1,720,980 research outputs found
Wind accretion in KQ Puppis
No full textFrom a multiwavelength long term monitoring of KQ Pup, we derive a revised orbital period of 9500 days. The presence of an accreting stream is put in evidence by a large decrease of the FUV continuum due to Rayleigh scattering, and by the appearance of redshifted absorptions since Φ = 0.82
Classical novae in outburst: The early evolution of the ultraviolet continuum
No full textIn the framework of a phenomenological study of the ultraviolet properties of classical novae in outburst, we have selected 12 objects among the best monitored at low resolution with the IUE satellite, and studied the temporal evolution of the ultraviolet continuum and of the O I 1300 Angstrom line flux during the early post-outburst phase. We confirm that the UV flux maximum takes place systematically after the visual maximum and that its time delay is a linear function of t(3). A linear dependence on t3 is also found for the duration of the UV outburst and for the time the O I line flux reaches a maximum. This latter time marks the start of the transition phase to nebular conditions. Within the uncertainties imposed by the sample of objects used and by the observational errors, these results suggest a quite homogeneous behaviour of classical novae in the ultraviolet range
Classical novae in outburst: evolution of the ultraviolet emission lines in CO novae
No full textA comparative study is made of the temporal changes of the ionization level in seven CO novae well monitored with the IUE satellite at low resolution. The investigation is based on the evolution of the fluxes in eight strong ultraviolet emission lines covering a wide range of ionization potentials, from Mg II (7.6 eV) to N V (77.5 eV). We find that the rate of increase of the ionization conditions in the emitting regions is uniform in the sample of novae considered, provided the time scale is normalized to the optical decay time t(3). The implications of this result for the nova ejected masses and for the nuclear turnoff time are discussed
The INES system - II. Ripple correction and absolute calibration for IUE high resolution spectra
No full textIn this paper we document the results of the study which led to the ripple correction and absolute calibration algorithms applied to the high resolution spectra processed with the NEWSIPS software for the Final archive of the IUE Project. In this analysis, based on a very large number of spectral we find that both the It and alpha parameters (not only the former as previously believed) vary with order number. This fact, together with the finding that the central peaks of the blaze function vary also as a function of the THDA temperature (for the SWP camera) and of the date of observations (for the LWP and LWR cameras), makes the ripple correction algorithm more complex than previously considered but, at the same time, considerably more reliable. As for the high resolution absolute calibration, the method followed is similar to the one implemented in IUESIPS. The internal accuracy of the high resolution calibration is about 4%. We note that the ripple correction and absolute calibration algorithms here described apply also to IUE data processed and distributed with the INES system
The INES system - III. Evaluation of IUE NEWSIPS high resolution spectra
No full textThis paper discusses the overall quality of IUE high resolution data processed with the NEWSIPS software in terms of flux and wavelength accuracy. It also describes the processing of NEWSIPS high resolution spectra within the framework of the ESA "IUE Newly. Extracted Spectra" (INES) System. This system provides the IUE high resolution data in two formats: the high resolution "concatenated" spectra: in which the spectral orders are connected; eliminating the overlap regions through a procedure designed to optimize the signal-to-noise ratio at the edges of the orders, and the "rebinned" spectra, i.e. the high resolution concatenated spectra resampled into the low resolution wavelength domain. Our study reveals the existence of a significant discrepancy in the wavelength scales of short and long wavelength NEWSIPS high resolution spectra. The INES processing applies a correction of +17.7 km s(-1) to the wavelength scale of the high resolution SWP spectra in order to provide an internally consistent velocity scale. Similarly, suitable corrections have been applied to long wavelength small aperture spectra. The new wavelength scale is, within the error:;, in good agreement with the optical velocity scale
Ripple correction and absolute calibration for Final Archive IUE high resolution spectra
No full textWe report a detailed study about the ripple correction and absolute calibration of IUE high resolution spectra processed with NEWSIPS (i.e. the IUE Final Archive processing scheme). The analysis, based on very many spectra obtained with the SWP, LWP and LWR cameras, shows that the empirical positions of the blaze peaks vary in a way which does not depend only on the spectrograph's optics, but also on the camera's spatial response. This latter has been successfully parametrized as a function of the camera head temperature for the SWP camera and of the observing date for the LWP and LWR cameras. The performance of the ripple correction algorithms so obtained represent an important improvement over the ones adopted for IUESIPS. The ripple corrected high resolution spectra were then used to derive a new high resolution absolute calibration, which is accurate to within 3-4%, all over the spectral range covered by the IUE cameras
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
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
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