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- Edelson, R. A., et al.
(författare)
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Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
- 1996
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
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Tidskriftsartikel (refereegranskat)abstract
- For pt.III see ibid., vol.470, no.1, p.349-63 (1996). Combines data from the three preceding papers in order to analyze the multi wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA=6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Aring. These data do not probe extreme ultraviolet (1200 Aring to 0.1 keV) or hard X-ray (250 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of lsim0.15 day between 1275 Aring and the other ultraviolet bands, lsim0.3 day between 1275 Aring and 1.5 keV, and lsim1 day between 1275 and 5125 Aring. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (ales-2.5)
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- Wang, L., et al.
(författare)
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Study of optical characteristics of damage in oxygen-implanted 6H-SiC
- 1999
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Ingår i: Journal of materials science letters. - 0261-8028 .- 1573-4811. ; 18:12, s. 979-982
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen ions, with an energy of 70 keV, and doses ranging from 5×1013 to 5×1015 cm-2, were implanted into 6H SiC. The damage energies were calculated as 0.93-93 eV/atom with the doses respectively. The dielectric function obtained from spectroscopic ellipsometry were quite sensitive to ion irradiation of the surface, while the first order Raman spectroscopy decreased in intensity with increasing O+ ion dose. The damage behavior characterized by optical measurements was in good agreement with characterization by Rutherford backscattering spectrometry and channeling and atomic force microscopy.
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