1,720,968 research outputs found
ROSAT, ASCA, and OSSE observations of the broad-line radio galaxy 3C 120
No full textWe present simultaneous observations of the superluminal radio galaxy 3C 120 performed with the ASCA and GRO (OSSE) satellites in 1994 February-March, as well as an analysis of all the ROSAT archival data. The ASCA spectrum of this object can be described by an absorbed (N-H = 1.6 x 10(21) cm(-2)) power law with a photon index of T-ASCA = 2 and a very broad (sigma > 0.8 keV) intense iron line (EW > 400 eV) at similar to 6 keV. The combined ASCA-OSSE data do not exclude the presence of a narrower (sigma = 0.4 keV) and less intense (EW < 300 eV) iron line plus a hard component, corresponding either to reflection from an accretion disk or to a flatter power law from a jet. However, a single power law plus broad Fe line is preferred from a statistical point of view by the ASCA data. The ROSAT data yield a column density in excess of the Galactic value. The spectral slopes, ranging from Gamma(ROSAT) = 2.5 to 3.3, are steeper than that measured by ASCA, suggesting the presence of a soft excess. The 0.1-2 keV power-law slope is variable and softer at higher intensity. These results show that the combined soft and hard X-ray spectrum of 3C 120 is rather complex. The intrinsic absorption, the soft excess, and the iron line indicate that the X-ray emission from this blazar-like radio galaxy is dominated by a Seyfert-like component, at least in the 0.1-10 keV energy band. The jet contribution, if present, becomes important only at higher energies
The High Energy view of the Broad Line Radio Galaxy 3C 111
No full text14 páginas, 9 figuras, 5 tablas.-- El Pdf del artículo es la versión pre-print: arXiv:1108.2609v1.-- et al.We present the analysis of Suzaku and XMM–Newton observations of the broad-line radio
galaxy (BLRG) 3C 111. Its high-energy emission shows variability, a harder continuum with
respect to the radio-quiet active galactic nucleus population, and weak reflection features.
Suzaku found the source in a minimum flux level; a comparison with the XMM–Newton data
implies an increase of a factor of 2.5 in the 0.5–10 keV flux, in the 6 months separating the
two observations. The iron K complex is detected in both data sets, with rather low equivalent
width(s). The intensity of the ironKcomplex does not respond to the change in continuum flux.
An ultrafast, high-ionization outflowing gas is clearly detected in the Suzaku/X-ray Imaging
Spectrometer data; the absorber is most likely unstable. Indeed, during the XMM–Newton
observation, which was 6 months after, the absorber was not detected. No clear rollover in
the hard X-ray emission is detected, probably due to the emergence of the jet as a dominant
component in the hard X-ray band, as suggested by the detection above ∼100 keV with the
GSO onboard Suzaku, although the present data do not allow us to firmly constrain the relative
contribution of the different components. The fluxes observed by the γ -ray satellites CGRO
and Fermi would be compatible with the putative jet component if peaking at energies E ∼ 100MeV. In the X-ray band, the jet contribution to the continuum starts to be significant only
above 10 keV. If the detection of the jet component in 3C 111 is confirmed, then its relative
importance in the X-ray energy band could explain the different observed properties in the
high-energy emission of BLRGs, which are otherwise similar in their other multiwavelength
properties. Comparison between X-ray and γ -ray data taken at different epochs suggests that
the strong variability observed for 3C 111 is probably driven by a change in the primary
continuum.LB acknowledges support from the Spanish Ministry of Science and
Innovation through a ‘Juan de la Cierva’ fellowship. Financial support
for this work was provided by the Spanish Ministry of Science
and Innovation, through research grant AYA2009-08059.Peer reviewe
X-Ray Evidence for the Accretion Disc-Outflow Connection in 3C 111
Full text linkWe present the spectral analysis of three Suzaku X-ray Imaging Spectrometer observations of 3C III requested to monitor the predicted variability of its ultrafast outflow on approximately 7 d time-scales. We detect an ionized iron emission line in the first observation and a blueshifted absorption line in the second, when the flux is approximately 30 per cent higher. The location of the material is constrained at less than 0.006 pc from the variability. Detailed modelling supports an identification with ionized reflection off the accretion disc at approximately 20-100rg from the black hole and a highly ionized and massive ultrafast outflow with velocity approximately 0.1c, respectively. The outflow is most probably accelerated by radiation pressure, but additional magnetic thrust cannot be excluded. The measured high outflow rate and mechanical energy support the claims that disc outflows may have a significant feedback role. This work provides the first direct evidence for an accretion disc-outflow connection in a radio-loud active galactic nucleus, possibly linked also to the jet activity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Comparison of Ejection Events in the Jet and Accretion Disc Outflows in 3C 111
Full text linkWe present a comparison of the parameters of accretion disc outflows and the jet of the broad-line radio galaxy 3C 111 on sub-pc scales. We make use of published X-ray observations of ultra-fast outflows (UFOs) and new 43 GHz VLBA images to track the jet knots ejection. We find that the superluminal jet coexists with the mildly relativistic outflows on sub-pc scales, possibly indicating a transverse stratification of a global flow. The two are roughly in pressure equilibrium, with the UFOs potentially providing additional support for the initial jet collimation. The UFOs are much more massive than the jet, but their kinetic power is probably about an order of magnitude lower, at least for the observations considered here. However, their momentum flux is equivalent and both of them are powerful enough to exert a concurrent feedback impact on the surrounding environment. A link between these components is naturally predicted in the context of MHD models for jet/outflow formation. However, given the high radiation throughput of AGNs, radiation pressure should also be taken into account. From the comparison with the long-term 2-10 keV RXTE light curve we find that the UFOs are preferentially detected during periods of increasing flux. We also find the possibility to place the UFOs within the known X-ray dips-jet ejection cycles, which has been shown to be a strong proof of the disc-jet connection, in analogue with stellar-mass black holes. However, given the limited number of observations presently available, these relations are only tentative and additional spectral monitoring is needed to test them conclusively
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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