3,908 research outputs found
Instrumentation
published or submitted for publicatio
A possible technique for cometary studies with high angular and spectral resolution
The echelle spectrographs, designed for and used at the Cassegrain stations of the KPNO and CTIO 4-meter telescopes, are capable of cometary spectroscopy with seeing-limited angular resolution along the slit and with spectral resolving power (lambda/delta lambda) ranging from 10 to the 4th power to 10 to the 5th power. Various gratings, cameras and detectors can be used in combination for specific studies in the 3000A to 10,000A range
Narrow passband imagery of comets
During an emission-line survey of the Milky Way, Comet West was accidently imaged through four different narrow passbands with a wide-field, image-intensified camera. Three passbands recorded very similar head plus tail structure. The fourth passband shows an additional large, diffuse component around the head. It was serendipitous that such was recorded as the filters, being selected for studies of emission nebulae, are not particularly suited for studies of comets. However the imagery, plus subsequent studies, suggests that much can be learned about the structure of comets using narrow passband imagery simultaneously with long slit spectroscopy
Evidence for an interplay between cell cycle progression and the initiation of differentiation between life cycle forms of African trypanosomes
Successful transmission of the African trypanosome between the mammalian host blood-stream and the tsetse fly vector involves dramatic alterations in the parasite's morphology and biochemistry. This differentiation through to the tsetse midgut procyclic form is accompanied by re-entry into a proliferative cell cycle. Using a synchronous differentiation model and a variety of markers diagnostic for progress through both differentiation and the cell cycle, we have investigated the interplay between these two processes. Our results implicate a relationship between the trypanosome cell cycle position and the perception of the differentiation signal and demonstrate that irreversible commitment to the differentiation occurs rapidly after induction. Furthermore, we show that re-entry into the cell cycle in the differentiating population is synchronous, and that once initiated, progress through the differentiation pathway can be uncoupled from progress through the cell cycle
Eta Carinae in the Context of the Most Massive Stars
Eta Car, with its historical outbursts, visible ejecta and massive, variable
winds, continues to challenge both observers and modelers. In just the past
five years over 100 papers have been published on this fascinating object. We
now know it to be a massive binary system with a 5.54-year period. In January
2009, Eta Car underwent one of its periodic low-states, associated with
periastron passage of the two massive stars. This event was monitored by an
intensive multi-wavelength campaign ranging from gamma-rays to radio. A large
amount of data was collected to test a number of evolving models including 3-D
models of the massive interacting winds. August 2009 was an excellent time for
observers and theorists to come together and review the accumulated studies, as
have occurred in four meetings since 1998 devoted to Eta Car. Indeed, Eta Car
behaved both predictably and unpredictably during this most recent periastron,
spurring timely discussions. Coincidently, WR140 also passed through periastron
in early 2009. It, too, is a intensively studied massive interacting binary.
Comparison of its properties, as well as the properties of other massive stars,
with those of Eta Car is very instructive. These well-known examples of evolved
massive binary systems provide many clues as to the fate of the most massive
stars. What are the effects of the interacting winds, of individual stellar
rotation, and of the circumstellar material on what we see as
hypernovae/supernovae? We hope to learn.Comment: 26 pages, 7 figures, IAU General Assembly Joint Discussion on Eta
Carinae in Context of the Most Massive Star
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