Astronomical instrumentation

Abstract:

Observations of Nova Aquilae obtained from the IUE, the Anglo-Australian Telescope, and the Westerbork Synthesis Radio Telescope are discussed. Light curves for B, V, and continuum fluxes at 2800 and 1300 A are presented. Velocities obtained from line profiles indicate the presence of three main gaseous components: a high velocity gas (HVG) component found only in absorption lines on D = 29 and 35, and a medium-velocity gas (MVG) and low-velocity gas component found in emission lines and, for the MVG, in the Na I D-line absorption. A model for thermal emission from the HVG is discussed. It is suggested that ionization in the MVG was maintained by photoionization. Properties of the dust grains are studied using data from absorption in the optical and UV and from emission in the IR.

Abstract:

The authors report spectral observations of η Carinae between 8 and 13 μm which compare the central peak of the homunculus with its periphery. The spectra not only show a lower effective temperature for the outer regions but also that the grains here have a different emissivity function. This has been shown to be consistent with the presence of large grains (Mitchell \amp Robinson, 1986) and here the modelling is extended to that of a spherical core containing small grains (a \cong 0.2 μm) and a disc of larger grains (a \cong 2.0 μm); the model predictions are consistent with observations.

Abstract:

An array spectrometer was used on the nights of 1985 May 30-June 1 to observe the disks of Uranus and Neptune in the spectral regions 7-14 and 17-23 μm with effective resolution elements ranging from 0.23 to 0.87 μm. In the long-wavelength region, the spectra are relatively smooth with the broad S(1) H2 collision-induced rotation line showing strong emission for Neptune. In the short-wavelength spectrum of Uranus, an emission feature attributable to C2H2 with a maximum stratospheric mixing ratio of 9 × 10-9 is apparent. An upper limit of 2 × 10-8 is placed on the maximum stratospheric mixing ratio of C2H6. The spectrum of Uranus is otherwise smooth and quantitatively consistent with the opacity provided by H2 collision-induced absorption and spectrally continuous stratospheric emission, as would be produced by aerosols. Upper limits to detecting the planet near 8 μm indicate a CH4 stratospheric mixing ratio of 1 × 10-5 or less, below a value consistent with saturation equilibrium at the temperature minimum. In the short-wavelength spectrum of Neptune, strong emission features of CH4 and C2H6 are evident and are consistent with local saturation equilibrium with maximum stratospheric mixing ratios of 0.02 and 6 × 10-6, respectively. Emission at 8-10 μm is most consistent with a [CH3D]/[CH4] volume abundance ratio of 5 × 10-5. The spectrum of Neptune near 13.5 μm is consistent with emission by stratospheric C2H2 in local saturation equilibrium and a maximum mixing ratio of 9 × 10-7. Radiance detected near 10.5 μm could be attributed to stratospheric C2H4 emission for a maximum mixing ratio of approximately 3 × 10-9. Quantitative results are considered preliminary, as some absolute radiance differences are noted with respect to earlier observations with discrete filters. © 1987.