1,721,051 research outputs found
Iron K alpha line intensity from accretion discs around rotating black holes
No full textWe calculate the iron fluorescent Kw. line intensity from an accretion disc orbiting around a maximally rotating black hole and illuminated by an X-ray source located on the hole rotation axis. We find that the line intensity can be much greater than that obtained from illuminated accretion discs around static black holes. This provides a possible explanation for the large iron line equivalent widths observed in some Seyfert 1 galaxies
LED Applications in Railway Signals: Wavelength and Intensity vs Temperature Variation
No full textIn recent years, light emitting diodes (LEDs) have entered the lighting market, offering consumers performance and features exceeding those of traditional lighting technologies. LEDs (light-emitting diodes) are becoming more common in safety signals for railroad, highway, automotive, and many other applications. In addition to having a longer life and greater durability than incandescent bulbs, LEDs are much more energy efficient than their incandescent counterparts. Since the heat from the junction must be dissipated into the ambient somehow, changing the ambient temperature af-fects the junction temperature and hence the emitted light. When the LEDs are used in the railway or traffic signals, the optical proprieties of these have to maintain more rigorous specifications. Therefore the development of signals using LED as light source, able to respect intensity specifications, is not simple. In this paper, we describe problems of the temperature dependent changes of LED intensity and color shift. Besides we will introduce an innovative technique, that we have developed, to allow the use of the LEDs in applications with rigorous specifications
Effects of Kerr space-time on spectral features from X-ray illuminated accretion discs
No full textWe performed detailed calculations of the relativistic effects acting on both the reflection continuum and the iron line from accretion discs around rotating black holes. Fully relativistic transfer of both illuminating and reprocessed photons has been considered in Kerr space-time. We calculated overall spectra, line profiles and integral quantities, and present their dependences on the black hole angular momentum. We show that the observed EW of the lines is substantially enlarged when the black hole rotates rapidly and/or the source of illumination is near above the hole. Therefore, such calculations provide a way to distinguish between different models of the central source
SORGENTI LUMINOSE A LED PER SEMAFORI: RISPETTO DELLE NORME
No full textIl lavoro dimostra che l’utilizzo combinato di due tipi di LED monocromatici (Giallo + Arancio) consente di realizzare un sistema semaforico in grado di rispettare le stringenti prescrizioni della norma UNI 9296. Misurando la temperatura ambiente e polarizzando con opportune correnti due cluster di LED, è possibile ottenere un sistema in grado di mantenere, in tutto il previsto range di temperatura, le corrette coordinate cromatiche.In this paper, we describe problems of the temperature dependent changes of LED colour
shift. Besides we will introduce an innovative technique that to allow the use of the LEDs in
applications with rigorous chromatic specifications
On the origin of the broad, relativistic iron line of MCG-6-30-15 observed by XMM-Newton
No full textThe relativistic iron line profile recently observed by XMM-Newton in the spectrum of the Seyfert 1 galaxy MCG-6-30-15 (Wilms et al. 2001) is discussed in the framework of the lamp-post model. It is shown that the steep disc emissivity, the large line equivalent width and the amount of Compton reflection can be self-consistently reproduced in this scenario
Stress and neuroendocrinimmune response: historical considerations and clinical implications
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