2,734 research outputs found
Is HE 0436-4717 Anemic? A deep look at a bare Seyfert 1 galaxy
A multi-epoch, multi-instrument analysis of the Seyfert 1 galaxy HE 0436-4717
is conducted using optical to X-ray data from XMM-Newton and Swift (including
the BAT). Fitting of the UV-to-X-ray spectral energy distribution shows little
evidence of extinction and the X-ray spectral analysis does not confirm
previous reports of deep absorption edges from OVIII. HE 0436-4717 is a "bare"
Seyfert with negligible line-of-sight absorption making it ideal to study the
central X-ray emitting region. Three scenarios were considered to describe the
X-ray data: partial covering absorption, blurred reflection, and soft
Comptonization. All three interpretations describe the 0.5-10.0 keV spectra
well. Extrapolating the models to 100 keV results in poorer fits for the the
partial covering model. When also considering the rapid variability during one
of the XMM-Newton observations, the blurred reflection model appears to
describe all the observations in the most self-consistent manner. If adopted,
the blurred reflection model requires a very low iron abundance in HE
0436-4717. We consider the possibilities that this is an artifact of the
fitting process, but it appears possible that it is intrinsic to the object.Comment: 7 tables, 11 figures, 16 pages; accepted for publication in MNRAS 17
Feb. 201
Special symmetries of the charged Kerr-AdS black hole of D=5 minimal gauged supergravity
In this note we prove that the Hamilton-Jacobi equation in the background of
the recently discovered charged Kerr-AdS black hole of D=5 minimal gauged
supergravity is separable, for arbitrary values of the two rotation parameters.
This allows us to write down an irreducible Killing tensor for the spacetime.
As a result we also show that the Klein-Gordon equation in this background is
separable. We also consider the Dirac equation in this background in the
special case of equal rotation parameters and show it has separable solutions.
Finally we discuss the near-horizon geometry of the supersymmetric limit of the
black hole.Comment: 7 pages, Latex. v2, two references added and discussion of near
horizon limit corrected and expande
Computation of Madelung Energies for Ionic Crystals of Variable Stoichiometries and Mixed Valencies and their application in Lithium-ion battery voltage modelling
Electrostatic energy (Madelung energy) is a major constituent of the cohesive
energy of ionic crystals. Several physicochemical properties of these materials
depend on the response of their electrostatic energy to a variety of applied
thermal, electrical and mechanical stresses. In the present study, a method has
been developed based on Ewalds technique, to compute the electrostatic energy
arising from ion-ion interactions in ionic crystals like LixMn2O4 with variable
stoichiometries and mixed valencies. An interesting application of this method
in computing the voltages of lithium ion batteries employing spinel cathodes is
presented for the first time. The advantages of the present method of
computation over existing methods are also discussed.Comment: 15 page
Residual stress, phase, microstructure and mechanical property studies of ultrafine bainitic steel through laser shock peening
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