3,040 research outputs found
A snapshot of the inner dusty regions of a RCrB-type variable
R Coronae Borealis variable stars are suspected to sporadically eject
optically thick dust clouds causing, when one of them lies on the
line-of-sight, a huge brightness decline in visible light. Mid-infrared
interferometric observations of RYSgr allowed us to explore the circumstellar
regions very close to the central star (~20-40 mas) in order to look for the
signature of any heterogeneities. Using the VLTI/MIDI instrument, five
dispersed visibility curves were recorded with different projected baselines
oriented towards two roughly perpendicular directions. The large spatial
frequencies visibility curves exhibit a sinusoidal shape whereas, at shorter
spatial frequencies visibility curves follow a Gaussian decrease. These
observations are well interpreted with a geometrical model consisting in a
central star surrounded by an extended circumstellar envelope in which one
bright cloud is embedded. Within this simple geometrical scheme, the inner
110AU dusty environment of RYSgr is dominated at the time of observations by a
single dusty cloud which, at 10mic represents ~10% of the total flux of the
whole system. The cloud is located at about 100stellar radii from the centre
toward the East-North-East direction (or the symmetric direction with respect
to centre) within a circumstellar envelope which FWHM is about 120stellar
radii. This first detection of a cloud so close to the central star, supports
the classical scenario of the RCrB brightness variations in the optical
spectral domain
Cultivar de Arroz de Terras Altas BRSGO Serra Dourada: Desempenho Produtivo em Roraima.
bitstream/item/135279/1/COT-175-N77.pd
Arroz Vermelho: Orientações técnicas para o manejo em lavouras de arroz irrigado em várzeas de Roraima.
bitstream/item/37030/1/DOC-41-2010-ID-44-1.pd
Evolução do Cultivo e Custo de Produção do Arroz Irrigado em Roraima
bitstream/item/35102/1/COT-47-2010-ID-13-1.pd
Desempenho produtivo da cultivar de Arroz de terras altas BRS Sertaneja em Roraima no perĂodo de 2002 a 2006.
bitstream/item/41044/1/BPD-25-2010-ID-54.pd
Comportamento fisiológico de sementes de branquilho (Sebastiania commersoniana (Baill.) Smith & Downs), Eufhorbiaceae em relação ao armazenamento.
Resumo
BRS Tropical: Nova cultivar de Arroz Para as Várzeas de Roraima.
bitstream/item/24082/1/tropical.pd
Comportamento fisiológico de sementes de pixiricão (Miconia cabucu Hoehne)- Melastomataceae- em relação ao armazenamento.
Resumo
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