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The massive stars in the R136 region of 30 Doradus.

Elson, Rebecca A. W.; Schade, David J.; Thomson, Robert C. +1 more

We present U and B photometry, based on Hubble Space Telescope observations, for 26 stars in the R136 region of the young cluster 30 Doradus in the Large Magellanic Cloud. It has been suggested that rich star clusters form through the coalescence of clumps, and it seems likely that the R136 region is such a clump. If it is in virial equilibrium th…

Computation of ephemerides for long-period variable stars for the HIPPARCOS mission

Figueras, F.; Barthes, D.; Mennessier, M. O. +2 more

In order to predict the luminosities of LPVs observed by Hipparcos, many visual light curves, characterized by irregularly spaced data, were analyzed using original and complementary methods. The obtained power spectra, including amplitudes and phases, are utilized in the computation of the ephemerides. The predictions are regularly checked with o…

UV spectroscopy of Z Chamaeleontis. II - The 1988 January normal outburst

Sonneborn, G.; Charles, P. A.; Hassall, B. J. M. +3 more

IUE observations taken during the 1988 January normal outburst of Z Cha are presented and a detailed comparison with the 1987 April superoutburst is made. The most important difference from the superoutburst is that the normal outburst continuum flux shows less than 10 percent orbital variation away from the eclipse, implying that there is no 'coo…

Properties of mass-loading shocks 2. Magnetohydrodynamics

Neubauer, F. M.; Zank, G. P.; Oughton, S. +1 more

The one-dimensional magnetohydrodynamics of shocked flows subjected to significant mass loading are considered. Recent observations at comets Giacobini-Zinner and Halley suggest that simple nonreacting MHD is an inappropriate description for active cometary bow shocks. The thickness of the observed cometary shock implies that mass loading represen…

Spectroscopic study of the atmospheric eclipsing binary VV Cephei.

Hack, M.; Boehm, C.; Engin, S. +3 more

We present the results of the study of 49 high dispersion spectrograms obtained at the Haute-Provence Observatory from July 1967 to January 1981, including the epoch of the eclipse of 1977. The radial velocity, intensity and profile variations of several absorption and emission lines are given. The ratio between the fluxes of the M2 giant and the …

Luminous Blue Variables; Quiescent and Eruptive States.

Wolf, B.

Extensive X-ray monitoring of the broad-line radio galaxy 3C 382.

Giommi, P.; Barr, P.

The results of an intensive monitoring campaign of the X-ray light curve of the broad- line radio galaxy 3C 382, performed using the EXOSAT observatory over a five-month period in summer 1985, are presented. Significant variations on a time-scale of several days are found in both the hard and soft X-ray bands, probably superimposed on a systematic…

Inner coma imaging of Comet Levy (1990c) with the Hubble space telescope

Feldman, P. D.; A'Hearn, M. F.; Weaver, H. A. +5 more

Comet Levy (1990c) was observed with the Hubble Space Telescope (HST) on UT 27 September 1990 when both the heliocentric and geocentric distances were ∼1 AU. Two sets of images of the comet were taken 6.5 hr apart with the Wide-Field Camera (WFC) through a broadband red filter that was selected to isolate continuum emission peaking sharply at the …

TYCHO photometry calibration and first results

Snijders, M. A. J.; Grewing, M.; Lindegren, L. +6 more

A description of the data reduction methods used for the Tycho photometry and the software package to implement these methods is presented. Results derived from a preliminary reduction of eight weeks of data employing these methods are reported. A critical discussion of the sources of photometric errors and the expected and achieved photometric ac…

EXOSAT Observations of the X-Ray Binary Pulsar 4U 1538-52

Cusumano, G.; Frontera, F.; Orlandini, M. +2 more

Results are reported from a temporal and spectral analysis performed on four EXOSAT observations, part of which were taken from the EXOSAT archive, carried out during March and August 1984. In the first observation an absorbing episode was detected, which may be attributed to an inhomogeneity in the stellar wind of QV Nor; the scale height of this…