1,723,907 research outputs found
Unveiling the AGN powering the "Composite" Seyfert/Star-forming galaxy NGC 7679: BeppoSAX and ASCA results
No full textWe discuss BeppoSAX observations and archive ASCA data of NGC 7679, a nearby, nearly face-on SB0 galaxy in which starburst and AGN activities coexist. The X-ray observations reveal a bright (L0.1-50 keV ∼ 2.9 × 1043 erg s-1) and variable source having a minimum observed doubling/halving time scale of ∼10-20 ksec. A simple power law with photon index of T ∼ 1.75 and small absorption (NH < 4 × 1020 cm-2) can reproduce the NGC 7679 spectrum from 0.1 up to 50 keV. These X-ray properties are unambiguous signs of Seyfert 1 activity in the nucleus of NGC 7679. The starburst activity, revealed by the IR emission, optical spectroscopy and Hα imaging, and dominating in the optical and IR bands, is clearly overwhelmed by the AGN in the X-ray band. Although, at first glance, this is similar to what is observed in other starburst-AGN galaxies (e.g. NGC 6240, NGC 4945), most strikingly here and at odds with the above examples, the X-ray spectrum of NGC 7679 does not appear to be highly absorbed. The main peculiarity of objects like NGC 7679 is not the strength of their starburst but the apparent optical weakness of the Seyfert 1 nucleus when compared with its X-ray luminosity. To date NGC 7679 is one of the few Seyfert 1/Starburst composites for which the broad-band X-ray properties have been investigated in detail. The results presented here imply that optical and infrared spectroscopy could be highly inefficient in revealing the presence of an AGN in these kinds of objects, which instead is clearly revealed from X-ray spectroscopic and variability investigations
[Newburgh & South Shore Ry., Engine Drawing Card, Sketch 7679]
No full textThis engine drawing card was created for Newburgh & South Shore Railway, Class 10-48 F. Section N-10F. Sketch 7679. Copy Spec. C-9078
Unveiling the AGN powering the "Composite" Seyfert/Star-forming galaxy NGC 7679: BeppoSAX and ASCA results
No full textWe discuss BeppoSAX observations and archive ASCA
data of NGC 7679, a nearby, nearly face-on SB0 galaxy in
which starburst and AGN activities coexist.
The X-ray
observations reveal a bright ( erg s-1) and variable source having a minimum
observed doubling/halving time scale of ~10-20 ksec. A simple
power law with photon index of and small
absorption ( cm-2) can reproduce the
NGC 7679 spectrum
from 0.1 up to 50 keV.
These X-ray properties are unambiguous signs of Seyfert 1 activity in the nucleus of NGC
7679. The starburst activity, revealed by the IR emission,
optical spectroscopy and Hα imaging, and
dominating in the optical and IR bands, is clearly overwhelmed by the
AGN in the X-ray band. Although, at first glance, this is similar
to what is observed in other starburst-AGN galaxies (e.g. NGC 6240,
NGC 4945),
most strikingly here and at odds with the
above examples, the X-ray spectrum of NGC 7679 does not appear to be
highly absorbed. The main
peculiarity of objects like NGC 7679 is not the strength of their
starburst but the apparent optical weakness of the Seyfert 1
nucleus when compared with its X-ray luminosity. To date NGC 7679
is one of the few Seyfert 1/Starburst composites for which the
broad-band X-ray properties have been investigated in detail. The
results presented here imply that optical and infrared spectroscopy
could be highly inefficient in revealing the presence of an AGN in
these kinds of objects, which instead is clearly revealed from
X-ray spectroscopic and variability investigations
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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
NGC 7679: an anomalous, composite Seyfert 1 galaxy whose X-ray luminous AGN vanishes at optical wavelengths
Get PDFMorphological disturbances and gas kinematics of the SB0 galaxy NGC 7679 = Arp 216 are investigated to understand the history of this highly composite object, where AGN and starburst signatures dominate in the X-ray and optical/IR regime, respectively. Perturbations of the ionized gas velocity field appear quite mild within 15'' (~5 kpc) of the center, so it can be straightforwardly modeled as a circularly rotating disk. Outside that radius, significant disturbances are seen. In particular, the eastern distorted arm as well as the huge neutral hydrogen bridge connecting NGC 7679 to the nearby Seyfert spiral NGC 7682 unambiguously represent the vestige of a close encounter of the two objects ~500 Myr ago. The relationship of such a past event with the much more recent, centrally located starburst (not older than 20 Myr) cannot be easily established. Together, the classification of NGC 7679 is less extreme than that proposed in the past, being simply a (disturbed) galaxy where starburst and AGN activity coexist with a starburst dominating the bolometric luminosity
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
- …
