Variabilidade espectral de estrelas T Tauri: GQ Lupi

Bolsa de Iniciação científica CNPQApresentamos a série temporal de observações de baixa resolução da estrela GQ Lupi, uma estrela T Tauri que apresenta fortes indícios de um disco de acresção circunstelar. Nosso conjunto de dados consiste em 18 observações realizadas durante 18 noites consecutivas no mês de Fevereiro de 1999. Medimos a distribuição do excesso de contínuo (velamento) e determinamos o velamento médio para cada noite de observação. A série temporal do velamento apresentou um comportamento senoidal com um período de aproximadamente 13 dias. Acreditamos que uma mancha quente na superfície estelar que rotacional junto com a estrela é a responsável por esse comportamento do velamento. A Fotometria da Gq Lupi encontrada na literatura e nossas observações espectrofotométricas de 1998 confirmam este período encontrado para o velamento. A série temporal do velamento não apresentou uma boa correlação com as linhas de emissão. Porém, correlações entre as linhas de emissão indicam uma região comum de formação ou um mecanismo físico governando suas luminosidades ao mesmo tempo. Os perfis P Cygni invertido praticamente desapareceram em relação aos dados de 1998. As observações foram realizadas no European Southern Observatory, La Silla, Chile sob o acordo ESO-ON

Como seria trabalhar astrobiologia na sala de aula?

Neste trabalho são apresentados os resultados preliminares de uma aula experimental vi¬sando conhecer os subsunçores dos alunos de ensino médio a respeito da Astrobiologia. Este tema foi escolhido de modo a potencializar a aprendizagem significativa devido a sua natureza interdisciplinar. A aula foi aplicada em uma turma de terceiro período do curso médio técnico em controle ambien¬tal em uma escola pública do município de Nilópolis. Os subsunçores expressos, por intermédio de um questionário com perguntas abertas e fechadas, versavam sobre a definição de Astrobiologia e da relacionabilidade entre as disciplinas no ensino médio. A partir dos dados coletados definiram-se os descritores dos grupos de respostas similares. Os resultados mostraram que muitos ainda desconhecem o tema abordado, porém possuem concepções prévias a respeito de vida extraterrestre, possivelmente devido às influências de filmes de ficção científica. Além disso, foram encontrados muitos elementos de interdisciplinaridade nas respostas dos alunos o que indica a relevância do tema para promover a aprendizagem significativa

Exploring Kepler Giant Planets in the Habitable Zone

The Kepler mission found hundreds of planet candidates within the habitable zones (HZ) of their host star, including over 70 candidates with radii larger than 3 Earth radii ($R_\oplus$) within the optimistic habitable zone (OHZ) (Kane et al. 2016). These giant planets are potential hosts to large terrestrial satellites (or exomoons) which would also exist in the HZ. We calculate the occurrence rates of giant planets ($R_p =$~3.0--25~$R_\oplus$) in the OHZ and find a frequency of $(6.5 \pm 1.9)\%$ for G stars, $(11.5 \pm 3.1)\%$ for K stars, and $(6 \pm 6)\%$ for M stars. We compare this with previously estimated occurrence rates of terrestrial planets in the HZ of G, K and M stars and find that if each giant planet has one large terrestrial moon then these moons are less likely to exist in the HZ than terrestrial planets. However, if each giant planet holds more than one moon, then the occurrence rates of moons in the HZ would be comparable to that of terrestrial planets, and could potentially exceed them. We estimate the mass of each planet candidate using the mass-radius relationship developed by Chen & Kipping (2016). We calculate the Hill radius of each planet to determine the area of influence of the planet in which any attached moon may reside, then calculate the estimated angular separation of the moon and planet for future imaging missions. Finally, we estimate the radial velocity semi-amplitudes of each planet for use in follow up observations.Comment: 19 Pages, 16 Figures, 5 Table

Exploring Kepler Giant Planets in the Habitable Zone

The Kepler mission found hundreds of planet candidates within the Habitable Zones (HZ) of their host star, including over 70 candidates with radii larger than three Earth radii (R⊕) within the optimistic HZ (OHZ). These giant planets are potential hosts to large terrestrial satellites (or exomoons) which would also exist in the HZ. We calculate the occurrence rates of giant planets (R_p = 3.0–25 R⊕) in the OHZ, and find a frequency of (6.5 ± 1.9)% for G stars, (11.5 ± 3.1)% for K stars, and (6 ± 6)% for M stars. We compare this with previously estimated occurrence rates of terrestrial planets in the HZ of G, K, and M stars and find that if each giant planet has one large terrestrial moon then these moons are less likely to exist in the HZ than terrestrial planets. However, if each giant planet holds more than one moon, then the occurrence rates of moons in the HZ would be comparable to that of terrestrial planets, and could potentially exceed them. We estimate the mass of each planet candidate using the mass–radius relationship developed by Chen & Kipping. We calculate the Hill radius of each planet to determine the area of influence of the planet in which any attached moon may reside, then calculate the estimated angular separation of the moon and planet for future imaging missions. Finally, we estimate the radial velocity semi-amplitudes of each planet for use in follow-up observations

Production of Oxidants by Ion Bombardment of Icy Moons in the Outer Solar System

Our groups in Brazil, France and Italy have been active, among others in the world, in performing experiments on physical-chemical effects induced by fast ions colliding with solids (frozen gases, carbonaceous and organic materials, silicates, etc.) of astrophysical interest. The used ions span a very large range of energies, from a few keV to hundreds MeV. Here we present a summary of the results obtained so far on the formation of oxidants (hydrogen peroxide and ozone) after ion irradiation of frozen water, carbon dioxide and their mixtures. Irradiation of pure water ice produces hydrogen peroxide whatever is the used ion and at different temperatures. Irradiation of carbon dioxide and water frozen mixtures result in the production of molecules among which hydrogen peroxide and ozone. The experimental results are discussed in the light of the relevance they have to support the presence of an energy source for biosphere on Europa and other icy moons in the outer Solar System.This research has been supported by the European COST Action CM0805: The Chemical Cosmos.Boduch, P.; Da Silveira, EF.; Domaracka, A.; Gomis Hilario, O.; Lv, XY.; Palumbo, ME.; Pilling, S.... (2011). Production of Oxidants by Ion Bombardment of Icy Moons in the Outer Solar System. Advances in Astronomy. 1-10. doi:10.1155/2011/327641S11

The Occurrence of Rocky Habitable-zone Planets around Solar-like Stars from Kepler Data

We present the occurrence rates for rocky planets in the habitable zones (HZs) of main-sequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent instellation flux, which allows us to track HZ planets. We define η⊕ as the HZ occurrence of planets with radii between 0.5 and 1.5 R⊕ orbiting stars with effective temperatures between 4800 and 6300 K. We find that η⊕ for the conservative HZ is between 0.37^(+0.48)_(−0.21) (errors reflect 68% credible intervals) and 0.60^(+0.90)_(−0.36) planets per star, while the optimistic HZ occurrence is between 0.58^(+0.73)_(−0.33) and 0.88^(+1.28)_(−0.51) planets per star. These bounds reflect two extreme assumptions about the extrapolation of completeness beyond orbital periods where DR25 completeness data are available. The large uncertainties are due to the small number of detected small HZ planets. We find similar occurrence rates between using Poisson likelihood Bayesian analysis and using Approximate Bayesian Computation. Our results are corrected for catalog completeness and reliability. Both completeness and the planet occurrence rate are dependent on stellar effective temperature. We also present occurrence rates for various stellar populations and planet size ranges. We estimate with 95% confidence that, on average, the nearest HZ planet around G and K dwarfs is ~6 pc away and there are ~4 HZ rocky planets around G and K dwarfs within 10 pc of the Sun

The Occurrence of Rocky Habitable Zone Planets Around Solar-Like Stars from Kepler Data

We present occurrence rates for rocky planets in the habitable zones (HZ) of main-sequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent instellation flux, which allows us to track HZ planets. We define $\eta_\oplus$ as the HZ occurrence of planets with radius between 0.5 and 1.5 $R_\oplus$ orbiting stars with effective temperatures between 4800 K and 6300 K. We find that $\eta_\oplus$ for the conservative HZ is between $0.37^{+0.48}_{-0.21}$ (errors reflect 68\% credible intervals) and $0.60^{+0.90}_{-0.36}$ planets per star, while the optimistic HZ occurrence is between $0.58^{+0.73}_{-0.33}$ and $0.88^{+1.28}_{-0.51}$ planets per star. These bounds reflect two extreme assumptions about the extrapolation of completeness beyond orbital periods where DR25 completeness data are available. The large uncertainties are due to the small number of detected small HZ planets. We find similar occurrence rates using both a Poisson likelihood Bayesian analysis and Approximate Bayesian Computation. Our results are corrected for catalog completeness and reliability. Both completeness and the planet occurrence rate are dependent on stellar effective temperature. We also present occurrence rates for various stellar populations and planet size ranges. We estimate with $95\%$ confidence that, on average, the nearest HZ planet around G and K dwarfs is about 6 pc away, and there are about 4 HZ rocky planets around G and K dwarfs within 10 pc of the Sun.Comment: To appear in The Astronomical Journa

Etude par spectroscopie infrarouge des effets d'irradiation de glaces d'intérêt astrophysique par des ions lourds

Dans le système solaire et dans les régions denses du milieu interstellaire, des manteaux de glaces constitués de petites molécules sont irradiés par des particules ionisantes : des photons, des électrons et des ions. L interaction entre les particules énergétiques et les manteaux induit plusieurs processus tels que les réactions chimiques, les changements de phase et la désorption de molécules. Les effets de l irradiation par des photons et des ions légers sont étudiés depuis 20 ans. Cependant, les expériences réalisées avec des ions lourds et rapides sont rares dans la littérature. Bien que les ions légers soient plus abondants, le grand pouvoir d arrêt et le haut rendement de pulvérisation des ions lourds peuvent compenser cet écart numérique. Ce travail résulte d un projet de collaboration entre la PUC-Rio et le CIMAP-GANIL. L objectif de ce projet est d étudier l effet de l irradiation de glaces astrophysiques avec des ions lourds et rapides. Les expériences ont été réalisées sur les lignes IRRSUD et SME du GANIL avec des ions Ni (46 et 537 MeV). L analyse des glaces a été faite par spectroscopie infrarouge par transformée de Fourier (FTIR). Quatre cibles ont été irradiées et analysées : H2O, CO, CO2 et H2O :CO :NH3. Les sections efficaces de destruction, de création des molécules produites et les rendements de pulvérisation ont été déterminés pour chaque cible. Les résultats obtenus montrent que les ions lourds sont plus efficaces que les protons pour la pulvérisation des manteaux de glaces alors que les protons sont eux plus efficace pour la synthèse de nouvelles molécules.In the Solar System, as well as inside the dense interstellar regions, ice mantles constituted by small molecules are exposed to ionizing radiation formed by photons, electrons and ions. As a result, chemical reactions, phase changes, desorption and other physical chemical processes occur in the ice. Among the ionizing projectiles, fast heavy ions play a particular role in the sense that they are relatively low abundant in space but have high ionizing power and are very efficient for inducing desorption. These cosmic events can be simulated in laboratory. The main goal of the current work is to identify and quantify the effects of the fast heavy ion interaction with ices. Experiments were performed at the medium energy facility at GANIL, where 46 and 537 MeV Ni ions irradiated four ices cooled down at about 13 K: H2O, CO, CO2 and the mixture H2O:NH3:CO. The molecular concentrations of these species and the formed ones were determined by infrared spectroscopy (FTIR) as a function of the beam fluence. From the acquired data, destruction and formation cross sections of molecular species were measured as well as the sputtering yields. Results show that protons are more efficient for producing new molecular species, while heavy ions are responsible for the desorption process. This work is collaboration between the PUC-Rio and CIMAP-GANIL institutions.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF