TY - JOUR A1 - Sander, Andreas Alexander Christoph A1 - Fürst, F. A1 - Kretschmar, P. A1 - Oskinova, Lidia M. A1 - Todt, Helge Tobias A1 - Hainich, Rainer A1 - Shenar, Tomer A1 - Hamann, Wolf-Rainer T1 - Coupling hydrodynamics with comoving frame radiative transfer BT - Stellar wind stratification in the high-mass X-ray binary Vela X-1 JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. To gain a realistic picture of the donor star in Vela X-1, we constructed a hydrodynamically consistent atmosphere model describing the wind stratification while properly reproducing the observed donor spectrum. To investigate how X-ray illumination affects the stellar wind, we calculated additional models for different X-ray luminosity regimes. Methods. We used the recently updated version of the Potsdam Wolf-Rayet code to consistently solve the hydrodynamic equation together with the statistical equations and the radiative transfer. Results. The wind flow in Vela X-1 is driven by ions from various elements, with Fe III and S III leading in the outer wind. The model-predicted mass-loss rate is in line with earlier empirical studies. The mass-loss rate is almost unaffected by the presence of the accreting NS in the wind. The terminal wind velocity is confirmed at u(infinity) approximate to 600 km s(-1). On the other hand, the wind velocity in the inner region where the NS is located is only approximate to 100 km s(-1), which is not expected on the basis of a standard beta-velocity law. In models with an enhanced level of X-rays, the velocity field in the outer wind can be altered. If the X-ray flux is too high, the acceleration breaks down because the ionization increases. Conclusions. Accounting for radiation hydrodynamics, our Vela X-1 donor atmosphere model reveals a low wind speed at the NS location, and it provides quantitative information on wind driving in this important HMXB. KW - stars: mass-loss KW - stars: winds, outflows KW - stars: early-type KW - stars: atmospheres KW - stars: massive KW - X-rays: binaries Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201731575 SN - 1432-0746 VL - 610 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Sander, Andreas Alexander Christoph A1 - Hamann, Wolf-Rainer A1 - Todt, Helge Tobias A1 - Hainich, Rainer A1 - Shenar, Tomer A1 - Ramachandran, Varsha A1 - Oskinova, Lidia M. T1 - The Galactic WC and WO stars BT - The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors JF - Astronomy and astrophysics : an international weekly journal N2 - Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. Thus, the determination of the WC star parameters is of major importance for several astrophysical fields. With Gaia DR2, for the first time parallaxes for a large sample of Galactic WC stars are available, removing major uncertainties inherent to earlier studies. In this work, we re-examine a previously studied sample of WC stars to derive key properties of the Galactic WC population. All quantities depending on the distance are updated, while the underlying spectral analyzes remain untouched. Contrasting earlier assumptions, our study yields that WC stars of the same subtype can significantly vary in absolute magnitude. With Gaia DR2, the picture of the Galactic WC population becomes more complex: We obtain luminosities ranging from log L/L-circle dot = 4.9-6.0 with one outlier (WR 119) having log L/L-circle dot = 4.7. This indicates that the WC stars are likely formed from a broader initial mass range than previously assumed. We obtain mass-loss rates ranging between log(M) over dot = -5.1 and -4.1, with (M) over dot proportional to L-0.68 and a linear scaling of the modified wind momentum with luminosity. We discuss the implications for stellar evolution, including unsolved issues regarding the need of envelope inflation to address the WR radius problem, and the open questions in regard to the connection of WR stars with Gamma-ray bursts. WC and WO stars are progenitors of massive black holes, collapsing either silently or in a supernova that most-likely has to be preceded by a WO stage. KW - stars: evolution KW - stars: mass-loss KW - stars: Wolf-Rayet KW - stars: massive KW - stars: distances KW - Galaxy: stellar content Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201833712 SN - 1432-0746 VL - 621 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Hainich, Rainer A1 - Ramachandran, Varsha A1 - Shenar, Tomer A1 - Sander, Andreas Alexander Christoph A1 - Todt, Helge Tobias A1 - Gruner, David A1 - Oskinova, Lidia M. A1 - Hamann, Wolf-Rainer T1 - PoWR grids of non-LTE model atmospheres for OB-type stars of various metallicities JF - Astronomy and astrophysics : an international weekly journal N2 - The study of massive stars in different metallicity environments is a central topic of current stellar research. The spectral analysis of massive stars requires adequate model atmospheres. The computation of such models is difficult and time-consuming. Therefore, spectral analyses are greatly facilitated if they can refer to existing grids of models. Here we provide grids of model atmospheres for OB-type stars at metallicities corresponding to the Small and Large Magellanic Clouds, as well as to solar metallicity. In total, the grids comprise 785 individual models. The models were calculated using the state-of-the-art Potsdam Wolf-Rayet (PoWR) model atmosphere code. The parameter domain of the grids was set up using stellar evolution tracks. For all these models, we provide normalized and flux-calibrated spectra, spectral energy distributions, feedback parameters such as ionizing photons, Zanstra temperatures, and photometric magnitudes. The atmospheric structures (the density and temperature stratification) are available as well. All these data are publicly accessible through the PoWR website. KW - stars: massive KW - stars: early-type KW - stars: atmospheres KW - stars: winds KW - outflows KW - stars: mass-loss KW - radiative transfer Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201833787 SN - 1432-0746 VL - 621 PB - EDP Sciences CY - Les Ulis ER - TY - RPRT A1 - Siedler, Thomas A1 - Anger, Silke A1 - Christoph, Bernhard A1 - Galkiewicz, Agata Danuta A1 - Margaryan, Shushanik A1 - Peter, Frauke A1 - Sandner, Malte T1 - War, international spillovers, and adolescents BT - evidence from Russia’s invasion of Ukraine in 2022 T2 - Discussion paper series N2 - Using novel longitudinal data, this paper studies the short- and medium-term effects of Russia's invasion of Ukraine on February 24, 2022 on social trust of adolescents in Germany. Comparing adolescents who responded to our survey shortly before the start of the war with those who responded shortly after the conflict began and applying difference-in-differences (DiD) models over time, we find a significant decline in the outcome after the war started. These findings provide new evidence on how armed conflicts influence social trust and well-being among young people in a country not directly involved in the war. KW - war KW - trust KW - social capital KW - Russia’s invasion of Ukraine Y1 - 2024 UR - https://www.iza.org/publications/dp/16921/war-international-spillovers-and-adolescents-evidence-from-russias-invasion-of-ukraine-in-2022 SN - 2365-9793 N1 - published in: Journal of Economic Behavior & Organization, 2024, 224, 181-193 VL - No. 16921 PB - IZA CY - Bonn ER - TY - RPRT A1 - Brodeur, Abel A1 - Mikola, Derek A1 - Cook, Nikolai A1 - Brailey, Thomas A1 - Briggs, Ryan A1 - Gendre, Alexandra de A1 - Dupraz, Yannick A1 - Fiala, Lenka A1 - Gabani, Jacopo A1 - Gauriot, Romain A1 - Haddad, Joanne A1 - Lima, Goncalo A1 - Ankel-Peters, Jörg A1 - Dreber, Anna A1 - Campbell, Douglas A1 - Kattan, Lamis A1 - Fages, Diego Marino A1 - Mierisch, Fabian A1 - Sun, Pu A1 - Wright, Taylor A1 - Connolly, Marie A1 - Hoces de la Guardia, Fernando A1 - Johannesson, Magnus A1 - Miguel, Edward A1 - Vilhuber, Lars A1 - Abarca, Alejandro A1 - Acharya, Mahesh A1 - Adjisse, Sossou Simplice A1 - Akhtar, Ahwaz A1 - Lizardi, Eduardo Alberto Ramirez A1 - Albrecht, Sabina A1 - Andersen, Synve Nygaard A1 - Andlib, Zubaria A1 - Arrora, Falak A1 - Ash, Thomas A1 - Bacher, Etienne A1 - Bachler, Sebastian A1 - Bacon, Félix A1 - Bagues, Manuel A1 - Balogh, Timea A1 - Batmanov, Alisher A1 - Barschkett, Mara A1 - Basdil, B. Kaan A1 - Dower, Jaromneda A1 - Castek, Ondrej A1 - Caviglia-Harris, Jill A1 - Strand, Gabriella Chauca A1 - Chen, Shi A1 - Chzhen, Asya A1 - Chung, Jong A1 - Collins, Jason A1 - Coppock, Alexander A1 - Cordeau, Hugo A1 - Couillard, Ben A1 - Crechet, Jonathan A1 - Crippa, Lorenzo A1 - Cui, Jeanne A1 - Czymara, Christian A1 - Daarstad, Haley A1 - Dao, Danh Chi A1 - Dao, Dong A1 - Schmandt, Marco David A1 - Linde, Astrid de A1 - Melo, Lucas De A1 - Deer, Lachlan A1 - Vera, Micole De A1 - Dimitrova, Velichka A1 - Dollbaum, Jan Fabian A1 - Dollbaum, Jan Matti A1 - Donnelly, Michael A1 - Huynh, Luu Duc Toan A1 - Dumbalska, Tsvetomira A1 - Duncan, Jamie A1 - Duong, Kiet Tuan A1 - Duprey, Thibaut A1 - Dworschak, Christoph A1 - Ellingsrud, Sigmund A1 - Elminejad, Ali A1 - Eissa, Yasmine A1 - Erhart, Andrea A1 - Etingin-Frati, Giulian A1 - Fatemi-Pour, Elaheh A1 - Federice, Alexa A1 - Feld, Jan A1 - Fenig, Guidon A1 - Firouzjaeiangalougah, Mojtaba A1 - Fleisje, Erlend A1 - Fortier-Chouinard, Alexandre A1 - Engel, Julia Francesca A1 - Fries, Tilman A1 - Fortier, Reid A1 - Fréchet, Nadjim A1 - Galipeau, Thomas A1 - Gallegos, Sebastián A1 - Gangji, Areez A1 - Gao, Xiaoying A1 - Garnache, Cloé A1 - Gáspár, Attila A1 - Gavrilova, Evelina A1 - Ghosh, Arijit A1 - Gibney, Garreth A1 - Gibson, Grant A1 - Godager, Geir A1 - Goff, Leonard A1 - Gong, Da A1 - González, Javier A1 - Gretton, Jeremy A1 - Griffa, Cristina A1 - Grigoryeva, Idaliya A1 - Grtting, Maja A1 - Guntermann, Eric A1 - Guo, Jiaqi A1 - Gugushvili, Alexi A1 - Habibnia, Hooman A1 - Häffner, Sonja A1 - Hall, Jonathan D. A1 - Hammar, Olle A1 - Kordt, Amund Hanson A1 - Hashimoto, Barry A1 - Hartley, Jonathan S. A1 - Hausladen, Carina I. A1 - Havránek, Tomáš A1 - Hazen, Jacob A1 - He, Harry A1 - Hepplewhite, Matthew A1 - Herrera-Rodriguez, Mario A1 - Heuer, Felix A1 - Heyes, Anthony A1 - Ho, Anson T. Y. A1 - Holmes, Jonathan A1 - Holzknecht, Armando A1 - Hsu, Yu-Hsiang Dexter A1 - Hu, Shiang-Hung A1 - Huang, Yu-Shiuan A1 - Huebener, Mathias A1 - Huber, Christoph A1 - Huynh, Kim P. A1 - Irsova, Zuzana A1 - Isler, Ozan A1 - Jakobsson, Niklas A1 - Frith, Michael James A1 - Jananji, Raphaël A1 - Jayalath, Tharaka A. A1 - Jetter, Michael A1 - John, Jenny A1 - Forshaw, Rachel Joy A1 - Juan, Felipe A1 - Kadriu, Valon A1 - Karim, Sunny A1 - Kelly, Edmund A1 - Dang, Duy Khanh Hoang A1 - Khushboo, Tazia A1 - Kim, Jin A1 - Kjellsson, Gustav A1 - Kjelsrud, Anders A1 - Kotsadam, Andreas A1 - Korpershoek, Jori A1 - Krashinsky, Lewis A1 - Kundu, Suranjana A1 - Kustov, Alexander A1 - Lalayev, Nurlan A1 - Langlois, Audrée A1 - Laufer, Jill A1 - Lee-Whiting, Blake A1 - Leibing, Andreas A1 - Lenz, Gabriel A1 - Levin, Joel A1 - Li, Peng A1 - Li, Tongzhe A1 - Lin, Yuchen A1 - Listo, Ariel A1 - Liu, Dan A1 - Lu, Xuewen A1 - Lukmanova, Elvina A1 - Luscombe, Alex A1 - Lusher, Lester R. A1 - Lyu, Ke A1 - Ma, Hai A1 - Mäder, Nicolas A1 - Makate, Clifton A1 - Malmberg, Alice A1 - Maitra, Adit A1 - Mandas, Marco A1 - Marcus, Jan A1 - Margaryan, Shushanik A1 - Márk, Lili A1 - Martignano, Andres A1 - Marsh, Abigail A1 - Masetto, Isabella A1 - McCanny, Anthony A1 - McManus, Emma A1 - McWay, Ryan A1 - Metson, Lennard A1 - Kinge, Jonas Minet A1 - Mishra, Sumit A1 - Mohnen, Myra A1 - Möller, Jakob A1 - Montambeault, Rosalie A1 - Montpetit, Sébastien A1 - Morin, Louis-Philippe A1 - Morris, Todd A1 - Moser, Scott A1 - Motoki, Fabio A1 - Muehlenbachs, Lucija A1 - Musulan, Andreea A1 - Musumeci, Marco A1 - Nabin, Munirul A1 - Nchare, Karim A1 - Neubauer, Florian A1 - Nguyen, Quan M. P. A1 - Nguyen, Tuan A1 - Nguyen-Tien, Viet A1 - Niazi, Ali A1 - Nikolaishvili, Giorgi A1 - Nordstrom, Ardyn A1 - Nü, Patrick A1 - Odermatt, Angela A1 - Olson, Matt A1 - ien, Henning A1 - Ölkers, Tim A1 - Vert, Miquel Oliver i. A1 - Oral, Emre A1 - Oswald, Christian A1 - Ousman, Ali A1 - Özak, Ömer A1 - Pandey, Shubham A1 - Pavlov, Alexandre A1 - Pelli, Martino A1 - Penheiro, Romeo A1 - Park, RyuGyung A1 - Martel, Eva Pérez A1 - Petrovičová, Tereza A1 - Phan, Linh A1 - Prettyman, Alexa A1 - Procházka, Jakub A1 - Putri, Aqila A1 - Quandt, Julian A1 - Qiu, Kangyu A1 - Nguyen, Loan Quynh Thi A1 - Rahman, Andaleeb A1 - Rea, Carson H. A1 - Reiremo, Adam A1 - Renée, Laëtitia A1 - Richardson, Joseph A1 - Rivers, Nicholas A1 - Rodrigues, Bruno A1 - Roelofs, William A1 - Roemer, Tobias A1 - Rogeberg, Ole A1 - Rose, Julian A1 - Roskos-Ewoldsen, Andrew A1 - Rosmer, Paul A1 - Sabada, Barbara A1 - Saberian, Soodeh A1 - Salamanca, Nicolas A1 - Sator, Georg A1 - Sawyer, Antoine A1 - Scates, Daniel A1 - Schlüter, Elmar A1 - Sells, Cameron A1 - Sen, Sharmi A1 - Sethi, Ritika A1 - Shcherbiak, Anna A1 - Sogaolu, Moyosore A1 - Soosalu, Matt A1 - Srensen, Erik A1 - Sovani, Manali A1 - Spencer, Noah A1 - Staubli, Stefan A1 - Stans, Renske A1 - Stewart, Anya A1 - Stips, Felix A1 - Stockley, Kieran A1 - Strobel, Stephenson A1 - Struby, Ethan A1 - Tang, John A1 - Tanrisever, Idil A1 - Yang, Thomas Tao A1 - Tastan, Ipek A1 - Tatić, Dejan A1 - Tatlow, Benjamin A1 - Seuyong, Féraud Tchuisseu A1 - Thériault, Rémi A1 - Thivierge, Vincent A1 - Tian, Wenjie A1 - Toma, Filip-Mihai A1 - Totarelli, Maddalena A1 - Tran, Van-Anh A1 - Truong, Hung A1 - Tsoy, Nikita A1 - Tuzcuoglu, Kerem A1 - Ubfal, Diego A1 - Villalobos, Laura A1 - Walterskirchen, Julian A1 - Wang, Joseph Taoyi A1 - Wattal, Vasudha A1 - Webb, Matthew D. A1 - Weber, Bryan A1 - Weisser, Reinhard A1 - Weng, Wei-Chien A1 - Westheide, Christian A1 - White, Kimberly A1 - Winter, Jacob A1 - Wochner, Timo A1 - Woerman, Matt A1 - Wong, Jared A1 - Woodard, Ritchie A1 - Wroński, Marcin A1 - Yazbeck, Myra A1 - Yang, Gustav Chung A1 - Yap, Luther A1 - Yassin, Kareman A1 - Ye, Hao A1 - Yoon, Jin Young A1 - Yurris, Chris A1 - Zahra, Tahreen A1 - Zaneva, Mirela A1 - Zayat, Aline A1 - Zhang, Jonathan A1 - Zhao, Ziwei A1 - Yaolang, Zhong T1 - Mass reproducibility and replicability BT - a new hope T2 - I4R discussion paper series N2 - This study pushes our understanding of research reliability by reproducing and replicating claims from 110 papers in leading economic and political science journals. The analysis involves computational reproducibility checks and robustness assessments. It reveals several patterns. First, we uncover a high rate of fully computationally reproducible results (over 85%). Second, excluding minor issues like missing packages or broken pathways, we uncover coding errors for about 25% of studies, with some studies containing multiple errors. Third, we test the robustness of the results to 5,511 re-analyses. We find a robustness reproducibility of about 70%. Robustness reproducibility rates are relatively higher for re-analyses that introduce new data and lower for re-analyses that change the sample or the definition of the dependent variable. Fourth, 52% of re-analysis effect size estimates are smaller than the original published estimates and the average statistical significance of a re-analysis is 77% of the original. Lastly, we rely on six teams of researchers working independently to answer eight additional research questions on the determinants of robustness reproducibility. Most teams find a negative relationship between replicators' experience and reproducibility, while finding no relationship between reproducibility and the provision of intermediate or even raw data combined with the necessary cleaning codes. KW - conomics KW - open science KW - political science KW - replication KW - reproduction KW - research transparency Y1 - 2024 SN - 2752-1931 IS - 107 PB - Institute for Replication CY - Essen ER - TY - JOUR A1 - Kolmakova, Olesya V. A1 - Gladyshev, Michail I. A1 - Fonvielle, Jeremy Andre A1 - Ganzert, Lars A1 - Hornick, Thomas A1 - Grossart, Hans-Peter T1 - Effects of zooplankton carcasses degradation on freshwater bacterial community composition and implications for carbon cycling JF - Environmental microbiology N2 - Non-predatory mortality of zooplankton provides an abundant, yet, little studied source of high quality labile organic matter (LOM) in aquatic ecosystems. Using laboratory microcosms, we followed the decomposition of organic carbon of fresh C-13-labelled Daphnia carcasses by natural bacterioplankton. The experimental setup comprised blank microcosms, that is, artificial lake water without any organic matter additions (B), and microcosms either amended with natural humic matter (H), fresh Daphnia carcasses (D) or both, that is, humic matter and Daphnia carcasses (HD). Most of the carcass carbon was consumed and respired by the bacterial community within 15 days of incubation. A shift in the bacterial community composition shaped by labile carcass carbon and by humic matter was observed. Nevertheless, we did not observe a quantitative change in humic matter degradation by heterotrophic bacteria in the presence of LOM derived from carcasses. However, carcasses were the main factor driving the bacterial community composition suggesting that the presence of large quantities of dead zooplankton might affect the carbon cycling in aquatic ecosystems. Our results imply that organic matter derived from zooplankton carcasses is efficiently remineralized by a highly specific bacterial community, but does not interfere with the bacterial turnover of more refractory humic matter. Y1 - 2018 U6 - https://doi.org/10.1111/1462-2920.14418 SN - 1462-2912 SN - 1462-2920 VL - 21 IS - 1 SP - 34 EP - 49 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Block, Benjamin D. A1 - Denfeld, Blaize A. A1 - Stockwell, Jason D. A1 - Flaim, Giovanna A1 - Grossart, Hans-Peter A1 - Knoll, Lesley B. A1 - Maier, Dominique B. A1 - North, Rebecca L. A1 - Rautio, Milla A1 - Rusak, James A. A1 - Sadro, Steve A1 - Weyhenmeyer, Gesa A. A1 - Bramburger, Andrew J. A1 - Branstrator, Donn K. A1 - Salonen, Kalevi A1 - Hampton, Stephanie E. T1 - The unique methodological challenges of winter limnology JF - Limnology and Oceanography: Methods N2 - Winter is an important season for many limnological processes, which can range from biogeochemical transformations to ecological interactions. Interest in the structure and function of lake ecosystems under ice is on the rise. Although limnologists working at polar latitudes have a long history of winter work, the required knowledge to successfully sample under winter conditions is not widely available and relatively few limnologists receive formal training. In particular, the deployment and operation of equipment in below 0 degrees C temperatures pose considerable logistical and methodological challenges, as do the safety risks of sampling during the ice-covered period. Here, we consolidate information on winter lake sampling and describe effective methods to measure physical, chemical, and biological variables in and under ice. We describe variation in snow and ice conditions and discuss implications for sampling logistics and safety. We outline commonly encountered methodological challenges and make recommendations for best practices to maximize safety and efficiency when sampling through ice or deploying instruments in ice-covered lakes. Application of such practices over a broad range of ice-covered lakes will contribute to a better understanding of the factors that regulate lakes during winter and how winter conditions affect the subsequent ice-free period. Y1 - 2018 U6 - https://doi.org/10.1002/lom3.10295 SN - 1541-5856 VL - 17 IS - 1 SP - 42 EP - 57 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Beisner, Beatrix E. A1 - Grossart, Hans-Peter A1 - Gasol, Josep M. T1 - A guide to methods for estimating phago-mixotrophy in nanophytoplankton JF - Journal of plankton research N2 - Growing attention to phytoplankton mixotrophy as a trophic strategy has led to significant revisions of traditional pelagic food web models and ecosystem functioning. Although some empirical estimates of mixotrophy do exist, a much broader set of in situ measurements are required to (i) identify which organisms are acting as mixotrophs in real time and to (ii) assess the contribution of their heterotrophy to biogeochemical cycling. Estimates are needed through time and across space to evaluate which environmental conditions or habitats favour mixotrophy: conditions still largely unknown. We review methodologies currently available to plankton ecologists to undertake estimates of plankton mixotrophy, in particular nanophytoplankton phago-mixotrophy. Methods are based largely on fluorescent or isotopic tracers, but also take advantage of genomics to identify phylotypes and function. We also suggest novel methods on the cusp of use for phago-mixotrophy assessment, including single-cell measurements improving our capacity to estimate mixotrophic activity and rates in wild plankton communities down to the single-cell level. Future methods will benefit from advances in nanotechnology, micromanipulation and microscopy combined with stable isotope and genomic methodologies. Improved estimates of mixotrophy will enable more reliable models to predict changes in food web structure and biogeochemical flows in a rapidly changing world. KW - flow cytometry KW - phagotrophy KW - phytoplankton KW - methods KW - fluorescence KW - microscopy KW - FISH KW - isotopic methods KW - phylotypes KW - carbon flows KW - gene sequencing Y1 - 2019 U6 - https://doi.org/10.1093/plankt/fbz008 SN - 0142-7873 SN - 1464-3774 VL - 41 IS - 2 SP - 77 EP - 89 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Arias-Andres, Maria A1 - Rojas-Jimenez, Keilor A1 - Grossart, Hans-Peter T1 - Collateral effects of microplastic pollution on aquatic microorganisms BT - An ecological perspective JF - Trends in Analytical Chemistry N2 - Microplastics (MP) provide a unique and extensive surface for microbial colonization in aquatic ecosystems. The formation of microorganism-microplastic complexes, such as biofilms, maximizes the degradation of organic matter and horizontal gene transfer. In this context, MP affect the structure and function of microbial communities, which in turn render the physical and chemical fate of MP. This new paradigm generates challenges for microbiology, ecology, and ecotoxicology. Dispersal of MP is concomitant with that of their associated microorganisms and their mobile genetic elements, including antibiotic resistance genes, islands of pathogenicity, and diverse metabolic pathways. Functional changes in aquatic microbiomes can alter carbon metabolism and food webs, with unknown consequences on higher organisms or human microbiomes and hence health. Here, we examine a variety of effects of MP pollution from the microbial ecology perspective, whose repercussions on aquatic ecosystems begin to be unraveled. (C) 2018 Elsevier B.V. All rights reserved. KW - Microplastics (MP) KW - Biofilms KW - HGT KW - Microbial ecology KW - Carbon cycling KW - Aquatic ecosystems KW - Health risk assessment Y1 - 2018 U6 - https://doi.org/10.1016/j.trac.2018.11.041 SN - 0165-9936 SN - 1879-3142 VL - 112 SP - 234 EP - 240 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Gebser, Martin A1 - Obermeier, Philipp A1 - Otto, Thomas A1 - Schaub, Torsten A1 - Sabuncu, Orkunt A1 - Van Nguyen, A1 - Tran Cao Son, T1 - Experimenting with robotic intra-logistics domains JF - Theory and practice of logic programming N2 - We introduce the asprilo1 framework to facilitate experimental studies of approaches addressing complex dynamic applications. For this purpose, we have chosen the domain of robotic intra-logistics. This domain is not only highly relevant in the context of today's fourth industrial revolution but it moreover combines a multitude of challenging issues within a single uniform framework. This includes multi-agent planning, reasoning about action, change, resources, strategies, etc. In return, asprilo allows users to study alternative solutions as regards effectiveness and scalability. Although asprilo relies on Answer Set Programming and Python, it is readily usable by any system complying with its fact-oriented interface format. This makes it attractive for benchmarking and teaching well beyond logic programming. More precisely, asprilo consists of a versatile benchmark generator, solution checker and visualizer as well as a bunch of reference encodings featuring various ASP techniques. Importantly, the visualizer's animation capabilities are indispensable for complex scenarios like intra-logistics in order to inspect valid as well as invalid solution candidates. Also, it allows for graphically editing benchmark layouts that can be used as a basis for generating benchmark suites. Y1 - 2018 U6 - https://doi.org/10.1017/S1471068418000200 SN - 1471-0684 SN - 1475-3081 VL - 18 IS - 3-4 SP - 502 EP - 519 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Liemohn, Michael W. A1 - McCollough, James P. A1 - Jordanova, Vania K. A1 - Ngwira, Chigomezyo M. A1 - Morley, Steven K. A1 - Cid, Consuelo A1 - Tobiska, W. Kent A1 - Wintoft, Peter A1 - Ganushkina, Natalia Yu A1 - Welling, Daniel T. A1 - Bingham, Suzy A1 - Balikhin, Michael A. A1 - Opgenoorth, Hermann J. A1 - Engel, Miles A. A1 - Weigel, Robert S. A1 - Singer, Howard J. A1 - Buresova, Dalia A1 - Bruinsma, Sean A1 - Zhelavskaya, Irina A1 - Shprits, Yuri A1 - Vasile, Ruggero T1 - Model Evaluation Guidelines for Geomagnetic Index Predictions JF - Space Weather: The International Journal of Research and Applications N2 - Geomagnetic indices are convenient quantities that distill the complicated physics of some region or aspect of near-Earth space into a single parameter. Most of the best-known indices are calculated from ground-based magnetometer data sets, such as Dst, SYM-H, Kp, AE, AL, and PC. Many models have been created that predict the values of these indices, often using solar wind measurements upstream from Earth as the input variables to the calculation. This document reviews the current state of models that predict geomagnetic indices and the methods used to assess their ability to reproduce the target index time series. These existing methods are synthesized into a baseline collection of metrics for benchmarking a new or updated geomagnetic index prediction model. These methods fall into two categories: (1) fit performance metrics such as root-mean-square error and mean absolute error that are applied to a time series comparison of model output and observations and (2) event detection performance metrics such as Heidke Skill Score and probability of detection that are derived from a contingency table that compares model and observation values exceeding (or not) a threshold value. A few examples of codes being used with this set of metrics are presented, and other aspects of metrics assessment best practices, limitations, and uncertainties are discussed, including several caveats to consider when using geomagnetic indices. Plain Language Summary One aspect of space weather is a magnetic signature across the surface of the Earth. The creation of this signal involves nonlinear interactions of electromagnetic forces on charged particles and can therefore be difficult to predict. The perturbations that space storms and other activity causes in some observation sets, however, are fairly regular in their pattern. Some of these measurements have been compiled together into a single value, a geomagnetic index. Several such indices exist, providing a global estimate of the activity in different parts of geospace. Models have been developed to predict the time series of these indices, and various statistical methods are used to assess their performance at reproducing the original index. Existing studies of geomagnetic indices, however, use different approaches to quantify the performance of the model. This document defines a standardized set of statistical analyses as a baseline set of comparison tools that are recommended to assess geomagnetic index prediction models. It also discusses best practices, limitations, uncertainties, and caveats to consider when conducting a model assessment. Y1 - 2018 U6 - https://doi.org/10.1029/2018SW002067 SN - 1542-7390 VL - 16 IS - 12 SP - 2079 EP - 2102 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Zhu, Hui A1 - Shprits, Yuri A1 - Chen, Lunjin A1 - Liu, Xu A1 - Kellerman, Adam C. T1 - An event on simultaneous amplification of exohiss and chorus waves associated with electron density enhancements JF - Journal of geophysical research : Space physics N2 - Whistler mode exohiss are the structureless hiss waves observed outside the plasma pause with featured equatorward Poynting flux. An event of the amplification of exohiss as well as chorus waves was recorded by Van Allen Probes during the recovery phase of a weak geomagnetic storm. Amplitudes of both types of the waves showed a significant increase at the regions of electron density enhancements. It is found that the electrons resonant with exohiss and chorus showed moderate pitch angle anisotropies. The ratio of the number of electrons resonating with exohiss to total electron number presented in-phase correlation with density variations, which suggests that exohiss can be amplified due to electron density enhancement in terms of cyclotron instability. The calculation of linear growth rates further supports above conclusion. We suggest that exohiss waves have potential to become more significant due to the background plasma fluctuation. Y1 - 2018 U6 - https://doi.org/10.1029/2017JA025023 SN - 2169-9380 SN - 2169-9402 VL - 123 IS - 11 SP - 8958 EP - 8968 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Oskinova, Lidia M. A1 - Feldmeier, Achim A1 - Hamann, Wolf-Rainer T1 - High-resolution X-ray spectroscopy of bright O-type stars JF - Monthly notices of the Royal Astronomical Society N2 - Archival X-ray spectra of the four prominent single, non-magnetic O stars zeta Pup, zeta Ori, xi Per and zeta Oph, obtained in high resolution with Chandra HETGS/MEG have been studied. The resolved X-ray emission line profiles provide information about the shocked, hot gas which emits the X-radiation, and about the bulk of comparably cool stellar wind material which partly absorbs this radiation. In this paper, we synthesize X-ray line profiles with a model of a clumpy stellar wind. We find that the geometrical shape of the wind inhomogeneities is important: better agreement with the observations can be achieved with radially compressed clumps than with spherical clumps. The parameters of the model, i.e. chemical abundances, stellar radius, mass-loss rate and terminal wind velocity, are taken from existing analyses of UV and optical spectra of the programme stars. On this basis, we also calculate the continuum-absorption coefficient of the cool-wind material, using the Potsdam Wolf-Rayet (POWR) model atmosphere code. The radial location of X-ray emitting gas is restricted from analysing the FIR line ratios of helium-like ions. The only remaining free parameter of our model is the typical distance between the clumps; here, we assume that at any point in the wind there is one clump passing by per one dynamical time-scale of the wind. The total emission in a model line is scaled to the observation. There is a good agreement between synthetic and observed line profiles. We conclude that the X-ray emission line profiles in O stars can be explained by hot plasma embedded in a cool wind which is highly clumped in the form of radially compressed shell fragments. KW - stars : individual : zeta Pup KW - stars : individual : zeta Ori KW - stars : individual : xi Per KW - stars : individual : zeta Oph KW - X-rays : stars Y1 - 2006 U6 - https://doi.org/10.1111/j.1365-2966.2006.10858.x SN - 0035-8711 VL - 372 SP - 313 EP - 326 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Robrade, Jan A1 - Oskinova, Lidia M. A1 - Schmitt, J. H. M. M. A1 - Leto, Paolo A1 - Trigilio, C. T1 - Outstanding X-ray emission from the stellar radio pulsar CU Virginis JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Among the intermediate-mass magnetic chemically peculiar (MCP) stars, CU Vir is one of the most intriguing objects. Its 100% circularly polarized beams of radio emission sweep the Earth as the star rotates, thereby making this strongly magnetic star the prototype of a class of nondegenerate stellar radio pulsars. While CU Vir is well studied in radio, its high-energy properties are not known. Yet, X-ray emission is expected from stellar magnetospheres and confined stellar winds. Aims. Using X-ray data we aim to test CU Vir for intrinsic X-ray emission and investigate mechanisms responsible for its generation. Methods. We present X-ray observations performed with XMM-Newton and Chandra and study obtained X-ray images, light curves, and spectra. Basic X-ray properties are derived from spectral modelling and are compared with model predictions. In this context we investigate potential thermal and nonthermal X-ray emission scenarios. Results. We detect an X-ray source at the position of CU Vir. With LX approximate to 3 x 10(28) erg s(-1) it is moderately X-ray bright, but the spectrum is extremely hard compared to other Ap stars. Spectral modelling requires multi-component models with predominant hot plasma at temperatures of about T-X = 25MK or, alternatively, a nonthermal spectral component. Both types of model provide a virtually equivalent description of the X-ray spectra. The Chandra observation was performed six years later than those by XMM-Newton, yet the source has similar X-ray flux and spectrum, suggesting a steady and persistent X-ray emission. This is further confirmed by the X-ray light curves that show only mild X-ray variability. Conclusions. CU Vir is also an exceptional star at X-ray energies. To explain its full X-ray properties, a generating mechanism beyond standard explanations, like the presence of a low-mass companion or magnetically confined wind-shocks, is required. Magnetospheric activity might be present or, as proposed for fast-rotating strongly magnetic Bp stars, the X-ray emission of CU Vir is predominantly auroral in nature. KW - individual: CU Vir KW - stars: activity KW - stars: chemically peculiar KW - stars: magnetic field KW - X-rays: stars Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201833492 SN - 1432-0746 VL - 619 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Oskinova, Lidia M. A1 - Bulik, Tomasz A1 - Gomez-Moran, Ada Nebot T1 - Infrared outbursts as potential tracers of common-envelope events in high-mass X-ray binary formation JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Classic massive binary evolutionary scenarios predict that a transitional common-envelope (CE) phase could be preceded as well as succeeded by the evolutionary stage when a binary consists of a compact object and a massive star, that is, a high-mass X-ray binary (HMXB). The observational manifestations of common envelope are poorly constrained. We speculate that its ejection might be observed in some cases as a transient event at mid-infrared (IR) wavelengths. Aims. We estimate the expected numbers of CE ejection events and HMXBs per star formation unit rate, and compare these theoretical estimates with observations. Methods. We compiled a list of 85 mid-IR transients of uncertain nature detected by the Spitzer Infrared Intensive Transients Survey and searched for their associations with X-ray, optical, and UV sources. Results. Confirming our theoretical estimates, we find that only one potential HMXB may be plausibly associated with an IR-transient and tentatively propose that X-ray source NGC4490-X40 could be a precursor to the SPIRITS 16az event. Among other interesting sources, we suggest that the supernova remnant candidate [BWL2012] 063 might be associated with SPIRITS 16ajc. We also find that two SPIRITS events are likely associated with novae, and seven have potential optical counterparts. Conclusions. The massive binary evolutionary scenarios that involve CE events do not contradict currently available observations of IR transients and HMXBs in star-forming galaxies. KW - X-rays: binaries KW - stars: massive KW - infrared: general KW - infrared: galaxies Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201832925 SN - 0004-6361 SN - 1432-0746 VL - 613 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Pillitteri, Ignazio A1 - Fossati, Luca A1 - Rodriguez, N. Castro A1 - Oskinova, Lidia M. A1 - Wolk, Scott J. T1 - Detection of magnetic field in the B2 star rho Ophiuchi A with ESO FORS2 JF - Astronomy and astrophysics : an international weekly journal N2 - Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them (similar to 10%) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V star rho Oph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyze spectra of rho Oph A obtained with the FORS2 spectrograph at ESO Very Large Telescope (VLT) at two epochs, and detect a longitudinal component of the magnetic field of the order of similar to 500 G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters of rho Oph A and further constrained its age. We conclude that rho Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars. KW - stars: activity KW - stars: early-type KW - stars: magnetic field KW - pulsars: individual: rho Ophiuchi A Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201732078 SN - 1432-0746 VL - 610 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Gruner, David A1 - Hainich, Rainer A1 - Sander, Andreas Alexander Christoph A1 - Shenar, Tomer A1 - Todt, Helge Tobias A1 - Oskinova, Lidia M. A1 - Ramachandran, Varsha A1 - Ayres, T. A1 - Hamann, Wolf-Rainer T1 - The extreme O-type spectroscopic binary HD 93129A A quantitative, multiwavelength analysis JF - Astronomy and astrophysics : an international weekly journal N2 - Context. HD 93129A was classified as the earliest O-type star in the Galaxy (O2 If*) and is considered as the prototype of its spectral class. However, interferometry shows that this object is a binary system, while recent observations even suggest a triple configuration. None of the previous spectral analyses of this object accounted for its multiplicity. With new high-resolution UV and optical spectra, we have the possibility to reanalyze this key object, taking its binary nature into account for the first time. Aims. We aim to derive the fundamental parameters and the evolutionary status of HD 93129A, identifying the contributions of both components to the composite spectrum Results. Despite the similar spectral types of the two components, we are able to find signatures from each of the components in the combined spectrum, which allows us to estimate the parameters of both stars. We derive log(L/L-circle dot) = 6.15, T-eff = 52 kK, and log (M)over dot = -4.7[M-circle dot yr(-1)] for the primary Aa, and log(L/L-circle dot) = 5.58, T-eff = 45 kK, and log (M)over dot = -5.8 [M(circle dot)yr(-1)] for the secondary Ab. Conclusions. Even when accounting for the binary nature, the primary of HD 93129A is found to be one of the hottest and most luminous O stars in our Galaxy. Based on the theoretical decomposition of the spectra, we assign spectral types O2 If* and O3 III(f*) to components Aa and Ab, respectively. While we achieve a good fit for a wide spectral range, specific spectral features are not fully reproduced. The data are not sufficient to identify contributions from a hypothetical third component in the system. KW - stars: individual: HD 93129A KW - stars: atmospheres KW - stars: fundamental parameters KW - stars: early-typeP Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201833178 SN - 1432-0746 VL - 621 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Hainich, Rainer A1 - Oskinova, Lidia M. A1 - Shenar, Tomer A1 - Marchant Campos, Pablo A1 - Eldridge, J. J. A1 - Sander, Andreas Alexander Christoph A1 - Hamann, Wolf-Rainer A1 - Langer, Norbert A1 - Todt, Helge Tobias T1 - Observational properties of massive black hole binary progenitors JF - Astronomy and astrophysics : an international weekly journal N2 - Context: The first directly detected gravitational waves (GW 150914) were emitted by two coalescing black holes (BHs) with masses of ≈ 36 M⊙ and ≈ 29 M⊙. Several scenarios have been proposed to put this detection into an astrophysical context. The evolution of an isolated massive binary system is among commonly considered models. Aims: Various groups have performed detailed binary-evolution calculations that lead to BH merger events. However, the question remains open as to whether binary systems with the predicted properties really exist. The aim of this paper is to help observers to close this gap by providing spectral characteristics of massive binary BH progenitors during a phase where at least one of the companions is still non-degenerate. Methods: Stellar evolution models predict fundamental stellar parameters. Using these as input for our stellar atmosphere code (Potsdam Wolf-Rayet), we compute a set of models for selected evolutionary stages of massive merging BH progenitors at different metallicities. Results: The synthetic spectra obtained from our atmosphere calculations reveal that progenitors of massive BH merger events start their lives as O2-3V stars that evolve to early-type blue supergiants before they undergo core-collapse during the Wolf-Rayet phase. When the primary has collapsed, the remaining system will appear as a wind-fed high-mass X-ray binary. Based on our atmosphere models, we provide feedback parameters, broad band magnitudes, and spectral templates that should help to identify such binaries in the future. Conclusions: While the predicted parameter space for massive BH binary progenitors is partly realized in nature, none of the known massive binaries match our synthetic spectra of massive BH binary progenitors exactly. Comparisons of empirically determined mass-loss rates with those assumed by evolution calculations reveal significant differences. The consideration of the empirical mass-loss rates in evolution calculations will possibly entail a shift of the maximum in the predicted binary-BH merger rate to higher metallicities, that is, more candidates should be expected in our cosmic neighborhood than previously assumed. KW - gravitational waves KW - binaries: close KW - stars: early-type KW - stars: atmospheres KW - stars: winds KW - outflows KW - stars: mass-loss Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201731449 SN - 1432-0746 VL - 609 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Fulmer, Leah M. A1 - Gallagher, John S. A1 - Hamann, Wolf-Rainer A1 - Oskinova, Lidia M. A1 - Ramachandran, Varsha T1 - Testing massive star evolution, star-formation history, and feedback at low metallicity BT - photometric analysis of OB stars in the SMC Wing JF - Astronomy and astrophysics : an international weekly journal N2 - Context. The supergiant ionized shell SMC-SGS 1 (DEM 167), which is located in the outer Wing of the Small Magellanic Cloud (SMC), resembles structures that originate from an energetic star-formation event and later stimulate star formation as they expand into the ambient medium. However, stellar populations within and surrounding SMC-SGS 1 tell a different story. Aims. We present a photometric study of the stellar population encompassed by SMC-SGS 1 in order to trace the history of such a large structure and its potential influence on star formation within the low-density, low-metallicity environment of the SMC. Methods. For a stellar population that is physically associated with SMC-SGS 1, we combined near-ultraviolet (NUV) photometry from the Galaxy Evolution Explorer with archival optical (V-band) photometry from the ESO Danish 1.54 m Telescope. Given their colors and luminosities, we estimated stellar ages and masses by matching observed photometry to theoretical stellar isochrone models. Results. We find that the investigated region supports an active, extended star-formation event spanning similar to 25-40 Myr ago, as well as continued star formation into the present. Using a standard initial mass function, we infer a lower bound on the stellar mass from this period of similar to 3 x 10(4) M-circle dot, corresponding to a star-formation intensity of similar to 6 x 10(-3) M-circle dot kpc(-2) yr(-1). Conclusions. The spatial and temporal distributions of young stars encompassed by SMC-SGS 1 imply a slow, consistent progression of star formation over millions of years. Ongoing star formation, both along the edge and interior to SMC-SGS 1, suggests a combined stimulated and stochastic mode of star formation within the SMC Wing. We note that a slow expansion of the shell within this low-density environment may preserve molecular clouds within the volume of the shell, leaving them to form stars even after nearby stellar feedback expels local gas and dust. KW - galaxies KW - stellar content KW - stars KW - formation KW - individual KW - Small KW - Magellanic Cloud Y1 - 2020 U6 - https://doi.org/10.1051/0004-6361/201834314 SN - 0004-6361 SN - 1432-0746 VL - 633 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Geist, Emily A1 - Gallagher, John S. A1 - Kotulla, Ralf A1 - Oskinova, Lidia M. A1 - Hamann, Wolf-Rainer A1 - Ramachandran, Varsha A1 - Sabbi, Elena A1 - Smith, Linda J. A1 - Kniazev, Alexey A1 - Nota, Antonella A1 - Rickard, Matthew J. T1 - Ionization and star formation in the giant H ii region SMC-N66 JF - Publications of the Astronomical Society of the Pacific N2 - The NGC 346 young stellar system and associated N66 giant H ii region in the Small Magellanic Cloud are the nearest example of a massive star-forming event in a low metallicity (Z approximate to 0.2Z (circle dot)) galaxy. With an age of less than or similar to 3 Myr this system provides a unique opportunity to study relationships between massive stars and their associated H ii region. Using archival data, we derive a total H alpha luminosity of L(H alpha) = 4.1 x 10(38) erg s(-1) corresponding to an H-photoionization rate of 3 x 10(50) s(-1). A comparison with a predicted stellar ionization rate derived from the more than 50 known O-stars in NGC 346, including massive stars recently classified from Hubble Space Telescope far-ultraviolet (FUV) spectra, indicates an approximate ionization balance. Spectra obtained with SALT suggest the ionization structure of N66 could be consistent with some leakage of ionizing photons. Due to the low metallicity, the FUV luminosity from NGC 346 is not confined to the interstellar cloud associated with N66. Ionization extends through much of the spatial extent of the N66 cloud complex, and most of the cloud mass is not ionized. The stellar mass estimated from nebular L(H alpha) appears to be lower than masses derived from the census of resolved stars which may indicate a disconnect between the formation of high and low mass stars in this region. We briefly discuss implications of the properties of N66 for studies of star formation and stellar feedback in low metallicity environments. Y1 - 2022 U6 - https://doi.org/10.1088/1538-3873/ac697b SN - 0004-6280 SN - 1538-3873 VL - 134 IS - 1036 PB - IOP Publishing CY - Bristol ER -