The Hunt for Exomoons with Kepler (HEK): I. Description of a New Observational Project

Two decades ago, empirical evidence concerning the existence and frequency of planets around stars, other than our own, was absent. Since this time, the detection of extrasolar planets from Jupiter-sized to most recently Earth-sized worlds has blossomed and we are finally able to shed light on the plurality of Earth-like, habitable planets in the cosmos. Extrasolar moons may also be frequent habitable worlds but their detection or even systematic pursuit remains lacking in the current literature. Here, we present a description of the first systematic search for extrasolar moons as part of a new observational project called "The Hunt for Exomoons with Kepler" (HEK). The HEK project distills the entire list of known transiting planet candidates found by Kepler (2326 at the time of writing) down to the most promising candidates for hosting a moon. Selected targets are fitted using a multimodal nested sampling algorithm coupled with a planet-with-moon light curve modelling routine. By comparing the Bayesian evidence of a planet-only model to that of a planet-with-moon, the detection process is handled in a Bayesian framework. In the case of null detections, upper limits derived from posteriors marginalised over the entire prior volume will be provided to inform the frequency of large moons around viable planetary hosts, eta-moon. After discussing our methodologies for target selection, modelling, fitting and vetting, we provide two example analyses.Comment: 21 pages, 8 figures, 4 tables, accepted in Ap

Self-consistent modeling of gamma-ray spectra from solar flares with the Monte Carlo simulation package FLUKA

We use the Monte Carlo particle physics code FLUKA (Fluktuierende Kaskade) to calculate γ -ray spectra expected from solar flare energetic ion distributions. The FLUKA code includes robust physics-based models for electromagnetic, hadronic and nuclear interactions, sufficiently detailed for it to be a useful tool for calculating nuclear de-excitation, positron-annihilation and neutron-capture line fluxes and shapes, as well as ≈GeV continuum radiation from pion decay products. We show nuclear de-excitation γ -ray line model spectra from a range of assumed primary accelerated ion distributions and find them to be in good agreement with those found using the code of Murphy et al. (2009). We also show full γ -ray model spectra which exhibit all the typical structures of γ -ray spectra observed in solar flares. From these model spectra we build templates which are incorporated into the software package Objective Spectral Executive (OSPEX) and used to fit the combined Fermi Gamma-ray Burst Monitor (GBM)/Large Area Telescope (LAT) spectrum of the 2010 June 12 solar flare, providing a statistically acceptable result. To the best of our knowledge, the fit carried out with the FLUKA templates for the full γ -ray spectrum can be regarded as the first attempt to use a single code to implement a self-consistent treatment of the several spectral components in the photon energy range from ≈100s keV to ≈100s MeV

A novel method for identifying exoplanetary rings

ABSTRACT: The discovery of rings around extrasolar planets (“exorings”) is one of the next breakthroughs in exoplanetary research. Previous studies have explored the feasibility of detecting exorings with present and futuren photometric sensitivities by seeking anomalous deviations in the residuals of a standard transit light curve fit, at the level of ~-100 ppm for Kronian rings. In this work, we explore two much larger observational consequences of exorings: (1) the significant increase in transit depth that may lead to the misclassification of ringed planetary candidates as false-positives and/or the underestimation of planetary density; and (2) the so-called “photo-ring” effect, a new asterodensity profiling effect, revealed by a comparison of the light curve derived stellar density to that measured with independent methods (e.g., asteroseismology). While these methods do not provide an unambiguous detection of exorings, we show that the large amplitude of these effects, combined with their relatively simple analytic description, makes them highly suited to large-scale surveys to identify candidate ringed planets worthy of more detailed investigation. Moreover, these methods lend themselves to ensemble analyses seeking to uncover evidence of a population of ringed planets. We describe the method in detail, develop the basic underlying formalism, and test it in the parameter space of rings and transit configuration. We discuss the prospects of using this method for the first systematic search of exoplanetary rings in the Kepler database and provide a basic computational code for implementing it

The PLATO 2.0 mission

PLATO 2.0 has recently been selected for ESA's M3 launch opportunity (2022/24). Providing accurate key planet parameters (radius, mass, density and age) in statistical numbers, it addresses fundamental questions such as: How do planetary systems form and evolve? Are there other systems with planets like ours, including potentially habitable planets? The PLATO 2.0 instrument consists of 34 small aperture telescopes (32 with 25 s readout cadence and 2 with 2.5 s candence) providing a wide field-of-view (2232 deg 2) and a large photometric magnitude range (4-16 mag). It focusses on bright (4-11 mag) stars in wide fields to detect and characterize planets down to Earth-size by photometric transits, whose masses can then be determined by ground-based radial-velocity follow-up measurements. Asteroseismology will be performed for these bright stars to obtain highly accurate stellar parameters, including masses and ages. The combination of bright targets and asteroseismology results in high accuracy for the bulk planet parameters: 2 %, 4-10 % and 10 % for planet radii, masses and ages, respectively. The planned baseline observing strategy includes two long pointings (2-3 years) to detect and bulk characterize planets reaching into the habitable zone (HZ) of solar-like stars and an additional step-and-stare phase to cover in total about 50 % of the sky. PLATO 2.0 will observe up to 1,000,000 stars and detect and characterize hundreds of small planets, and thousands of planets in the Neptune to gas giant regime out to the HZ. It will therefore provide the first large-scale catalogue of bulk characterized planets with accurate radii, masses, mean densities and ages. This catalogue will include terrestrial planets at intermediate orbital distances, where surface temperatures are moderate. Coverage of this parameter range with statistical numbers of bulk characterized planets is unique to PLATO 2.0. The PLATO 2.0 catalogue allows us to e.g.: - complete our knowledge of planet diversity for low-mass objects, - correlate the planet mean density-orbital distance distribution with predictions from planet formation theories,- constrain the influence of planet migration and scattering on the architecture of multiple systems, and - specify how planet and system parameters change with host star characteristics, such as type, metallicity and age. The catalogue will allow us to study planets and planetary systems at different evolutionary phases. It will further provide a census for small, low-mass planets. This will serve to identify objects which retained their primordial hydrogen atmosphere and in general the typical characteristics of planets in such low-mass, low-density range. Planets detected by PLATO 2.0 will orbit bright stars and many of them will be targets for future atmosphere spectroscopy exploring their atmosphere. Furthermore, the mission has the potential to detect exomoons, planetary rings, binary and Trojan planets. The planetary science possible with PLATO 2.0 is complemented by its impact on stellar and galactic science via asteroseismology as well as light curves of all kinds of variable stars, together with observations of stellar clusters of different ages. This will allow us to improve stellar models and study stellar activity. A large number of well-known ages from red giant stars will probe the structure and evolution of our Galaxy. Asteroseismic ages of bright stars for different phases of stellar evolution allow calibrating stellar age-rotation relationships. Together with the results of ESA's Gaia mission, the results of PLATO 2.0 will provide a huge legacy to planetary, stellar and galactic science

Modelagem de processos nucleares de alta energia em explosões solares utilizando o pacote FLUKA

A emissão de raios-\u1d6fe em explosões solares é produzida por interações de elétrons e íons primários acelerados a altas energias com núcleos na atmosfera solar ambiente. A análise dos espectros de raios-\u1d6fe observados durante as explosões solares fornece diagnósticos importantes sobre os mecanismos de aceleração das partículas primárias e sobre a estrutura e evolução do plasma ambiente. Neste trabalho investigamos os processos nucleares de alta energia que ocorrem em explosões solares utilizando o FLUKA, um pacote de rotinas integradas de uso geral para o cálculo Monte Carlo do transporte e das interações de partículas na matéria. Nosso principal objetivo é validar o FLUKA como ferramenta efetiva para a modelagem de processos nucleares no contexto de explosões solares. Para tanto, realizamos simulações do espectro de raios-\u1d6fe considerando modelos realísticos para a atmosfera solar ambiente e feixes de íons acelerados (prótons, partículas-\u1d6fc e núcleos mais pesados) com diferentes distribuições energéticas e angulares. A partir dos resultados obtidos nas simulações com o FLUKA, construímos templates para o espectro de emissão de linhas de desexcitação nuclear e para o espectro completo de emissão de raios-\u1d6fe, os quais foram incorporados ao programa OSPEX para o ajuste de espectros de eventos observados. Utilizando esses templates em combinação com funções-padrão disponíveis no programa OSPEX obtivemos ajustes estatisticamente razoáveis para os espectros de raios-\u1d6fe das explosões solares de 23 de julho de 2002 e 12 de junho de 2010, semelhantes aos ajustes obtidos com templates construídos a partir de espectros de emissão de linhas de desexcitação nuclear calculados com o código desenvolvido por Murphy et al. (2009). Até onde sabemos, os ajustes realizados com os templates FLUKA para o espectro completo de emissão de raios-\u1d6fe podem ser considerados como a primeira tentativa de utilizar um único código para implementar um tratamento auto-consistente das várias componentes espectrais na faixa de energia de ∼ 100’s keV a ∼ 100’s MeV.The emission of \u1d6fe-rays in solar flares is produced by interactions of primary electrons and ions accelerated to high energies with nuclei in the ambient solar atmosphere. The analysis of the \u1d6fe-ray spectra observed during solar flares provides important diagnostics on the mechanisms of primary particle acceleration and on the structure and evolution of the ambient plasma. In this work we investigate the high energy nuclear processes that occur in solar flares using FLUKA, a package of general purpose integrated routines for Monte Carlo calculations of particle transport and interactions in matter. Our main aim is to validate FLUKA as an effective tool for the modeling of nuclear processes in the context of solar flares. In order to accomplish that, we have performed simulations of the \u1d6fe-ray spectrum considering realistic models for the ambient solar atmosphere and beams of accelerated ions (protons, \u1d6fc-particles and heavier nuclei) with different energy and angular distributions. From the results obtained in the simulations with FLUKA, we have built templates for the nuclear de-excitation lines emission spectrum and for the full \u1d6fe-ray emission spectrum, which were incorporated to the program OSPEX for the fitting of spectra from observed events. Using these templates in combination with standard-functions avaiable in the programa OSPEX we have obtained statistically reasonable fittings for the \u1d6fe-ray spectra of the July 23, 2002 and June 12, 2010 solar flares, similar to the fittings obtained with templates built from nuclear de-excitation lines emission spectra calculated with the code developed by Murphy et al. (2009). To the best of our knowledge, the fittings carried out with the FLUKA templates for the full \u1d6fe-ray emission spectrum can be regarded as the first attempt to use a single code to implement a self-consistent treatment of the several spectral components in the energy range from ∼ 100’s keV to ∼ 100’s MeV.Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorFundo Mackenzie de Pesquis

Continuum resonances with shielded Coulomb-like potential and Efimov effect

Motivated by the possibility of the second energy level (0 (2) (+) ) of C-12 (in a three-alpha model) to turn into an Efimov state, we study a simple non-realistic toy model formed by three bosons interacting by the phenomenological s-wave Ali-Bodmer potential plus a Coulomb interaction. An artificial three-body potential was used to create a resonance with energy close to the energy of the 0 (2) (+) of C-12, 0.38 MeV. The strength of the Coulomb potential is decreased until the energies of the two alpha pairs are zero. The system was placed inside a harmonic trap and a stabilization method has been used to calculate the energies of the resonances. We found that the shielded-Coulomb potential, which keeps the long tail, is not able to produce the Efimov effect. The energy of the three alphas decreases only to 0.19 MeV when the two-body energy crosses the threshold to become bound.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Scales, Universality and Finite-Range Correction in Three-body Systems

The scale invariance manifested by the weakly-bound Efimov states implies that all the Efimov spectrum can be merged in a single scaling function. By considering this scaling function, the ratio between two consecutive energy levels, E3 (N+1) and E3 (N), can be obtained from a two-body low-energy observable (usually the scattering length a), given in units of the three-body energy level N. The zero-ranged scaling function is improved by incorporating finite range corrections in first order of r0/a (r0 is the potential effective range). The critical condition for three-identical bosons in s-wave, when the excited E3 (N+1) state disappears in the 2 + 1 threshold, is given by √E2/E3 (N) ≈ 0.38+0.12(r0/a). © 2012 Springer-Verlag