1. A systematically selected sample of luminous, long-duration, ambiguous nuclear transientsP. Wiseman, R. D. Williams, I. Arcavi, L. Galbany, M. J. Graham, S. Hönig, M. Newsome, B. Subrayan, Mark Sullivan, Tanja Petrushevska, 2025, izvirni znanstveni članek Opis: ABSTRACT
We present a search for luminous long-duration ambiguous nuclear transients (ANTs) similar to the unprecedented discovery of the extreme ambiguous event AT2021lwx with a $\gt 150$ d rise time and luminosity $10^{45.7}$ erg s$^{-1}$. We use the Lasair transient broker to search Zwicky Transient Facility (ZTF) data for transients lasting more than one year and exhibiting smooth declines. Our search returns 59 events, 7 of which we classify as ANTs assumed to be driven by accretion onto supermassive black holes. We propose the remaining 52 are stochastic variability from regular supermassive black hole accretion rather than distinct transients. We supplement the seven ANTs with three nuclear transients in ZTF that fail the light curve selection but have clear single flares and spectra that do not resemble typical active galactic nucleus. All of these 11 ANTs have a mid-infrared flare from an assumed dust echo, implying the ubiquity of dust around the black holes giving rise to ANTs. No events are more luminous than AT2021lwx, but one (ZTF19aamrjar) has twice the duration and a higher integrated energy release. On the other extreme, ZTF20abodaps reaches a luminosity close to AT2021lwx with a rise time $\lt 20$ d and that fades smoothly in $\gt 600$ d. We define a portion of rise-time versus flare amplitude space that selects ANTs with $\sim 50$ per cent purity against variable AGNs. We calculate a volumetric rate of $\gtrsim 3\times 10^{-11}$ Mpc$^{-1}$ yr$^{-1}$, consistent with the events being caused by tidal disruptions of intermediate and high-mass stars.
Ključne besede: tidal disruption events, accretion
Objavljeno v RUNG: 06.02.2025; Ogledov: 398; Prenosov: 8
 Celotno besedilo (5,37 MB)
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2. Atmospheric chemistry and physics in the atmosphere of a developed megacity (London): An overview of the REPARTEE experiment and its conclusionsRoy M Harrison, Manuel DallOsto, David C S Beddows, Alistair J Thorpe, William J Bloss, James D Allan, Hugh Coe, James R Dorsey, Martin W Gallagher, Claire Martin, John Whitehead, Paul I Williams, Roderick L Jones, Justin M Langridge, A K Benton, Stephen M Ball, Ben Langford, C Nicholas Hewitt, Brian Davison, Damien Martin, K Fredrik Peterson, Stephen J Henshaw, Iain R. White, Dudley E Shallcross, Janet F Barlow, Tyrone Dunbar, Fay Davies, Eiko Nemitz, Gavin J Phillips, Carole Helfter, Chiara F Di Marco, Steven Smith, 2012, pregledni znanstveni članek Opis: The Regents Park and Tower Environmental Experiment (REPARTEE) comprised two campaigns in London in October 2006 and October/November 2007. The experiment design involved measurements at a heavily trafficked roadside site, two urban background sites and an elevated site at 160-190 m above ground on the BT Tower, supplemented in the second campaign by Doppler lidar measurements of atmospheric vertical structure. A wide range of measurements of airborne particle physical metrics and chemical composition were made as well as measurements of a considerable range of gas phase species and the fluxes of both particulate and gas phase substances. Significant findings include (a) demonstration of the evaporation of traffic-generated nanoparticles during both horizontal and vertical atmospheric transport; (b) generation of a large base of information on the fluxes of nanoparticles, accumulation mode particles and specific chemical components of the aerosol and a range of gas phase species, as well as the elucidation of key processes and comparison with emissions inventories; (c) quantification of vertical gradients in selected aerosol and trace gas species which has demonstrated the important role of regional transport in influencing concentrations of sulphate, nitrate and secondary organic compounds within the atmosphere of London; (d) generation of new data on the atmospheric structure and turbulence above London, including the estimation of mixed layer depths; (e) provision of new data on trace gas dispersion in the urban atmosphere through the release of purposeful tracers; (f) the determination of spatial differences in aerosol particle size distributions and their interpretation in terms of sources and physico-chemical transformations; (g) studies of the nocturnal oxidation of nitrogen oxides and of the diurnal behaviour of nitrate aerosol in the urban atmosphere, and (h) new information on the chemical composition and source apportionment of particulate matter size fractions in the atmosphere of London derived both from bulk chemical analysis and aerosol mass spectrometry with two instrument types.
Ključne besede: megacity, trace gas, urban atmosphere, atmospheric transport, chemical composition, aerosol
Objavljeno v RUNG: 18.07.2019; Ogledov: 4448; Prenosov: 0
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3. Electrical characteristics of the vertical GaN rectifiers fabricated on bulk GaN waferYaqi Wang, Hui Xu, Siddharth Alur, Yogesh Sharma, Fei Tong, Patrick Gartland, Tamara Issacs-Smith, Claude Ahyi, John Williams, Minseo Park, Ginger Wheeler, Mark Johnson, Andrew A. Allerman, Andrew Hanser, Tanya Paskova, Edward A. Preble, Keith R. Evans, 2011, izvirni znanstveni članek Ključne besede: GaN, rectifier
Objavljeno v RUNG: 17.01.2017; Ogledov: 5466; Prenosov: 0
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4. Biofunctionalized AlGaN/GaN high electron mobility transistor for DNA hybridization detectionResham Thapa, Siddharth Alur, Kyusang Kim, Fei Tong, Yogesh Sharma, Moonil Kim, Claude Ahyi, Jing Dai, Jong Wook Hong, Michael Bozack, John Williams, Ahjeong Son, Amir Dabiran, Minseo Park, 2012, izvirni znanstveni članek Ključne besede: AlGaN/GaN HEMT, DNA hybridization detection
Objavljeno v RUNG: 16.01.2017; Ogledov: 5932; Prenosov: 0
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5. Flexible organic/inorganic hybrid solar cells based on conjugated polymer and ZnO nanorod arrayFei Tong, Kyusang Kim, Daniel Martinez, Resham Thapa, Ayayi Ahyi, John Williams, Dong-Joo Kim, Sungkoo Lee, Eunhee Lim, Kyeong K Lee, Minseo ParK, 2012, izvirni znanstveni članek Ključne besede: organic/inorganic hybrid solar cells, conjugated polymer, ZnO nanorod array
Objavljeno v RUNG: 16.01.2017; Ogledov: 5802; Prenosov: 0
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6. Growth of ZnO Nanorod Arrays on Flexible Substrates: Effect of Precursor Solution ConcentrationFei Tong, Kyusang Kim, Yaqi Wang, Resham Thapa, Yogesh Sharma, Aaron Modic, Ayayi Ahyi, Tamara Issacs-Smith, John Williams, Hosang Ahn, Hyejin Park, Dong-Joo Kim, Sungkoo Lee, Eunhee Lim, Kyeong K. Lee, Minseo Park, 2012, izvirni znanstveni članek Ključne besede: ZnO Nanorod Arrays, ITO-PET, solution growth
Objavljeno v RUNG: 16.01.2017; Ogledov: 5827; Prenosov: 0
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7. Ultra-low leakage and high breakdown Schottky diodes fabricated on free-standing GaN substrateYaqi Wang, Siddharth Alur, Yogesh Sharma, Fei Tong, Resham Thapa, Patrick Gartland, Tamara Issacs-Smith, Claude Ahyi, John Williams, Minseo Park, Mark Johnson, Tanya Paskova, Edward A Preble, Keith Evans, 2011, izvirni znanstveni članek Ključne besede: free-standing GaN substrate, Ultra-low leakage and high breakdown Schottky diodes
Objavljeno v RUNG: 16.01.2017; Ogledov: 5356; Prenosov: 0
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