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An interpretation of the spectral variations of theta Coronae Borealis.
Underhill, A. B.
Measurements are presented of the strengths and displacements of sharp absorption components of the resonance lines of Si IV, C IV, and Al III in the spectrum of θ CrB. No evidence is found for mass loss at a detectable rate. A qualitative model of a Be star is developed. It is suggested that the spectral variations of θ CrB are the result of chan…
Numerous Blended Fev Fevi Emission Lines Identified in the Ultraviolet Spectrum of the WN6 Star HD192163
Nugis, T.; Sapar, A.
X-ray emission from the cataclysmic variable PG 0834+488.
Cook, M. C.
A 5-hr observation of PG0834+488 using the EXOSAT X-ray observatory has resulted in its detection as an X-ray source. The light curve shows marginal evidence for variability but no coherent periodicities were found. The X-ray spectrum was hard, with a photon index of ≡1.36, and the low-energy absorption implied a low column density NH ≡…
Evidence for supermassive stars in three Seyfert galaxy nuclei from IUE spectra.
Stoner, R.; Ptak, R.
The variability in the ultraviolet continua and the C IV 1550 A emission profiles in the three Seyfert 1 galaxies NGC 4151, NGC 5548, and Fairall 9 are consistent with origin in supermassive stars undergoing explosive mass loss. Blackbody fits to continua of each imply a single thermal source whose area either remains constant or increases moderat…
IUE observations of HD 164615.
Rucinski, S. M.
It is seen that HD 164615 with its spectral type F2 IV-V and (B - V) = 0.34 mag must be an exception to the rule that stars earlier than about F7 V cannot develop large spots. Abt, Bollinger and Burke (1983) found a periodic modulation of its brightness by 0.05 magnitude which they interpreted as resulting from the rotation of dark spots across th…
EXOSAT Observations of M Dwarfs
Schmitt, J. H. M. M.; Sztajno, M.
We give a progress report of our EXOSAT observations of active M dwarfs. The possibilities of filter spectroscopy of coronal X-ray sources using the available CMA filters are discussed, and we confirm that M dwarfs are rather hot coronal sources with X-ray temperatures in excess of 107 K, a result previously obtained with the Einstein O…
The ultraviolet spectrum of the planetary nebula M 3-27.
Feibelman, W. A.
The planetary nebula M3-27 was observed in the low-dispersion mode of the IUE satellite in the region 1150 A-3200 A. A fairly strong continuum was seen to extend down to 1150 A, superposed with a relatively small number of emission lines. A high electron density is inferred from forbidden O III but regions of lower density also exist. The ultravio…
An Investigation Into the Nature of the 4.4-HOUR Periodic Source 4U1755-33
Parmar, A. N.; White, N. E.; Mason, K. O. +1 more
We present the results of a continuous 18 hour observation of 4U1755-33 made with the European Space Agency's EXOSAT Observatory. Four 50 min dips in X-ray intensity were observed equally spaced with a period of 4.4 hrs, confirming the periodicity first suggested in White et al. (1984). The dips are spectrally independent. We examine the propertie…
The outer layers of the beta Cephei stars BW VUL and sigma Sco.
Blomme, R.; Hensberge, H.
Mass loss rates for the Beta Cephei stars BW Vul and Sigma Sco have been derived from the C IV and Si IV resonance lines, which are formed in the outflowing layers. Assuming an ionization fraction log q(C IV) = -1.9, mass losses of 1.4 and 1.9 x 10 to the -9th solar mass/yr are predicted for BW Vul and Sigma Sco, respectively. In the case of BW Vu…
M 62 : an RR Lyrae-rich, UV-bright galactic globular cluster.
Tarenghi, M.; Caloi, V.; Castellani, V.
The central region of the globular cluster M62 was observed with IUE. The authors confirm that, in the UV, M62 is the brightest cluster observed up to now in the galaxy. This RR Lyrae-rich system is another example of an UV-bright cluster with a horizontal branch not confined to the blue. The interpretation of UV excesses from spiral nuclei and el…