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&

Spin-polarized transport in ferromagnetic multilayered semiconductor nanostructures

The occurrence of inhomogeneous spin-density distribution in multilayered ferromagnetic diluted magnetic semiconductor nanostructures leads to strong dependence of the spin-polarized transport properties on these systems. The spin-dependent mobility, conductivity and resistivity in (Ga,Mn)As/GaAs,(Ga,Mn)N/GaN, and (Si,Mn)/Si multilayers are calculated as a function of temperature, scaled by the average magnetization of the diluted magnetic semiconductor layers. An increase of the resistivity near the transition temperature is obtained. We observed that the spin-polarized transport properties changes strongly among the three materials.Comment: 3 pages, 4 figure

New Constraints on the Variable Equation of State Parameter from X-Ray Gas Mass Fractions and SNe Ia

Recent measurements are suggesting that we live in a flat Universe and that its present accelerating stage is driven by a dark energy component whose equation of state may evolve in time. Assuming two different parameterizations for the function $\omega(z)$, we constrain their free parameters from a joint analysis involving measurements from X-Ray luminosity of galaxy clusters and SNe type Ia data.Comment: paper, 6 pages, 1 figure Accepted by Int. Journal of Modern Physics D (IJPMD

Cancellation of atmospheric turbulence effects in entangled two-photon beams

Turbulent airflow in the atmosphere and the resulting random fluctuations in its refractive index have long been known as a major cause of image deterioration in astronomical imaging and figures among the obstacles for reliable optical communication when information is encoded in the spatial profile of a laser beam. Here we show that using correlation imaging and a suitably prepared source of photon pairs, the most severe of the disturbances inflicted on the beam by turbulence can be cancelled out. Other than a two-photon light source, only linear passive optical elements are needed and, as opposed to adaptive optics techniques, our scheme does not rely on active wavefront correction.Comment: 5 pages, 3 figure

O Projeto Rondon e os impactos na vida dos acadêmicos da PUCPR

Trabalho apresentado no II Congresso Nacional do PROJETO RONDON, realizado em Florianópolis, SC, no período de 23 a 25 de setembro de 2015 - Universidade Federal de Santa Catarina.O Brasil possui 202.033.670 habitantes distribuídos em 8.515.767,049 km² (IBGE, 2014). Esses são 2 indicadores utilizados amplamente para se definir o contexto físico do país. Porém é necessário ir além, pois nesse território tão grande e diversificado encontram-se muitas etnias, culturas e povos. É preciso aprender a história do Brasil, mas também percorrê-lo, conhecer de perto a sua realidade. Em função disso, o Projeto Rondon foi criado, e durante as décadas de 1970 e 1980 permaneceu em plena atividade, levando desenvolvimento para as regiões mais afastadas do país, além de permitir aos acadêmicos de todo o Brasil a visão real de sua nação. Em 1989 o programa foi extinto, voltando somente 15 anos depois e com uma nova forma, a qual a Pontifícia Universidade Católica do Paraná (PUCPR) participa enviando projetos desde 2011. Em razão desses 5 anos de atuação é que o objetivo do trabalho se encontra, avaliando de que forma a ação dos acadêmicos têm se dado e os impactos que foram observados após o retorno. De acordo com o histórico das operações têm-se informações referentes ao ano de atuação, conjunto e curso do acadêmico, onde se pode analisar através de gráficos e tabelas como se deu a atuação da universidade e o perfil do acadêmico que procura o Projeto Rondon na instituição. Primeiramente, pode-se constatar que durante os 5 anos a PUCPR participou de 11 operações, nos conjuntos A e B. A universidade tem um núcleo que é responsável por selecionar os acadêmicos interessados em fazer parte do Projeto Rondon, pois há uma procura muito significativa. Na seleção avalia-se o aluno de acordo com o perfil descrito no guia do rondonista. A PUCPR adota a metodologia onde quem elabora integralmente o projeto são os acadêmicos selecionados, o qual exige muito estudo e pesquisa, procurando mostrar ao aluno que é possível colocar seus conhecimentos em prol da cidadania, despertando profissionais protagonistas e lideranças comprometidas. Procurou-se analisar como foi e esta sendo a atuação dos acadêmicos após a experiência e foi instigante perceber o espírito de cidadania preconizado pelo projeto, pois é possível evidenciar o envolvimento em outras iniciativas sociais, ONG’s e até mesmo como isso implica no projeto de vida e suas escolhas profissionais

Evidence for a spectroscopic direct detection of reflected light from 51 Peg b

The detection of reflected light from an exoplanet is a difficult technical challenge at optical wavelengths. Even though this signal is expected to replicate the stellar signal, not only is it several orders of magnitude fainter, but it is also hidden among the stellar noise. We apply a variant of the cross-correlation technique to HARPS observations of 51 Peg to detect the reflected signal from planet 51 Peg b. Our method makes use of the cross-correlation function of a binary mask with high-resolution spectra to amplify the minute planetary signal that is present in the spectra by a factor proportional to the number of spectral lines when performing the cross correlation. The resulting cross-correlation functions are then normalized by a stellar template to remove the stellar signal. Carefully selected sections of the resulting normalized CCFs are stacked to increase the planetary signal further. The recovered signal allows probing several of the planetary properties, including its real mass and albedo. We detect evidence for the reflected signal from planet 51 Peg b at a significance of 3\sigma_noise. The detection of the signal permits us to infer a real mass of 0.46^+0.06_-0.01 M_Jup (assuming a stellar mass of 1.04\;M_Sun) for the planet and an orbital inclination of 80^+10_-19 degrees. The analysis of the data also allows us to infer a tentative value for the (radius-dependent) geometric albedo of the planet. The results suggest that 51Peg b may be an inflated hot Jupiter with a high albedo (e.g., an albedo of 0.5 yields a radius of 1.9 \pm 0.3 R_Jup for a signal amplitude of 6.0\pm0.4 x 10^-5). We confirm that the method we perfected can be used to retrieve an exoplanet's reflected signal, even with current observing facilities. The advent of next generation of observing facilities will yield new opportunities for this type of technique to probe deeper into exoplanets.Comment: 9 pages, 6 figure