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Prediction of the heliospheric current sheet tilt: 1992 - 1996
Hoeksema, J. T.; McComas, D. J.; Suess, S. T.
Heliospheric current sheet tilt evolves systematically over the solar cycle. Here we show that this evolution is different than the sunspot cycle and that tilt for the period 1992 - 1996 can be predicted using persistence. That is, the tilt over the coming cycle will be the same as for the past cycle. The Ulysses spacecraft has passed Jupiter and …
The Drift of Saturn's North Polar Spot Observed by the Hubble Space Telescope
Caldwell, J.; Hua, X. -M.; Turgeon, B. +2 more
Polar projections of 50 images of Saturn at 889 nanometers and 25 images at 718 nanometers taken by the Hubble Space Telescope in November 1990, as well as 3 images at each wavelength taken in June 1991, have been examined. Among them, 31 show the north polar spot, which is associated with Saturn's polar hexagon, in locations suitable for measurem…
Ultraviolet Continuum Variability and Visual Flickering in the Peculiar Object MWC 560
Sonneborn, G.; Michalitsianos, A. G.; Shore, S. N. +8 more
High-speed U-band photometry of the peculiar emission object MWC 560 obtained with the ground-based instrumentation, and V-band photometry obtained with the International Ultraviolet Explorer-Fine Error Sensor indicates irregular brightness variations are quasi-periodic. Multiple peaks of relative brightness power indicate statistically significan…
Spectroscopic Observations of V443 Herculis: A Symbiotic Binary With Low Mass White Dwarfs
Mikolajewska, Joanna; Kenyon, Scott J.; Dobrzycka, Danuta
We present an analysis of new and existing photometric and spectroscopic observations of the symbiotic binary V443 Herculis. This binary system consists of a normal M5 giant and a hot compact star. These two objects have comparable luminosities: about 1500 solar for the M5 giant and about 1000 solar for the compact star. We identify three nebular …
Absolute Proper Motion and Space Motion of the Globular Cluster M15
Le Campion, J. -F.; Odenkirchen, M.; Geffert, M. +1 more
We have separated cluster members and field stars for stars in a region around the globular cluster M 15. The membership of ultraviolet bright stars of M 15 is discussed. The absolute proper motion of M 15 has been determined with respect to the PPM catalogue. An extragalactic calibration of the proper motions has been performed. The calibration w…
Cosmic-abundance absorption dips in X1755-33.
Church, M. J.; Balucinska-Church, M.
Results of spectral analysis for the source X1755-33 using the 1984 EXOSAT/ME data are presented, with spectral fitting made to the complete 18-h observation by dividing it into 314 consecutive 400-s timebins. It is found that spectral changes take place on time scales of this order and that analysis of longer sections of data can lead to errors. …
The broad-band X-ray spectral variability of MRK 841.
Nandra, K.; Turner, T. J.; Done, C. +3 more
The results of a detailed spectral analysis of four X-ray observations of the luminous Seyfert 1.5 galaxy Mrk 841, performed using the EXOSAT and Ginga satellites over the period 1984 June to 1990 July, are reported. Preliminary results from a short ROSAT PSPC observation of Mrk 841 in 1990 July are also presented. Variability is apparent in both …
Ultraviolet spectroscopic variability of the WN5 star HD 50896 : timescales and linear physical dimensions of the perturbations.
Howarth, I. D.; Willis, A. J.; Smith, L. J. +4 more
We present the results of an analysis of a sequence of 130 high resolution SWP IUE spectra of the WN 5 star HD 50896 obtained over a period of 6 consecutive days in December 1988. Substantial variability has been found in the absorption and emission components of the major P Cygni profiles of N V 1250 A, C IV 1550 A, He II 1640 A, and N IV 1718 A …
Star Counts from the Hubble Space Telescope Snapshot Survey. I. Galactic Models
Gould, A.; Maoz, D.; Bahcall, J. N.
We report on a photometric study of stars from 450 fields at high Galactic latitudes that were observed in the Hubble Space Telescope Snapshot Survey to an average limiting apparent magnitude of V = 21.4. There are 166 fields that contain quasars selected in radio, X-ray, and color-excess surveys. This sample of 273 stars is free of selection bias…
NGC 5018: A Metal-poor Giant Elliptical
Burstein, David; Bertola, Francesco; Buson, Lucio M.
NGC 5018 is a luminous elliptical galaxy with colors and optical absorption-line spectrum similar to those of M32, which is 40 times fainter in luminosity. This giant elliptical is one of the more extreme examples of a minority of elliptical galaxies (perhaps as many as 20%) whose colors are significantly bluer, and Mg_2_ indices significantly wea…