Impact of micro-telluric lines on precise radial velocities and its correction

Context: In the near future, new instruments such as ESPRESSO will arrive, allowing us to reach a precision in radial-velocity measurements on the order of 10 cm/s. At this level of precision, several noise sources that until now have been outweighed by photon noise will start to contribute significantly to the error budget. The telluric lines that are not neglected by the masks for the radial velocity computation, here called micro-telluric lines, are one such noise source. Aims: In this work we investigate the impact of micro-telluric lines in the radial velocities calculations. We also investigate how to correct the effect of these atmospheric lines on radial velocities. Methods: The work presented here follows two parallel lines. First, we calculated the impact of the micro-telluric lines by multiplying a synthetic solar-like stellar spectrum by synthetic atmospheric spectra and evaluated the effect created by the presence of the telluric lines. Then, we divided HARPS spectra by synthetic atmospheric spectra to correct for its presence on real data and calculated the radial velocity on the corrected spectra. When doing so, one considers two atmospheric models for the synthetic atmospheric spectra: the LBLRTM and TAPAS. Results: We find that the micro-telluric lines can induce an impact on the radial velocities calculation that can already be close to the current precision achieved with HARPS, and so its effect should not be neglected, especially for future instruments such as ESPRESSO. Moreover, we find that the micro-telluric lines' impact depends on factors, such as the radial velocity of the star, airmass, relative humidity, and the barycentric Earth radial velocity projected along the line of sight at the time of the observation.Comment: Accepted in A&

Comportamento de plantas de açaizeiro em relação a diferentes doses de NPK na fase de formação e produção.

O presente trabalho tem como objetivo determinar os níveis de nitrogênio, fósforo e potássio adequados para a fase de formação e produção do açaizeiro no Nordeste Paraense. O estudo foi desenvolvido no município de Inhangapi, em Latossolo Amarelo textura média, com delineamento em blocos ao acaso no esquema fatorial fracionado (4 x 4 x 4)½, em blocos incompletos. Os dados obtidos foram avaliados estatisticamente, através de análise de variância (teste F), para todas as variáveis. Curvas de regressão foram ajustadas para avaliação das respostas a aplicação de N, P, K em função das variáveis. Os resultados indicaram que as doses mais adequadas para o primeiro ano, foram: 50g por planta de N, 55g por planta de P2O5 e 124g por planta de K2O e para o segundo ano foram: 117 g de N, 158 g de P2O5 e 170 g por planta de K2O

Avaliação e seleção de bulbos de cebola de baixo teor de ácido pirúvico de cultivares adaptadas ao Nordeste.

Diferente de outros países, o Brasil não desenvolveu populações de cebola com baixa pungência, o que poderia aumentar o consumo nacional e criar novas oportunidades para os agricultores. O objetivo deste trabalho foi avaliar o teor de ácido pirúvico em algumas populações de cebola desenvolvidas para o Nordeste brasileiro para orientar trabalhos de melhoramento da espécie. Foram avaliados bulbos de cinco variedades de cebola cultivados nos Campos Experimentais de Bebedouro e Mandacaru/Embrapa Semiárido, em 2010. As condições de cultivo e manejo de fertilizantes foram semelhantes nos dois locais. Os bulbos foram quantificados para o teor de ácido pirúvico por espectrofotometria, sendo selecionados aqueles com teor menor que 5 μmol/mL. Dos 206 bulbos de Bebedouro, os teores de ácido pirúvico variaram de 3,02 μmol/mL a 14,22 μmol/mL de suco de cebola, dos quais selecionou-se 14 (6,8%). Dos 360 bulbos, colhidos no Campo Experimental de Mandacaru, os teores de ácido pirúvico variaram de 3,65 μmol/mL a 18,52 μmol/mL de suco de cebola; destes 13 (3,6%) foram selecionados. Obteve-se sementes em 18 plantas dos 27 bulbos selecionados, o que possibilitará um novo ciclo de seleção recorrente, visando o desenvolvimento de populações de cebola com baixos teores de ácido pirúvico para o Nordeste brasileiro

Anomalous pressure effect on the magnetic ordering in multiferroic BiMnO3

We report the magnetic field dependent dc magnetization and the pressure-dependent (pmax ~ 16 kbar) ac susceptibilities Xp(T) on both powder and bulk multiferroic BiMnO3 samples, synthesized in different batches under high pressure. A clear ferromagnetic (FM) transition is observed at TC ~ 100 K, and increases with magnetic field. The magnetic hysteresis behavior is similar to that of a soft ferromagnet. Ac susceptibility data indicate that both the FM peak and its temperature (TC) decrease simultaneously with increasing pressure. Interestingly, above a certain pressure (9 ~ 11 kbar), another peak appears at Tp ~ 93 K, which also decreases with increasing pressure, with both these peaks persisting over some intermediate pressure range (9 ~ 13 kbar). The FM peak disappears with further application of pressure; however, the second peak survives until present pressure limit (pmax ~ 16 kbar). These features are considered to originate from the complex interplay of the magnetic and orbital structure of BiMnO3 being affected by pressure.Comment: 4 pages,4 figures, publised in Physical Review B 78, 092404/200

Gravitational baryogenesis in Gauss-Bonnet braneworld cosmology

The mechanism of gravitational baryogenesis, based on the CPT-violating gravitational interaction between the derivative of the Ricci scalar curvature and the baryon-number current, is investigated in the context of the Gauss-Bonnet braneworld cosmology. We study the constraints on the fundamental five-dimensional gravity scale, the effective scale of B-violation and the decoupling temperature, for the above mechanism to generate an acceptable baryon asymmetry during the radiation-dominated era. The scenario of gravitational leptogenesis, where the lepton-number violating interactions are associated with the neutrino mass seesaw operator, is also considered.Comment: 8 pages, 3 figures, final version to appear in Phys. Rev.

Building analytical three-field cosmological models

A difficult task to deal with is the analytical treatment of models composed by three real scalar fields, once their equations of motion are in general coupled and hard to be integrated. In order to overcome this problem we introduce a methodology to construct three-field models based on the so-called "extension method". The fundamental idea of the procedure is to combine three one-field systems in a non-trivial way, to construct an effective three scalar field model. An interesting scenario where the method can be implemented is within inflationary models, where the Einstein-Hilbert Lagrangian is coupled with the scalar field Lagrangian. We exemplify how a new model constructed from our method can lead to non-trivial behaviors for cosmological parameters.Comment: 11 pages, and 3 figures, updated version published in EPJ