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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…
Spectroscopic Observations of the Detached Binary PG 1413+015
Bergeron, P.; Green, Richard; Liebert, James +1 more
We present improved estimates of the stellar parameters of the eclipsing, precataclysmic binary system PG 1413 + 015 (GH Vir), which has an orbital period of only 8h16m. Model atmosphere fits a Balmer line profiles yield T(eff) = 48,800 +/- 1200 K and log g = 7.70 +/- 0.11 for the DAO white dwarf primary star, from which a mass of 0.51 +/- 0.04 so…
The Ultraviolet--to--Near-Infrared Spectral Flux Distribution of Four BL Lacertae Objects
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +3 more
We report on simultaneous UV, optical, and near-IR observations of four BL Lac objects. For three objects (PKS 0118-27, PKS 0301-24, and PKS 1538+14), we find that the spectral flux distribution from 8 x 10^13^ to 2.5 x 10^15^ Hz is well described by a single power law with spectral index α_v_ = 1.2, α_v_ = 1.0, and α_v_ = 1.3, respectively. For H…
The X-ray time variability and spectrum of gamma Cassiopeiae (X 0053+604).
Stella, L.; Parmar, A. N.; White, N. E. +1 more
A 30 h duration EXOSAT observation made in 1985 December is used to examine the X-ray time variability and spectrum of the Be star γ Cassiopeiae (X 0053+604). We find that the X-ray lightcurve is dominated by irregular energy-independent flaring on time-scales ≳ 100 s. This flaring markedly decreases the sensitivity to any periodic signals. We fin…
AGN X-ray light curves - shot noise or low-dimensional attractor ?
McHardy, Ian M.; Czerny, Bozena; Lehto, Harry J.
We use correlation integrals to determine whether the X-ray variability of AGN, as seen in EXOSAT observations, arises from chaotic systems. We distinguish three characteristic types of behaviour. We also analyse a number of simulated light curves, to investigate the poorly understood limitations to the correlation integral method caused by noise …