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Faint object camera observations of M 87 : the jet and nucleus.

Boksenberg, A.; Barbieri, C.; Weigelt, G. +16 more

Ultraviolet and optical images of the central region and jet of the nearby elliptical galaxy M87 have been obtained with ~0.1 arcsec resolution in several spectral bands with the Faint Object Camera (FOC) on the Hubble Space Telescope, including polarisation images. Deconvolution enhances the contrast of the complex structure and filamentary patte…

Non-LTE line formation for iron group elements.

Butler, K.; Becker, S. R.

A non-LTE line formation calculation for Fe v is introduced. The data for radiative bound-bound transitions which have been derived as part of this work are described and their accuracy is evaluated. The theoretical non-LTE spectrum of Fe v is compared to the HST spectrum of the sdO star BD + 75 deg 325 resulting in a determination of the iron abu…

R Aquarii : an attempt at a unified model.

Burgarella, D.; Vogel, M.; Paresce, F.

Consideration is given to a new model of R Aqr in which the binary system is composed of an M7 Mira with a mass of about 1.5 solar mass, a temperature of about 2800 K, a bolometric magnitude of about -4.56, and a radius of about 300 solar radii, plus a hot stellar source in an intermediate phase between a subdwarf and a white dwarf with a radiatio…

The Cramer-Rao lower bound and stellar photometry with aberrated HST images

Jakobsen, P.; Greenfield, P.; Jedrzejewski, R.

The Cramer-Rao lower bound theorem of statistics is applied to the problem of extracting 2D stellar photometry from aberrated Hubble Space Telescope camera images. The theorem is used to derive a simple and general expression for the best possible photometric precision that can be derived from a given image, regardless of what image processing or …

Near-ultraviolet imaging of Jupiter's satellite Io with the Hubble Space Telescope

Boksenberg, A.; Barbieri, C.; Sartoretti, P. +7 more

The surface of Jupiter's Galilean satellite Io has been resolved for the first time in the near ultraviolet at 2850 A by the Faint Object Camera (FOC) on the Hubble Space Telescope (HST). The restored images reveal significant surface structure down to the resolution limit of the optical system corresponding to approximately 250 km at the sub-eart…