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P.T. O'Brien K. Page J.N. Reeves K. Pounds M.J.L. Turner E.M. Puchnarewicz 《Monthly notices of the Royal Astronomical Society》2001,327(4):L37-L41
We present XMM-Newton observations of Mrk 359, the first narrow-line Seyfert 1 galaxy (NLS1) discovered. Even among NLS1s, Mrk 359 is an extreme case with extraordinarily narrow optical emission lines. The XMM-Newton data show that Mrk 359 has a significant soft X-ray excess which displays only weak absorption and emission features. The continuum, including reflection, is flatter than that of the typical NLS1, with . A strong emission line of equivalent width ≈200 eV is also observed, centred near 6.4 keV. We fit this emission with two line components of approximately equal strength: a broad iron line from an accretion disc and a narrow, unresolved core. The unresolved line core has an equivalent width of ≈120 eV and is consistent with fluorescence from neutral iron in distant reprocessing gas, possibly in the form of a 'molecular torus'. Comparison of the narrow-line strengths in Mrk 359 and other low–moderate luminosity Seyfert 1 galaxies with those in QSOs suggests that the solid angle subtended by the distant reprocessing gas decreases with increasing active galactic nucleus luminosity. 相似文献
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This is the first part of a two-part paper presenting a new method for treating convective-dispersive transport. The motivation for developing this technique arises from the demands of performing a risk assessment for a nuclear waste repository. These demands include computational efficiency over a relatively large range of Peclet numbers, the ability to handle chains of decaying radionuclides with rather extreme contrasts in both solution velocities and half lives, and the ability to treat leach- or solubility-limited sources. To the extent it has been tested to date, the distributed velocity method (DVM) appears to satisfy these demands. This part contains an overall introduction and presents the mathematical theory, numerical implementation, and example results. 相似文献
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Extreme X-ray variability in the luminous quasar PDS 456 总被引：1，自引：0，他引：1