TY - JOUR A1 - Seiler, Michael A1 - Seiß, Martin A1 - Hoffmann, Holger A1 - Spahn, Frank T1 - Hydrodynamic Simulations of Asymmetric Propeller Structures in Saturn's Rings JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series N2 - The observation of the non-Keplerian behavior of propeller structures in Saturn's outer A ring raises the question: how does the propeller respond to the wandering of the central embedded moonlet? Here, we study numerically how the structural imprint of the propeller changes for a libration of the moonlet. It turns out that the libration induces an asymmetry in the propeller, which depends on the libration period and amplitude of the moonlet. Further, we study the dependence of the asymmetry on the libration period and amplitude for a moonlet with a 400 m Hill radius, which is located in the outer A ring. This allows us to apply our findings to the largest known propeller Blériot, which is expected to be of a similar size. For Blériot, we can conclude that, supposing the moonlet is librating with the largest observed period of 11.1 yr and an azimuthal amplitude of about 1845 km, a small asymmetry should be measurable but depends on the moonlet's libration phase at the observation time. The longitude residuals of other trans-Encke propellers (e.g., Earhart) show amplitudes similar to Blériot, which might allow us to observe larger asymmetries due to their smaller azimuthal extent, allowing us to scan the whole gap structure for asymmetries in one observation. Although the librational model of the moonlet is a simplification, our results are a first step toward the development of a consistent model for the description of the formation of asymmetric propellers caused by a freely moving moonlet. KW - Hydrodynamics KW - methods: data analysis KW - methods: numerical KW - planets and satellites: dynamical evolution and stability KW - planets and satellites: individual (Saturn) KW - planets and satellites: rings Y1 - 2019 U6 - https://doi.org/10.3847/1538-4365/ab26b0 SN - 0067-0049 SN - 1538-4365 VL - 243 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Niven, Robert K. A1 - Abel, Markus A1 - Schlegel, Michael A1 - Waldrip, Steven H. T1 - Maximum Entropy Analysis of Flow Networks: Theoretical Foundation and Applications JF - Entropy N2 - The concept of a "flow network"-a set of nodes and links which carries one or more flows-unites many different disciplines, including pipe flow, fluid flow, electrical, chemical reaction, ecological, epidemiological, neurological, communications, transportation, financial, economic and human social networks. This Feature Paper presents a generalized maximum entropy framework to infer the state of a flow network, including its flow rates and other properties, in probabilistic form. In this method, the network uncertainty is represented by a joint probability function over its unknowns, subject to all that is known. This gives a relative entropy function which is maximized, subject to the constraints, to determine the most probable or most representative state of the network. The constraints can include "observable" constraints on various parameters, "physical" constraints such as conservation laws and frictional properties, and "graphical" constraints arising from uncertainty in the network structure itself. Since the method is probabilistic, it enables the prediction of network properties when there is insufficient information to obtain a deterministic solution. The derived framework can incorporate nonlinear constraints or nonlinear interdependencies between variables, at the cost of requiring numerical solution. The theoretical foundations of the method are first presented, followed by its application to a variety of flow networks. KW - maximum entropy analysis KW - flow network KW - probabilistic inference Y1 - 2019 U6 - https://doi.org/10.3390/e21080776 SN - 1099-4300 VL - 21 IS - 8 SP - 776 PB - MDPI CY - Basel ER - TY - JOUR A1 - Cheng, Xiao A1 - Böker, Alexander A1 - Tsarkova, Larisa T1 - Temperature-Controlled Solvent Vapor Annealing of Thin Block Copolymer Films JF - Polymers N2 - Solvent vapor annealing is as an effective and versatile alternative to thermal annealing to equilibrate and control the assembly of polymer chains in thin films. Here, we present scientific and practical aspects of the solvent vapor annealing method, including the discussion of such factors as non-equilibrium conformational states and chain dynamics in thin films in the presence of solvent. Homopolymer and block copolymer films have been used in model studies to evaluate the robustness and the reproducibility of the solvent vapor processing, as well as to assess polymer-solvent interactions under confinement. Advantages of utilizing a well-controlled solvent vapor environment, including practically interesting regimes of weakly saturated vapor leading to poorly swollen states, are discussed. Special focus is given to dual temperature control over the set-up instrumentation and to the potential of solvo-thermal annealing. The evaluated insights into annealing dynamics derived from the studies on block copolymer films can be applied to improve the processing of thin films of crystalline and conjugated polymers as well as polymer composite in confined geometries. KW - solvent vapor annealing KW - block copolymer films KW - ellipsometry KW - guided self assembly Y1 - 2019 U6 - https://doi.org/10.3390/polym11081312 SN - 2073-4360 VL - 11 IS - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Deschler, Felix A1 - Neher, Dieter A1 - Schmidt-Mende, Lukas T1 - Perovskite semiconductors for next generation optoelectronic applications JF - APL Materials Y1 - 2019 U6 - https://doi.org/10.1063/1.5119744 SN - 2166-532X VL - 7 IS - 8 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Becker, George D. A1 - Pettini, Max A1 - Rafelski, Marc A1 - Boera, Elisa A1 - Christensen, Lise A1 - Cupani, Guido A1 - Ellison, Sara L. A1 - Farina, Emanuele Paolo A1 - Fumagalli, Michele A1 - Lopez, Sebastian A1 - Neeleman, Marcel A1 - Ryan-Weber, Emma A1 - Worseck, Gabor T1 - The Evolution of OI over 3.2 < z < 6.5: Reionization of the Circumgalactic Medium JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present a survey for metal absorption systems traced by neutral oxygen over 3.2 < z < 6.5. Our survey uses Keck/ESI and VLT/X-Shooter spectra of 199 QSOs with redshifts up to 6.6. In total, we detect 74 OI absorbers, of which 57 are separated from the background QSO by more than 5000 km s(-1). We use a maximum likelihood approach to fit the distribution of OI lambda 1302 equivalent widths in bins of redshift and from this determine the evolution in number density of absorbers with W-1302 > 0.05 angstrom, of which there are 49 nonproximate systems in our sample. We find that the number density does not monotonically increase with decreasing redshift, as would naively be expected from the buildup of metal-enriched circumgalactic gas with time. The number density over 4.9 < z < 5.7 is a factor of 1.7-4.1 lower (68% confidence) than that over 5.7 < z < 6.5, with a lower value at z < 5.7 favored with 99% confidence. This decrease suggests that the fraction of metals in a low-ionization phase is larger at z similar to 6 than at lower redshifts. Absorption from highly ionized metals traced by CIV is also weaker in higher-redshift OI systems, supporting this picture. The evolution of OI absorbers implies that metal-enriched circumgalactic gas at z similar to 6 is undergoing an ionization transition driven by a strengthening ultraviolet background. This in turn suggests that the reionization of the diffuse intergalactic medium may still be ongoing at or only recently ended by this epoch. Y1 - 2019 U6 - https://doi.org/10.3847/1538-4357/ab3eb5 SN - 0004-637X SN - 1538-4357 VL - 883 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Shprits, Yuri Y. A1 - Vasile, Ruggero A1 - Zhelayskaya, Irina S. T1 - Nowcasting and Predicting the Kp Index Using Historical Values and Real-Time Observations JF - Space Weather: The International Journal of Research and Applications N2 - Current algorithms for the real-time prediction of the Kp index use a combination of models empirically driven by solar wind measurements at the L1 Lagrange point and historical values of the index. In this study, we explore the limitations of this approach, examining the forecast for short and long lead times using measurements at L1 and Kp time series as input to artificial neural networks. We explore the relative efficiency of the solar wind-based predictions, predictions based on recurrence, and predictions based on persistence. Our modeling results show that for short-term forecasts of approximately half a day, the addition of the historical values of Kp to the measured solar wind values provides a barely noticeable improvement. For a longer-term forecast of more than 2 days, predictions can be made using recurrence only, while solar wind measurements provide very little improvement for a forecast with long horizon times. We also examine predictions for disturbed and quiet geomagnetic activity conditions. Our results show that the paucity of historical measurements of the solar wind for high Kp results in a lower accuracy of predictions during disturbed conditions. Rebalancing of input data can help tailor the predictions for more disturbed conditions. KW - Kp index KW - geomagnetic activity KW - empirical prediction KW - solar wind KW - forecast KW - AI Y1 - 2019 U6 - https://doi.org/10.1029/2018SW002141 SN - 1542-7390 VL - 17 IS - 8 SP - 1219 EP - 1229 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Wilkin, Kyle J. A1 - Parrish, Robert M. A1 - Yang, Jie A1 - Wolf, Thomas J. A. A1 - Nunes, J. Pedro F. A1 - Gühr, Markus A1 - Li, Renkai A1 - Shen, Xiaozhe A1 - Zheng, Qiang A1 - Wang, Xijie A1 - Martinez, Todd J. A1 - Centurion, Martin T1 - Diffractive imaging of dissociation and ground-state dynamics in a complex molecule JF - Physical review : A, Atomic, molecular, and optical physics N2 - We have investigated the structural dynamics in photoexcited 1,2-diiodotetrafluoroethane molecules (C2F4I2) in the gas phase experimentally using ultrafast electron diffraction and theoretically using FOMO-CASCI excited-state dynamics simulations. The molecules are excited by an ultraviolet femtosecond laser pulse to a state characterized by a transition from the iodine 5p perpendicular to orbital to a mixed 5p parallel to sigma hole and CF2 center dot antibonding orbital, which results in the cleavage of one of the carbon-iodine bonds. We have observed, with sub-Angstrom resolution, the motion of the nuclear wave packet of the dissociating iodine atom followed by coherent vibrations in the electronic ground state of the C2F4I radical. The radical reaches a stable classical (nonbridged) structure in less than 200 fs. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevA.100.023402 SN - 2469-9926 SN - 2469-9934 VL - 100 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Irrgang, Andreas A1 - Geier, Stephan A1 - Heber, Ulrich A1 - Kupfer, Thomas A1 - Fürst, F. T1 - PG 1610+062: a runaway B star challenging classical ejection mechanisms JF - Astronomy and astrophysics : an international weekly journal N2 - Hypervelocity stars are rare objects, mostly main-sequence (MS) B stars, traveling so fast that they will eventually escape from the Milky Way. Recently, it has been shown that the popular Hills mechanism, in which a binary system is disrupted via a close encounter with the supermassive black hole at the Galactic center, may not be their only ejection mechanism. The analyses of Gaia data ruled out a Galactic center origin for some of them, and instead indicated that they are extreme disk runaway stars ejected at velocities exceeding the predicted limits of classical scenarios (dynamical ejection from star clusters or binary supernova ejection). We present the discovery of a new extreme disk runaway star, PG 1610+062, which is a slowly pulsating B star bright enough to be studied in detail. A quantitative analysis of spectra taken with ESI at the Keck Observatory revealed that PG 1610+062 is a late B-type MS star of 4–5 M⊙ with low projected rotational velocity. Abundances (C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe) were derived differentially with respect to the normal B star HD 137366 and indicate that PG 1610+062 is somewhat metal rich. A kinematic analysis, based on our spectrophotometric distance (17.3 kpc) and on proper motions from Gaia’s second data release, shows that PG 1610+062 was probably ejected from the Carina-Sagittarius spiral arm at a velocity of 550 ± 40 km s−1, which is beyond the classical limits. Accordingly, the star is in the top five of the most extreme MS disk runaway stars and is only the second among the five for which the chemical composition is known. KW - stars: abundances KW - stars: individual: HD 137366 KW - stars: kinematics and dynamics KW - stars: individual: PG 1610+062 KW - stars: early-type Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201935429 SN - 1432-0746 VL - 628 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Henkel, Carsten A1 - Jacob, Georg A1 - Stopp, Felix A1 - Schmidt-Kaler, Ferdinand A1 - Keil, Mark A1 - Japha, Yonathan A1 - Folman, Ron T1 - Stern-Gerlach splitting of low-energy ion beams JF - New journal of physics : the open-access journal for physics N2 - We present a feasibility study with several magnetic field configurations for creating spin-dependent forces that can split a low-energy ion beam by the Stern-Gerlach (SG) effect. To the best of our knowledge, coherent spin-splittings of charged particles have yet to be realised. Our proposal is based on ion source parameters taken from a recent experiment that demonstrated single-ion implantation from a high-brightness ion source combined with a radio-frequency Paul trap. The inhomogeneous magnetic fields can be created by permanently magnetised microstructures or from current-carrying wires with sizes in the micron range, such as those recently used in a successful implementation of the SG effect with neutral atoms. All relevant forces (Lorentz force and image charges) are taken into account, and measurable splittings are found by analytical and numerical calculations. KW - spin-dependent forces KW - Stern-Gerlach effect KW - ion optics KW - beam splitter KW - magnetic microstructures Y1 - 2019 U6 - https://doi.org/10.1088/1367-2630/ab36c7 SN - 1367-2630 VL - 21 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Kurths, Jürgen A1 - Agarwal, Ankit A1 - Shukla, Roopam A1 - Marwan, Norbert A1 - Maheswaran, Rathinasamy A1 - Caesar, Levke A1 - Krishnan, Raghavan A1 - Merz, Bruno T1 - Unravelling the spatial diversity of Indian precipitation teleconnections via a non-linear multi-scale approach JF - Nonlinear processes in geophysics N2 - A better understanding of precipitation dynamics in the Indian subcontinent is required since India's society depends heavily on reliable monsoon forecasts. We introduce a non-linear, multiscale approach, based on wavelets and event synchronization, for unravelling teleconnection influences on precipitation. We consider those climate patterns with the highest relevance for Indian precipitation. Our results suggest significant influences which are not well captured by only the wavelet coherence analysis, the state-of-the-art method in understanding linkages at multiple timescales. We find substantial variation across India and across timescales. In particular, El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) mainly influence precipitation in the south-east at interannual and decadal scales, respectively, whereas the North Atlantic Oscillation (NAO) has a strong connection to precipitation, particularly in the northern regions. The effect of the Pacific Decadal Oscillation (PDO) stretches across the whole country, whereas the Atlantic Multidecadal Oscillation (AMO) influences precipitation particularly in the central arid and semi-arid regions. The proposed method provides a powerful approach for capturing the dynamics of precipitation and, hence, helps improve precipitation forecasting. Y1 - 2019 U6 - https://doi.org/10.5194/npg-26-251-2019 SN - 1023-5809 SN - 1607-7946 VL - 26 IS - 3 SP - 251 EP - 266 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Wolf, Thomas J. A. A1 - Parrish, Robert M. A1 - Myhre, Rolf H. A1 - Martinez, Todd J. A1 - Koch, Henrik A1 - Gühr, Markus T1 - Observation of Ultrafast Intersystem Crossing in Thymine by Extreme Ultraviolet Time-Resolved Photoelectron Spectroscopy JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - We studied the photoinduced ultrafast relaxation dynamics of the nucleobase thymine using gas-phase time-resolved photoelectron spectroscopy. By employing extreme ultraviolet pulses from high harmonic generation for photoionization, we substantially extend our spectral observation window with respect to previous studies. This enables us to follow relaxation of the excited state population all the way to low-lying electronic states including the ground state. In thymine, we observe relaxation from the optically bright (1)pi pi* state of thymine to a dark (1)n pi* state within 80 +/- 30 fs. The (1)n pi* state relaxes further within 3.5 +/- 0.3 ps to a low-lying electronic state. By comparison with quantum chemical simulations, we can unambiguously assign its spectroscopic signature to the (3)pi pi* state. Hence, our study draws a comprehensive picture of the relaxation mechanism of thymine including ultrafast intersystem crossing to the triplet manifold. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpca.9b05573 SN - 1089-5639 SN - 1520-5215 VL - 123 IS - 32 SP - 6897 EP - 6903 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Nikolis, Vasileios C. A1 - Mischok, Andreas A1 - Siegmund, Bernhard A1 - Kublitski, Jonas A1 - Jia, Xiangkun A1 - Benduhn, Johannes A1 - Hörmann, Ulrich A1 - Neher, Dieter A1 - Gather, Malte C. A1 - Spoltore, Donato A1 - Vandewal, Koen T1 - Strong light-matter coupling for reduced photon energy losses in organic photovoltaics JF - Nature Communications N2 - Strong light-matter coupling can re-arrange the exciton energies in organic semiconductors. Here, we exploit strong coupling by embedding a fullerene-free organic solar cell (OSC) photo-active layer into an optical microcavity, leading to the formation of polariton peaks and a red-shift of the optical gap. At the same time, the open-circuit voltage of the device remains unaffected. This leads to reduced photon energy losses for the low-energy polaritons and a steepening of the absorption edge. While strong coupling reduces the optical gap, the energy of the charge-transfer state is not affected for large driving force donor-acceptor systems. Interestingly, this implies that strong coupling can be exploited in OSCs to reduce the driving force for electron transfer, without chemical or microstructural modifications of the photoactive layer. Our work demonstrates that the processes determining voltage losses in OSCs can now be tuned, and reduced to unprecedented values, simply by manipulating the device architecture. Y1 - 2019 U6 - https://doi.org/10.1038/s41467-019-11717-5 SN - 2041-1723 VL - 10 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Stolterfoht, Martin A1 - Caprioglio, Pietro A1 - Wolff, Christian Michael A1 - Marquez, Jose A. A1 - Nordmann, Joleik A1 - Zhang, Shanshan A1 - Rothhardt, Daniel A1 - Hörmann, Ulrich A1 - Amir, Yohai A1 - Redinger, Alex A1 - Kegelmann, Lukas A1 - Zu, Fengshuo A1 - Albrecht, Steve A1 - Koch, Norbert A1 - Kirchartz, Thomas A1 - Saliba, Michael A1 - Unold, Thomas A1 - Neher, Dieter T1 - The impact of energy alignment and interfacial recombination on the internal and external open-circuit voltage of perovskite solar cells JF - Energy & environmental science N2 - Charge transport layers (CTLs) are key components of diffusion controlled perovskite solar cells, however, they can induce additional non-radiative recombination pathways which limit the open circuit voltage (V-OC) of the cell. In order to realize the full thermodynamic potential of the perovskite absorber, both the electron and hole transport layer (ETL/HTL) need to be as selective as possible. By measuring the photoluminescence yield of perovskite/CTL heterojunctions, we quantify the non-radiative interfacial recombination currents in pin- and nip-type cells including high efficiency devices (21.4%). Our study comprises a wide range of commonly used CTLs, including various hole-transporting polymers, spiro-OMeTAD, metal oxides and fullerenes. We find that all studied CTLs limit the V-OC by inducing an additional non-radiative recombination current that is in most cases substantially larger than the loss in the neat perovskite and that the least-selective interface sets the upper limit for the V-OC of the device. Importantly, the V-OC equals the internal quasi-Fermi level splitting (QFLS) in the absorber layer only in high efficiency cells, while in poor performing devices, the V-OC is substantially lower than the QFLS. Using ultraviolet photoelectron spectroscopy and differential charging capacitance experiments we show that this is due to an energy level mis-alignment at the p-interface. The findings are corroborated by rigorous device simulations which outline important considerations to maximize the V-OC. This work highlights that the challenge to suppress non-radiative recombination losses in perovskite cells on their way to the radiative limit lies in proper energy level alignment and in suppression of defect recombination at the interfaces. Y1 - 2019 U6 - https://doi.org/10.1039/c9ee02020a SN - 1754-5692 SN - 1754-5706 VL - 12 IS - 9 SP - 2778 EP - 2788 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Le Corre, Vincent M. A1 - Stolterfoht, Martin A1 - Perdigón-Toro, Lorena A1 - Feuerstein, Markus A1 - Wolff, Christian Michael A1 - Gil-Escrig, Lidon A1 - Bolink, Henk J. A1 - Neher, Dieter A1 - Koster, L. Jan Anton T1 - Charge Transport Layers Limiting the Efficiency of Perovskite Solar Cells: How To Optimize Conductivity, Doping, and Thickness JF - ACS Applied Energy Materials N2 - Perovskite solar cells (PSCs) are one of the main research topics of the photovoltaic community; with efficiencies now reaching up to 24%, PSCs are on the way to catching up with classical inorganic solar cells. However, PSCs have not yet reached their full potential. In fact, their efficiency is still limited by nonradiative recombination, mainly via trap-states and by losses due to the poor transport properties of the commonly used transport layers (TLs). Indeed, state-of-the-art TLs (especially if organic) suffer from rather low mobilities, typically within 10(-5) and 10(-2) cm(-2) V-1 s(-1), when compared to the high mobilities, 1-10 cm(-2) V-1 s(-1), measured for perovskites. This work presents a comprehensive analysis of the effect of the mobility, thickness, and doping density of the transport layers based on combined experimental and modeling results of two sets of devices made of a solution-processed high-performing triple-cation (PCE approximate to 20%). The results are also cross-checked on vacuum-processed MAPbI(3) devices. From this analysis, general guidelines on how to optimize a TL are introduced and especially a new and simple formula to easily calculate the amount of doping necessary to counterbalance the low mobility of the TLs. KW - perovskite solar cells KW - transport layers KW - conductivity KW - doping KW - charge transport Y1 - 2019 U6 - https://doi.org/10.1021/acsaem.9b00856 SN - 2574-0962 VL - 2 IS - 9 SP - 6280 EP - 6287 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Tubiana, C. A1 - Rinaldi, G. A1 - Guettler, C. A1 - Snodgrass, C. A1 - Shi, X. A1 - Hu, X. A1 - Marschall, R. A1 - Fulle, M. A1 - Bockeele-Morvan, D. A1 - Naletto, G. A1 - Capaccioni, F. A1 - Sierks, H. A1 - Arnold, G. A1 - Barucci, M. A. A1 - Bertaux, J-L A1 - Bertini, I A1 - Bodewits, D. A1 - Capria, M. T. A1 - Ciarniello, M. A1 - Cremonese, G. A1 - Crovisier, J. A1 - Da Deppo, V A1 - Debei, S. A1 - De Cecco, M. A1 - Deller, J. A1 - De Sanctis, M. C. A1 - Davidsson, B. A1 - Doose, L. A1 - Erard, S. A1 - Filacchione, G. A1 - Fink, U. A1 - Formisano, M. A1 - Fornasier, S. A1 - Gutierrez, P. J. A1 - Ip, W-H A1 - Ivanovski, S. A1 - Kappel, David A1 - Keller, H. U. A1 - Kolokolova, L. A1 - Koschny, D. A1 - Krueger, H. A1 - La Forgia, F. A1 - Lamy, P. L. A1 - Lara, L. M. A1 - Lazzarin, M. A1 - Levasseur-Regourd, A. C. A1 - Lin, Z-Y A1 - Longobardo, A. A1 - Lopez-Moreno, J. J. A1 - Marzari, F. A1 - Migliorini, A. A1 - Mottola, S. A1 - Rodrigo, R. A1 - Taylor, F. A1 - Toth, I A1 - Zakharov, V T1 - Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta JF - Astronomy and astrophysics : an international weekly journal N2 - Context. On 27 April 2015, when comet 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving toward perihelion, the OSIRIS and VIRTIS-M instruments on board the Rosetta spacecraft simultaneously observed the evolving dust and gas coma during a complete rotation of the comet. Aims. We aim to characterize the spatial distribution of dust, H2O, and CO2 gas in the inner coma. To do this, we performed a quantitative analysis of the release of dust and gas and compared the observed H2O production rate with the rate we calculated using a thermophysical model. Methods. For this study we selected OSIRIS WAC images at 612 nm (dust) and VIRTIS-M image cubes at 612 nm, 2700 nm (H2O emission band), and 4200 nm (CO2 emission band). We measured the average signal in a circular annulus to study the spatial variation around the comet, and in a sector of the annulus to study temporal variation in the sunward direction with comet rotation, both at a fixed distance of 3.1 km from the comet center. Results. The spatial correlation between dust and water, both coming from the sunlit side of the comet, shows that water is the main driver of dust activity in this time period. The spatial distribution of CO2 is not correlated with water and dust. There is no strong temporal correlation between the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0 degrees subsolar longitude, which is not pronounced in the water production. At the same epoch, there is also a maximum in CO2 production. An excess of measured water production with respect to the value calculated using a simple thermophysical model is observed when the head lobe and regions of the southern hemisphere with strong seasonal variations are illuminated (subsolar longitude 270 degrees-50 degrees). A drastic decrease in dust production when the water production (both measured and from the model) displays a maximum occurs when typical northern consolidated regions are illuminated and the southern hemisphere regions with strong seasonal variations are instead in shadow (subsolar longitude 50 degrees-90 degrees). Possible explanations of these observations are presented and discussed. KW - comets: general KW - comets: individual: 67P/Churyumov-Gerasimenko KW - methods: data analysis Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201834869 SN - 1432-0746 VL - 630 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Rinaldi, G. A1 - Formisano, M. A1 - Kappel, David A1 - Capaccioni, F. A1 - Bockelee-Morvan, D. A1 - Cheng, Y-C A1 - Vincent, J-B A1 - Deshapriya, P. A1 - Arnold, G. A1 - Capria, M. T. A1 - Ciarniello, M. A1 - De Sanctis, M. C. A1 - Doose, L. A1 - Erard, S. A1 - Federico, C. A1 - Filacchione, G. A1 - Fink, U. A1 - Leyrat, C. A1 - Longobardo, A. A1 - Magni, G. A1 - Mighorini, A. A1 - Mottola, S. A1 - Naletto, G. A1 - Raponi, A. A1 - Taylor, F. A1 - Tosi, F. A1 - Tozzi, G. P. A1 - Salatti, M. T1 - Analysis of night-side dust activity on comet 67P observed by VIRTIS-M BT - a new method to constrain the thermal inertia on the surface JF - Astronomy and astrophysics : an international weekly journal N2 - On 2015 July 18, near perihelion at a heliocentric distance of 1.28 au, the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS-M) on board the Rosetta spacecraft had the opportunity of observing dust activity in the inner coma with a view of the night side (shadowed side) of comet 67P/Churyumov-Gerasimenko. At the time of the measurements we present here, we observe a dust plume that originates on the far side of the nucleus. We are able to identify the approximate location of its source at the boundary between the Hapi and Anuket regions, and we find that it has been in darkness for some hours before the observation. Assuming that this time span is equal to the conductive time scale, we obtain a thermal inertia in the range 25-36 W K-1 m(-2) s(-1/2). These thermal inertia values can be used to verify with a 3D finite-element method (REM) numerical code whether the surface and subsurface temperatures agree with the values found in the literature. We explored three different configurations: (1) a layer of water ice mixed with dust beneath a dust mantle of 5 mm with thermal inertia of 36 J m(-2) K-1 S-0.5 ; (2) the same structure, but with thermal inertia of 100 J m(-2) K-1 S-0.5; (3) an ice-dust mixture that is directly exposed. Of these three configurations, the first seems to be the most reasonable, both for the low thermal inertia and for the agreement with the surface and subsurface temperatures that have been found for the comet 67P/Churyumov-Gerasimenko. The spectral properties of the plume show that the visible dust color ranged from 16 +/- 4.8%/100 nm to 13 +/- 2.6%/100 nm, indicating that this plume has no detectable color gradient. The morphology of the plume can be classified as a narrow jet that has an estimated total ejected mass of between 6 and 19 tons when we assume size distribution indices between -2.5 and -3. KW - comets: general KW - comets: individual: 67P/Churyumov-Gerasimenko KW - infrared: planetary systems Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201834907 SN - 1432-0746 VL - 630 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Schaffenroth, Veronika A1 - Barlow, Brad N. A1 - Geier, Stephan A1 - Vuckovic, Maja A1 - Kilkenny, D. A1 - Wolz, M. A1 - Kupfer, Thomas A1 - Heber, Ulrich A1 - Drechsel, H. A1 - Kimeswenger, S. A1 - Marsh, T. A1 - Wolf, M. A1 - Pelisoli, Ingrid Domingos A1 - Freudenthal, Joseph A1 - Dreizler, S. A1 - Kreuzer, S. A1 - Ziegerer, E. T1 - The EREBOS project: Investigating the effect of substellar and low-mass stellar companions on late stellar evolution Survey, target selection, and atmospheric parameters JF - Astronomy and astrophysics : an international weekly journal N2 - Eclipsing post-common-envelope binaries are highly important for resolving the poorly understood, very short-lived common-envelope phase of stellar evolution. Most hot subdwarfs (sdO/Bs) are the bare helium-burning cores of red giants that have lost almost all of their hydrogen envelope. This mass loss is often triggered by common-envelope interactions with close stellar or even substellar companions. Cool companions to hot subdwarf stars such as late-type stars and brown dwarfs are detectable from characteristic light-curve variations - reflection effects and often eclipses. In the recently published catalog of eclipsing binaries in the Galactic Bulge and in the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey, we discovered 125 new eclipsing systems showing a reflection effect seen by visual inspection of the light curves and using a machine-learning algorithm, in addition to the 36 systems previously discovered by the Optical Gravitational Lesing Experiment (OGLE) team. The Eclipsing Reflection Effect Binaries from Optical Surveys (EREBOS) project aims at analyzing all newly discovered eclipsing binaries of the HW Vir type (hot subdwarf + close, cool companion) based on a spectroscopic and photometric follow up to derive the mass distribution of the companions, constrain the fraction of substellar companions, and determine the minimum mass needed to strip off the red-giant envelope. To constrain the nature of the primary we derived the absolute magnitude and the reduced proper motion of all our targets with the help of the parallaxes and proper motions measured by the Gaia mission and compared those to the Gaia white-dwarf candidate catalog. It was possible to derive the nature of a subset of our targets, for which observed spectra are available, by measuring the atmospheric parameter of the primary, confirming that less than 10% of our systems are not sdO/Bs with cool companions but are white dwarfs or central stars of planetary nebula. This large sample of eclipsing hot subdwarfs with cool companions allowed us to derive a significant period distribution for hot subdwarfs with cool companions for the first time showing that the period distribution is much broader than previously thought and is ideally suited to finding the lowest-mass companions to hot subdwarf stars. The comparison with related binary populations shows that the period distribution of HW Vir systems is very similar to WD+dM systems and central stars of planetary nebula with cool companions. In the future, several new photometric surveys will be carried out, which will further increase the sample of this project, providing the potential to test many aspects of common-envelope theory and binary evolution. KW - binaries: eclipsing KW - brown dwarfs KW - binaries: spectroscopic KW - binaries: close KW - subdwarfs KW - surveys Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201936019 SN - 1432-0746 VL - 630 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Mehrabi, Pedram A1 - Schulz, Eike C. A1 - Dsouza, Raison A1 - Müller-Werkmeister, Henrike A1 - Tellkamp, Friedjof A1 - Miller, R. J. Dwayne A1 - Pai, Emil F. T1 - Time-resolved crystallography reveals allosteric communication aligned with molecular breathing JF - Science N2 - A comprehensive understanding of protein function demands correlating structure and dynamic changes. Using time-resolved serial synchrotron crystallography, we visualized half-of-the-sites reactivity and correlated molecular-breathing motions in the enzyme fluoroacetate dehalogenase. Eighteen time points from 30 milliseconds to 30 seconds cover four turnover cycles of the irreversible reaction. They reveal sequential substrate binding, covalent-intermediate formation, setup of a hydrolytic water molecule, and product release. Small structural changes of the protein mold and variations in the number and placement of water molecules accompany the various chemical steps of catalysis. Triggered by enzyme-ligand interactions, these repetitive changes in the protein framework’s dynamics and entropy constitute crucial components of the catalytic machinery. Y1 - 2019 U6 - https://doi.org/10.1126/science.aaw9904 SN - 0036-8075 SN - 1095-9203 VL - 365 IS - 6458 SP - 1167 EP - 1170 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Deb, Marwan A1 - Popova, Elena A1 - Hehn, Michel A1 - Keller, Niels A1 - Petit-Watelot, Sebastien A1 - Bargheer, Matias A1 - Mangin, Stephane A1 - Malinowski, Gregory T1 - Damping of Standing Spin Waves in Bismuth-Substituted Yttrium Iron Garnet as Seen via the Time-Resolved Magneto-Optical Kerr Effect JF - Physical review applied N2 - We investigate spin-wave resonance modes and their damping in insulating thin films of bismuth-substituted yttrium iron garnet by performing femtosecond magneto-optical pump-probe experiments. For large magnetic fields in the range below the magnetization saturation, we find that the damping of high-order standing spin-wave (SSW) modes is about 40 times lower than that for the fundamental one. The observed phenomenon can be explained by considering different features of magnetic anisotropy and exchange fields that, respectively, define the precession frequency for fundamental and high-order SSWs. These results provide further insight into SSWs in iron garnets and may be exploited in many new photomagnonic devices. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevApplied.12.044006 SN - 2331-7019 VL - 12 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Pittarello, Lidia A1 - Goderis, Steven A1 - Soens, Bastien A1 - McKibbin, Seann J. A1 - Giuli, Gabriele A1 - Bariselli, Federico A1 - Dias, Bruno A1 - Helber, Bernd A1 - Lepore, Giovanni Orazio A1 - Vanhaecke, Frank A1 - Köberl, Christian A1 - Magin, Thierry E. A1 - Claeys, Philippe T1 - Meteoroid atmospheric entry investigated with plasma flow experiments: Petrography and geochemistry of the recovered material JF - Icarus : international journal of solar system studies N2 - Melting experiments attempting to reproduce some of the processes affecting asteroidal and cometary material during atmospheric entry have been performed in a high enthalpy facility. For the first time with the specific experimental setup, the resulting material has been recovered, studied, and compared with natural analogues, focusing on the thermal and redox reactions triggered by interaction between the melt and the atmospheric gases under high temperature and low pressure conditions. Experimental conditions were tested across a range of parameters, such as heat flux, experiment duration, and pressure, using two types of sample holders materials, namely cork and graphite. A basalt served as asteroidal analog and to calibrate the experiments, before melting a H5 ordinary chondrite meteorite. The quenched melt recovered after the experiments has been analyzed by mu-XRF, EDS-SEM, EMPA, LA-ICP-MS, and XANES spectroscopy. The glass formed from the basalt is fairly homogeneous, depleted in highly volatile elements (e.g., Na, K), relatively enriched in moderately siderophile elements (e.g., Co, Ni), and has reached an equilibrium redox state with a lower Fe3+/Fe-tot ratio than that in the starting material. Spherical objects, enriched in SiO2, Na2O and K2O, were observed, inferring condensation from the vaporized material. Despite instantaneous quenching, the melt formed from the ordinary chondrite shows extensive crystallization of mostly olivine and magnetite, the latter indicative of oxygen fugacity compatible with presence of both Fe2+ and Fe3+. Similar features have been observed in natural meteorite fusion crusts and in micrometeorites, implying that, at least in terms of maximum temperature reached and chemical reactions, the experiments have successfully reproduced the conditions likely encountered by extraterrestrial material following atmospheric entry. KW - Melting experiments KW - Atmospheric entry KW - Meteorites KW - Fusion crust KW - Redox Y1 - 2019 U6 - https://doi.org/10.1016/j.icarus.2019.04.033 SN - 0019-1035 SN - 1090-2643 VL - 331 SP - 170 EP - 178 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Abeysekara, A. U. A1 - Archer, A. A1 - Benbow, Wystan A1 - Bird, Ralph A1 - Brill, A. A1 - Brose, Robert A1 - Buchovecky, M. A1 - Calderon-Madera, D. A1 - Christiansen, J. L. A1 - Cui, W. A1 - Daniel, M. K. A1 - Falcone, A. A1 - Feng, Q. A1 - Fernandez-Alonso, M. A1 - Finley, J. P. A1 - Fortson, Lucy A1 - Furniss, Amy A1 - Gent, A. A1 - Giuri, C. A1 - Gueta, O. A1 - Hanna, David A1 - Hassan, T. A1 - Hervet, Oliver A1 - Holder, J. A1 - Hughes, G. A1 - Humensky, T. B. A1 - Johnson, Caitlin A. A1 - Kaaret, P. A1 - Kertzman, M. A1 - Kieda, David A1 - Krause, Maria A1 - Krennrich, F. A1 - Kumar, S. A1 - Lang, M. J. A1 - Maier, Gernot A1 - Moriarty, P. A1 - Mukherjee, Reshmi A1 - Nievas-Rosillo, M. A1 - Ong, R. A. A1 - Pfrang, Konstantin Johannes A1 - Pohl, Martin A1 - Prado, R. R. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Ribeiro, D. A1 - Richards, G. T. A1 - Roache, E. A1 - Rovero, A. C. A1 - Sadeh, Iftach A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, Karlen A1 - Sushch, Iurii A1 - Svraka, T. A1 - Weinstein, A. A1 - Wells, R. M. A1 - Wilcox, Patrick A1 - Wilhelm, Alina A1 - Williams, David Arnold A1 - Williamson, T. J. A1 - Zitzer, B. T1 - Measurement of the Extragalactic Background Light Spectral Energy Distribution with VERITAS JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The extragalactic background light (EBL), a diffuse photon field in the optical and infrared range, is a record of radiative processes over the universe?s history. Spectral measurements of blazars at very high energies (>100 GeV) enable the reconstruction of the spectral energy distribution (SED) of the EBL, as the blazar spectra are modified by redshift- and energy-dependent interactions of the gamma-ray photons with the EBL. The spectra of 14 VERITAS-detected blazars are included in a new measurement of the EBL SED that is independent of EBL SED models. The resulting SED covers an EBL wavelength range of 0.56?56 ?m, and is in good agreement with lower limits obtained by assuming that the EBL is entirely due to radiation from cataloged galaxies. KW - Extragalactic astronomy KW - Active galactic nuclei KW - Diffuse radiation KW - Cosmology Y1 - 2019 U6 - https://doi.org/10.3847/1538-4357/ab4817 SN - 0004-637X SN - 1538-4357 VL - 885 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Soupiona, Ourania A1 - Samaras, Stefanos A1 - Ortiz-Amezcua, Pablo A1 - Böckmann, Christine A1 - Papayannis, Alexandros D. A1 - Moreira, Gregori De Arruda A1 - Benavent-Oltra, Jose Antonio A1 - Guerrero-Rascado, Juan Luis A1 - Bedoya-Velásquez, Andres Esteban A1 - Olmo-Reyes, Francisco José A1 - Román, Roberto A1 - Kokkalis, Panagiotis A1 - Mylonaki, Maria A1 - Alados-Arboledas, Lucas A1 - Papanikolaou, Christina Anna A1 - Foskinis, Romanos T1 - Retrieval of optical and microphysical properties of transported Saharan dust over Athens and Granada based on multi-wavelength Raman lidar measurements: Study of the mixing processes JF - Atmospheric environment : air pollution ; emissions, transport and dispersion, transformation, deposition effects, micrometeorology, urban atmosphere, global atmosphere N2 - In this paper we extract the aerosol microphysical properties for a collection of mineral dust cases measured by multi-wavelength depolarization Raman lidar systems located at the National Technical University of Athens (NTUA, Athens, Greece) and the Andalusian Institute for Earth System Research (IISTA-CEAMA, Granada, Spain). The lidar-based retrievals were carried out with the Spheroidal Inversion eXperiments software tool (SphInX) developed at the University of Potsdam (Germany). The software uses regularized inversion of a two-dimensional enhancement of the Mie model based on the spheroid-particle approximation with the aspect ratio determining the particle shape. The selection of the cases was based on the transport time from the source regions to the measuring sites. The aerosol optical depth as measured by AERONET ranged from 0.27 to 0.54 (at 500 nm) depending on the intensity of each event. Our analysis showed the hourly mean particle linear depolarization ratio and particle lidar ratio values at 532 nm ranging from 11 to 34% and from 42 to 79 sr respectively, depending on the mixing status, the corresponding air mass pathways and their transport time. Cases with shorter transport time showed good agreement in terms of the optical and SphInX-retrieved microphysical properties between Athens and Granada providing a complex refractive index value equal to 1.4 + 0.004i. On the other hand, the results for cases with higher transport time deviated from the aforementioned ones as well as from each other, providing, in particular, an imaginary part of the refractive index ranging from 0.002 to 0.005. Reconstructions of two-dimensional shape-size distributions for each selected layer showed that the dominant effective particle shape was prolate with diverse spherical contributions. The retrieved volume concentrations reflect overall the intensity of the episodes. Y1 - 2019 U6 - https://doi.org/10.1016/j.atmosenv.2019.116824 SN - 1352-2310 SN - 1873-2844 VL - 214 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Baran, Andrzej S. A1 - Telting, J. H. A1 - Jeffery, C. Simon A1 - Ostensen, R. H. A1 - Vos, Joris A1 - Reed, M. D. A1 - Vŭcković, Maja T1 - K2 observations of the sdBV plus dM/bd binaries PHL457 and EQPsc JF - Monthly notices of the Royal Astronomical Society N2 - We present an analysis of two pulsating subdwarf B stars PHL 457 and EQ Psc observed during the K2 mission. The K2 light curves of both stars show variation consistent with irradiation of a cooler companion by the hot subdwarf. They also show higher frequency oscillations consistent with pulsation. Using new spectroscopic data, we measured the radial velocity, effective temperature, surface gravity, and helium abundance of both hot subdwarfs as a function of orbital phase. We confirm the previously published spectroscopic orbit of PHL 457, and present the first spectroscopic orbit of EQ Psc. The orbital periods are 0.313 and 0.801 d, respectively. For EQPsc, we find a strong correlation between T-eff and orbital phase, due to contribution of light from the irradiated companion. We calculated amplitude spectra, identified significant pulsation frequencies, and searched for multiplets and asymptotic period spacings. By means of multiplets and period spacing, we identified the degrees of several pulsation modes in each star. The g-mode multiplets indicate subsynchronous core rotation with periods of 4.6 d (PHL 457) and 9.4 d (EQ Psc). We made spectral energy disctribution (SED) fits of PHL 457 and EQ Psc using available broad-band photometry and Gaia data. While the SED of PHL 457 shows no evidence of a cool companion, the SED for EQPsc clearly shows an infrared (IR) access consistent with a secondary with a temperature of about 6800K and a radius of 0.23 R-circle dot. This is the first detection of an IR access in any sdB + dM binary. KW - binaries: general KW - stars: individual (PHL 457, EQ Psc) KW - stars: oscillations (including pulsations) Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz2209 SN - 0035-8711 SN - 1365-2966 VL - 489 IS - 2 SP - 1556 EP - 1571 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Eliazar, Iddo A1 - Metzler, Ralf A1 - Reuveni, Shlomi T1 - Poisson-process limit laws yield Gumbel max-min and min-max JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - “A chain is only as strong as its weakest link” says the proverb. But what about a collection of statistically identical chains: How long till all chains fail? The answer to this question is given by the max-min of a matrix whose (i,j)entry is the failure time of link j of chain i: take the minimum of each row, and then the maximum of the rows' minima. The corresponding min-max is obtained by taking the maximum of each column, and then the minimum of the columns' maxima. The min-max applies to the storage of critical data. Indeed, consider multiple backup copies of a set of critical data items, and consider the (i,j) matrix entry to be the time at which item j on copy i is lost; then, the min-max is the time at which the first critical data item is lost. In this paper we address random matrices whose entries are independent and identically distributed random variables. We establish Poisson-process limit laws for the row's minima and for the columns' maxima. Then, we further establish Gumbel limit laws for the max-min and for the min-max. The limit laws hold whenever the entries' distribution has a density, and yield highly applicable approximation tools and design tools for the max-min and min-max of large random matrices. A brief of the results presented herein is given in: Gumbel central limit theorem for max-min and min-max Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevE.100.022129 SN - 2470-0045 SN - 2470-0053 VL - 100 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Eliazar, Iddo A1 - Metzler, Ralf A1 - Reuveni, Shlomi T1 - Gumbel central limit theorem for max-min and min-max JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - The max-min and min-max of matrices arise prevalently in science and engineering. However, in many real-world situations the computation of the max-min and min-max is challenging as matrices are large and full information about their entries is lacking. Here we take a statistical-physics approach and establish limit laws—akin to the central limit theorem—for the max-min and min-max of large random matrices. The limit laws intertwine random-matrix theory and extreme-value theory, couple the matrix dimensions geometrically, and assert that Gumbel statistics emerge irrespective of the matrix entries' distribution. Due to their generality and universality, as well as their practicality, these results are expected to have a host of applications in the physical sciences and beyond. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevE.100.020104 SN - 2470-0045 SN - 2470-0053 VL - 100 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Erdmann, Maren A1 - Kupsch, Andreas A1 - Müller, Bernd Randolf A1 - Hentschel, Manfred P. A1 - Niebergall, Ute A1 - Böhning, Martin A1 - Bruno, Giovanni T1 - Diesel-induced transparency of plastically deformed high-density polyethylene JF - Journal of materials science N2 - High-density polyethylene becomes optically transparent during tensile drawing when previously saturated with diesel fuel. This unusual phenomenon is investigated as it might allow conclusions with respect to the material behavior. Microscopy, differential scanning calorimetry, density measurements are applied together with two scanning X-ray scattering techniques: wide angle X-ray scattering (WAXS) and X-ray refraction, able to extract the spatially resolved crystal orientation and internal surface, respectively. The sorbed diesel softens the material and significantly alters the yielding characteristics. Although the crystallinity among stretched regions is similar, a virgin reference sample exhibits strain whitening during stretching, while the diesel-saturated sample becomes transparent. The WAXS results reveal a pronounced fiber texture in the tensile direction in the stretched region and an isotropic orientation in the unstretched region. This texture implies the formation of fibrils in the stretched region, while spherulites remain intact in the unstretched parts of the specimens. X-ray refraction reveals a preferred orientation of internal surfaces along the tensile direction in the stretched region of virgin samples, while the sample stretched in the diesel-saturated state shows no internal surfaces at all. Besides from stretching saturated samples, optical transparency is also obtained from sorbing samples in diesel after stretching. Y1 - 2019 U6 - https://doi.org/10.1007/s10853-019-03700-8 SN - 0022-2461 SN - 1573-4803 VL - 54 IS - 17 SP - 11739 EP - 11755 PB - Springer CY - New York ER - TY - JOUR A1 - Pelisoli, Ingrid Domingos A1 - Vos, Joris T1 - Gaia Data Release 2 catalogue of extremely low-mass white dwarf candidates JF - Monthly notices of the Royal Astronomical Society N2 - Extremely low-mass white dwarf stars (ELMs) are M < 0.3 M-circle dot helium-core white dwarfs born either as a result of a common-envelope phase or after a stable Roche lobe overflow episode in a multiple system. The Universe is not old enough for ELMs to have formed through single-star evolution channels. As remnants of binary evolution, ELMs can shed light onto the poorly understood phase of common-envelope evolution and provide constraints to the physics of mass accretion. Most known ELMs will merge in less than a Hubble time, providing an important contribution to the signal to be detected by upcoming space-based gravitational wave detectors. There are currently less than 150 known ELMs; most were selected by colour, focusing on hot objects, in a magnitude-limited survey of the Northern hemisphere only. Recent theoretical models have predicted a much larger space density for ELMs than estimated observationally based on this limited sample. In order to perform meaningful comparisons with theoretical models and test their predictions, a larger well-defined sample is required. In this work, we present a catalogue of ELM candidates selected from the second data release of Gaia (DR2). We have used predictions from theoretical models and analysed the properties of the known sample to map the space spanned by ELMs in the Gaia Hertzsprung-Russell diagram. Defining a set of colour cuts and quality flags, we have obtained a final sample of 5762 ELM candidates down to T-eff approximate to 5000 K. KW - catalogues KW - surveys KW - binaries: close KW - white dwarfs Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz1876 SN - 0035-8711 SN - 1365-2966 VL - 488 IS - 2 SP - 2892 EP - 2903 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Krapf, Diego A1 - Metzler, Ralf T1 - Strange interfacial molecular dynamics JF - Physics today Y1 - 2019 U6 - https://doi.org/10.1063/PT.3.4294 SN - 0031-9228 SN - 1945-0699 VL - 72 IS - 9 SP - 48 EP - 54 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Berg, Trystyn A. M. A1 - Ellison, Sara L. A1 - Sanchez-Ramirez, Ruben A1 - Lopez, Sebastian A1 - Becker, George D. A1 - Christensen, Lise A1 - Cupani, Guido A1 - Denney, Kelly D. A1 - Worseck, Gabor T1 - Sub-damped Lyman alpha systems in the XQ-100 survey - I. Identification and contribution to the cosmological H I budget JF - Monthly notices of the Royal Astronomical Society KW - galaxies: high-redshift KW - galaxies: ISM KW - quasars: absorption lines Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz2012 SN - 0035-8711 SN - 1365-2966 VL - 488 IS - 3 SP - 4356 EP - 4369 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Gong, Chen Chris A1 - Libeskind, Noam I. A1 - Tempel, Elmo A1 - Guo, Quan A1 - Gottloeber, Stefan A1 - Yepes, Gustavo A1 - Wang, Peng A1 - Sorce, Jenny A1 - Pawlowski, Marcel T1 - The origin of lopsided satellite galaxy distribution in galaxy pairs JF - Monthly notices of the Royal Astronomical Society N2 - It is well known that satellite galaxies are not isotropically distributed among their host galaxies as suggested by most interpretations of the Λ cold dark matter (ΛCDM) model. One type of anisotropy recently detected in the Sloan Digital Sky Survey (and seen when examining the distribution of satellites in the Local Group and in the Centaurus group) is a tendency to be so-called lopsided. Namely, in pairs of galaxies (like Andromeda and the Milky Way) the satellites are more likely to inhabit the region in between the pair, rather than on opposing sides. Although recent studies found a similar set-up when comparing pairs of galaxies in ΛCDM simulations indicating that such a set-up is not inconsistent with ΛCDM, the origin has yet to be explained. Here we examine the origin of such lopsided set-ups by first identifying such distributions in pairs of galaxies in numerical cosmological simulations, and then tracking back the orbital trajectories of satellites (which at z = 0 display the effect). We report two main results: first, the lopsided distribution was stronger in the past and weakens towards z = 0. Secondly, the weakening of the signal is due to the interaction of satellite galaxies with the pair. Finally, we show that the z = 0 signal is driven primarily by satellites that are on first approach, who have yet to experience a ‘flyby’. This suggests that the signal seen in the observations is also dominated by dynamically young accretion events. KW - galaxies: evolution KW - galaxies: formation KW - galaxy: kinematics and dynamics KW - Local Group KW - dark matter KW - cosmology: theory Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz1917 SN - 0035-8711 SN - 1365-2966 VL - 488 IS - 3 SP - 3100 EP - 3108 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Hani, Maan H. A1 - Ellison, Sara L. A1 - Sparre, Martin A1 - Grand, Robert J. J. A1 - Pakmor, Rüdiger A1 - Gómez, Facundo A. A1 - Springel, Volker T1 - The diversity of the circumgalactic medium around z=0 Milky Way-mass galaxies from the Auriga simulations JF - Monthly notices of the Royal Astronomical Society N2 - Galaxies are surrounded by massive gas reservoirs ( i.e. the circumgalactic medium; CGM) which play a key role in their evolution. The properties of the CGM, which are dependent on a variety of internal and environmental factors, are often inferred from absorption line surveys which rely on a limited number of single lines-of-sight. In this work we present an analysis of 28 galaxy haloes selected from the Auriga project, a cosmological magneto-hydrodynamical zoom-in simulation suite of isolated MilkyWay-mass galaxies, to understand the impact of CGM diversity on observational studies. Although the Auriga haloes are selected to populate a narrow range in halo mass, our work demonstrates that the CGM of L-star galaxies is extremely diverse: column densities of commonly observed species span similar to 3-4 dex and their covering fractions range from similar to 5 to 90 per cent. Despite this diversity, we identify the following correlations: 1) the covering fractions ( CF) of hydrogen and metals of the Auriga haloes positively correlate with stellar mass, 2) the CF of H I, C IV, and Si II anticorrelate with active galactic nucleus luminosity due to ionization effects, and 3) the CF of H I, C IV, and Si II positively correlate with galaxy disc fraction due to outflows populating the CGM with cool and dense gas. The Auriga sample demonstrates striking diversity within the CGM of L-star galaxies, which poses a challenge for observations reconstructing CGM characteristics from limited samples, and also indicates that long-term merger assembly history and recent star formation are not the dominant sculptors of the CGM. KW - methods: numerical KW - galaxies: evolution KW - galaxies: haloes Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz1708 SN - 0035-8711 SN - 1365-2966 VL - 488 IS - 1 SP - 135 EP - 152 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Teichmann, Erik A1 - Rosenblum, Michael T1 - Solitary states and partial synchrony in oscillatory ensembles with attractive and repulsive interactions JF - Chaos : an interdisciplinary journal of nonlinear science N2 - We numerically and analytically analyze transitions between different synchronous states in a network of globally coupled phase oscillators with attractive and repulsive interactions. The elements within the attractive or repulsive group are identical, but natural frequencies of the groups differ. In addition to a synchronous two-cluster state, the system exhibits a solitary state, when a single oscillator leaves the cluster of repulsive elements, as well as partially synchronous quasiperiodic dynamics. We demonstrate how the transitions between these states occur when the repulsion starts to prevail over attraction. Y1 - 2019 U6 - https://doi.org/10.1063/1.5118843 SN - 1054-1500 SN - 1089-7682 VL - 29 IS - 9 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Diercke, Andrea A1 - Kuckein, Christoph A1 - Denker, Carsten T1 - Dynamics and connectivity of an extended arch filament system JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. In this study, we analyzed a filament system, which expanded between moving magnetic features (MMFs) of a decaying sunspot and opposite flux outside of the active region from the nearby quiet-Sun network. This configuration deviated from a classical arch filament system (AFS), which typically connects two pores in an emerging flux region. Thus, we called this system an extended AFS. We contrasted classical and extended AFSs with an emphasis on the complex magnetic structure of the latter. Furthermore, we examined the physical properties of the extended AFS and described its dynamics and connectivity. Methods. The extended AFS was observed with two instruments at the Dunn Solar Telescope (DST). The Rapid Oscillations in the Solar Atmosphere (ROSA) imager provided images in three different wavelength regions, which covered the dynamics of the extended AFS at different atmospheric heights. The Interferometric Bidimensional Spectropolarimeter (IBIS) provided spectroscopic Ha data and spectropolarimetric data that was obtained in the near-infrared (NIR) Call lambda 8542 angstrom line. We derived the corresponding line-of-sight (LOS) velocities and used He II lambda 304 angstrom extreme ultraviolet (EUV) images of the Atmospheric Imaging Assembly (AIA) and LOS magnetograms of the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) as context data. Results. The NIR Call Stokes-V maps are not suitable to definitively define a clear polarity inversion line and to classify this chromospheric structure. Nevertheless, this unusual AFS connects the MMFs of a decaying sunspot with the network field. At the southern footpoint, we measured that the flux decreases over time. We find strong downflow velocities at the footpoints of the extended AFS, which increase in a time period of 30 min. The velocities are asymmetric at both footpoints with higher velocities at the southern footpoint. An EUV brigthening appears in one of the arch filaments, which migrates from the northern footpoint toward the southern one. This activation likely influences the increasing redshift at the southern footpoint. Conclusions. The extended AFS exhibits a similar morphology as classical AFSs, for example, threaded filaments of comparable length and width. Major differences concern the connection from MMFs around the sunspot with the flux of the neighboring quietSun network, converging footpoint motions, and longer lifetimes of individual arch filaments of about one hour, while the extended AFS is still very dynamic. KW - methods: observational KW - Sun: filaments, prominences KW - Sun: activity KW - techniques: image processing KW - Sun: chromosphere Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201935583 SN - 1432-0746 VL - 629 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Shoaee, Safa A1 - Armin, Ardalan A1 - Stolterfoht, Martin A1 - Hosseini, Seyed Mehrdad A1 - Kurpiers, Jona A1 - Neher, Dieter T1 - Decoding Charge Recombination through Charge Generation in Organic Solar Cells JF - Solar RRL N2 - The in-depth understanding of charge carrier photogeneration and recombination mechanisms in organic solar cells is still an ongoing effort. In donor:acceptor (bulk) heterojunction organic solar cells, charge photogeneration and recombination are inter-related via the kinetics of charge transfer states-being singlet or triplet states. Although high-charge-photogeneration quantum yields are achieved in many donor:acceptor systems, only very few systems show significantly reduced bimolecular recombination relative to the rate of free carrier encounters, in low-mobility systems. This is a serious limitation for the industrialization of organic solar cells, in particular when aiming at thick active layers. Herein, a meta-analysis of the device performance of numerous bulk heterojunction organic solar cells is presented for which field-dependent photogeneration, charge carrier mobility, and fill factor are determined. Herein, a "spin-related factor" that is dependent on the ratio of back electron transfer of the triplet charge transfer (CT) states to the decay rate of the singlet CT states is introduced. It is shown that this factor links the recombination reduction factor to charge-generation efficiency. As a consequence, it is only in the systems with very efficient charge generation and very fast CT dissociation that free carrier recombination is strongly suppressed, regardless of the spin-related factor. KW - charge generation KW - charge transfers KW - non-Langevin recombination KW - spin-related factors Y1 - 2019 U6 - https://doi.org/10.1002/solr.201900184 SN - 2367-198X VL - 3 IS - 11 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Peter, Franziska A1 - Gong, Chen Chris A1 - Pikovskij, Arkadij T1 - Microscopic correlations in the finite-size Kuramoto model of coupled oscillators JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - Supercritical Kuramoto oscillators with distributed frequencies can be separated into two disjoint groups: an ordered one locked to the mean field, and a disordered one consisting of effectively decoupled oscillators-at least so in the thermodynamic limit. In finite ensembles, in contrast, such clear separation fails: The mean field fluctuates due to finite-size effects and thereby induces order in the disordered group. This publication demonstrates this effect, similar to noise-induced synchronization, in a purely deterministic system. We start by modeling the situation as a stationary mean field with additional white noise acting on a pair of unlocked Kuramoto oscillators. An analytical expression shows that the cross-correlation between the two increases with decreasing ratio of natural frequency difference and noise intensity. In a deterministic finite Kuramoto model, the strength of the mean-field fluctuations is inextricably linked to the typical natural frequency difference. Therefore, we let a fluctuating mean field, generated by a finite ensemble of active oscillators, act on pairs of passive oscillators with a microscopic natural frequency difference between which we then measure the cross-correlation, at both super- and subcritical coupling. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevE.100.032210 SN - 2470-0045 SN - 2470-0053 VL - 100 IS - 3 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Merchel, Silke A1 - Gärtner, Andreas A1 - Beutner, Sabrina A1 - Bookhagen, Bodo A1 - Chabilan, Amelie T1 - Attempts to understand potential deficiencies in chemical procedures for AMS: Cleaning and dissolving quartz for Be-10 and Al-26 analysis JF - Nuclear instruments & methods in physics research : a journal on accelerators, instrumentation and techniques applied to research in nuclear and atomic physics, materials science and related fields in physics, Section B, Beam interactions with materials and atoms N2 - The purity of the analysed samples (e.g. quartz) with respect to chemical composition and radionuclide contamination is essential for geomorphologic applications using so-called terrestrial cosmogenic nuclides (TCNs). To guarantee this, numerous cleaning and dissolution procedures have been developed. At the DREsden Accelerator Mass Spectrometry (DREAMS) facility, we also work on enhancing the chemical quartz-enrichment methodology from bulk rock and dissolution of quartz. Repeated exposure of the bulk material to acid mixtures (HCl/H2SiF6) at room temperature for cleaning and its monitoring by optical microscopy works for most quartz-rich samples. The quartz dissolution in HF under rather mild conditions (at room temperature on a shaker-table) has the advantage to leave difficult-to-dissolve minerals (e.g., tourmaline, zircon, rutile, sillimanite, kyanite, chromite, corundum), not separated by other physical methods before, as residue. Our comparison with a high-temperature dissolution method (in a microwave) indicates an additional amount of interfering elements, such as in average about 3 mg of Ti, more than 7 mg of Al, and about 22 mu g of Be (for 50 g SiO2), is added to the sample, hence showing the superiority of our mild method. This way, we reduce problems for chemistry and AMS, but also ensure better comparability to production rates of cleaner stoichiometric quartz from calibration sites. KW - Accelerator mass spectrometry KW - In-situ KW - Terrestrial cosmogenic nuclide KW - Residue KW - Quartz Y1 - 2019 U6 - https://doi.org/10.1016/j.nimb.2019.02.007 SN - 0168-583X SN - 1872-9584 VL - 455 SP - 293 EP - 299 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pico, Tamara A1 - Mitrovica, Jerry X. A1 - Perron, J. Taylor A1 - Ferrier, Ken L. A1 - Braun, Jean T1 - Influence of glacial isostatic adjustment on river evolution along the US mid-Atlantic coast JF - Earth & planetary science letters N2 - Long-term river evolution depends partly on crustal deformation, which shapes the topography crossed by rivers. On glacial timescales, ice-sheet growth and decay can produce crustal vertical motion of ∼10 mm/yr resulting from the solid Earth's adjustment to variations in ice and water loads, comparable to tectonically-driven rates in the most rapidly uplifting mountains on Earth. This process of glacial isostatic adjustment (GIA) can influence river courses and drainage basins substantially, particularly near former ice margins. We explore the extent to which GIA influenced the evolution of rivers along the United States east coast during the last glacial cycle. We compute gravitationally self-consistent GIA responses that incorporate recent constraints on the Laurentide Ice Sheet history through the last glacial build-up phase, and we connect the predicted variations in topography to abrupt changes in river dynamics recorded in the Hudson, Delaware, Susquehanna, and Potomac Rivers from 40 ka to present. To the extent that increases in sediment transport capacity imply increases in river incision rate, the GIA-driven changes in slope and drainage area are consistent with episodes of erosion and sedimentation observed in the Hudson, Delaware, and Potomac Rivers, but inconsistent with the observed accelerated river incision in the Susquehanna River at 30-14 ka. These analyses add to a growing body of evidence showing that GIA strongly influences river evolution over millennial timescales. KW - glacial-isostatic adjustment KW - US east coast river geomorphology KW - river dynamics on glacial timescales Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2019.06.026 SN - 0012-821X SN - 1385-013X VL - 522 SP - 176 EP - 185 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Castillo, Angelica M. A1 - Shprits, Yuri Y. A1 - Ganushkina, Natalia A1 - Drozdov, Alexander A1 - Aseev, Nikita A1 - Wang, Dedong A1 - Dubyagin, Stepan T1 - Simulations of the inner magnetospheric energetic electrons using the IMPTAM-VERB coupled model JF - Journal of Atmospheric and Solar-Terrestrial Physics N2 - In this study, we present initial results of the coupling between the Inner Magnetospheric Particle Transport and Acceleration Model (IMPTAM) and the Versatile Electron Radiation Belt (VERB-3D) code. IMPTAM traces electrons of 10-100 keV energies from the plasma sheet (L = 9 Re) to inner L-shell regions. The flux evolution modeled by IMPTAM is used at the low energy and outer L* computational boundaries of the VERB code (assuming a dipole approximation) to perform radiation belt simulations of energetic electrons. The model was tested on the March 17th, 2013 storm, for a six-day period. Four different simulations were performed and their results compared to satellites observations from Van Allen probes and GOES. The coupled IMPTAM-VERB model reproduces evolution and storm-time features of electron fluxes throughout the studied storm in agreement with the satellite data (within similar to 0.5 orders of magnitude). Including dynamics of the low energy population at L* = 6.6 increases fluxes closer to the heart of the belt and has a strong impact in the VERB simulations at all energies. However, inclusion of magnetopause losses leads to drastic flux decreases even below L* = 3. The dynamics of low energy electrons (max. 10s of keV) do not affect electron fluxes at energies >= 900 keV. Since the IMPTAM-VERB coupled model is only driven by solar wind parameters and the Dst and Kp indexes, it is suitable as a forecasting tool. In this study, we demonstrate that the estimation of electron dynamics with satellite-data-independent models is possible and very accurate. KW - Electron populations KW - Radiation belts KW - IMPTAM KW - VERB Y1 - 2019 U6 - https://doi.org/10.1016/j.jastp.2019.05.014 SN - 1364-6826 SN - 1879-1824 VL - 191 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Saha, Sourav A1 - Owen, Lewis A. A1 - Orr, Elizabeth N. A1 - Caffee, Marc W. T1 - High-frequency Holocene glacier fluctuations in the Himalayan-Tibetan orogen JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Holocene glacial chronostratigraphies in glaciated valleys spread throughout the Himalayan-Tibetan orogen, including the Himalaya, Tibet, Pamir, and Tian Shan, are developed using a landsystems approach, detailed geomorphic mapping, and new and published Be-10 surface exposure dating. New studies in the Kulti valley of Lahul and the Parkachik valley of the Nun Kun massif of the Himalaya of northern India define three glacier advances at similar to 14.7, 12.2, 0.5 ka, in addition to one historically dated late 19th Century advance in the Kulti valley, and one Late Holocene advance at similar to 0.2 ka in the Parkachik valley. Three major climatic groups (subdivided into five climatic zones) are defined across the orogen using Cluster Analysis (CA) and Principal Component Analysis (PCA) to identify glaciated regions with comparable climatic characteristics to evaluate the timing, and extent of Holocene glacier advances across these regions. Our regional analyses across the Himalayan-Tibetan orogen suggest at least one Lateglacial (similar to 15.3-11.8 ka) and five Himalayan-Tibetan Holocene glacial stages (HTHS) at similar to 11.5-9.5, similar to 8.8-7.7, similar to 7.0-3.2, similar to 2.3-1.0, and <1 ka. The extent (amplitude) of glacier advances in 77 glaciated valleys is reconstructed and defined using equilibrium-line altitudes (ELAs). Modern glacier hypsometries are also assessed to help explain the intra-regional variations in glacier amplitudes during each regional glacier advance. A linear inverse glacier flow model is used to decipher the net changes in temperature (Delta T) between periods of reconstructed regional glacier advances in 66 glaciated valleys across different climatic regions throughout the orogen. The Be-10, ELAs, and Delta T data suggest enhanced monsoonal and increased precipitation during the Early Holocene, followed by relative cooling and increased aridity during the Mid- and Late Holocene that influenced glaciation. The sublimation-dominated cold-based glaciers in the northern regions of Himalayan-Tibetan orogen are more affected during these shifts in climate than the temperate glaciers in the south. (C) 2019 Elsevier Ltd. All rights reserved. KW - Holocene KW - Glaciation Central Asia KW - Cosmogenic isotopes KW - Paleoclimate modeling KW - Equilibrium-line altitudes Y1 - 2019 U6 - https://doi.org/10.1016/j.quascirev.2019.07.021 SN - 0277-3791 VL - 220 SP - 372 EP - 400 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Latour, Marilyn A1 - Dorsch, Matti A1 - Heber, Ulrich T1 - Heavy metal enrichment in the intermediate He-sdOB pulsator Feige 46 JF - Astronomy and astrophysics : an international weekly journal N2 - The intermediate He-enriched hot subdwarf star Feige 46 was recently reported as the second member of the V366 Aqr (or He-sdOBV) pulsating class. Feige 46 is very similar to the prototype of the class, LS IV-14 degrees 116, not only in terms of pulsational properties, but also in terms of atmospheric parameters and kinematic properties. LS IV-14 degrees 116 is additionally characterized by a very peculiar chemical composition, with extreme overabundances of the trans-iron elements Ge, Sr, Y, and Zr. We investigate the possibility that the similarity between the two pulsators extends to their chemical composition. We retrieved archived optical and UV spectroscopic observations of Feige 46 and performed an abundance analysis using model atmospheres and synthetic spectra computed with TLUSTY and SYNSPEC. In total, we derived abundances for 16 elements and provide upper limits for four additional elements. Using absorption lines in the optical spectrum of the star we measure an enrichment of more than 10 000x solar for yttrium and zirconium. The UV spectrum revealed that strontium is equally enriched. Our results confirm that Feige 46 is not only a member of the now growing group of heavy metal subdwarfs, but also has an abundance pattern that is remarkably similar to that of LS IV-14 degrees 116. KW - stars: abundances KW - subdwarfs KW - stars: individual: Feige 46 Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201936247 SN - 1432-0746 VL - 629 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Teomy, Eial A1 - Metzler, Ralf T1 - Transport in exclusion processes with one-step memory: density dependence and optimal acceleration JF - Journal of physics : A, Mathematical and theoretical N2 - We study a lattice gas of persistent walkers, in which each site is occupied by at most one particle and the direction each particle attempts to move to depends on its last step. We analyse the mean squared displacement (MSD) of the particles as a function of the particle density and their persistence (the tendency to continue moving in the same direction). For positive persistence the MSD behaves as expected: it increases with the persistence and decreases with the density. However, for strong anti-persistence we find two different regimes, in which the dependence of the MSD on the density is non-monotonic. For very strong anti-persistence there is an optimal density at which the MSD reaches a maximum. In an intermediate regime, the MSD as a function of the density exhibits both a minimum and a maximum, a phenomenon which has not been observed before. We derive a mean-field theory which qualitatively explains this behaviour. KW - exclusion process KW - persistence KW - lattice gas Y1 - 2019 U6 - https://doi.org/10.1088/1751-8121/ab37e4 SN - 1751-8113 SN - 1751-8121 VL - 52 IS - 38 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Ratzloff, Jeffrey K. A1 - Barlow, Brad N. A1 - Kupfer, Thomas A1 - Corcoran, Kyle A. A1 - Geier, Stephan A1 - Bauer, Evan A1 - Corbett, Henry T. A1 - Howard, Ward S. A1 - Glazier, Amy A1 - Law, Nicholas M. T1 - EVR-CB-001: An Evolving, Progenitor, White Dwarf Compact Binary Discovered with the Evryscope JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present EVR-CB-001, the discovery of a compact binary with an extremely low-mass (0.21 +/- 0.05M(circle dot)) helium core white dwarf progenitor (pre-He WD) and an unseen low-mass (0.32 +/- 0.06M(circle dot)) helium white dwarf (He WD) companion. He WDs are thought to evolve from the remnant helium-rich core of a main-sequence star stripped during the giant phase by a close companion. Low-mass He WDs are exotic objects (only about 0.2% of WDs are thought to be less than 0.3 M-circle dot), and are expected to be found in compact binaries. Pre-He WDs are even rarer, and occupy the intermediate phase after the core is stripped, but before the star becomes a fully degenerate WD and with a larger radius (approximate to 0.2R(circle dot)) than a typical WD. The primary component of EVR-CB-001 (the pre-He WD) was originally thought to be a hot subdwarf (sdB) star from its blue color and under-luminous magnitude, characteristic of sdBs. The mass, temperature (T-eff = 18,500 +/- 500 K), and surface gravity (log(g) = 4.96 +/- 0.04) solutions from this work are lower than values for typical hot subdwarfs. The primary is likely to be a post-red-giant branch, pre-He WD contracting into a He WD, and at a stage that places it nearest to sdBs on color-magnitude and T-eff-log(g) diagrams. EVR-CB-001 is expected to evolve into a fully double degenerate, compact system that should spin down and potentially evolve into a single hot subdwarf star. Single hot subdwarfs are observed, but progenitor systems have been elusive. Y1 - 2019 U6 - https://doi.org/10.3847/1538-4357/ab3727 SN - 0004-637X SN - 1538-4357 VL - 883 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Norell, Jesper A1 - Eckert, Sebastian A1 - Van Kuiken, Benjamin E. A1 - Föhlisch, Alexander A1 - Odelius, Michael T1 - Ab initio simulations of complementary K-edges and solvatization effects for detection of proton transfer in aqueous 2-thiopyridone JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - The nitrogen and sulfur K-edge X-ray absorption spectra of aqueous 2-thiopyridone, a model system for excited-state proton transfer in several recent time-resolved measurements, have been simulated from ab initio molecular dynamics. Spectral signatures of the local intra- and inter-molecular structure are identified and rationalized, which facilitates experimental interpretation and optimization. In particular, comparison of aqueous and gas phase spectrum simulations assesses the previously unquantified solvatization effects, where hydrogen bonding is found to yield solvatochromatic shifts up to nearly 1 eV of the main peak positions. Thereby, while each K-edge can still decisively determine the local protonation of its core-excited site, only their combined, complementary fingerprints allow separating all of the three relevant molecular forms, giving a complete picture of the proton transfer. Y1 - 2019 U6 - https://doi.org/10.1063/1.5109840 SN - 0021-9606 SN - 1089-7690 VL - 151 IS - 11 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Schlemm, Tanja A1 - Levermann, Anders T1 - A simple stress-based cliff-calving law JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Over large coastal regions in Greenland and Antarctica the ice sheet calves directly into the ocean. In contrast to ice-shelf calving, an increase in calving from grounded glaciers contributes directly to sea-level rise. Ice cliffs with a glacier freeboard larger than approximate to 100 m are currently not observed, but it has been shown that such ice cliffs are increasingly unstable with increasing ice thickness. This cliff calving can constitute a self-amplifying ice loss mechanism that may significantly alter sea-level projections both of Greenland and Antarctica. Here we seek to derive a minimalist stress-based parametrization for cliff calving from grounded glaciers whose freeboards exceed the 100m stability limit derived in previous studies. This will be an extension of existing calving laws for tidewater glaciers to higher ice cliffs. To this end we compute the stress field for a glacier with a simplified two-dimensional geometry from the two-dimensional Stokes equation. First we assume a constant yield stress to derive the failure region at the glacier front from the stress field within the glacier. Secondly, we assume a constant response time of ice failure due to exceedance of the yield stress. With this strongly constraining but very simple set of assumptions we propose a cliff-calving law where the calving rate follows a power-law dependence on the freeboard of the ice with exponents between 2 and 3, depending on the relative water depth at the calving front. The critical freeboard below which the ice front is stable decreases with increasing relative water depth of the calving front. For a dry water front it is, for example, 75 m. The purpose of this study is not to provide a comprehensive calving law but to derive a particularly simple equation with a transparent and minimalist set of assumptions. Y1 - 2019 U6 - https://doi.org/10.5194/tc-13-2475-2019 SN - 1994-0416 SN - 1994-0424 VL - 13 IS - 9 SP - 2475 EP - 2488 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Rüdiger, Günther A1 - Küker, Manfred A1 - Kapyla, P. J. A1 - Strassmeier, Klaus G. T1 - Antisolar differential rotation of slowly rotating cool stars JF - Astronomy and astrophysics : an international weekly journal N2 - Rotating stellar convection transports angular momentum towards the equator, generating the characteristic equatorial acceleration of the solar rotation while the radial flux of angular momentum is always inwards. New numerical box simulations for the meridional cross-correlation < u(theta)u(phi)>, however, reveal the angular momentum transport towards the poles for slow rotation and towards the equator for fast rotation. The explanation is that for slow rotation a negative radial gradient of the angular velocity always appears, which in combination with a so-far neglected rotation-induced off-diagonal eddy viscosity term nu(perpendicular to) provides "antisolar rotation" laws with a decelerated equator Similarly, the simulations provided positive values for the rotation-induced correlation < u(r)u(theta)>, which is relevant for the resulting latitudinal temperature profiles (cool or warm poles) for slow rotation and negative values for fast rotation. Observations of the differential rotation of slowly rotating stars will therefore lead to a better understanding of the actual stress-strain relation, the heat transport, and the underlying model of the rotating convection. KW - stars: solar-type KW - convection KW - stars: rotation KW - turbulence Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201935280 SN - 1432-0746 VL - 630 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Mack, Daniel Emil A1 - Laquai, Rene A1 - Mueller, Bernd A1 - Helle, Oliver A1 - Sebold, Doris A1 - Vassen, Robert A1 - Bruno, Giovanni T1 - Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing JF - Journal of the American Ceramic Society N2 - Degradation of thermal barrier coatings (TBCs) in gas-turbine engines due to calcium-magnesium-aluminosilicate (CMAS) glassy deposits from various sources has been a persistent issue since many years. In this study, state of the art electron microscopy was correlated with X-ray refraction techniques to elucidate the intrusion of CMAS into the porous structure of atmospheric plasma sprayed (APS) TBCs and the formation and growth of cracks under thermal cycling in a burner rig. Results indicate that the sparse nature of the infiltration as well as kinetics in the burner rig are majorly influenced by the wetting behavior of the CMAS. Despite the obvious attack of CMAS on grain boundaries, the interaction of yttria-stabilized zirconia (YSZ) with intruded CMAS has no immediate impact on structure and density of internal surfaces. At a later stage the formation of horizontal cracks is observed in a wider zone of the TBC layer. KW - characterization KW - CMAS KW - synchrotron X-ray refraction radiography KW - thermal barrier coatings Y1 - 2019 U6 - https://doi.org/10.1111/jace.16465 SN - 0002-7820 SN - 1551-2916 VL - 102 IS - 10 SP - 6163 EP - 6175 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Iwamoto, Masanori A1 - Amano, Takanobu A1 - Hoshino, Masahiro A1 - Matsumoto, Yosuke A1 - Niemiec, Jacek A1 - Ligorini, Arianna A1 - Kobzar, Oleh A1 - Pohl, Martin T1 - Precursor Wave Amplification by Ion-Electron Coupling through Wakefield in Relativistic Shocks JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - We investigated electromagnetic precursor wave emission in relativistic shocks by using two-dimensional particle-in-cell simulations. We found that the wave amplitude is significantly enhanced by a positive feedback process associated with ion-electron coupling through the wakefields for high magnetization. The wakefields collapse during the nonlinear process of the parametric decay instability in the near-upstream region, where nonthermal electrons and ions are generated. The intense coherent emission and the particle acceleration may operate in high-energy astrophysical objects. Y1 - 2019 U6 - https://doi.org/10.3847/2041-8213/ab4265 SN - 2041-8205 SN - 2041-8213 VL - 883 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Raddi, Roberto A1 - Hollands, M. A. A1 - Koester, D. A1 - Hermes, J. J. A1 - Gansicke, B. T. A1 - Heber, Ulrich A1 - Shen, Ken J. A1 - Townsley, D. M. A1 - Pala, Anna Francesca A1 - Reding, J. S. A1 - Toloza, O. F. A1 - Pelisoli, Ingrid Domingos A1 - Geier, Stephan A1 - Fusillo, Nicola Pietro Gentile A1 - Munari, Ullisse A1 - Strader, J. T1 - Partly burnt runaway stellar remnants from peculiar thermonuclear supernovae JF - Monthly notices of the Royal Astronomical Society N2 - We report the discovery of three stars that, along with the prototype LP 40-365, form a distinct class of chemically peculiar runaway stars that are the survivors of thermonuclear explosions. Spectroscopy of the four confirmed LP 40-365 stars finds ONe-dominated atmospheres enriched with remarkably similar amounts of nuclear ashes of partial O- and Si-burning. Kinematic evidence is consistent with ejection from a binary supernova progenitor; at least two stars have rest-frame velocities indicating they are unbound to the Galaxy. With masses and radii ranging between 0.20 and 0.28M(circle dot) and between 0.16 and 0.60 R-circle dot, respectively, we speculate these inflated white dwarfs are the partly burnt remnants of either peculiar Type Iax or electron-capture supernovae. Adopting supernova rates from the literature, we estimate that similar to 20 LP 40-365 stars brighter than 19 mag should be detectable within 2 kpc from the Sun at the end of the Gaia mission. We suggest that as they cool, these stars will evolve in their spectroscopic appearance, and eventually become peculiar O-rich white dwarfs. Finally, we stress that the discovery of new LP 40-365 stars will be useful to further constrain their evolution, supplying key boundary conditions to the modelling of explosion mechanisms, supernova rates, and nucleosynthetic yields of peculiar thermonuclear explosions. KW - stars: individual: LP 40-365 KW - subdwarfs KW - supernovae: general KW - white dwarfs KW - Galaxy: kinematics and dynamics Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz1618 SN - 0035-8711 SN - 1365-2966 VL - 489 IS - 2 SP - 1489 EP - 1508 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Löbling, Lisa A1 - Rauch, Thomas A1 - Bertolami Miller, Marcelo Miguel A1 - Todt, Helge Tobias A1 - Friederich, F. A1 - Ziegler, M. A1 - Werner, Klaus A1 - Kruk, J. W. T1 - Spectral analysis of the hybrid PG 1159-type central stars of the planetary nebulae Abell 43 and NGC7094 JF - Monthly notices of the Royal Astronomical Society N2 - Stellar post asymptotic giant branch (post-AGB) evolution can be completely altered by a final thermal pulse (FTP) which may occur when the star is still leaving the AGB (AFTP), at the departure from the AGB at still constant luminosity (late TP, LTP) or after the entry to the white-dwarf cooling sequence (very late TP, VLTP). Then convection mixes the Herich material with the H-rich envelope. According to stellar evolution models the result is a star with a surface composition of H approximate to 20 per cent by mass (AFTP), approximate to 1 per cent (LTP), or (almost) no H (VLTP). Since FTP stars exhibit intershell material at their surface, spectral analyses establish constraints for AGB nucleosynthesis and stellar evolution. We performed a spectral analysis of the so-called hybrid PG 1159-type central stars (CS) of the planetary nebulae Abell 43 and NGC7094 by means of non-local thermodynamical equilibrium models. We confirm the previously determined effective temperatures of T-eff = 115 000 +/- 5 000K and determine surface gravities of log (g /(cm s(-2))) = 5.6 +/- 0.1 for both. From a comparison with AFTP evolutionary tracks, we derive stellar masses of 0.57(-0.04)(+0.07)M(circle dot) and determine the abundances of H, He, and metals up to Xe. Both CS are likely AFTP stars with a surface H mass fraction of 0.25 +/- 0.03 and 0.15 +/- 0.03, respectively, and an Fe deficiency indicating subsolar initial metallicities. The light metals show typical PG 1159-type abundances and the elemental composition is in good agreement with predictions from AFTP evolutionary models. However, the expansion ages do not agree with evolution time-scales expected from the AFTP scenario and alternatives should be explored. KW - stars: abundances KW - stars: AGB and post-AGB KW - stars: atmospheres KW - stars: evolution KW - stars: individual: WD1751+106 KW - stars: individual: WD2134+125 Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz1994 SN - 0035-8711 SN - 1365-2966 VL - 489 IS - 1 SP - 1054 EP - 1071 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Saha, Sourav A1 - Owen, Lewis A. A1 - Orr, Elizabeth N. A1 - Caffee, Marc W. T1 - Cosmogenic Be-10 and equilibrium-line altitude dataset of Holocene glacier advances in the Himalayan-Tibetan orogen JF - Data in brief N2 - A comprehensive analysis of the variable temporal and spatial responses of tropical-subtropical high-altitude glaciers to climate change is critical for successful model predictions and environmental risk assessment in the Himalayan-Tibetan orogen. High-frequency Holocene glacier chronostratigraphies are therefore reconstructed in 79 glaciated valleys across the orogen using 519 published and 16 new terrestrial cosmogenic 10Be exposure age dataset. Published 10Be ages are compiled only for moraine boulders (excluding bedrock ages). These ages are recalculated using the latest ICE-D production rate calibration database and the scaling scheme models. Outliers for the individual moraine are detected using the Chauvenet's criterion. In addition, past equilibrium-line altitudes (ELAs) are determined using the area-altitude (AA), area accumulation ratio (AAR), and toe-headwall accumulation ratio (THAR) methods for each glacier advance. The modern maximum elevations of lateral moraines (MELM) are also used to estimate modern ELAs and as an independent check on mean ELAs derived using the above three methods. These data may serve as an essential archive for future studies focusing on the cryospheric and environmental changes in the Himalayan-Tibetan orogen. A more comprehensive analysis of the published and new 10Be ages and ELA results and a list of references are presented in Saha et al. (2019, High-frequency Holocene glacier fluctuations in the Himalayan-Tibetan orogen. Quaternary Science Reviews, 220, 372–400). KW - Cosmogenic nuclides KW - Equilibrium-line altitudes KW - Holocene KW - Central asia KW - Glaciation Y1 - 2019 U6 - https://doi.org/10.1016/j.dib.2019.104412 SN - 2352-3409 VL - 26 PB - Elsevier CY - Amsterdam ER -