1,141 research outputs found

    The Intermediate Line Region and the Baldwin Effect

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    Statistical investigations of samples of quasars have established that clusters of properties are correlated. The strongest trends among the ultraviolet emission-line properties are characterized by the object-to-object variation of emission from low-velocity gas, the so-called ``intermediate-line region'' or ILR. The strongest trends among the optical emission-line properties are characterized by the object-to-object variation of the line intensity ratio of [O III] 5007 to optical Fe II. Additionally, the strength of ILR emission correlates with [O III]/Fe II, as well as with radio and X-ray properties. The fundamental physical parameter driving these related correlations is not yet identified. Because the variation in the ILR dominates the variation in the equivalent widths of lines showing the Baldwin effect, it is important to understand whether the physical parameter underlying this variation also drives the Baldwin effect or is a primary source of scatter in the Baldwin effect.Comment: 11 pages, to appear in the proceedings of the meeting on "Quasars as Standard Candles for Cosmology" held on May 18-22, 1998, at La Serena, Chile. To be published by ASP, editor G. Ferlan

    X-ray and optical counterparts of hard X-ray selected sources from the SHEEP survey: first results

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    We present followup observations of five hard X-ray sources from the ASCA 5-10 keV SHEEP survey, which has a limiting flux of ∌10−13\sim 10^{-13} erg cm−2^{-2} s−1^{-1}. Chandra data have been obtained to improve the X-ray positions from a few arcmin to <1â€Čâ€Č<1'', which allows unambiguous optical identification. While the objects almost certainly house AGN based on their X-ray luminosity, optical spectroscopy reveals a variety of properties. The identifications indicate that the SHEEP survey samples the same populations as deeper surveys which probe the origin of the X-ray background, but because the SHEEP sources are far brighter, they are more amenable to detailed followup work. We find a variety of classifications and properties, including a type II QSO, a galaxy undergoing star formation, and a broad-line AGN which has a very hard X-ray spectrum, indicating substantial absorption in the X-ray but none in the optical. Two objects have X-ray/optical flux ratios which, were they at an X-ray flux level typical of objects in Chandra deep surveys, would place them in the ``optically faint'' category. They are both identified with broad line QSOs at z∌1\sim 1. Clearly this survey - which is relatively unbiased against obscured objects - is revealing a set of remarkable objects quite different to the familiar classes of AGN found in previous optical and soft X-ray surveys.Comment: 5 pages, 3 figures. MNRAS, in pres

    The Profiles of H-Beta and [OIII] 5007 in Radio-Loud Quasars

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    Moderate-resolution spectra of the HÎČ\beta--[O III] λ\lambda5007 region have been obtained for 41 radio-loud quasars in order to investigate relationships among their broad- and narrow-line profiles, radio structures, and X-ray properties. Spectra from the literature have been included to form a data set of 60 radio-loud quasars. A variety of statistical analyses have been performed, identifying several strong, related trends. The FWHM, equivalent width, and degree of redward asymmetry of HÎČ\beta increase with decreasing radio core dominance (an orientation indicator), whereas the FWHM of [O III] λ\lambda5007 increases with luminosity and αox\alpha_{ox}. These and other effects are briefly discussed.Comment: To appear in the Astrophysical Journal Supplement. Warning: A large paper, 360kb uuencoded, compressed postscript, including figures (except Fig. 1a-g, the spectra, which are at the ftp site below) and tables. The entire paper is also available by anonymous ftp at ftp://pan.as.utexas.edu/pub/HBpreprint

    From Service to Experience: Understanding and Defining the Hospitality Business

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    Failure adequately to define or understand hospitality as a commercial phenomenon has created a fragmented academic environment and a schizophrenia in the industry that has the potential to limit its development as a global industry. This article suggests that, by redefining hospitality as behaviour and experience, a new perspective emerges that has exciting implications for the management of hospitality businesses. A framework to describe hospitality in the commercial domain is proposed. This framework suggests a focus on the host–guest relationship, generosity, theatre and performance, ‘lots of little surprises’, and the security of strangers – a focus that provides guests with experiences that are personal, memorable and add value to their lives
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