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A comparison between the Hercules X-1 pre-eclipse and anomalous dips.
Parmar, A. N.; Reynolds, A. P.
We report the properties of three pre-eclipse and two anomalous dips from Hercules X-1 using data from the EXOSAT Observatory. The anomalous dips are shorter, lasting ~1hr compared to lower limits of ~3hr for the pre-eclipse dips, and shallower, never resulting in more than 91+/-4% of the 2-17keV flux being obscured, compared to the pre-eclipse di…
HST observations of 3C305.
Sparks, W. B.; Macchetto, F.; Miley, G. K. +1 more
We present and discuss Hubble Space Telescope observations of the low-redshift radio galaxy 3C305 0.1" resolution images in [OII] and continuum bands are compared with VLA 2cm radio data. We quantify the radio-optical position offset in the northern lobe of the source and use this to constrain models of the interaction of radio jets with the ISM. …
HST-GHRS observations of α Piscis Austrini. Evidence of no gas content in the circumstellar environment.
Deleuil, M.; Ferlet, R.; Vidal-Madjar, A. +4 more
The origin of the gaseous disk around the star β Pictoris is still unclear. A way to progress is to search for gas signatures in the environment of other stars presenting known IR excesses as initially discovered with the IRAS satellite. Recently, Cheng et al. (1994) reported the possible detection of circumstellar gas absorptions in the spectrum …
Anomalous gallium line profiles in HgMn stars: possible evidence for chemically stratified atmospheres.
Smith, Keith C.
An analysis of co-added high-resolution IUE spectra is presented for three mercury-manganese stars (µ Lep, HR 2844, and HR 7143) which exhibit anomalous Gaiii λ1495 resonance line profiles. This line appears to have unusually weak wings in these stars when compared with synthetic profiles computed under the conventional assumptions of atmosp…
Hubble Space Telescope astrometric observations of pre-main sequence stars from the HIPPARCOS Program. II.
Lattanzi, M. G.; Bucciarelli, B.; Bernacca, P. L. +2 more
We report on high angular resolution observations with Fine Guidance Sensor (FGS) No. 3 aboard the Hubble Space Telescope of five low-mass pre-main sequence stars (T Tauri stars), which have also been observed with the Hipparcos satellite. We have observed BP Tau, RU Lup, RY Lup, AK Sco, and DI Cep and have found that none of them have companions …
Detection of an X-ray flare on the low-activity G 8 III-type giant β Boo.
Reimers, D.; Huensch, M.
We present ROSAT observations of an X-ray flare on the G8III-type giant β Boo, which seems to be the first known flare on a single, low-activity, late-type giant. The flare occured on 8 August 1993. The PSPC count rate increased within ~5 minutes nearly by a factor of 10. Most of the decay phase could be traced, before the observation interval end…
EXOSAT observations of the ultra-soft X-ray binary 4U 1957+11.
Stella, L.; Israel, G. L.; Ricci, D.
We present results from the analysis of the two EXOSAT observations of the low mass X-ray binary (LMXRB) 4U 1957+11. The 1-20keV spectrum of the source is best fitted by a power law model with exponential cutoff, that provides an approximation of a thermal Comptonisation spectrum. The cutoff energy (~2keV), as well as the X-ray colours, are interm…
Properties of the HIPPARCOS Input Catalogue
Evans, D. W.; Arenou, F.; Lindegren, L. +17 more
The positions, proper motions, magnitudes and colour indices contained in the Hipparcos Input Catalogue are compared with preliminary Hipparcos mission results. The Hipparcos data considered, the `combined 30-month solution', or H30, is a preliminary catalogue derived from the analysis of the first 30 months of data (out of a total of 37 months), …
Results on TYCHO photometry.
Snijders, M. A. J.; Grewing, M.; Evans, D. W. +8 more
The final Tycho database will contain astrometric and photometric data for about 1 million stars. Here we discuss the results of the Tycho photometric calibration for about 80% of the data acquired by the star mapper of the Hipparcos satellite and estimate the photometric precision in the final Tycho photometric data base. For a non-variable star …
On the evolutionary status of the LMC cluster NGC 2004.
Caloi, V.; Cassatella, A.
IUE observations of hot stars in the LMC young cluster NGC 2004 have been used to derive effective temperatures and bolometric luminosities well below the turn-off. No star is found close to the upper main sequence. Massive stars appear arranged on a vertical sequence at temperatures much lower than those of the ZAMS. Among the fainter objects, th…