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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…
Observations of 3C 273 With the Goddard High Resolution Spectrograph on the Hubble Space Telescope
Savage, B. D.; Ebbets, D. C.; Carpenter, K. G. +21 more
The observations of the quasar 3C 273 taken with the Goddard High Resolution Spectrograph in 1991 February are presented here. We have included both the reduced raw data, and smoothed and deconvolved spectra. Also, a list of observed absorption lines is presented. The data comprise 11 spectra, including 1 low resolution observation and 10 medium r…
The Galactic Halo and Local Intergalactic Medium toward PKS 2155-304
Boggess, A.; Urry, C. M.; Grady, C. A. +3 more
The first HST GHRS spectra of the bright BL Lacertae object PKS 2155-304, acquired using the G140L configuration show a smooth, featureless continuum with superposed sharp absorption. This absorption is due to both gas in the Galactic halo above the south Galactic pole and what are identified as five to six low redshift Lyα absorption systems aris…
The atmospheric composition, extinction and luminosity of the LBV star R71
Stahl, O.; Lennon, D. J.; Kudritzki, R. -P. +1 more
ESO 3.6m Caspec spectra of the LMC luminous blue variable (LBV) taken at minimum have been analysed using NLTE model atmospheres and line formation calculations to derive atmospheric parameters and chemical composition. Using the silicon ionization balance and the hydrogen Balmer lines we deriveT eff =17250, log g=1.80 and a microturbu…
He 3-519: A Peculiar Post-LBV, Pre-WN Star?
Humphreys, Roberta M.; Davidson, Kris; Terzian, Yervant +1 more
We report IUE and ground-based data indicating that the star He 3-519 has a distance of roughly 8 kpc and an absolute bolometric magnitude of about -11, comparable to AG Car. Its luminosity, spectrum, and large, massive circumstellar shell indicate that this may be a post-LBV object which has not yet become a full-fledged WN star. One notable pecu…
Hubble Space Telescope Astrometric Observations of Pre-Main Sequence Stars from the HIPPARCOS Program
Badiali, M.; Cardini, D.; Emanuele, A. +6 more
We report on the first set of high angular resolution observations with Fine Guidance Sensor (FGS) #3 aboard the Hubble Space Telescope of a sample of T-Tauri and Herbig Ae/Be pre-main sequence stars, which have also been observed with the HIPPARCOS satellite. Among the 5 Ae/Be stars observed so far of particular interest is the new double HIPPARC…
Source characteristics and locations of hectometric radio emissions from the northern Jovian hemisphere
Stone, R. G.; Fainberg, J.; Reiner, M. J.
Northern Jovian hectometric (HOM) radio emissions, detected from high Jovian latitudes by the Unified Radio and Plasma Wave (URAP) experiment on the Ulysses spacecraft, were observed at all Jovian longitudes. This emission was observed to be predominantly right-hand circularly polarized, but some left-hand circular polarization was observed implyi…