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Ian Lewis Michael Balogh Roberto De Propris Warrick Couch Richard Bower Alison Offer Joss Bland-Hawthorn Ivan K. Baldry Carlton Baugh Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Nicholas Cross Gavin Dalton Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Edward Hawkins Carole Jackson Ofer Lahav Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg John A. Peacock Will Percival Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,334(3):673-683
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We present high signal-to-noise spectropolarimetry of the WC7+OB star WR 137 (HD 192641) covering the spectral range from 3600Å to 1.1µm. The polarization spectrum shows unambiguous evidence for an intrinsic polarization vector. 相似文献
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Philip J.Armitage Ian A.Bonnell 《Monthly notices of the Royal Astronomical Society》2002,330(1):L11-L14
We show that the dearth of brown dwarfs in short-period orbits around Solar-mass stars – the brown dwarf desert – can be understood as a consequence of inward migration within an evolving protoplanetary disc. Brown dwarf secondaries forming at the same time as the primary star have masses which are comparable to the initial mass of the protoplanetary disc. Subsequent disc evolution leads to inward migration, and destruction of the brown dwarf, via merger with the star. This is in contrast with massive planets, which avoid this fate by forming at a later epoch when the disc is close to being dispersed. Within this model, a brown dwarf desert arises because the mass at the hydrogen-burning limit is coincidentally comparable to the initial disc mass for a Solar mass star. Brown dwarfs should be found in close binaries around very low mass stars, around other brown dwarfs, and around Solar-type stars during the earliest phases of star formation. 相似文献
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V. R. Eke Carlos S. Frenk Carlton M. Baugh Shaun Cole Peder Norberg John A. Peacock Ivan K. Baldry Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto de Propris Simon P. Driver George Efstathiou Richard S. Ellis Karl Glazebrook Carole A. Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve J. Maddox Darren Madgwick Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,355(3):769-784
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Continuous monitoring of dissolved organic matter (DOM) character and concentration at hourly resolution is rare, despite the importance of analysing organic matter variability at high‐temporal resolution to evaluate river carbon budgeting, river water health by detecting episodic pollution and to determine short‐term variations in chemical and ecological function. The authors report a 2‐week experiment performed on DOM sampled from Bournbrook, Birmingham, UK, an urban river for which spectrophotometric (fluorescence, absorbance), physiochemical (dissolved organic carbon [DOC], electrical conductivity, pH) and isotopic (D/H) parameters have been measured at hourly frequency. Our results show that the river had sub‐daily variations in both organic matter concentration and characteristics. In particular, after relatively high‐magnitude precipitation events, organic carbon concentration increased, with an associated increase in intensity of both humic‐like and tryptophan‐like fluorescence. D/H isotopic ratio demonstrates different hydrological responses to different rainfall events, and organic matter character reflects this difference. Events with precipitation < 2 mm typically yielded isotopically heavy water with relatively hydrophilic DOM and relatively low specific absorbance. Events with precipitation > 2 mm had isotopically lighter water with higher specific absorbance and a decrease in the proportion of microbially derived to humic‐like fluorescence. In our heavily urbanized catchment, we interpret these signals as one where riverine DOM is dominated by storm sewer‐derived ‘old’ organic matter at low‐rainfall amounts and a mixed signal at high‐precipitation amounts where ‘event’ surface runoff‐derived organic matter dominate during storm sewer and combined sewer overflow routed DOM. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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