Tidal Evolution of Close-in Extra-Solar Planets

The distribution of eccentricities e of extra-solar planets with semi-major axes a > 0.2 AU is very uniform, and values for e are relatively large, averaging 0.3 and broadly distributed up to near 1. For a < 0.2 AU, eccentricities are much smaller (most e < 0.2), a characteristic widely attributed to damping by tides after the planets formed and the protoplanetary gas disk dissipated. Most previous estimates of the tidal damping considered the tides raised on the planets, but ignored the tides raised on the stars. Most also assumed specific values for the planets' poorly constrained tidal dissipation parameter Qp. Perhaps most important, in many studies, the strongly coupled evolution between e and a was ignored. We have now integrated the coupled tidal evolution equations for e and a over the estimated age of each planet, and confirmed that the distribution of initial e values of close-in planets matches that of the general population for reasonable Q values, with the best fits for stellar and planetary Q being ~10^5.5 and ~10^6.5, respectively. The accompanying evolution of a values shows most close-in planets had significantly larger a at the start of tidal migration. The earlier gas disk migration did not bring all planets to their current orbits. The current small values of a were only reached gradually due to tides over the lifetimes of the planets. These results may have important implications for planet formation models, atmospheric models of "hot Jupiters", and the success of transit surveys.Comment: accepted to Ap

Critical behavior of Born Infeld AdS black holes in higher dimensions

Based on a canonical framework, we investigate the critical behavior of Born-Infeld AdS black holes in higher dimensions. As a special case, considering the appropriate limit, we also analyze the critical phenomena for Reissner Nordstrom AdS black holes. The critical points are marked by the divergences in the heat capacity at constant charge. The static critical exponents associated with various thermodynamic entities are computed and shown to satisfy the thermodynamic scaling laws. These scaling laws have also been found to be compatible with the static scaling hypothesis. Furthermore, we show that the values of these exponents are universal and do not depend on the spatial dimensionality of the AdS space. We also provide a suggestive way to calculate the critical exponents associated with the spatial correlation which satisfy the scaling laws of second kind.Comment: LaTex, 22 pages, 12 figures, minor modifications in text, To appear in Phys. Rev.

The New Transiting Planet OGLE-TR-56b: Orbit and Atmosphere

Motivated by the identification of the very close-in extrasolar giant planet OGLE-TR-56b, we explore the implications of its existence on problems of tidal dissipation, planet migration, and atmospheric stability. The small orbit of OGLE-TR-56b makes the planet an interesting test particle case for tidal dissipation in stellar convection zones. We show that it favors prescriptions of suppressed convective eddy viscosity. Precise timing of the transits of OGLE-TR-56b might place interesting constraints on stellar convection theory, if orbital period change is detected in the near future.Comment: 12 pages, 1 figure, submitted to ApJ

Staart beter bewaard door afleidingsmateriaal?

Meer activiteit en meer aandacht voor afleidingsmateriaal leidt bij biggen met intacte staarten tot minder staartbijten

Low State of the X-ray Burster SLX 1732-304 in the Globular Cluster Terzan 1 According to RXTE Data

Observations of the X-ray burster SLX 1732-304 in the globular cluster Terzan 1 with the PCA/RXTE instrument in April 1997 are presented. The source was in a low state; its flux in the standard X-ray band was half the flux recorded by the ART-P/Granat telescope also during its low state. At the same time, its spectrum was softer than the ART-P spectrum; it was well described by a power law with a photon index of 2.3 without any evidence of a high-energy cutoff.Comment: 8 pages, 3 figures. Accepted to publication in Astronomy Letter

On the central structure of M15

We present a detailed comparison between the latest observational data on the kinematical structure of the core of M15, obtained with the Hubble STIS and WFPC2 instruments, and the results of dynamical simulations carried out using the special-purpose GRAPE-6 computer. The observations imply the presence of a significant amount of dark matter in the cluster core. In our dynamical simulations, neutron stars and/or massive white dwarfs concentrate to the center through mass segregation, resulting in a sharp increase in $M/L$ toward the center. While consistent with the presence of a central black hole, the Hubble data can also be explained by this central concentration of stellar-mass compact objects. The latter interpretation is more conservative, since such remnants result naturally from stellar evolution, although runaway merging leading to the formation of a black hole may also occur for some range of initial conditions. We conclude that no central massive object is required to explain the observational data, although we cannot conclusively exclude such an object at the level of $\sim500-1000$ solar masses. Our findings are unchanged when we reduce the assumed neutron-star retention fraction in our simulations from 100% to 0%.Comment: 12 pages, 4 figures. Accepted for publication in ApJ

Semicarbazide-sensitive amine oxidase (SSAO): from cell to circulation

Semicarbazide-sensitive amine oxidase (SSAO) is a multi-functional enzyme widely present in nature. It converts primary amines into their corresponding aldehydes, while generating H(2)O(2) and NH(3). In mammals, SSAO circulates in plasma, while a membrane-bound form (often referred to as vascular adhesion protein-1, VAP-1) is found in many tissues and organs, especially in adipocytes and vascular endothelial and smooth muscle cells. In recent years, evidence has been accumulating that SSAO has a role in protein cross-linking, formation of advanced glycation end-products, atherogenesis, glucose regulation and leukocyte extravasation at inflammation sites. Plasma SSAO is quite stable in healthy adults, but is elevated in diabetes mellitus (both type 1 and type 2), congestive heart failure and liver cirrhosis. The origin of circulating SSAO remains unclear, but recent evidence from clinical studies and from (transgenic) animal studies suggests that adipocytes and vascular endothelial cells may be the most important source. Studies with cell cultures show evidence that the membrane-bound SSAO can be split off from the cells, thus giving rise to the (truncated) circulating form of SSAO. In some pathological conditions the diseased organ may be the main source of the elevated plasma SSAO. Little is known as yet about the regulation of plasma SSAO. Thyroid hormone appears to play a (modest) role in this respect. Further evidence from clinical, animal and cell-culture studies, helped by the new availability of selective SSAO inhibitors, is needed to shed more light on the question of the regulation of SSAO

Thermodynamic Geometry Of Charged Rotating BTZ Black Holes

We study the thermodynamics and the thermodynamic geometries of charged rotating BTZ (CR-BTZ) black holes in (2+1)-gravity. We investigate the thermodynamics of these systems within the context of the Weinhold and Ruppeiner thermodynamic geometries and the recently developed formalism of geometrothermodynamics (GTD). Considering the behavior of the heat capacity and the Hawking temperature, we show that Weinhold and Ruppeiner geometries cannot describe completely the thermodynamics of these black holes and of their limiting case of vanishing electric charge. In contrast, the Legendre invariance imposed on the metric in GTD allows one to describe the CR-BTZ black holes and their limiting cases in a consistent and invariant manner

SB9: The Ninth Catalogue of Spectroscopic Binary Orbits

The Ninth Catalogue of Spectroscopic Binary Orbits (http://sb9.astro.ulb.ac.be) continues the series of compilations of spectroscopic orbits carried out over the past 35 years by Batten and collaborators. As of 2004 May 1st, the new Catalogue holds orbits for 2,386 systems. Some essential differences between this catalogue and its predecessors are outlined and three straightforward applications are presented: (1) Completeness assessment: period distribution of SB1s and SB2s; (2) Shortest periods across the H-R diagram; (3) Period-eccentricity relation.Comment: Accepte for publication in A&A, 6 pages, 6 figure

Investigating the flyby scenario for the HD 141569 system

HD 141569, a triple star system, has been intensively observed and studied for its massive debris disk. It was rather regarded as a gravitationally bound triple system but recent measurements of the HD 141569A radial velocity seem to invalidate this hypothesis. The flyby scenario has therefore to be investigated to test its compatibility with the observations. We present a study of the flyby scenario for the HD141569 system, by considering 3 variants: a sole flyby, a flyby associated with one planet and a flyby with two planets. We use analytical calculations and perform N-body numerical simulations of the flyby encounter. The binary orbit is found to be almost fixed by the observational constraint on a edge-on plane with respect to the observers. If the binary has had an influence on the disk structure, it should have a passing time at the periapsis between 5000 and 8000 years ago and a distance at periapsis between 600 and 900 AU. The best scenario for reproducing the disk morphology is a flyby with only 1 planet. For a 2 Mj (resp. 8 Mj) planet, its eccentricity must be around 0.2 (resp. below 0.1). In the two cases, its apoapsis is about 130 AU. Although the global disk shape is reasonably well reproduced, some features cannot be explain by the present model and the likehood of the flyby event remains an issue. Dynamically speaking, HD 141569 is still a puzzling system