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We studied the photopic spectral sensitivity in the green-backed firecrown, Sephanoides sephaniodes, a South American hummingbird, and its possible ecological relationship with preferred flowers and body colouration. Avian colour vision is in general tetrachromatic with at least four types of cones, which vary in sensitivity from the near ultraviolet (UV)(More)
The theory of radiation driven wind including stellar rotation is reexamined. After a suitable change of variables, a new equation for the mass loss rate is derived analytically. The solution of this equation remains within 1% confidence when compared with numerical solutions. Also, a non-linear equation for the position of the critical (singular) point is(More)
The effects of rapid rotation and bi–stability upon the density contrast between the equatorial and polar directions of a B[e] supergiant are re–investigated. Based upon a new slow solution for different high rotational radiation driven winds (Curé 2004) and the fact that bi–stability allows a change in the line–force parameters (α, k, and δ), the(More)
The topological analysis from Bjorkman (1995) for the standard model that describes the winds from hot stars by Castor, Abbott & Klein (1975) has been extended to include the effect of stellar rotation and changes in the ionization of the wind. The differential equation for the momentum of the wind is non–linear and transcendental for the velocity gradient.(More)
We present a numerical model to fit the electroretinogram (ERG), a gross evoked eye visual potential, that originate in the retina through photons absorption by photoreceptors and then involve the contribution form others retinal neurons. We use the ERG measured in a hummingbird, to evaluate the most likely retinal mechanism - cones visual pigments and(More)
Context. Recently, evidence for the presence of weak magnetic fields in Herbig Ae/Be stars has been found in several studies. Aims. We seek to expand the sample of intermediate-mass pre-main sequence stars with circular polarization data to measure their magnetic fields, and to determine whether magnetic field properties in these stars are correlated with(More)
Key words polarization – stars: early-type – stars: magnetic fields We report the results of our search for magnetic fields in a sample of 16 field Be stars, the binary emission-line B-type star υ Sgr, and in a sample of fourteen members of the open young cluster NGC 3766 in the Carina spiral arm. The sample of cluster members includes Be stars, normal(More)
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