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UV-bright stars in galactic globular clusters, their far-UV spectra and their contribution to the globular cluster luminosity.
de Boer, K. S.
Ultraviolet-bright stars in 7 galactic globular clusters have been observed with 4 - 7 Å spectral resolution between 1150 Å and 3200 Å. The UV-bright stars, which are in the post-AGB (PAGB) phase of evolution, have effective temperatures between 19,000 and 35,000K, and have luminosities of about 103.3L_sun;. They generate on average abo…
The gamma-ray deficit toward the Galactic Center.
Hermsen, W.; Bloemen, J. B. G. M.; Blitz, L. +1 more
The gamma-ray flux (E greater than 300 MeV) from the central few hundred parsecs of the Milky Way is shown to be nearly an order of magnitude smaller than the value expected from the H2 masses generally estimated to be present in the center and from the average gamma-ray emissivity measured for the disk. This result implies that in the Galactic ce…
The ultraviolet spectrum of the companion of Mira (omicron Ceti) : observational evidence for a disk formed by wind accretion.
Reimers, D.; Cassatella, A.
The authors present extensive IUE observations of the companion of Mira (ο Cet B). It is shown that the UV continuum observed with IUE is exclusively due to Mira B at Mira A minimum. The UV continuum appears to vary erratically with a total range of ±30% within days or weeks. The white dwarf companion of Mira A itself is not seen and must be coole…
Ultraviolet spectra of the central stars of large planetary nebulae.
Feibelman, W. A.; Kaler, J. B.
The authors have examined the ultraviolet spectra of 32 planetary nebula nuclei with the IUE. Almost all the nebulae are quite large, with radii greater than 0.2 pc, and all are hot, with Zanstra temperatures ≥70,000K. In most cases, the fluxes at 1500 Å are closely consistent with the visual magnitudes and the assumption of a hot blackbody. The a…
Continuous rapid X-ray variability and spectral changes in NGC 4051.
Elvis, M.; Watson, M. G.; Lawrence, A. +1 more
The observation of rapid X-ray variability in active galaxies is of great potential interest. In Seyfert galaxies, variability on a time-scale of days seems common, but fast (minutes-hours) variability is apparently very rare. In a variability survey with the HEAO-1 A2 experiment, Tennant and Mushotzky (1983) found only one object to vary on short…
Detailed observations of NGC 4151 with the IUE - IV. Absorption line spectrum and variability.
Tanzi, E. G.; Perola, G. C.; Boksenberg, A. +7 more
A detailed analysis is presented of the ultraviolet (λλ1150 - 3200 Å) absorption spectrum of the NGC 4151 Seyfert nucleus. The IUE data base consisted of high-dispersion (Δλ ≡ 0.2 Å) spectra at 5 epochs, and 137 low-dispersion (Δλ ≡ 4 - 8 Å) spectra at 31 epochs from 1978 February to 1980 May, together with further low-dispersion data in 1980 - 81…
The discovery of low-level iron K line emission from CYG X-1.
White, N. E.; Barr, P.; Page, C. G.
The results of seven observations of the X-ray spectrum of Cyg X-1, made using the gas scintillation proportional counter on board the Exosat Observatory are presented. The discovery of a broad emission feature at 6.2 keV is reported with an equivalent width of typically 120 eV. The line is resolved to have an FWHM of about 1.2 keV. There is no ev…
Stellar winds from hot stars in the Magellanic clouds.
Conti, P. S.; Garmany, C. D.
O and B stars in the LMC and SMC have been observed with the IUE in order to compare their winds and mass loss rates with those of their galactic counterparts. It is found that while the wind terminal velocities are generally about 20 percent lower than in galactic stars of the same spectral type, it is not clear that the mass loss rates are signi…
The massive wind of S Dor.
Waters, L. B. F. M.; Stahl, O.; Leitherer, C. +4 more
Photometric and spectroscopic observations and UV spectrograms of the variable star S Dor are presented. The equipment used to obtain these data are described. The pseudophotosphere indicated by the absorption lines is examined; pulsation-like motions in the pseudophotosphere are detected. The UV data, which are characterized by Fe II and ionized …
An X-ray, optical and radio study of PKS 0745-191 : a massive coolingflow.
McHardy, I.; Fabian, A. C.; Elvis, M. +7 more
The X-ray source 3A 0745-191 is identified with intracluster gas surrounding the giant galaxy containing the radio source, PKS 0745-191, which lies at z = 0.1. The gas is cooling at the unprecedented rate of 1000 M_sun;yr-1. Optical line-emitting gas extends more than 10 kpc from the centre of the galaxy and corroborates the high mass-f…