bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activity-Induced Radial Velocity Variation of M Dwarf Stars
Authors: Andersen Jan Marie , Korhonen Heidi 
Published: April 2014

AbstractStellar magnetic activity manifests itself in a variety of ways including starspots–cool, dark regions on the stellar surface. Starspots can cause variations (‘jitter’) in spectral line-profiles which can mimic the radial velocity (RV) variations caused by an orbiting planet, or create RV noise that can drown out a planetary signature. Cool, low-mass M dwarf stars can be highly active, which can make detection of potentially habitable planets around these stars difficult. We investigate radial velocity variations caused by different activity (spot) patterns on M dwarf stars in order to determine the limits of detectability for small planets orbiting active M dwarfs. We report on our progress toward the aim of answering the following questions: What types of spot patterns are realistic for M dwarf stars? What effect will spots have on M dwarf RV measurements? Can jitter from M dwarf spots mimic planetary signals? What is the ideal observing wavelength to reduce M dwarf jitter?
The Elemental Compositions of Extrasolar Planetesimals
Authors: Jura M. 
Published: April 2014

AbstractEvidence is now compelling that most externally-polluted white dwarfs derive their heavy atoms by accretion from asteroids – the building blocks of rocky planets. Optical and ultraviolet spectroscopy of a small sample of suitable white dwarf stars shows that to zeroth order, the accreted extrasolar parent bodies compositionally resemble bulk Earth. (1) Extrasolar planetesimals are at least 85% by mass composed of O, Mg, Si and Fe. (2) Compared to the Sun, C is often deficient, usually by at least a factor of 10 and therefore comprises less than 1% of an extrasolar planetesimal's mass. At least to-date, C has never been found to be enhanced as would be expected if carbon-rich planetesimals have formed. (3) While there may be individual exceptions, considered as a whole, the population of extrasolar asteroids accreted onto a well-defined sample of local white dwarf stars is less than 1% water by mass.
Laminar Accretion in the Habitable Zone of Protoplanetary Disks
Authors: Bai Xue-Ning , Stone James M. 
Published: April 2014

AbstractProtoplanetary disks (PPDs) are widely believed to be turbulent as a result of the magnetorotational instability (MRI). We perform magnetohydrodynamical simulations of PPDs that for the first time, take into account both Ohmic resistivity and ambipolar diffusion in a self-consistent manner. We show that in the inner region of PPDs that corresponds the habitable zone, the MRI is completely suppressed due to the interplay between magnetic field and ambipolar diffusion. The gas in this region is laminar throughout the entire vertical extent of the disk. Instead of MRI-driven accretion, a strong magnetocentrifugal wind is launched that efficiently carries away disk angular momentum. A physical wind geometry requires the presence of a strong current layer that is offset from the disk midplane where horizontal magnetic fields flip. We show that the entire accretion flow proceeds through this strong current layer. The non-turbulent nature of the gas flow strongly favors the habitable zone as the site for planetesimal formation, and has important implications for their subsequent growth into terrestrial planets.
Type I Planet Migration in Weakly Magnetized Laminar Disks
Authors: Guilet Jérôme , Baruteau Clément , Papaloizou John C. B. 
Published: April 2014

AbstractPlanet migration plays a crucial role in shaping planetary systems, and has therefore received a lot of attention in recent years in an effort to compare the statistical properties of observed exoplanets with the predictions of planet formation and migration theories. By modifying the propagation properties of the waves induced by the planet in the disk, the presence of a strong magnetic field can dramatically influence planet migration, in some cases reversing its direction. The more realistic case of a weaker magnetic field is less clear, although turbulent MHD simulations by Baruteau et al. (2011) suggest an effect on the corotation torque. Here, we present a study of the corotation torque in 2D laminar disks containing a toroidal magnetic field. We performed MHD simulations of the interaction between the magnetic field and the horseshoe motion of the gas, and found that this results in an additional corotation torque. This additional torque can be strong enough to reverse migration even for a field which pressure is only one percent of the thermal pressure. We speculate that this could lead to long range outward migration in the outer part of protoplanetary disks and may explain the observations by direct imaging of planets at several tens of AU from their star like the 4 planets system HR 8799.
Determining the Origin of Inner Planetary System Debris Orbiting the Dustiest Main Sequence Stars
Authors: Melis Carl , Zuckerman B. , Rhee Joseph H. , Song Inseok , Murphy S. J. , Bessell M. S. 
Published: April 2014

AbstractWe develop a means to distinguish between warm dusty circumstellar debris disks produced by steady state collisional evolution of a planetesimal belt or through transient events.
Angular Momenta of Collided Rarefied Preplanetesimals
Authors: Ipatov Sergei I. 
Published: April 2014

AbstractThe angular momenta of rarefied preplanetesimals needed for formation of small-body binaries can be obtained at collisions of preplanetesimals. Trans-Neptunian objects, including trans-Neptunian binaries, could be formed from contracting rarefied preplanetesimals.
Atmospheric Characterization of Cold Exoplanets Using a 1.5-m Space Coronagraph
Authors: Maire Anne-Lise , Galicher Raphaël , Boccaletti Anthony , Baudoz Pierre , Schneider Jean , Cahoy Kerri , Stam Daphne , Traub Wesley 
Published: April 2014

AbstractWe present numerical results of the science performance of the SPICES mission, which aims to characterize the spectro-polarimetric properties of cold exoplanets and circumstellar disks in the visible. We focus on the instrument ability to retrieve the spectral signatures of molecular species, clouds and surface of super-Earths in the habitable zone of solar-type stars. Considering realistic reflected planet spectra and instrument limitation, we show that SPICES could analyse the atmosphere and surface of a few super-Earths within 5 pc of the Sun.
Cloud and Gas Ionisation in Atmosphere of Gas-Giant Planets
Authors: Helling Ch. , Jardine M. , Stark C. , Rimmer P. , Diver D. 
Published: April 2014

AbstractThe steady increase of the sample of know extrasolar planets broadens our knowledge and at the same time, reveals our lack of understanding. Habitability is a wide expression, needing planet formation theory and microphysics of cloud formation at the same time. The habitability of a planet depends, amongst other things, on how much radiation reached the ground and how much of potentially dangerous radiation is absorbed on the way through the atmosphere. For this, we need to understand cloud formation and it's impact on the atmosphere.We have studied the formation of mineral clouds on planetary atmospheres by a kinetic approach which allows us to predict the size distribution and material composition of the cloud particles. With these results we show that mineral cloud particles can be electrically charged and at which point inside a cloud charge separation will cause an electric field breakdown. Such streamer processes result in an extreme increase of the local number of free charges. Given the strong magnetic field in Brown Dwarfs and maybe in giant gas planets, these charges will than be accelerated upward out of the atmosphere where they become detectable as radio emission.
Climate of Eccentric Terrestrial Planets with Carbonate-Silicate Geochemical Cycle
Authors: Kadoya Shintaro , Tajika Eiichi , Watanabe Yoshiyasu 
Published: April 2014

AbstractRecent discovery of extrasolar planets indicates that some of them have much higher eccentricity than the planets in the solar system. Here, we investigate the climate of such eccentric terrestrial planets with oceans and carbonate-silicate geochemical cycles. We find that the climate of the planets are dependent on the annual mean insolation as shown in previous works. We also find that the planets orbiting slightly further from our Sun than the Earth are globally ice-covered even if the carbonate-silicate geochemical cycle works under the same CO2 degassing rate as on the present Earth. However, when the CO2 degassing rate is higher, the planets avoid being globally ice-covered owing to the high level.
Climate of Extraterrestrial Planets with Oceans and Carbonate-Silicate Geochemical Cycle Under Various Obliquities
Authors: Watanabe Yoshiyasu , Tajika Eiichi , Kadoya Shintaro 
Published: April 2014

AbstractWe systematically investigated the climate of water-rich terrestrial planets with a negative feedback mechanism of carbonate-silicate geochemical cycle against the climate under various obliquities and semi-major axes. We found that, while the permanent ice-cap mode (partially ice-covered throughout the year) and the seasonal ice-cap mode (partially ice-covered seasonally) exist stably at low obliquity conditions, the ranges of semi-major axis for these climate modes shrink and finally disappear with an increase of obliquity. When carbonate-silicate geochemical cycle is taken into account, the ranges of semi-major axis for all the climate modes expand at any obliquities, compared with the cases without carbonate-silicate geochemical cycle, indicating that the carbonate-silicate geochemical cycle strongly stabilizes the climate for the planets with any obliquities inside the habitable zone.
The Complete Evaporation Limit of Land Planets
Authors: Takao Yuya , Genda Hidenori , Wakida Miyuki , Abe Yutaka 
Published: April 2014

AbstractPlanets with very little amount of water on their surface, called “land planets”, have wider habitable zones than that of Earth-like “aqua planets” (Abe et al. 2011). We investigated complete evaporation of surface liquid water for land planets using 1D energy balance model (EBM). We found that complete evaporation occurs when the planetary flux at the dry edge, which is defined as the boundary between the dry zone and the wet zone, exceeds the critical radiation flux of water saturated atmosphere. We define “complete evaporation limit” as the minimum insolation for complete evaporation that a planet receives. This limit depends on latitude of the dry edge, efficiency of meridional heat transport, and atmospheric character that modify the value of the critical flux.
Mass-Radius Relationships of Rocky Exoplanets
Authors: Sohl Frank , Wagner Frank W. , Rauer Heike 
Published: April 2014

AbstractMass and radius of planets transiting their host stars are provided by radial velocity and photometric observations. Structural models of solid exoplanet interiors are then constructed by using equations of state for the radial density distribution, which are compliant with the thermodynamics of the high-pressure limit. However, to some extent those structural models suffer from inherent degeneracy or non-uniqueness problems owing to a principal lack of knowledge of the internal differentiation state and/or the possible presence of an optically thick atmosphere. We here discuss the role of corresponding measurement errors, which adversely affect determinations of a planet's mean density and bulk chemical composition. Precise measurements of planet radii will become increasingly important as key observational constraints for radial density models of individual solid low-mass exoplanets or super-Earths.
Anelastic Tidal Dissipation in Multi-Layer Planets
Authors: Remus Françcoise , Mathis Stéphane , Zahn Jean-Paul , Lainey Valéry 
Published: April 2014

AbstractEarth-like planets have anelastic mantles, whereas giant planets may have anelastic cores. As for the fluid parts, the tidal dissipation of these regions, gravitationally perturbed by a companion, highly depends on its internal friction and thus its internal structure. Therefore, modeling this kind of interaction presents a high interest to constrain planetary interiors, whose properties are still quite uncertain. Here, we examine the anelastic tidal dissipation in deep planetary interiors, in presence of a fluid envelope, and taking into account its dependence on the rheology.Taking plausible values for the anelastic parameters, and discussing the frequency-dependence of the anelastic dissipation, we show how this mechanism may compete with the dissipation in fluid layers, when applied to Jupiter- and Saturn-like planets. We also discuss the case of the icy giants Uranus and Neptune. Finally, we show how the results may be implemented to describe the dynamical evolution of planetary systems.
Direct Imaging of Planet Transit Events
Authors: van Belle Gerard T. , von Braun Kaspar , Boyajian Tabetha , Schaefer Gail 
Published: April 2014

AbstractExoplanet transit events are attractive targets for the ultrahigh-resolution capabilities afforded by optical interferometers. The intersection of two developments in astronomy enable direct imaging of exoplanet transits: first, improvements in sensitivity and precision of interferometric instrumentation; and second, identification of ever-brighter host stars. Efforts are underway for the first direct high-precision detection of closure phase signatures with the CHARA Array and Navy Precision Optical Interferometer. When successful, these measurements will enable recovery of the transit position angle on the sky, along with characterization of other system parameters, such as stellar radius, planet radius, and other parameters of the transit event. This technique can directly determine the planet's radius independent of any outside observations, and appears able to improve substantially upon other determinations of that radius; it will be possible to extract wavelength dependence of that radius determination, for connection to characterization of planetary atmospheric composition & structure. Additional directly observed parameters - also not dependent on transit photometry or spectroscopy - include impact parameter, transit ingress time, and transit velocity.
Starspot-Induced Radial Velocity Jitter During a Stellar Cycle
Authors: Korhonen Heidi , Andersen Jan Marie , Järvinen Silva 
Published: April 2014

AbstractLate-type stars exhibit cool regions on their surface, the stellar equivalent of sunspots. These dark starspots can also mimic the radial velocity variations caused by orbiting planets, making it at times difficult to distinguish between planets and activity signatures. The amount of spots on the Sun and other cool stars changes cyclically during an activity cycle, which has length varying from about a year to longer than the solar 11 years. In this work we investigate the influence of varying amount of starspots on the sparsely sampled radial velocity observations - which are the norm in the radial velocity studies searching for exoplanets on wide orbits. We study two simulated cases: one with a random spot configuration, and one where the spot occurrence is concentrated. In addition we use Doppler images of young solar analogue V889 Her as a high activity case.
Superflares on Late-Type Stars
Authors: Maehara Hiroyuki , Shibayama Takuya , Notsu Yuta , Notsu Shota , Nagao Tanashi , Honda Satoshi , Nogami Daisaku , Shibata Kazunari 
Published: April 2014

AbstractWe present the results of an extensive survey of superflares on late-type stars (G, K, and M-type main sequence stars) using the Kepler satellite data. Wefound about 6,800 superflares on late-type stars from the data of about 120,000 stars observed over 500 days. The total bolometric energy of superflares in oursample ranges from 1032 erg to 1036 erg. Our data suggest that the occurrencefrequency of superflares depends on the surface temperature and the rotationperiod of stars. Superflares on M-type stars occur about 10-100 times morefrequently than those on G-type stars. Our results suggest that the average frequency ofsuperflares releasing 1034–1035 erg of energy (100-1,000 times larger than the largestsolar flares) on M-type stars and Sun-like stars is once in 10 years and once in a few thousand years respectively.
A High Resolution Spectrograph at Weihai Observatory
Authors: Gao Dongyang , Ren Dayong 
Published: April 2014

AbstractWeihai Echelle Spectrograph (WES) is the first the fiber-fed echelle spectrograph in China. WES can provide data for the studies of metal abundance of stars, exoplanets researches and asteroseismology, etc. A brief description of its design and performance is given.
Simulator for Microlens Planet Surveys
Authors: Ipatov Sergei I. , Horne Keith , Alsubai Khalid A. , Bramich Daniel M. , Dominik Martin , Hundertmark Markus P. G. , Liebig Christine , Snodgrass Colin D. B. , Street Rachel A. , Tsapras Yiannis 
Published: April 2014

AbstractWe summarize the status of a computer simulator for microlens planet surveys. The simulator generates synthetic light curves of microlensing events observed with specified networks of telescopes over specified periods of time. Particular attention is paid to models for sky brightness and seeing, calibrated by fitting to data from the OGLE survey and RoboNet observations in 2011. Time intervals during which events are observable are identified by accounting for positions of the Sun and the Moon, and other restrictions on telescope pointing. Simulated observations are then generated for an algorithm that adjusts target priorities in real time with the aim of maximizing planet detection zone area summed over all the available events. The exoplanet detection capability of observations was compared for several telescopes.
HSTEP – Homogeneous Studies of Transiting Extrasolar Planets
Authors: Southworth John 
Published: April 2014

AbstractThis paper presents a summary of the HSTEP project: an effort to calculate the physical properties of the known transiting extrasolar planets using a homogeneous approach. I discuss the motivation for the project, list the 83 planets which have already been studied, run through some important aspects of the methodology, and finish with a synopsis of the results.
The ELODIE and SOPHIE Search for Northern Extrasolar Planets: Jupiter-Analogs around Sun-Like Stars
Authors: Boisse I. , Pepe F. , Perrier C. , Queloz D. , Bouchy F. , Santos N. C. ,   the SOPHIE team
Published: April 2014

AbstractWe present radial-velocity measurements (RV) obtained in one of the numbers of programs underway to search for extrasolar planets with the spectrograph SOPHIE at the 1.93-m telescope of the Observatoire de Haute-Provence. Targets were selected from catalogs observed with ELODIE, which had been mounted previously at the telescope, in order to detect long-period planets with an extended database close to 15 years.
Reprograming of gut microbiome energy metabolism by theFUT2Crohn’s disease risk polymorphism
Authors: Tong Maomeng , McHardy Ian , Ruegger Paul , Goudarzi Maryam , Kashyap Purna C , Haritunians Talin , Li Xiaoxiao , Graeber Thomas G , Schwager Emma , Huttenhower Curtis , Fornace Albert J , Sonnenburg Justin L , McGovern Dermot P B , Borneman James , Braun Jonathan 
Published: April 2014

AbstractFucosyltransferase 2 (FUT2) is an enzyme that is responsible for the synthesis of the H antigen in body fluids and on the intestinal mucosa. The H antigen is an oligosaccharide moiety that acts as both an attachment site and carbon source for intestinal bacteria. Non-secretors, who are homozygous for the loss-of-function alleles of FUT2 gene (sese), have increased susceptibility to Crohn’s disease (CD). To characterize the effect of FUT2 polymorphism on the mucosal ecosystem, we profiled the microbiome, meta-proteome and meta-metabolome of 75 endoscopic lavage samples from the cecum and sigmoid of 39 healthy subjects (12 SeSe, 18 Sese and 9 sese). Imputed metagenomic analysis revealed perturbations of energy metabolism in the microbiome of non-secretor and heterozygote individuals, notably the enrichment of carbohydrate and lipid metabolism, cofactor and vitamin metabolism and glycan biosynthesis and metabolism-related pathways, and the depletion of amino-acid biosynthesis and metabolism. Similar changes were observed in mice bearing the FUT2−/− genotype. Metabolomic analysis of human specimens revealed concordant as well as novel changes in the levels of several metabolites. Human metaproteomic analysis indicated that these functional changes were accompanied by sub-clinical levels of inflammation in the local intestinal mucosa. Therefore, the colonic microbiota of non-secretors is altered at both the compositional and functional levels, affecting the host mucosal state and potentially explaining the association of FUT2 genotype and CD susceptibility.
Mutation rate plasticity in rifampicin resistance depends on Escherichia coli cell–cell interactions
Authors: Krašovec Rok , Belavkin Roman V. , Aston John A. D. , Channon Alastair , Aston Elizabeth , Rash Bharat M. , Kadirvel Manikandan , Forbes Sarah , Knight Christopher G. 
Published: April 2014

AbstractVariation of mutation rate at a particular site in a particular genotype, in other words mutation rate plasticity (MRP), can be caused by stress or ageing. However, mutation rate control by other factors is less well characterized. Here we show that in wild-typeEscherichia coli(K-12 and B strains), the mutation rate to rifampicin resistance is plastic and inversely related to population density: lowering density can increase mutation rates at least threefold. This MRP is genetically switchable, dependent on the quorum-sensing geneluxS—specifically its role in the activated methyl cycle—and is socially mediated via cell–cell interactions. Although we identify an inverse association of mutation rate with fitness under some circumstances, we find no functional link with stress-induced mutagenesis. Our experimental manipulation of mutation rates via the social environment raises the possibility that such manipulation occurs in nature and could be exploited medically.