Search Publications
HST-GHRS observations of β Pictoris: additional evidence for infalling comets
Deleuil, M.; Feldman, P. D.; Moos, H. W. +9 more
Variable redshifted absorption features observed in the spectrum of β Pictoris have been attributed to comet-like bodies falling towards the star. The high quality data obtained in December 1992 at the unprecedented resolution and sensitivity of the GHRS reinforces the model that both the changes in spectral line shapes as well as the very presenc…
Is there primordial gas in IZw 18 ?
Kunth, D.; Sargent, W. L. W.; Lequeux, J. +1 more
The dwarf emission line galaxy IZw 18 has one of the lowest known O/H abundance ratios (O/H = 1.75 10^-5^) deduced from its emission lines. Its two main emission patches are associated with two extended HI clouds with very high column densities (N(HI) = 10^22^ H atoms cm^-2^). We have obtained spectra of the northwest emission region with the GHRS…
GHRS observations of Sirius-A I. Interstellar clouds toward Sirius and Local Cloud ionization
Bertaux, J. L.; Ferlet, R.; Vidal-Madjar, A. +2 more
Echelle spectra of Sirius-A have been obtained with the Goddard High-Resolution Spectrograph (GHRS) on board the Hubble Space Telescope (HST). Interstellar absorption lines of iron and magnesium clearly show for the first time the presence of two distinct interstellar clouds between the Sun and Sirius at 2.7pc. Their projected heliocentric velocit…
Sub-arcsecond 2D photometry and spectroscopy of the nucleus of M 31 : the supermassive black hole revisited.
Emsellem, E.; Bacon, R.; Monnet, G. +1 more
Sub-arcsecond imagery (HRCAM, 0.35" - 0.57" FWHM) and two- dimensional spectrography (TIGER, 0.9" FWHM) of the central nucleus of M 31 have been obtained at CFHT. The photometric data clearly show the double-peaked nucleus, in excellent agreement with a recent HST image by Lauer et al. (1993). We built deconvolved surface brightness models, using …
FOS observations of G117-B15A and the blue edge of the ZZ Ceti instability strip.
Koester, D.; Vauclair, G.; Allard, N. F.
From an analysis of FOS observations of G117-B15A, one of the hottest members of the ZZ Ceti class, we derive an effective temperature of 12250+/-125K. Since several other DA near the blue edge of the instability strip must have very similar temperatures according to their UV spectra, it is likely that the blue edge is lower than assumed until now…
Spectral analysis of the hottest known helium-rich white dwarf: KPD0005+5106.
Werner, K.; Heber, U.; Fleming, T.
We present a non-LTE model atmosphere analysis of the helium-rich white dwarf KPD0005+5106. The analysis is based on optical spectra obtained at the Calar Alto 3.5m telescope, ultraviolet observations retrieved from the Hubble Space Telescope data archive, and X-ray data recorded during the ROSAT all-sky survey. From the optical and ultraviolet He…
New HST observations of the core of R Aquarii I. Imaging.
Paresce, Francesco; Hack, Warren
The inner region of the symbiotic system R Aquarii was imaged with the Faint Object Camera on the Hubble Space Telescope (HST) in order to determine the source and structure of the highly collimated bipolar jet near the central Mira variable. Coverage over both a wide wavelength and temporal range was ensured by exposures through narrow and medium…
Boron in the extreme Population II star HD 140283 and the production of light elements in the Early Galaxy
Gilmore, G.; Gustafsson, B.; Lambert, D. L. +4 more
Using observations of the 2496.7A Bi line with the HST GHRS at a nominal resolving power of 90,000, we have found the abundance of boron of HD140283 to be logɛ_B_(=12+log(N_B_/N_H_))=0.34+/-0.20. This result is found when a significant non-LTE effect in the formation of the Bi line is taken into account. The resulting N_B_/N_Be_ ratio is about 17 …
The IMF and the extinction law in M 101: HST FOS spectra of extragalactic HII regions.
Benvenuti, P.; Rosa, M. R.
We present medium resolution HST FOS spectra of the ionizing star clusters in four giant HII regions in the spiral galaxy M101, spanning a range in [O/H] from 8.2 to 8.9. The observed energy distributions in the wavelength range 1150A to 8200A are compared to population synthesis models of extremely young star clusters, taking into account the att…
HST observations of globular clusters in M 31 I. Surface photometry of 13 objects.
Cacciari, C.; Federici, L.; Ferraro, F. R. +8 more
We present the initial results of a study of globular clusters in M 31, using the Faint Object Camera (FOC) on the Hubble Space Telescope (HST). The sample of objects consists of 13 clusters spanning a range of properties. Three independent image deconvolution techniques were used in order to compensate for the optical problems of the HST, leading…