A high-velocity ionized outflow and XUV photosphere in the narrow emission line quasar PG1211+143   总被引：1，自引：0，他引：1  

K. A. Pounds  J. N. Reeves  A. R. King  K. L. Page  P. T. O'Brien  M. J. L. Turner 《Monthly notices of the Royal Astronomical Society》2003,345(3):705-713

We report on the analysis of a ∼60-ks XMM–Newton observation of the bright, narrow emission line quasar PG1211+143. Absorption lines are seen in both European Photon Imaging Camera and Reflection Grating Spectrometer spectra corresponding to H- and He-like ions of Fe, S, Mg, Ne, O, N and C. The observed line energies indicate an ionized outflow velocity of ∼24 000 km s⁻¹. The highest energy lines require a column density of   N _H∼ 5 × 10²³ cm⁻²  , at an ionization parameter of  log ξ∼ 3.4  . If the origin of this high-velocity outflow lies in matter being driven from the inner disc, then the flow is likely to be optically thick within a radius of ∼130 Schwarzschild radii, providing a natural explanation for the big blue bump (and strong soft X-ray) emission in PG1211+143.  相似文献   

Modelling the effect of low soil temperatures on transpiration by Scots pine     

Per‐Erik Mellander  Manfred Sthli  David Gustafsson  Kevin Bishop 《水文研究》2006,20(9):1929-1944

For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring‐early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70‐year‐old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high‐latitude stands. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

The ELAIS deep X-ray survey – I. Chandra source catalogue and first results     

J. C. Manners †  O. Johnson  O. Almaini  C. J. Willott  E. Gonzalez-Solares  A. Lawrence  R. G. Mann  I. Perez-Fournon  J. S. Dunlop  R. G. McMahon  S. J. Oliver  M. Rowan-Robinson  S. Serjeant 《Monthly notices of the Royal Astronomical Society》2003,343(1):293-305

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A Chandra observation of the X-ray environment and jet of 3C 296     

M. J. Hardcastle  D. M. Worrall  M. Birkinshaw  R. A. Laing  A. H. Bridle 《Monthly notices of the Royal Astronomical Society》2005,358(3):843-850

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Infrared observations of serendipitous hard Chandra X-ray sources     

C. S. Crawford  A. C. Fabian  P. Gandhi  R. J. Wilman  R. M. Johnstone 《Monthly notices of the Royal Astronomical Society》2001,324(2):427-442

We present observations of a sample of optically faint, hard X-ray sources of the kind likely to be responsible for much of the hard X-ray background. We confirm that such sources are easily detected in the near-infrared, and find that they have a featureless continuum suggesting that the active nucleus is heavily obscured. The infrared colours of the majority of the targets observed are consistent with absorbed elliptical host galaxies at z =1–2. It is likely that we are observing some of the brighter members of the important new class of X-ray type II quasars.  相似文献   

Dissolved organic carbon dynamics in two streams draining forested catchments at loch ard,Scotland     

Ian C. Grieve 《水文研究》1994,8(5):457-464

Dissolved organic carbon (DOC) was measured at four or eight hour intervals between mid-1989 and mid-1991 in two catchments in west central Scotland. The experimental catchment had been recently clear-felled and the control remained under forest. The amount of DOC varied during individual storm events following the stream hydro-graph. Maximum variations were found in the summer half-year and in the clear-felled catchment. There was also evidence of the exhaustion of DOC in the later events of a sequence. Differences between the catchments were related to catchment characteristics and to land-use change. The reduced magnitude of variation in DOC with discharge in the control stream was due to the influence of a wetland area through which the stream flowed. The mean DOC concentrations were similar in the two streams and annual exports were 15 g m^?2 from the control and 16g m^?2 from the felled catchment. The stream draining the clear-felled catchment had greater high flow DOC concentrations in the summer half-year, probably due to the effect of greater mean summer temperatures on DOC release and of the greater supply of organic debris in the stream channel.  相似文献   

The relationship between X-ray variability amplitude and black hole mass in active galactic nuclei     

Paul M. O'Neill  Kirpal Nandra  Iossif E. Papadakis  T. J. Turner 《Monthly notices of the Royal Astronomical Society》2005,358(4):1405-1416

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The unresolved hard X-ray background: the missing source population implied by the Chandra and XMM–Newton deep fields     

M. A. Worsley  A. C. Fabian  F. E. Bauer  D. M. Alexander  G. Hasinger  S. Mateos  H. Brunner  W. N. Brandt  D. P. Schneider 《Monthly notices of the Royal Astronomical Society》2005,357(4):1281-1287

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A warped m= 2 water maser disc in V778 Cyg?     

Natalia Babkovskaia  Juri Poutanen  Anita M. S. Richards  Ryszard Szczerba 《Monthly notices of the Royal Astronomical Society》2006,370(4):1921-1927

The silicate carbon star V778 Cyg is a source of 22-GHz water maser emission which was recently resolved by MERLIN. Observations revealed an elongated     -like structure along which the velocities of the maser features show a linear dependence on the impact parameter. This is consistent with a doubly warped   m = 2  disc observed edge-on. Water masers and silicate dust emission (detected by the Infrared Astronomical Satellite and Infrared Space Observatory ) have a common origin in O-rich material and are likely to be co-located in the disc. We propose a detailed self-consistent model of a masing gas–dust disc around a companion to the carbon star in a binary system, which allows us to estimate the companion mass of  1.7 ± 0.1 M_⊙  , the disc radius of  40 ± 3  au and the distance between companions of ∼80 au. Using a dust–gas coupling model for water masing, we calculate the maser power self-consistently, accounting for both the gas and the dust energy balances. Comparing the simulation results with the observational data, we deduce the main physical parameters of the masing disc, such as the gas and dust temperatures and their densities. We also present an analysis of the stability of the disc.  相似文献   

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco     

Haydon P. Mort  Thierry Adatte  Gerta Keller  David Bartels  Karl B. Fllmi  Philipp Steinmann  Zsolt Berner  E.H. Chellai 《Cretaceous Research》2008,29(5-6):1008

With a multi-proxy approach, an attempt was made to constrain productivity and bottom-water redox conditions and their effects on the phosphorus accumulation rate at the Mohammed Plage section on the Tarfaya coast, Morocco, during the Cenomanian-Turonian Anoxic Event (OAE 2). A distinct δ¹³C_org isotope excursion of +2.5‰ occurs close to the top of the section. The unusually abrupt shift of the isotope excursion and disappearance of several planktonic foraminiferal species (e.g. Rotalipora cushmani and Rotalipora greenhornensis) in this level suggests a hiatus of between 40–60 kyrs at the excursion onset. Nevertheless, it was possible to determine both the long-term environmental history as well as the processes that took place immediately prior to and during OAE 2. TOC% values increase gradually from the base of the section to the top (from 2.5% to 10%). This is interpreted as the consequence of a long-term eustatic sea-level rise and subsidence causing the encroachment of less oxic waters into the Tarfaya Basin. Similarly a reduction in the mineralogically constructed ‘detrital index’ can be explained by the decrease in the continental flux of terrigenous material due to a relative sea-level rise. A speciation of phosphorus in the upper part of the section, which spans the start and mid-stages of OAE 2, shows overall higher abundances of P_reactive mass accumulation rates before the isotope excursion onset and lower values during the plateau. Due to the probable short hiatus, the onset of the decrease in phosphorus content relative to the isotope excursion is uncertain, although the excursion plateau already contains lower concentrations. The C_org/P_total and V/Al ratios suggest that this reduction was mostly likely caused by a decrease in the available bottom oxygen content (probably as a result of higher productivity) and a corresponding fall in the phosphorus retention ability of the sediment. Productivity appears to have remained high during the isotope plateau possibly due to a combination of ocean-surface fertilisation via increased aridity (increased K/Al and Ti/Al ratios) and/or higher dissolved inorganic phosphorus content in the water column as a result of the decrease in sediment P retention. The evidence for decreased P-burial has been observed in many other palaeoenvironments during OAE 2. Tarfaya's unique upwelling paleosituation provides strong evidence that the nutrient recycling was a global phenomenon and therefore a critical factor in starting and sustaining OAE 2.  相似文献