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Institution

Keele University

EducationNewcastle-under-Lyme, United Kingdom
About: Keele University is a education organization based out in Newcastle-under-Lyme, United Kingdom. It is known for research contribution in the topics: Population & Stars. The organization has 11318 authors who have published 26323 publications receiving 894671 citations. The organization is also known as: Keele University.
Topics: Population, Stars, Health care, Galaxy, Planet


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors estimate the location and energetics of the associated ultrafast outflows (UFOs) using the results of a previous X-ray photo-ionization modelling of blue-shifted Fe K absorption lines on a sample of 42 radio-quiet AGNs observed with XMM-Newton.
Abstract: Using the results of a previous X-ray photo-ionization modelling of blue-shifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval approx.0.0003-0.03pc (approx.10(exp 2)-10(exp 4)tau(sub s) from the central black hole, consistent with what is expected for accretion disk winds/outflows. The mass outflow rates are constrained between approx.0.01- 1 Stellar Mass/y, corresponding to approx. or >5-10% of the accretion rates. The average lower-upper limits on the mechanical power are logE(sub K) approx. or = 42.6-44.6 erg/s. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN r.osmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyferts galaxies .

202 citations

Book ChapterDOI
John A. Sloboda1
01 Jan 1992

202 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present comprehensive photometric and spectroscopic observations of the faint transient SN 2008S discovered in the nearby galaxy NGC 6946, and propose that this is evidence for an explosion and formation of a super-asymptotic giant branch progenitor star embedded within a thick circumstellar gaseous envelope.
Abstract: We present comprehensive photometric and spectroscopic observations of the faint transient SN 2008S discovered in the nearby galaxy NGC 6946. SN 2008S exhibited slow photometric evolution and almost no spectral variability during the first nine months, implying a long photon diffusion time and a high-density circumstellar medium. Its bolometric luminosity (≃10^(41) erg s^(−)1 at peak) is low with respect to most core-collapse supernovae but is comparable to the faintest Type II-P events. Our quasi-bolometric light curve extends to 300 d and shows a tail phase decay rate consistent with that of ^(56)Co. We propose that this is evidence for an explosion and formation of ^(56)Ni (0.0014 ± 0.0003 M_⊙). Spectra of SN 2008S show intense emission lines of Hα, [Ca ii] doublet and Ca ii near-infrared (NIR) triplet, all without obvious P-Cygni absorption troughs. The large mid-infrared (MIR) flux detected shortly after explosion can be explained by a light echo from pre-existing dust. The late NIR flux excess is plausibly due to a combination of warm newly formed ejecta dust together with shock-heated dust in the circumstellar environment. We reassess the progenitor object detected previously in Spitzer archive images, supplementing this discussion with a model of the MIR spectral energy distribution. This supports the idea of a dusty, optically thick shell around SN 2008S with an inner radius of nearly 90 au and outer radius of 450 au, and an inferred heating source of 3000 K. The luminosity of the central star is L ≃ 10^(4.6) L_⊙ . All the nearby progenitor dust was likely evaporated in the explosion leaving only the much older dust lying further out in the circumstellar environment. The combination of our long-term multiwavelength monitoring data and the evidence from the progenitor analysis leads us to support the scenario of a weak electron-capture supernova explosion in a super-asymptotic giant branch progenitor star (of initial mass 6–8 M_⊙ ) embedded within a thick circumstellar gaseous envelope. We suggest that all of main properties of the electron-capture SN phenomenon are observed in SN 2008S and future observations may allow a definitive answer.

202 citations

Journal ArticleDOI
TL;DR: In this article, groundwater and surface water interaction in two conifer swamps located in headwater catchments with contrasting till depth, typical of the southern Canadian Shield, were studied from June 1990 to August 1992.

202 citations

Journal ArticleDOI
TL;DR: It is found that both the high stable and moderate increasing trajectories were associated with depressive symptoms, a higher frequency of visits to the doctor, and lower perceived general health at age 17.

201 citations


Authors

Showing all 11402 results

NameH-indexPapersCitations
George Davey Smith2242540248373
Simon D. M. White189795231645
James F. Wilson146677101883
Stephen O'Rahilly13852075686
Wendy Taylor131125289457
Nicola Maffulli115157059548
Georg Kresse111430244729
Patrick B. Hall11147068383
Peter T. Katzmarzyk11061856484
John F. Dovidio10946646982
Elizabeth H. Blackburn10834450726
Mary L. Phillips10542239995
Garry P. Nolan10447446025
Wayne W. Hancock10350535694
Mohamed H. Sayegh10348538540
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202344
2022155
20211,473
20201,377
20191,178
20181,106