09 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT PIA/BASAL AFB-170002 Millenium Institute of Astrophysics (MAS) of the Iniciativa Cientifica Milenio del Ministerio de Economia, Fomento y Turismo de Chile IC120009 Polish National Science Centre 2016/21/N/ST9/03310 German Research Foundation (DFG) EXC-2094-390783311 National Science Center, Poland, Sonata BIS project 2018/30/E/ST9/00598 NTT telescopes in La Silla 074.D-0318 074.D-0505 082.D-0499 083.D-0549 084.D-0591 086.D-0078 091,D-0469(A) 0100.D-0339(A) 098.D-0263(A,B) 097.D-0400(A) 0102.D-0469(B) 0102.D-0590(B)

We use photometric and spectroscopic observations of the eclipsing binary E32 in the globular cluster 47 Tuc to derive the masses, radii, and luminosities of the component stars. The system has an orbital period of 40.9 d, a markedly eccentric orbit with e = 0.24, and is shown to be a member of or a recent escaper from the cluster. We obtain Mp = 0.862 ± 0.005 M, Rp = 1.183 ± 0.003 R, Lp = 1.65 ± 0.05 L for the primary and Ms = 0.827 ± 0.005 M, Rs = 1.004 ± 0.004 R, Ls = 1.14 ± 0.04 L for the secondary. Based on these data and on an earlier analysis of the binary V69 in 47 Tuc, we measure the distance to the cluster from the distance moduli of the component stars, and, independently, from a colour – surface brightness calibration. We obtain 4.55 ± 0.03 and 4.50 ± 0.07 kpc, respectively – values compatible within 1 σ with recent estimates based on Gaia DR2 parallaxes. By comparing the M–R diagram of the two binaries and the colour–magnitude diagram of 47 Tuc to Dartmouth model isochrones we estimate the age of the cluster to be 12.0 ± 0.5 Gyr, and the helium abundance of the cluster to be Y ≈ 0.25., Erratum published in volume 494, issue 1, pages 846-9, May 2020. DOI: 10.1093/mnras/staa686

We introduce and present results from the COCOA (Cluster simulatiOn Comparison with ObservAtions) code that has been developed to create idealized mock photometric observations using results from numerical simulations of star cluster evolution. COCOA is able to present the output of realistic numerical simulations of star clusters carried out using Monte Carlo or \textit{N}-body codes in a way that is useful for direct comparison with photometric observations. In this paper, we describe the COCOA code and demonstrate its different applications by utilizing globular cluster (GC) models simulated with the MOCCA (MOnte Carlo Cluster simulAtor) code. COCOA is used to synthetically observe these different GC models with optical telescopes, perform PSF photometry and subsequently produce observed colour magnitude diagrams. We also use COCOA to compare the results from synthetic observations of a cluster model that has the same age and metallicity as the Galactic GC NGC 2808 with observations of the same cluster carried out with a 2.2 meter optical telescope. We find that COCOA can effectively simulate realistic observations and recover photometric data. COCOA has numerous scientific applications that maybe be helpful for both theoreticians and observers that work on star clusters. Plans for further improving and developing the code are also discussed in this paper., 18 pages, 12 figures, accepted for publication in MNRAS. Revised manuscript has a new title, better quality figures and many other improvements. COCOA can be downloaded from: https://github.com/abs2k12/COCOA (comments are welcome)

We analyze a 162 ks HETG Chandra observation of the O7.5 III(n)((f)) star xi Per, together with contemporaneous H alpha observations. The X-ray spectrum of this star is similar to other single O stars, and not pathological in any way. Its UV wind lines are known to display cyclical time variability, with a period of 2.086 days, which is thought to be associated with co-rotating interaction regions (CIRs). We examine the Chandra and H alpha data for variability on this time scale. We find that the X-rays vary by about 15% over the course of the observations and that this variability is out of phase with variable absorption on the blue wing of the H alpha profiles (assumed to be a surrogate for the UV absorption associated with CIRs). While not conclusive, both sets of data are consistent with models where the CIRs are either a source of X-rays or modulate them., Accepted by MNRAS. 9 pages, 9 figures

Scientific workflow systems are designed to compose and execute either a series of computational or data manipulation steps, or workflows in a scientific application. They are usually a part of a larger eScience environment. The usage of workflow systems, however very beneficial, is mostly not irrelevant for scientists. There are many requirements for additional functionalities around scientific workflows systems that need to be taken into account, like the ability of sharing workflows, provision of the user-friendly GUI tools for automation of some tasks or submission to distributed computing infrastructures, etc. In this paper we present tools developed in response to the requirements of three different scientific communities. These tools simplify and empower their work with the Kepler scientific workflow system. The usage of such tools and services is presented on Nanotechnology, Astronomy and Fusion scenarios examples.

We introduce and present preliminary results from COCOA (Cluster simulatiOn Comparison with ObservAtions) code for a star cluster after 12 Gyrs of evolution simulated using the MOCCA code. The COCOA code is being developed to quickly compare results of numerical simulations of star clusters with observational data. We use COCOA to obtain parameters of the projected cluster model. For comparison, a FITS file of the projected cluster was provided to observers so that they could use their observational methods and techniques to obtain cluster parameters. The results show that the similarity of cluster parameters obtained through numerical simulations and observations depends significantly on the quality of observational data and photometric accuracy., Comment: 2 pages, 1 figure, Conference proceedings for poster presented at IAUS 312

With the recent advent of new-generation observational instruments, astronomy enters the 'data flood' era. The growing scale and complication of astronomical activities forces scientists to look for new technologies and tools. A workflow environment seems to be a good solution for many new requirements, but before scientists can use it commonly, it has to be suitably adapted and simplified. We have created ai¾źuniversal environment based on the Kepler workflow system that empowers scientists with such capabilities. It offers three access levels depending on the needs and skills of the user: 1 Kepler desktop application extended by our library of domain specific modules and workflows, 2 web application used to share workflows, 3 cloud service with on-demand Virtual Research Environment consisting of a set of tools and applications useful for astronomers. Our environment includes also interoperability mechanisms with the Virtual Observatory and other domain-specific tools and services.

et al., The Kepler scientific workflow system enables creation, execution and sharing of workflows across a broad range of scientific and engineering disciplines while also facilitating remote and distributed execution of workflows. In this paper, we present and compare different approaches to distributed execution of workflows using the Kepler environment, including a distributed data-parallel framework using Hadoop and Stratosphere, and Cloud and Grid execution using Serpens, Nimrod/K and Globus actors. We also present real-life applications in computational chemistry, bioinformatics and computational physics to demonstrate the usage of different distributed computing capabilities of Kepler in executable workflows. We further analyze the differences of each approach and provide a guidance for their applications., The research leading to these results has received funding from different projects and funding schema, including: the European Community’s Seventh Framework Programme under grant agreement RI-261323 (EGI-InsPIRE), the European Communities under the contracts of Association between EURATOM and CEA, IPPLM, carried out within the framework of the Task Force on Integrated Tokamak Modeling of the EFDA, the Polish project PLGrid Plus under the contract POIG 02.03.00-00-096/10, NSF ABI Award DBI-1062565 for bioKepler, partial financial support from the Spanish Ministerio de Economia y Competitividad AYA 2010-21766-C03-01 and Consolider Ingenio 2010 CSD2010-00064 projects, and from the Juan de la Cierva programme.

Quasars, as the most luminous persistent sources in the Universe, have broad applications for cosmological studies. In particular, they can be employed to directly measure the expansion history of the Universe, similarly to SNe Ia. The advantage of quasars is that they are numerous, cover a broad range of redshifts, up to $z = 7$, and do not show significant evolution of metallicity with redshift. The idea is based on the relation between the time delay of an emission line and the continuum, and the absolute monochromatic luminosity of a quasar. For intermediate redshift quasars, the suitable line is Mg II. Between December 2012 and March 2014, we performed five spectroscopic observations of the QSO CTS C30.10 ($z = 0.900$) using the South African Large Telesope (SALT), supplemented with photometric monitoring, with the aim of determining the variability of the line shape, changes in the total line intensity and in the continuum. We show that the method is very promising., Comment: Proceedings of IAU Symposium 308 "The Zeldovich Universe: Genesis and Growth of the Cosmic Web", 23-28 June 2014, Tallinn, Estonia

The growing scale and complexity of cataloguing and analyzing of astronomical data forces scientists to look for a new technologies and tools. The workflow environments seem best suited for their needs, but in practice they proved to be too complicated for most users. Before such environments are used commonly, they have to be properly adapted for specific needs of the scientific domain. To that end, we have created a universal solution based on the Kepler workflow environment. It consists of a library of domain modules, ready-to-use workflows and additional services for sharing and running workflows. There are three access levels depending on the needs and skills of the user: 1) desktop application, 2) web application 3) on-demand Virtual Research Environment. The whole solution is set up in the context of Polish Grid Infrastructure, enabling access to its resources. For flexibility it includes interoperability mechanisms with the domain specific applications and services (including astronomical Virtual Observatory) as well as with other domain grid services.

The surface brightness -- colour relation (SBCR) is a basic tool in establishing precise and accurate distances within the Local Group. Detached eclipsing binary stars with accurately determined radii and trigonometric parallaxes allow for a calibration of the SBCRs with unprecedented accuracy. We analysed four nearby eclipsing binary stars containing late F-type main sequence components: AL Ari, AL Dor, FM Leo and BN Scl. We determined very precise spectroscopic orbits and combined them with high precision ground- and space-based photometry. We derived the astrophysical parameters of their components with mean errors of 0.1% for mass and 0.4% for radius. We combined those four systems with another 24 nearby eclipsing binaries with accurately known radii from the literature for which $Gaia$ EDR3 parallaxes are available, in order to derive the SBCRs. The resulting SBCRs cover stellar spectral types from B9 V to G7 V. For calibrations we used Johnson optical $B$ and $V$, $Gaia$ $G_{\rm BP}$ and $G$ and 2MASS $JHK$ bands. The most precise relations are calibrated using the infrared $K$ band and allow to predict angular diameters of A-, F-, and G-type dwarf and subgiant stars with a precision of 1%., Accepted for publication in Astronomy & Astrophysics, 17 pages