bluuebunny/crossref_metadata_2025_split huggingface dataset:
First Results of the SkyMapper Transient Survey
Authors: Möller A. , Tucker B. E. , Armstrong P. , Chang S.-W. , Lowson N. , Onken C. A. , Panther F. , Ridden-Harper R. , Ruiter A. J. , Scalzo R. , Schmidt B. P. , Seitenzahl I. R. , Sommer N. E. , Wolf C. , Yuan F. , Zhang B. 
Published: August 2019

AbstractThe SkyMapper Transient survey (SMT) is exploring variability in the southern sky by performing (a) a rolling search to discover and study supernovæ, and (b) a Target of Opportunity programme that uses the robotic SkyMapper Telescope at Siding Spring Observatory. The supernova survey is obtaining a non-targeted sample of Type Ia supernovæ (SNe Ia) at low redshifts, z < 0.1, and studying other interesting transients found with the search strategy. We have a Target of Opportunity programme with an automatic response mechanism to search for optical counterparts to gravitational-wave and fast radio-burst events; it benefits from SkyMapper’s large field of view of 5.7 sq. deg. and a rapid data reduction pipeline.We present first results of the SMT survey. The SMT pipeline can process and obtain potential candidates within 12 hours of observation. It disentangles real transients from processing artefacts using a machine-learning algorithm. To date, SMT has discovered over 60 spectroscopically confirmed supernovæ, several peculiar objects, and over 40 SNe Ia including one (SNIa 2016hhd) which was found within the first few days of explosion. We have also participated in searches for optical counterparts of gravitational waves, fast radio bursts and other transients, and have published observations of the optical counterpart of the gravitational-wave event GW170817. We also participate in coordinated observations with the Deeper Wider Faster programme, and the Kepler K2 cosmology project.
The High-Cadence Transient Survey (HiTS): Early Supernova Light-Curves
Authors: Förster F. 
Published: August 2019

AbstractSupernovae (SNe) are cosmic explosions which are usually represented in a small region of the luminosity–time-scale diagram when discussing the variable sky. However, there are different time-scales involved in the evolution of SNe that are not reflected by that representation. This talk reviewed some of the physical mechanisms driving the SN light-curve diversity, especially at early times. It then discussed our efforts in the astroinformatics laboratory at CMM and at MAS to discover very young SNe using large etendue telescopes such as Blanco/DECam; those efforts led to the real-time discovery of more than one hundred SNe, some of them very young, under the High cadence Transient Survey (HiTS). We showed that, by comparing hydrodynamical models in the literature with HiTS SNe using Markov Chain Monte Carlo to sample from the posterior in a Bayesian approach, we can constrain the physical parameters that are driving the early time-evolution of these events. We also discussed how these data are being used for different projects, such as the discovery of asteroids and variable stars, and for testing different machine-learning algorithms in an interdisciplinary approach.
Time-Domain Studies with Astrosat
Authors: Hutchings J. B. 
Published: August 2019

AbstractAstrosat is a multi-instrument orbiting observatory that was launched in 2015 by the Indian Space Research Organization (ISRO). The same field of view is observed simultaneously at wavelengths ranging from gamma ray to the optical blue. This talk described the observatory’s performance, with emphasis on time-domain studies, and gave examples of results.
OCTOCAM – a New Workhorse Instrument for Transient Follow-up at Gemini South
Authors: Thöne C. C. , de Ugarte Postigo A. 
Published: August 2019

AbstractOctocam is an 8-channel VIS and NIR imager and spectrograph to be installed at Gemini South in 2022. It provides simultaneous imaging in g’,r’,i’,z,Y,J,H,KS bands or simultaneous spectroscopy at a resolution of ∼4000, together with high time-resolution options. Additional capabilities such as spectropolarimetry or an Integral Field Unit could be added as an upgrade later. These properties makes it very well suited as a follow-up instrument for transient searches. It is planned as a dedicated follow-up instrument for LSST, and will start operations at the same time as the LSST main survey. Octocam was conceived as a consortium consisting of South-West Research Institute in San Antonio, Texas, IAA-CSIC in Granada, FRACTAL SLNE in Madrid, and George Washington University.
Probing Convective Mixing in Stellar Interiors with α Centauri A and B
Authors: Joyce M. , Chaboyer B. 
Published: August 2019

AbstractThe bright nearby binary α Centauri constitutes an excellent laboratory for testing stellar evolution models. The mass, radius, and luminosity of α Cen A and B are known to better than 1% accuracy thanks to recent interferometric and adaptive optical observations, and p-mode oscillations have been observed in both stars. We present new stellar models which fit simultaneously the classical and seismic observations, with particular emphasis on the convective mixing length parameter MLT – the adaptivity of which is necessary to fit the models to observations. The oscillation data provide an important constraint on the models, as the small frequency separation is sensitive to the composition gradient in the core of the stars, while the large frequency separation constrains the mean density of the stars, providing an independent check on the mass and radius.
First Results from Project SUNBIRD: Supernovæ UNmasked By Infra-Red Detection
Authors: Kool E. C. , Ryder S. D. , Kankare E. , Reynolds T. , Mattila S. , Pérez-Torres M. , McDermid R. 
Published: August 2019

AbstractMeasurements of current rates of core-collapse supernovæ (CCSNe) suffer from significant uncertainties, probably due to the large fraction of CCSNe that explode in crowded regions which have bright background emission and significant dust extinction. Conventional optical (seeing-limited) SN surveys generally fail to detect them, but including them is crucial to the accurate determination of CCSN rates. Project SUNBIRD aims to tighten the present constraints on the fraction of CCSNe that are missed by conventional SN surveys. We are monitoring more than 25 dusty luminous infrared galaxies that are actively star-forming, for evidence of dust-obscured CCSNe, in an effort to characterise the population of CCSNes exploding in those nuclear regions of dusty LIRGs. We observe in the near-infrared, which is less affected by dust extinction compared to the optical; we are using Gemini South and Keck, and we make use of state-of-the-art laser guide-star adaptive optics instruments to achieve a spatial resolution <0’.1, which is sufficient to resolve close to the galactic nucleus.During the project’s first year we discovered three CCSNe and one candidate one, with nuclear offsets as small as 200 pc, as cited in the poster. Aggregating the new discoveries with the CCSNe found in previous programmes employing AO, we compared the distribution of nuclear offsets of AO CCSN discoveries with all other documented CCSNe discovered in LIRGs. The poster showed that our method is singularly effective at uncovering CCSNe in the nuclear regions of LIRGs, and that while optical surveys dominate SNe discoveries far from a galaxy’s centre, near infra-red AO observations are needed to probe the regions within 1 kpc of the nucleus.
Coupling Radioactive Waste Glass Dissolution Measurements in Generic Groundwaters With Reactive Transport Modeling of Repository Scenarios
Authors: Iwalewa T. M. , Farnan I. 
Published: August 2019

AbstractThe reliable simulation of radionuclide migration away from the near field of a geological repository for safety analyses requires a fundamental understanding of processes in the near field. We focus this study on investigating the behavior of UK MW25 waste glass (a nonradioactive simulant of U.K. Magnox glass) and other near‐field components in a geological repository over long periods of time. The approach used involved a two‐step process: waste glass dissolution measurements and modeling in potential repository groundwaters, and reactive transport simulation of radionuclide release and transport in the near field. The Stage 1 rate of MW25 measured in lower‐strength‐sedimentary‐rock groundwater was found to be slightly higher than that measured in higher‐strength‐rock groundwater. Experimental results show the critical role of groundwater chemistry on waste glass dissolution kinetics. Reactive transport model parameterization was accomplished by coupling direct laboratory measurements and literature data with transport processes. The results revealed that 79Se, 99Tc, and 237Np are the radionuclides that will have the greatest impact on the environment at long times. The performance assessment results show that the improvement afforded by the addition of a copper canister in the waste package, as opposed to having only a steel canister, is marginal and higher strength rock would be a more effective barrier at long time than lower strength sedimentary rock in terms of restricting the transport of the radionuclides. Our model provides deep insights into the contribution of waste glass durability and other near‐field components in the containment and retardation of radionuclide transport.
Role of Ammonia on the Feedback Between AWC and Inorganic Aerosol Formation During Heavy Pollution in the North China Plain
Authors: Ge Baozhu , Xu Xiaobin , Ma Zhiqiang , Pan Xiaole , Wang Zhe , Lin Weili , Ouyang Bin , Xu Danhui , Lee James , Zheng Mei , Ji Dongsheng , Sun Yele , Dong Huabin , Squires Freya Anne , Fu Pingqing , Wang Zifa 
Published: August 2019

AbstractAtmospheric NH3 plays a vital role not only in the environmental ecosystem but also in atmosphere chemistry. To further understand the effects of NH3 on the formation of haze pollution in Beijing, ambient NH3 and related species were measured and simulated at high resolutions during the wintertime Air Pollution and Human Health‐Beijing (APHH‐Beijing) campaign in 2016. We found that the total NHx (gaseous NH3+particle NH4+) was mostly in excess of the SO42−‐NO3−‐NH4+‐water equilibrium system during our campaign. This NHx excess made medium aerosol acidity, with the median pH value being 3.6 and 4.5 for polluted and nonpolluted conditions, respectively, and enhanced the formation of particle phase nitrate. Our analysis suggests that NH4NO3 is the most important factor driving the increasing of aerosol water content with NO3− controlling the prior pollution stage and NH4+ the most polluted stage. Increased formation of NH4NO3 under excess NHx, especially during the nighttime, may trigger the decreasing of aerosol deliquescence relative humidity even down to less than 50% and hence lead to hygroscopic growth even under RH conditions lower than 50% and the wet aerosol particles become better medium for rapid heterogeneous reactions. A further increase of RH promotes the positive feedback “aerosol water content‐heterogeneous reactions” and ultimately leads to the formation of severe haze. Modeling results by Nested Air Quality Prediction Monitor System (NAQPMS) show the control of 20% NH3 emission may affect 5–11% of particulate matter PM2.5 formation under current emissions conditions in the North China Plain.
Expansion of Coccidioidomycosis Endemic Regions in the United States in Response to Climate Change
Authors: Gorris Morgan E. , Treseder Kathleen K. , Zender Charles S. , Randerson James T. 
Published: August 2019

AbstractCoccidioidomycosis (Valley fever) is a fungal disease endemic to the southwestern United States. Across this region, temperature and precipitation influence the extent of the endemic region and number of Valley fever cases. Climate projections for the western United States indicate that temperatures will increase and precipitation patterns will shift, which may alter disease dynamics. We estimated the area potentially endemic to Valley fever using a climate niche model derived from contemporary climate and disease incidence data. We then used our model with projections of climate from Earth system models to assess how endemic areas will change during the 21st century. By 2100 in a high warming scenario, our model predicts that the area of climate‐limited endemicity will more than double, the number of affected states will increase from 12 to 17, and the number of Valley fever cases will increase by 50%. The Valley fever endemic region will expand north into dry western states, including Idaho, Wyoming, Montana, Nebraska, South Dakota, and North Dakota. Precipitation will limit the disease from spreading into states farther east and along the central and northern Pacific coast. This is the first quantitative estimate of how climate change may influence Valley fever in the United States. Our predictive model of Valley fever endemicity may provide guidance to public health officials to establish disease surveillance programs and design mitigation efforts to limit the impacts of this disease.
Spectral Signatures of Adiabatic Electron Acceleration at Saturn Through Corotation Drift Cancelation
Authors: Sun Y. X. , Roussos E. , Krupp N. , Zong Q. G. , Kollmann P. , Zhou X. Z. 
Published: August 2019

AbstractThe energetic electron spectra of Saturn's radiation belts are studied using Cassini's 13 years of measurements by the Magnetosphere Imaging Instrument/Low Energy Magnetospheric Measurement System detector. We find that between L shells (L) of 10 and 4.5 the differential flux spectrum of 0.3‐ to 1.6‐MeV electrons evolves from a single power law to two power law functions separated at an energy cutoff (Ec). We show that inside L∼8, Ec has an L shell dependence that tracks consistently the energy of corotation drift cancelation (or resonance) ECDR, that is, the energy at which magnetic electron drifts and azimuthal corotation cancel, and is not associated with the absorbing effects of Saturn's moons. Ec also deviates from what conservation of the first adiabatic invariant would dictate. Our results verify that electrons around ECDR can be transported radially very efficiently by variable convective flows, such as those related to the noon‐midnight electric field in Saturn's magnetosphere.
Increasing Synchrony of Annual River‐Flood Peaks and Growing Season in Europe
Authors: Balke Thorsten , Nilsson Christer 
Published: August 2019

AbstractIn a changing climate, time sensitive ecological interactions such as pollination and predation are vulnerable to temporal mismatch with direct consequences for ecosystem functioning. It is not known if synchrony and asynchrony of ecological and physical processes such as flood disturbance and plant phenology may similarly be affected by climate change. Here, by spatially merging temperature and flood peak data, we show for the first time that in Central and Eastern Europe, annual river flood peaks increasingly occur within the thermal growing season. This is due to the combined effect of earlier spring onsets and later flood peaks. Such increased physical‐phenological synchrony may especially impact river biogeomorphology and riparian floodplain ecosystem functioning through uprooting of seedlings and increased hydraulic roughness during major flood events.
Energy Conversion and Electron Acceleration in the Magnetopause Reconnection Diffusion Region
Authors: Pritchard K. R. , Burch J. L. , Fuselier S. A. , Webster J. M. , Torbert R. B. , Argall M. R. , Broll J. , Genestreti K. J. , Giles B. L. , Le Contel O. , Mukherjee J. , Phan T. D. , Rager A. C. , Russell C. T. , Strangeway R. J. 
Published: August 2019

AbstractData are analyzed from a Magnetospheric Multiscale encounter with a dayside magnetopause reconnection region on 29 December 2016. The uniqueness of the event stems from the small (~7 km) average spacecraft separation and the sequential sampling of an electron diffusion region with electron crescent distributions. We quantitatively investigate the earthward acceleration of magnetosheath electrons through the in‐plane null by the polarization electric field EN that points radially outward from the magnetopause. The results compare favorably with previous plasma simulations with one important difference that the reconnection electric field (EM) extends throughout the region of strong EN so that both fields energize electrons in the same region. This acceleration is quantified here for the first time. As the spacecraft penetrate deeper into the region of enhanced EN, the magnetic reflection of lower‐energy electrons produces a thinner crescent.
Remote Magnetometry With Mesospheric Sodium Based on Gated Photon Counting
Authors: Fan T. , Yang X. , Dong J. , Zhang L. , Cui S. , Qian J. , Dong R. , Deng K. , Zhou T. , Wei K. , Feng Y. , Chen W. 
Published: August 2019

AbstractRemote detection of geomagnetic fields in the mesosphere would provide a powerful tool for mapping and interpreting Earth's lithospheric magnetic fields, monitoring magnetic disturbances in conjunction with the aurora, and making long‐term measurements of ionospheric currents at polar regions. Based on gated photon counting and direct frequency sweep, a remote magnetometry scheme with precession of mesospheric sodium was demonstrated. The technique of gated photon counting has an advantage in background light suppression and has the potential to achieve altitude‐resolved magnetic field measurements with an optimized laser source. An intensity‐modulated laser beam was utilized to optically pump sodium atoms in the mesopause, and a ground‐based telescope collects fluorescent echoes to infer the magnetic field. The experiment was carried out at Lijiang observatory where we validated this technique and measured the geomagnetic field with a sensitivity of 849 nT/Hz1/2, which can be improved through further optimization.
Icecap and Subglacial Crustal Deformation Inferred From SAR Pixel Tracking: The 2014 Dike Intrusion Episode in the Bárðarbunga Volcanic System, Iceland
Authors: Himematsu Yuji , Sigmundsson Freysteinn , Furuya Masato 
Published: August 2019

AbstractBárðarbunga is an active volcano beneath the Vatnajökull icecap in Iceland, where a subglacial dike intrusion occurred in 2014. This area has been studied with interferometric synthetic aperture radar, an important geodetic method that measures crustal deformation; however, ice/snow cover on volcanoes impedes the mapping of crustal deformation because of decorrelation problems. Previous geodetic observations have reported deformation signals at ice‐free regions of a major dike formed in 2014 in the Bárðarbunga volcanic system, but direct observations of the subglacial crustal deformation associated with the dike intrusion have been limited. We applied a pixel tracking approach to various satellite synthetic aperture radar (SAR) data over the northern part of the Vatnajokull icecap and the Holuhraun plain. The pixel tracking data revealed not only crustal deformation fields in the ice‐free region of the magma intrusion, which covers only about 20% of the entire length of dike, but also icecap surface movements over the subglacial part of the dike in the ablation area of the Vatnajökull icecap. Signals above the icecap, suggesting subsidence due to subglacial graben formation, are consistent with the dike propagation path inferred from seismicity during the episode. By subtracting the scaled pre‐diking signals from the co‐diking signals, we corrected for the steady‐state icecap flow signals to derive the subglacial crustal deformations. We showed that the inferred subglacial crustal deformation signals can significantly contribute to the improvement of dike opening/faulting distributions. Applying the pixel tracking to satellite images will enable mapping subglacial crustal deformation in the case of subglacial volcanic activity.
Particle Migration and Clogging in Porous Media: A Convergent Flow Microfluidics Study
Authors: Liu Q. , Zhao B. , Santamarina J. C. 
Published: August 2019

AbstractThe migration and retention of fine particles in porous media are important phenomena in natural processes and engineering applications. Migrating particles experience physicochemical interactions with carrier fluids, pore walls, and other migrating particles. The governing dimensionless ratios capture particle‐level forces, flow conditions, and geometric characteristics. This study explores micron‐size particle migration and retention in microfluidic chips during convergent radial flow, which is the prevalent flow condition in water extraction and oil production. Pore‐scale observations reveal the role of electrostatic interactions on clogging mechanisms: Glass particles experience retardation‐accumulation bridging, while quasi‐buoyant latex particles involve capture and clogging. Consequently, flow rates exert opposite effects on the clogging behavior of inertial glass particles versus electrostatically affected latex particles. Migrating particles experience a varying fluid velocity field in convergent radial flow, and clogging reflects the evolving local conditions (Nad, Ar, Stk, and Re). In particular, clogged pores alter local flow and promote further clogging nearby. Pore network model simulations suggest that such “dependent clogging” lowers the permeability of the porous medium more effectively than independent clogging at random locations.
Constraining Emissions of Volatile Organic Compounds Over the Indian Subcontinent Using Space‐Based Formaldehyde Measurements
Authors: Chaliyakunnel Sreelekha , Millet Dylan B. , Chen Xin 
Published: August 2019

AbstractIndia is an air pollution mortality hot spot, but regional emissions are poorly understood. We present a high‐resolution nested chemical transport model (GEOS‐Chem) simulation for the Indian subcontinent and use it to interpret formaldehyde (HCHO) observations from two satellite sensors (OMI and GOME‐2A) in terms of constraints on regional volatile organic compound (VOC) emissions. We find modeled biogenic VOC emissions to be overestimated by ~30–60% for most locations and seasons, and derive a best estimate biogenic flux of 16 Tg C/year subcontinent‐wide for year 2009. Terrestrial vegetation provides approximately half the total VOC flux in our base‐case inversions (full uncertainty range: 44–65%). This differs from prior understanding, in which biogenic emissions represent >70% of the total. Our derived anthropogenic VOC emissions increase slightly (13–16% in the base case, for a subcontinent total of 15 Tg C/year in 2009) over RETRO year 2000 values, with some larger regional discrepancies. The optimized anthropogenic emissions agree well with the more recent CEDS inventory, both subcontinent‐wide (within 2%) and regionally. An exception is the Indo‐Gangetic Plain, where we find an underestimate for both RETRO and CEDS. Anthropogenic emissions thus constitute 37–50% of the annual regional VOC source in our base‐case inversions and exceed biogenic emissions over the Indo‐Gangetic Plain, West India, and South India, and over the entire subcontinent during winter and post‐monsoon. Fires are a minor fraction (<7%) of the total regional VOC source in the prior and optimized model. However, evidence suggests that VOC emissions in the fire inventory used here (GFEDv4) are too low over the Indian subcontinent.
Future Directions for Whole Atmosphere Modeling: Developments in the Context of Space Weather
Authors: Jackson David R. , Fuller‐Rowell Tim J. , Griffin Dan J. , Griffith Matthew J. , Kelly Christopher W. , Marsh Daniel R. , Walach Maria‐Theresia 
Published: August 2019

AbstractCoupled Sun‐to‐Earth models represent a key part of the future development of space weather forecasting. With respect to predicting the state of the thermosphere and ionosphere, there has been a recent paradigm shift; it is now clear that any self‐respecting model of this region needs to include some representation of forcing from the lower atmosphere, as well as solar and geomagnetic forcing. Here we assess existing modeling capability and set out a road map for the important next steps needed to ensure further advances. These steps include a model verification strategy, analysis of the impact of nonhydrostatic dynamical cores, and a cost‐benefit analysis of model chemistry for weather and climate applications.