Transiting Disintegrating Planetary Debris around WD 1145+017

More than a decade after astronomers realized that disrupted planetary material likely pollutes the surfaces of many white dwarf stars, the discovery of transiting debris orbiting the white dwarf WD 1145+017 has opened the door to new explorations of this process. We describe the observational evidence for transiting planetary material and the current theoretical understanding (and in some cases lack thereof) of the phenomenon.Comment: Invited review chapter. Accepted March 23, 2017 and published October 7, 2017 in the Handbook of Exoplanets. 15 pages, 10 figure

Effects of wet CO oxidation on the operation of engines and power generators

A simplified method is used to determine the optimum water content in the flue gases of charcoal gasifiers to be utilized as alternative fuels in the operation of engines and gas turbines for power generation. Computational models of plug flow reactors and well stirred reactors are employed to simulate the reaction and post-flame zones, adopting different chemical mechanisms. In the simulations reactants enter the reactors at 1000 K, 1 atm and equivalence ratio 0.25. It was observed that mixtures about 3% to 4% in volume of water vapor allow to obtain optimal operation characteristics, including high blowout limit, low ignition delay, maximum reaction zone temperature, high CO2 prodution and low thermal NO formation. It was observed that increasing water contents reduce significantly ignition times up to 3% in volume, while blowout mass flow rates increase continuously up to 6 % in volume, the maximum value considered. Formation of NO decreases continuously with humidity after the flame zone, while there are peaks of NO formation within the flame zone below 1% in volume. Higher water vapor content decreases the final temperatures below 1700 K, leading to a lower thermal efficiency. The method can be used to estimate optimum operational conditions with other input parameters

Detection of transit timing variations in excess of one hour in the Kepler multi-planet candidate system KOI 806 with the GTC

We report the detection of transit timing variations (TTVs) well in excess of one hour in the Kepler multi-planet candidate system KOI 806. This system exhibits transits consistent with three separate planets -- a Super-Earth, a Jupiter, and a Saturn -- lying very nearly in a 1:2:5 resonance, respectively. We used the Kepler public data archive and observations with the Gran Telescopio de Canarias to compile the necessary photometry. For the largest candidate planet (KOI 806.02) in this system, we detected a large transit timing variation of -103.5$\pm$6.9 minutes against previously published ephemeris. We did not obtain a strong detection of a transit color signature consistent with a planet-sized object; however, we did not detect a color difference in transit depth, either. The large TTV is consistent with theoretical predictions that exoplanets in resonance can produce large transit timing variations, particularly if the orbits are eccentric. The presence of large TTVs among the bodies in this systems indicates that KOI806 is very likely to be a planetary system. This is supported by the lack of a strong color dependence in the transit depth, which would suggest a blended eclipsing binary.Comment: 9 pages, 4 figures, accepted into A&A Letter

Estudo de caso da utilização de resíduos do plantio de palma na produção de farinha de mandioca de um município da microrregião da Bacia do Rio Capim - PA.

O município de São Domingos do Capim possui uma economia familiar baseada na monocultura da mandioca para a produção de farinha. O beneficiamento da farinha tem um processo lento e trabalhoso desenvolvida por pequenos produtores da zona rural. A mandioca (Manihot esculenta Cratz) ocupa papel relevante na alimentação, economia e cultura dos povos da Região Amazônica, o Estado do Pará ocupa o 1º lugar, como maior produtor e consumidor nacional. Das monoculturas empregadas na região,o cultivo do dendê desponta como umas das mais promissoras implantada no país. Contudo tal cultura gera uma grande quantidade de resíduos sólidos, que gira em torno de 39% do total de biomassa a serem descartados sem nenhuma perspectiva de reaproveitamento. O objetivo deste trabalho foi constatar a possível adequação de novas técnicas de queima nos fornos de barro utilizados no processo de fabricação da farinha utilizando os resíduos de palma como suplemento a lenha

Doppler imaging of the planetary debris disc at the white dwarf SDSS J122859.93+104032.9

Debris discs which orbit white dwarfs are signatures of remnant planetary systems. We present 12 yr of optical spectroscopy of the metal-polluted white dwarf SDSS J1228+1040, which shows a steady variation in the morphology of the 8600 Å Ca II triplet line profiles from the gaseous component of its debris disc. We identify additional emission lines of O I, Mg I, Mg II, Fe II and Ca II in the deep co-added spectra. These emission features (including Ca H & K) exhibit a wide range in strength and morphology with respect to each other and to the Ca II triplet, indicating different intensity distributions of these ionic species within the disc. Using Doppler tomography, we show that the evolution of the Ca II triplet profile can be interpreted as the precession of a fixed emission pattern with a period in the range 24–30 yr. The Ca II line profiles vary on time-scales that are broadly consistent with general relativistic precession of the debris disc

Intermediate mass black holes in AGN disks: I. Production & Growth

Here we propose a mechanism for efficiently growing intermediate mass black holes (IMBH) in disks around supermassive black holes. Stellar mass objects can efficiently agglomerate when facilitated by the gas disk. Stars, compact objects and binaries can migrate, accrete and merge within disks around supermassive black holes. While dynamical heating by cusp stars excites the velocity dispersion of nuclear cluster objects (NCOs) in the disk, gas in the disk damps NCO orbits. If gas damping dominates, NCOs remain in the disk with circularized orbits and large collision cross-sections. IMBH seeds can grow extremely rapidly by collisions with disk NCOs at low relative velocities, allowing for super-Eddington growth rates. Once an IMBH seed has cleared out its feeding zone of disk NCOs, growth of IMBH seeds can become dominated by gas accretion from the AGN disk. However, the IMBH can migrate in the disk and expand its feeding zone, permitting a super-Eddington accretion rate to continue. Growth of IMBH seeds via NCO collisions is enhanced by a pile-up of migrators. We highlight the remarkable parallel between the growth of IMBH in AGN disks with models of giant planet growth in protoplanetary disks. If an IMBH becomes massive enough it can open a gap in the AGN disk. IMBH migration in AGN disks may stall, allowing them to survive the end of the AGN phase and remain in galactic nuclei. Our proposed mechanisms should be more efficient at growing IMBH in AGN disks than the standard model of IMBH growth in stellar clusters. Dynamical heating of disk NCOs by cusp stars is transferred to the gas in a AGN disk helping to maintain the outer disk against gravitational instability. Model predictions, observational constraints and implications are discussed in a companion paper (Paper II).Comment: 11 pages, 4 figures, MNRAS (accepted

O aumento da produção de carvão vegetal por meio carbonização em alta pressão.

Carvão vegetal é largamente utilizado em alguns setores da indústria brasileira, e o estudo de dispositivos para melhorar a conversão de biomassa em carvão é muito importante para o setor. A carbonização em alta pressão testadas neste trabalho é uma possível rota para o aumento da produção de carvão. Os experimentos foram realizados em um reator de leito fixo usando uma resistência de cartucho como elemento de aquecimento, tendo a temperatura monitorada por um termopar associado a um controlador PID. O tempo de aquecimento, a taxa de aquecimento, a pressão e o tempo de residência foram monitorados para estabelecer maiores rendimentos na produção de carvão. A taxa de aquecimento foi mantida em 20°C/min. O tempo de residência variou de um baixo nível de 55 minutos para um nível elevado de 95 minutos e os níveis de pressão partiu da pressão atmosférica e uma pressão de 5 bar positiva. Utilizaram-se no processo endocarpo de dendê (Elaeis guianeensis) e serragem de eucalipto (Eucalyptus spp.), contudo nos testes em pressão positiva somente a serragem pode ser neste momento testada. Com a pressão atmosférica e o tempo de permanência em 55 minutos o rendimento em carvão da serragem de eucalipto foi de 43%, enquanto que a 5 bar e 95 minutos de tempo de residência do rendimento foi de 47%. O endocarpo de dendê teve um rendimento de 41% e foi medida apenas a pressão atmosférica. Estes resultados indicam que uma pressão positiva aumenta o rendimento em carvão vegetal e que possivelmente fará o mesmo com as outras materiais primas a serem utilizadas, incluindo o endocarpo de dendê, o qual será o próximo passo do trabalho

Mapping Exoplanets

The varied surfaces and atmospheres of planets make them interesting places to live, explore, and study from afar. Unfortunately, the great distance to exoplanets makes it impossible to resolve their disk with current or near-term technology. It is still possible, however, to deduce spatial inhomogeneities in exoplanets provided that different regions are visible at different times---this can be due to rotation, orbital motion, and occultations by a star, planet, or moon. Astronomers have so far constructed maps of thermal emission and albedo for short period giant planets. These maps constrain atmospheric dynamics and cloud patterns in exotic atmospheres. In the future, exo-cartography could yield surface maps of terrestrial planets, hinting at the geophysical and geochemical processes that shape them.Comment: Updated chapter for Handbook of Exoplanets, eds. Deeg & Belmonte. 17 pages, including 6 figures and 4 pages of reference