Relativistic Effects on the Appearance of a Clothed Black Hole

For an accretion disk around a black hole, the strong relativistic effects affect every aspect of the radiation from the disk, including its spectrum, light-curve, and image. This work investigates in detail how the images of a thin disk around a black hole will be distorted, and what the observer will see from different viewing angles and in different energy bands.Comment: 4 pages, 5 figures. Based on the poster presented at the Sixth Pacific Rim Conference on Stellar Astrophysics (Xi'an, China, July 11-17, 2002). Color versions of figures are given separatel

Sm-Nd and C-isotope chemostratigraphy of Ordovician epeiric sea carbonates, midcontinent of North America

Interpreting and correlating epeiric sea sequences is key to understanding ancient marine environments. As a result, eNd, d13C and Sm/Nd profiles are developed as tools for interpreting epeiric sea carbonates. Previously, eNd and d13C profiles in epeiric sea carbonates have been used to study changes in the Nd isotope balance and C-cycle of adjacent ocean water. Instead, eNd, d13C and Sm/Nd profiles of Ordovician Midcontinent carbonates of North America demonstrate that fluctuations in sea level and depth are driving local changes in the eNd, d13C and Sm/Nd composition of epeiric seawater. Dissolved Nd derived from the Transcontinental Arch, Taconic Highlands and the Iapetus Ocean determine the eNd composition of Midcontinent seawater. As sea level fluctuated, submergence of the Arch and an influx of Iapetus ocean waters adjusted the Nd isotope balance of epeiric seawater. As a result, eNd profiles can be used to track the submergence history of the Late Ordovician Midcontinent. Comparison of stratigraphic variations in carbonate Sm/Nd ratios with sea level curves, conodont paleoecology, and the eNd profiles also suggests that variations in Sm/Nd ratios are related to changes in depth. However, processes effecting Sm/Nd ratios in epeiric seas may be varied and require further investigation. Sea level fluctuations and the waxing and waning of cool, nutrient rich, oxygen poor Iapetus waters onto the craton adjusted productivity and organic carbon burial rates on the Ordovician Midcontinent. Close to the Transcontinental Arch sea level rise caused an increase in organic carbon burial and productivity, while close to the Sebree Trough, and the influx of Iapetus waters, sea level rise caused a decrease in organic carbon burial and productivity. Differences in local C-cycling across a single epeiric sea encourage caution when using d13C profiles from epeiric sea carbonates to track changes in the C-cycle of adjacent oceans. Because of their connection to sea level fluctuations, variations in the eNd, d13C and Sm/Nd profiles can also used to correlate Ordovician Midcontinent carbonates. However, the ability to correlate coeval strata using these profiles is limited by changes in depositional environment across the craton, which cause excursions to be absent, dampened, or magnified

The relativistic Iron K-alpha line from an accretion disc onto a static non-baryonic compact object

This paper continues the study of the properties of an accretion disc rotating around a non-baryonic (assumed super-massive) compact object. This kind of objects, generically known as boson stars, were earlier proposed as a possible alternative scenario to the existence of super-masive black holes in the center of every galaxy. A dilute boson star has also been proposed as a large part of the non-baryonic dark matter, flattening galactic rotational velocities curves. In this contribution, we compute the profile of the emission lines of Iron; its shape has been for long known as a useful diagnosis of the space-time geometry. We compare with the case of a Schwarzschild black hole, concluding that the differences are observationally distinguishable.Comment: 14 pages, 7 figure

Accretion Disk Illumination in Schwarzschild and Kerr Geometries: Fitting Formulae

We describe the methodology and compute the illumination of geometrically thin accretion disks around black holes of arbitrary spin parameter $a$ exposed to the radiation of a point-like, isotropic source at arbitrary height above the disk on its symmetry axis. We then provide analytic fitting formulae for the illumination as a function of the source height $h$ and the black hole angular momentum $a$. We find that for a source on the disk symmetry axis and $h/M > 3$, the main effect of the parameter $a$ is allowing the disk to extend to smaller radii (approaching $r/M \to 1$ as $a/M \to 1$) and thus allow the illumination of regions of much higher rotational velocity and redshift. We also compute the illumination profiles for anisotropic emission associated with the motion of the source relative to the accretion disk and present the fractions of photons absorbed by the black hole, intercepted by the disk or escaping to infinity for both isotropic and anisotropic emission for $a/M=0$ and $a/M=0.99$. As the anisotropy (of a source approaching the disk) increases the illumination profile reduces (approximately) to a single power-law, whose index, $q$, because of absorption of the beamed photons by the black hole, saturates to a value no higher than $q \gtrsim 3$. Finally, we compute the fluorescence Fe line profiles associated with the specific illumination and compare them among various cases.Comment: 26 pages, 21 b/w figures, accepted for publication in the Astrophysical Journal as of 4/16/200

Ray-tracing in four and higher dimensional black holes: An analytical approximation

We study null rays propagation in a spacetime of static Schwarzschild--Tangherlini black holes in arbitrary number of dimensions. We focus on the bending angle and the retarded time delay for rays emitted in the vicinity of a black hole and propagating to the infinity. We obtain an analytic expression in terms of elementary functions which approximate the bending angle and time delay in these spacetimes with high accuracy. We analyze the relative error of the developed analytic approximations and show that it is quite small in the complete domain of the parameter space for the rays reaching the infinity and for different number of the spacetime dimensions. Possible applications of the obtained results are briefly discussed.Comment: 12 pages, 11 figures, text added to the figures along the abscissa and ordinate axes, typing errors corrected, some new text added in the main text also. Accepted for publication in Physical Review

Optics in the Schwarzschild space-time

Realistic modelling of radiation transfer in and from variable accretion disks around black holes requires the solution of the problem: find the constants of motion and equation of motion of a light-like geodesic connecting two arbitrary points in space. Here we give the complete solution of this problem in the Schwarzschild space-time.Comment: 14 pages, 10 figures, type C orbits added, analytic solutions for time of flight of photons for all 3 types of orbits adde

State of the art in bile analysis in forensic toxicology

AbstractIn forensic toxicology, alternative matrices to blood are useful in case of limited, unavailable or unusable blood sample, suspected postmortem redistribution or long drug intake-to-sampling interval. The present article provides an update on the state of knowledge for the use of bile in forensic toxicology, through a review of the Medline literature from 1970 to May 2015. Bile physiology and technical aspects of analysis (sampling, storage, sample preparation and analytical methods) are reported, to highlight specificities and consequences from an analytical and interpretative point of view. A table summarizes cause of death and quantification in bile and blood of 133 compounds from more than 200 case reports, providing a useful tool for forensic physicians and toxicologists involved in interpreting bile analysis. Qualitative and quantitative interpretation is discussed. As bile/blood concentration ratios are high for numerous molecules or metabolites, bile is a matrix of choice for screening when blood concentrations are low or non-detectable: e.g., cases of weak exposure or long intake-to-death interval. Quantitative applications have been little investigated, but small molecules with low bile/blood concentration ratios seem to be good candidates for quantitative bile-based interpretation. Further experimental data on the mechanism and properties of biliary extraction of xenobiotics of forensic interest are required to improve quantitative interpretation