ChemInform Abstract: Enzymatic Method of Preparation of Optically Active trans‐2‐Aminocyclohexanol Derivatives.

Ursini, A.; Maragni, Paolo; Bismara, C.; Tamburini, B.

doi:10.1002/chin.199928036

Cited by 1 publication

(2 citation statements)

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“…In this case, within the observation duration no clearcut constant HR time interval is present and a definition of the constant level underneath the variation components is possible only through the fitting process: our best fit defines 3 gaussian components that can be easily recognized in the figure. For this specific case our result is confirmed by the spectral analysis (Ursini et al 2014) from which the authors conclude that the three components shown in Fig. 1 c are originated by the interposition of an obscuring cloud and cannot be due to a change in the emitting source spectral index.…”

Section: A Systematic Search: Our Methods Of Investigationsupporting

confidence: 78%

“…-In order to check this important point, we performed a complete spectral analysis on a subsample of five bright unobscured AGNs with significant HR variability (those with no spectral variability obviously do not need any check to confirm the constancy of γ). In this study, presented in the second paper of this series (Ursini et al 2014) we fully confirm that all the cases with ∆(HR)/HR > 0.1 are best reproduced through occultation events, while the variability in the only source in the sample with ∆(HR)/HR < 0.1 can be also explained through intrinsic variability of γ.…”

Section: Effects Of Spectral Index Changessupporting

confidence: 77%

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Search for X-ray occultations in active galactic nuclei

Torricelli‐Ciamponi¹,

Pietrini²,

Risaliti³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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Recent time-resolved spectral studies of a few Active Galactic Nuclei in hard X-rays revealed occultations of the X-ray primary source probably by Broad Line Region (BLR) clouds. An important open question on the structure of the circumnuclear medium of AGN is whether this phenomenon is common, i.e. whether a significant fraction of the X-ray absorption in AGN is due to BLR clouds. Here we present the first attempt to perform this kind of analysis in a homogeneous way, on a statistically representative sample of AGN, consisting of the ∼40 brightest sources with long XMM-Newton and/or Suzaku observations. We describe our method, based on a simple analysis of hardness-ratio light curves, and its validation through a complete spectroscopic analysis of a few cases. We find that X-ray eclipses, most probably due to clouds at the distance of the BLR, are common in sources where the expected occultation time is compatible with the observation time, while they are not found in sources with longer estimated occultation times. Overall, our results show that occultations by BLR clouds may be responsible for most of the observed X-ray spectral variability at energies higher than 2 keV, on time scales longer than a few ks.

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Section: A Systematic Search: Our Methods Of Investigationsupporting

confidence: 78%

Section: Effects Of Spectral Index Changessupporting

confidence: 77%