HD60532, a planetary system in a 3:1 mean motion resonance

In a recent paper it was reported a planetary system around the star HD60532, composed by two giant planets in a possible 3:1 mean motion resonance, that should be confirmed within the next decade. Here we show that the analysis of the global dynamics of the system allows to confirm this resonance. The present best fit to data already corresponds to this resonant configuration and the system is stable for at least 5Gry. The 3:1 resonance is so robust that stability is still possible for a wide variety of orbital parameters around the best fit solution and also if the inclination of the system orbital plane with respect to the plane of the sky is as small as 15 deg. Moreover, if the inclination is taken as a free parameter in the adjustment to the observations, we find an inclination ~ 20 deg, which corresponds to M_b =3.1 M_Jup and M_c = 7.4 M_Jup for the planetary companions.Comment: 4 Pages, 4 Figures, accepted by A&

Complete determination of the orbital parameters of a system with N+1 bodies using a simple Fourier analysis of the data

Here we show how to determine the orbital parameters of a system composed of a star and N companions (that can be planets, brown-dwarfs or other stars), using a simple Fourier analysis of the radial velocity data of the star. This method supposes that all objects in the system follow keplerian orbits around the star and gives better results for a large number of observational points. The orbital parameters may present some errors, but they are an excellent starting point for the traditional minimization methods such as the Levenberg-Marquardt algorithms.Comment: 4 page

On the equilibrium rotation of Earth-like extra-solar planets

The equilibrium rotation of tidally evolved "Earth-like" extra-solar planets is often assumed to be synchronous with their orbital mean motion. The same assumption persisted for Mercury and Venus until radar observations revealed their true spin rates. As many of these planets follow eccentric orbits and are believed to host dense atmospheres, we expect the equilibrium rotation to differ from the synchronous motion. Here we provide a general description of the allowed final equilibrium rotation states of these planets, and apply this to already discovered cases in which the mass is lower than twelve Earth-masses. At low obliquity and moderate eccentricity, it is shown that there are at most four distinct equilibrium possibilities, one of which can be retrograde. Because most presently known "Earth-like" planets present eccentric orbits, their equilibrium rotation is unlikely to be synchronous.Comment: 4 pages, 2 figures. accepted for publication in Astronomy and Astrophysics. to be published in Astronomy and Astrophysic

Anisotropic simplicial minisuperspace model

The computation of the simplicial minisuperspace wavefunction in the case of anisotropic universes with a scalar matter field predicts the existence of a large classical Lorentzian universe like our own at late timesComment: 19 pages, Latex, 6 figure

Stellar wobble caused by a nearby binary system: eccentric and inclined orbits

Most extrasolar planets currently known were discovered by means of an indirect method that measures the stellar wobble caused by the planet. We previously studied a triple system composed of a star and a nearby binary on circular coplanar orbits. We showed that although the effect of the binary on the star can be differentiated from the stellar wobble caused by a planet, because of observational limitations the two effects may often remain indistinguishable. Here, we develop a model that applies to eccentric and inclined orbits. We show that the binary's effect is more likely to be mistaken by planet(s) in the case of coplanar motion observed equator-on. Moreover, when the orbits are eccentric, the magnitude of the binary's effect may be larger than in the circular case. Additionally, an eccentric binary can mimic two planets with orbital periods in the ratio 2/1. However, when the star's orbit around the binary's center of mass has a high eccentricity and a reasonably well-constrained period, it should be easier to distinguish the binary's effect from a planet.Comment: 10 pages, 9 figures, 2 table

Tidal Evolution of Exoplanets

Tidal effects arise from differential and inelastic deformation of a planet by a perturbing body. The continuous action of tides modify the rotation of the planet together with its orbit until an equilibrium situation is reached. It is often believed that synchronous motion is the most probable outcome of the tidal evolution process, since synchronous rotation is observed for the majority of the satellites in the Solar System. However, in the 19th century, Schiaparelli also assumed synchronous motion for the rotations of Mercury and Venus, and was later shown to be wrong. Rather, for planets in eccentric orbits synchronous rotation is very unlikely. The rotation period and axial tilt of exoplanets is still unknown, but a large number of planets have been detected close to the parent star and should have evolved to a final equilibrium situation. Therefore, based on the Solar System well studied cases, we can make some predictions for exoplanets. Here we describe in detail the main tidal effects that modify the secular evolution of the spin and the orbit of a planet. We then apply our knowledge acquired from Solar System situations to exoplanet cases. In particular, we will focus on two classes of planets, "Hot-Jupiters" (fluid) and "Super-Earths" (rocky with atmosphere).Comment: 30 pages, 19 figures. Chapter in Exoplanets, ed. S. Seager, to be published by University of Arizona Pres

Nutrition and the gastrointestinal tract

In this year’s issue, we again have a high-calibre collection of topical reviews. Gracie and Ford commence with an assessment of the role of symbiotics (i.e. probiotics and prebiotics given together) in patients with irritable bowel syndrome. They first review the many randomized trials of probiotics and the significant and persistent reductions in symptoms that (on balance) these yield – that may persist after the end of treatment. Pain, bloating and flatulence are all better than with placebo with a range of different regimens. However, although symbiotics appear promising, their current conclusion is that the evidence for superiority over probiotics alone is lacking. Jin and Vos then consider the pathophysiology of nonalcoholic fatty liver disease and specifically the role of fructose. Their synthesis of the literature includes the conclusion that unregulated lipogenesis is key to nonalcoholic fatty liver disease, linked to generalized increases in visceral adiposity – in turn probably secondary to changes in the intestinal microbiota. Dietary fructose seems an important determinant of these phenomena, and early-in-life exposure appears of most significance. Although dogmatic advice is not justified, continuing to argue for limitation of dietary fructose seems wise. Barrett et al. consider the immune response in patients on artificial nutrition in the current context wherein we aim for enteral nutrition whenever possible – thus recognizing that patients who need parenteral nutrition are then an especially high-risk group. They conclude from AQ3 a wide consideration of animal and human data that the intestinal epithelial barrier is significantly compromised and to a clinically relevant extent in patients on exclusive parenteral nutrition. They encourage targeted new work to exploit the mechanisms that have now been unearthed, such that future parenteral nutrition could be used with fewer adverse immunological consequences. Plank and Russell look at nutrition in liver transplantation incorporating new data from patients with concomitantmorbid obesity. It is of course clear that obesity is a perioperative risk factor but we lack proof that pretransplant weight loss would change this. The main issue here is probably the sarcopenic element, and weight loss without muscle preservation (or growth) would be unlikely to help. As obese patients are AQ4 being transplanted, better data are clearly needed to guide optimal nutritional strategies. After a comprehensive review on the state of the art on gluten sensitivity in the absence of coeliac disease by David Sanders, the issue finishes with a intriguing article by Murphy et al. in which they consider the evidence that chronic disease is made more likely by changes in the gut microbiota driven by a high-fat diet. Although dysbiosis is present and linked to obesity, on present evidence, this falls short of a direct causal relationship. We feel confident that readers will find plenty to provoke thought and hopefully to stimulate research in the many loci where data are sparse or inconclusive

Tourism Demand in Portugal: Market Perspectives

Tourism has experienced different levels of development in the different regions of Portugal. To frame this development, several panel data models were estimated. The main objective is to explain the evolution of overnight stays by nationality in each region. Secondary data from 2000 to 2010 was used. The analysis includes the main tourism markets, such as the United Kingdom, Germany, the Netherlands, Ireland, France and Spain. Tourism literature suggests that, among others, the main determinants of tourism demand are Income (GDP), population, tourist´s income by place of residence, households’ consumption, unemployment rate, inflation rate, compensation of employees, comparative prices and households’ investment rate. It is observed that, although significant, the explanatory power of these variables varies according to the origin and the destination region considered