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    Large-scale globally propagating coronal waves
    (Katlenburg-Lindau : MPS, 2015) Warmuth, Alexander
    Large-scale, globally propagating wave-like disturbances have been observed in the solar chromosphere and by inference in the corona since the 1960s. However, detailed analysis of these phenomena has only been conducted since the late 1990s. This was prompted by the availability of high-cadence coronal imaging data from numerous spaced-based instruments, which routinely show spectacular globally propagating bright fronts. Coronal waves, as these perturbations are usually referred to, have now been observed in a wide range of spectral channels, yielding a wealth of information. Many findings have supported the “classical” interpretation of the disturbances: fast-mode MHD waves or shocks that are propagating in the solar corona. However, observations that seemed inconsistent with this picture have stimulated the development of alternative models in which “pseudo waves” are generated by magnetic reconfiguration in the framework of an expanding coronal mass ejection. This has resulted in a vigorous debate on the physical nature of these disturbances. This review focuses on demonstrating how the numerous observational findings of the last one and a half decades can be used to constrain our models of large-scale coronal waves, and how a coherent physical understanding of these disturbances is finally emerging.
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    The stratorotational instability of Taylor-Couette flows with moderate Reynolds numbers
    (London [u.a.] : Taylor and Francis, 2017) Rüdiger, G.; Seelig, T.; Schultz, M.; Gellert, M.; Egbers, C.; Harlander, U.
    In view of new experimental data the instability against adiabatic nonaxisymmetric perturbations of a Taylor-Couette flow with an axial density stratification is considered in dependence of the Reynolds number (Re) of rotation and the Brunt-Väisälä number (Rn) of the stratification. The flows at and beyond the Rayleigh limit become unstable between a lower and an upper Reynolds number (for fixed Rn). The rotation can thus be too slow or too fast for the stratorotational instability. The upper Reynolds number above which the instability decays, has its maximum value for the potential flow (driven by cylinders rotating according to the Rayleigh limit) and decreases strongly for flatter rotation profiles finally leaving only isolated islands of instability in the (Rn/Re) map. The maximal possible rotation ratio μmax only slightly exceeds the shear value of the quasi-uniform flow with Uφ≃const. Along and between the lines of neutral stability the wave numbers of the instability patterns for all rotation laws beyond the Rayleigh limit are mainly determined by the Froude number Fr which is defined by the ratio between Re and Rn. The cells are highly prolate for Fr > 1 so that measurements for too high Reynolds numbers become difficult for axially bounded containers. The instability patterns migrate azimuthally slightly faster than the outer cylinder rotates.
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    Worldwide variations in artificial skyglow
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2015) Kyba, Christopher C.M.; Tong, Kai Pong; Bennie, Jonathan; Birriel, Ignacio; Birriel, Jennifer J.; Cool, Andrew; Danielsen, Arne; Davies, Thomas W.; den Outer, Peter N.; Edwards, William; Ehlert, Rainer; Falchi, Fabio; Fischer, Jürgen; Giacomelli, Andrea; Giubbilini, Francesco; Haaima, Marty; Hesse, Claudia; Heygster, Georg; Hölker, Franz; Inger, Richard; Jensen, Linsey J.; Kuechly, Helga U.; Kuehn, John; Langill, Phil; Lolkema, Dorien E.; Nagy, Matthew; Nievas, Miguel; Ochi, Nobuaki; Popow, Emil; Posch, Thomas; Puschnig, Johannes; Ruhtz, Thomas; Schmidt, Wim; Schwarz, Robert; Schwope, Axel; Spoelstra, Henk; Tekatch, Anthony; Trueblood, Mark; Walker, Constance E.; Weber, Michael; Welch, Douglas L.; Zamorano, Jaime; Gaston, Kevin J.
    Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties. Skyglow is observed to vary over four orders of magnitude, a range hundreds of times larger than was the case before artificial light. Nearly all of the study sites were polluted by artificial light. A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. Overcast skies ranged from a third darker to almost 18 times brighter than clear. Clear sky radiances estimated by the World Atlas of Artificial Night Sky Brightness were found to be overestimated by ~25%; our dataset will play an important role in the calibration and ground truthing of future skyglow models. Most of the brightly lit sites darkened as the night progressed, typically by ~5% per hour. The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program.
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    High-Resolution Arrayed-Waveguide-Gratings in Astronomy: Design and Fabrication Challenges
    (Basel : MDPI, 2017) Stoll, Andreas; Zhang, Ziyang; Haynes, Roger; Roth, Martin
    A comprehensive design of a folded-architecture arrayed-waveguide-grating (AWG)-device, targeted at applications as integrated photonic spectrographs (IPS) in near-infrared astronomy, is presented. The AWG structure is designed for the astronomical H-band (1500 nm-1800 nm) with a theoretical maximum resolving power R = 60,000 at 1630 nm. The geometry of the device is optimized for a compact structure with a footprint of 5.5 cm × 3.93 cm on SiO2 platform. To evaluate the fabrication challenges of such high-resolution AWGs, effects of random perturbations of the effective refractive index (RI) distribution in the free propagation region (FPR), as well as small variations of the array waveguide optical lengths are numerically investigated. The results of the investigation show a dramatic degradation of the point spread function (PSF) for a random effective RI distribution with variance values above ~10-4 for both the FPR and the waveguide array. Based on the results, requirements on the fabrication technology for high-resolution AWG-based spectrographs are given in the end.
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    A Leak in the Academic Pipeline : Identity and Health Among Postdoctoral Women
    (Lausanne : Frontiers Research Foundation, 2019) Ysseldyk, Renate; Greenaway, Katharine H.; Hassinger, Elena; Zutrauen, Sarah; Lintz, Jana; Bhatia, Maya P.; Frye, Margaret; Starkenburg, Else; Tai, Vera
    Several challenges (e.g., sexism, parental leave, the glass ceiling, etc.) disproportionately affect women in academia (and beyond), and thus perpetuate the leaky pipeline metaphor for women who opt-out of an academic career. Although this pattern can be seen at all levels of the academic hierarchy, a critical time for women facing such challenges is during the postdoctoral stage, when personal life transitions and professional ambitions collide. Using a social identity approach, we explore factors affecting the mental health of postdoctoral women, including identity development (e.g., as a mother, a scientist) and lack of control (uncertainty about one’s future personal and professional prospects), which likely contribute to the leak from academia. In this mixed-method research, Study 1 comprised interviews with postdoctoral women in North America (n = 13) and Europe (n = 8) across a range disciplines (e.g., psychology, physics, political science). Common themes included the negative impact of career uncertainty, gender-based challenges (especially sexism and maternity leave), and work-life balance on mental and physical health. However, interviewees also described attempts to overcome gender inequality and institutional barriers by drawing on support networks. Study 2 comprised an online survey of postdoctoral women (N = 146) from a range of countries and academic disciplines to assess the relationships between social identification (e.g., disciplinary, gender, social group), perceived control (i.e., over work and life), and mental health (i.e., depression, anxiety, stress, and life satisfaction). Postdoctoral women showed mild levels of stress and depression, and were only slightly satisfied with life. They also showed only moderate levels of perceived control over one’s life and work. However, hierarchical regression analyses revealed that strongly identifying with one’s discipline was most consistently positively associated with both perceived control and mental health. Collectively, these findings implicate the postdoctoral stage as being stressful and tenuous for women regardless of academic background or nationality. They also highlight the importance of disciplinary identity as a potentially protective factor for mental health that, in turn, may diminish the rate at which postdoctoral women leak from the academic pipeline.
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    Vorbereitende Arbeiten für die Instrumente STIX und EPT für die Sondenmission Solar Orbiter der ESA : Schlussbericht zum Vorhaben
    (Hannover : Technische Informationsbibliothek (TIB), 2010) Mann, Gottfried
    [no abstract available]
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    The dynamical evolution of planetary nebulae
    (Bristol : IOP Publ., 2016) Schönberner, Detlef
    Based on modern 1D-radiation-hydrodynamics simulations of formation and evolution of planetary nebulae, I discuss in detail the basic dynamical processes responsible for the "grand design" of most planetary nebulae, i.e. their double-shell morphology and their typical expansion properties. Special emphasis is given for a proper definition of a nebula's true expansion rate and its relation to spectroscopically measurable Doppler velocities of the expanding material. It is found that the typical nebular expansion is about twice as fast as hitherto assumed, viz. ≃45 kms-1.
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    The Optical Variability of the BL Lac AO 0235+164
    (Basel : MDPI, 2016) Fan, Junhui; Kurtanidze, Omar; Liu, Yi; Liu, Xiang; Richter, Gotthard; Nikolashvili, Maria; Kurtanidze, Sophia; Chanishvili, Revaz; Wang, Hongtao; Sasada, Mahito; Zhou, Aiying; Lin, Chao; Yuan, Yuhai
    In this work, we present optical R band observations of AO 0235+164 carried out during the period of November 2006 to December 2012 using the Ap6E CCD camera attached to the primary focus of the 70 cm meniscus telescope at Abastumani Observatory, Georgia. It shows a large variation of ΔR = 4.88 mag (14.19–19.07 mag) and a short time scale of ΔTv = 73.5 min during our monitoring period. When periodicity analysis methods are applied to the R-band data from both historic and our observations, periods P1 = 8.26 yr and P2 = 0.54 yr are found.
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    The Fifteenth Data Release of the Sloan Digital Sky Surveys: First Release of MaNGA-derived Quantities, Data Visualization Tools, and Stellar Library
    (Chicago, Ill. [u.a.] : Univ. of Chicago Press, 2019) Aguado, D. S.; Ahumada, Romina; Almeida, Andrés; Anderson, Scott F.; Andrews, Brett H.; Anguiano, Borja; Ortíz, Erik Aquino; Aragón-Salamanca, Alfonso; Argudo-Fernández, Maria; Aubert, Marie; Avila-Reese, Vladimir; Seong Hwang, Ho; Ibarra-Medel, Héctor J.; Eduardo Jimenez Angel, Camilo; Johnson, Jennifer; Jones, Amy; Jönsson, Henrik; Kinemuchi, Karen; Kollmeier, Juna; Krawczyk, Coleman; Kreckel, Kathryn; Badenes, Carles; Kruk, Sandor; Lacerna, Ivan; Lan, Ting-Wen; Lane, Richard R.; Law, David R.; Lee, Young-Bae; Li, Cheng; Lian, Jianhui; Lin, Lihwai; Lin, Yen-Ting; Barboza Rembold, Sandro; Lintott, Chris; Long, Dan; Longa-Peña, Penélope; Ted Mackereth, J.; de la Macorra, Axel; Majewski, Steven R.; Malanushenko, Olena; Manchado, Arturo; Maraston, Claudia; Mariappan, Vivek; Barger, Kat; Marinelli, Mariarosa; Marques-Chaves, Rui; Masseron, Thomas; Masters, Karen L.; McDermid, Richard M.; Medina Peña, Nicolás; Meneses-Goytia, Sofia; Merloni, Andrea; Merrifield, Michael; Meszaros, Szabolcs; Barrera-Ballesteros, Jorge; Minniti, Dante; Minsley, Rebecca; Muna, Demitri; Myers, Adam D.; Nair, Preethi; Correa do Nascimento, Janaina; Newman, Jeffrey A.; Nitschelm, Christian; Olmstead, Matthew D; Oravetz, Audrey; Bates, Dominic; Oravetz, Daniel; Ortega Minakata, René A.; Pace, Zach; Padilla, Nelson; Palicio, Pedro A.; Pan, Kaike; Pan, Hsi-An; Parikh, Taniya; Parker, James; Peirani, Sebastien; Bautista, Julian; Penny, Samantha; Percival, Will J.; Perez-Fournon, Ismael; Peterken, Thomas; Pinsonneault, Marc H.; Prakash, Abhishek; Raddick, M. Jordan; Raichoor, Anand; Riffel, Rogemar A.; Riffel, Rogério; Beaton, Rachael L.; Rix, Hans-Walter; Robin, Annie C.; Roman-Lopes, Alexandre; Rose, Benjamin; Ross, Ashley J.; Rossi, Graziano; Rowlands, Kate; Rubin, Kate H. R.; Sánchez, Sebastián F.; Sánchez-Gallego, José R.; Beers, Timothy C.; Sayres, Conor; Schaefer, Adam; Schiavon, Ricardo P.; Schimoia, Jaderson S.; Schlafly, Edward; Schlegel, David; Schneider, Donald P.; Schultheis, Mathias; Seo, Hee-Jong; Shamsi, Shoaib J.; Belfiore, Francesco; Shao, Zhengyi; Shen, Shiyin; Shetty, Shravan; Simonian, Gregory; Smethurst, Rebecca J.; Sobeck, Jennifer; Souter, Barbara J.; Spindler, Ashley; Stark, David V.; Stassun, Keivan G.; Bernardi, Mariangela; Steinmetz, Matthias; Storchi-Bergmann, Thaisa; Stringfellow, Guy S.; Suárez, Genaro; Sun, Jing; Taghizadeh-Popp, Manuchehr; Talbot, Michael S.; Tayar, Jamie; Thakar, Aniruddha R.; Thomas, Daniel; Bershady, Matthew; Tissera, Patricia; Tojeiro, Rita; Troup, Nicholas W.; Unda-Sanzana, Eduardo; Valenzuela, Octavio; Vargas-Magaña, Mariana; Antonio Vázquez-Mata, José; Wake, David; Alan Weaver, Benjamin; Weijmans, Anne-Marie; Beutler, Florian; Westfall, Kyle B.; Wild, Vivienne; Wilson, John; Woods, Emily; Yan, Renbin; Yang, Meng; Zamora, Olga; Zasowski, Gail; Zhang, Kai; Zheng, Zheng; Bird, Jonathan; Zheng, Zheng; Zhu, Guangtun; Zinn, Joel C.; Zou, Hu; Bizyaev, Dmitry; Blanc, Guillermo A.; Blanton, Michael R.; Blomqvist, Michael; Bolton, Adam S.; Boquien, Médéric; Borissova, Jura; Bovy, Jo; Nielsen Brandt, William; Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Burgasser, Adam; Byler, Nell; Cano Diaz, Mariana; Cappellari, Michele; Carrera, Ricardo; Cervantes Sodi, Bernardo; Chen, Yanping; Cherinka, Brian; Doohyun Choi, Peter; Chung, Haeun; Coffey, Damien; Comerford, Julia M.; Comparat, Johan; Covey, Kevin; da Silva Ilha, Gabriele; da Costa, Luiz; Sophia Dai, Yu; Damke, Guillermo; Darling, Jeremy; Davies, Roger; Dawson, Kyle; de Sainte Agathe, Victoria; Deconto Machado, Alice; Del Moro, Agnese; De Lee, Nathan; Diamond-Stanic, Aleksandar M.; Domínguez Sánchez, Helena; Donor, John; Drory, Niv; du Mas des Bourboux, Hélion; Duckworth, Chris; Dwelly, Tom; Ebelke, Garrett; Emsellem, Eric; Escoffier, Stephanie; Fernández-Trincado, José G.; Feuillet, Diane; Fischer, Johanna-Laina; Fleming, Scott W.; Fraser-McKelvie, Amelia; Freischlad, Gordon; Frinchaboy, Peter M.; Fu, Hai; Galbany, Lluís; Garcia-Dias, Rafael; García-Hernández, D. A.; Alberto Garma Oehmichen, Luis; Antonio Geimba Maia, Marcio; Gil-Marín, Héctor; Grabowski, Kathleen; Gu, Meng; Guo, Hong; Ha, Jaewon; Harrington, Emily; Hasselquist, Sten; Hayes, Christian R.; Hearty, Fred; Hernandez Toledo, Hector; Hicks, Harry; Hogg, David W.; Holley-Bockelmann, Kelly; Holtzman, Jon A.; Hsieh, Bau-Ching; Hunt, Jason A. S.
    Twenty years have passed since first light for the Sloan Digital Sky Survey (SDSS). Here, we release data taken by the fourth phase of SDSS (SDSS-IV) across its first three years of operation (2014 July–2017 July). This is the third data release for SDSS-IV, and the 15th from SDSS (Data Release Fifteen; DR15). New data come from MaNGA—we release 4824 data cubes, as well as the first stellar spectra in the MaNGA Stellar Library (MaStar), the first set of survey-supported analysis products (e.g., stellar and gas kinematics, emission-line and other maps) from the MaNGA Data Analysis Pipeline, and a new data visualization and access tool we call "Marvin." The next data release, DR16, will include new data from both APOGEE-2 and eBOSS; those surveys release no new data here, but we document updates and corrections to their data processing pipelines. The release is cumulative; it also includes the most recent reductions and calibrations of all data taken by SDSS since first light. In this paper, we describe the location and format of the data and tools and cite technical references describing how it was obtained and processed. The SDSS website (www.sdss.org) has also been updated, providing links to data downloads, tutorials, and examples of data use. Although SDSS-IV will continue to collect astronomical data until 2020, and will be followed by SDSS-V (2020–2025), we end this paper by describing plans to ensure the sustainability of the SDSS data archive for many years beyond the collection of data.
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    A multiwavelength study of the Stingray Nebula; properties of the nebula, central star, and dust
    (Bristol : IOP Publ., 2016) Otsuka, Masaaki; Parthasarathy, Mudumba; Tajitsu, Akito; Hubrig, Swetlana
    We performed a detail chemical abundance analysis and photo-ionization modeling of the Stingray Nebula (Hen3-1357, Parthasarathy et al. 1993[1]) to more characterize this PN. We calculated nine elemental abundances using collisionally excited lines (CELs) and recombination lines (RLs). The RL C/O ratio indicates that this PN is O-rich, which is supported by the detection of the broad amorphous silicate features at 9 and 18 μm By photo-ionization modeling, we investigated properties of the central star and derived the gas and dust masses. The nebular elemental abundances, the core-mass of the central star, and the gas mass are in agreement with the AGB model for the initially 1.5 M⊙ stars with the Z = 0.008.