Search Publications
EXOSAT Observations of the X-Ray Binary Pulsar 4U 1538-52
Cusumano, G.; Frontera, F.; Orlandini, M. +2 more
Results are reported from a temporal and spectral analysis performed on four EXOSAT observations, part of which were taken from the EXOSAT archive, carried out during March and August 1984. In the first observation an absorbing episode was detected, which may be attributed to an inhomogeneity in the stellar wind of QV Nor; the scale height of this…
Ultraviolet Imaging Telescope Photometry of Massive Stars: The OB Association NGC 206 in M31
O'Connell, Robert W.; Bohlin, Ralph C.; Smith, Andrew M. +6 more
The Ultraviolet Imaging Telescope (UIT) obtained UV images of the giant M31 OB association NGC 206. Magnitudes in bands at 1520 and 2490 A were obtained for 30 massive stars, which demonstrate the effectiveness of UIT for photometry of moderately crowded hot stars to V ~ 21. The UV colors and magnitudes observed for stars in NGC 206 place them in …
X-Ray Observations of the Seyfert 1 Galaxy MCG 2-58-22
Ghosh, K. K.; Soundararajaperumal, S.
Results of the detailed X-ray (0.1-10 keV) spectral analysis of the Seyfert 1 galaxy, MCG 2-58-22, are presented based on the EXOSAT observations on 1984 November 16-26. X-ray spectra of this source were obtained from the EXOSAT archives. Weak, soft flux (0.1-2 keV) variations were found on time scales of 2-3 days, and no variations of the hard fl…
AL II Emission-Line Strengths in Low-Density Astrophysical Plasmas
Feibelman, W. A.; Keenan, F. P.; Harra, L. K. +1 more
Theoretical values of the emission-line ratio R are derived for the transitions 3s2 1S-3s3p 3P2 and 3s2 1S-3s3p 3P1 in Al II, at 2660 and 2669 A, respectively. These ratios are compared with IUE observations of the planetary nebula NGC 7027 and the symbiotic star RR Tel, to illustrate the usefulness of the R as an electron density diagnostics. A v…
EXOSAT Observations of the Broad-Line Radio Galaxy 3C 382
Ghosh, K. K.; Soundararajaperumal, S.
X-ray observations of the broad-line radio galaxy 3C 382 were carried out with EXOSAT on many occasions (>20) between 1983 and 1985. Low and Medium Energy (LE and ME) spectra of this source were obtained from the EXOSAT data base. The hard-X-ray luminosity light curve of 3C 382 which was constituted from Ariel V, HEAO 1, Einstein, EXOSAT, and G…
Absorption-Line Profiles in a Companion Spectrum of a Mass-losing Cool Supergiant
Boehm-Vitense, Erika; Rodrigues, Liliya L.
Cool star winds can best be observed in resonance absorption lines seen in the spectrum of a hot companion, due to the wind passing in front of the blue star. We calculated absorption line profiles that would be seen in the ultraviolet part of the blue companion spectrum. Line profiles are derived for different radial dependences of the cool star …
Fe II Fluorescence and Anomalous C IV Doublet Intensities in Symbiotic Novae
Kafatos, M.; Michalitsianos, A. G.; Meier, S. R.
The variation of absolute intensities of Bowen-excited Fe II emission in the symbiotic stars RR Tel, RX Pup, and AG Peg is examined. The C IV doublet intensity ratios in RR Tel were not anomalous between 1979 and 1989, and the ratio had typical values within the optically thin range. The intensity of individual Fe II Bowen-excited lines is correla…
X-Ray Continuum and Line Emission of the Seyfert Galaxy MCG-5-23-16
Singh, K. P.; Rao, A. R.; Vahia, M. N.
We report observations of X-ray continuum and line emission from the highly absorbed and variable Seyfert galaxy MCG -5-23-16, using the low- energy and the medium-energy detectors of the EXOSAT Observatory. The galaxy was observed in 1983 December and in 1984 May. The X-ray intensity of the source is observed to vary by ~25% in the hard (2-10 keV…
X-Ray to Infrared Observations of the Cataclysmic Variable KO Velorum (E1013-477)
Maraschi, L.; Chiappetti, L.; Motch, C. +6 more
Simultaneous photometric and spectrometric observations of the source E1013 - 477 in X-ray, UV, optical, and IR bands are presented. Evidence is found in support of the recently proposed orbital period of 10.12 hr. The X-ray spectra (0.1-10 keV) are well fitted by a single power law of photon index -0.8 with interstellar absorption NH not greater …
Ultraviolet Observations of the Symbiotic Star AS 296
Feibelman, W. A.; Moreno, H.; Gutierrez-Moreno, A.
AS 296 is a well-known S-type symbiotic star which underwent an optical outburst during 1988. In this paper, UV data based on IUE observations obtained both during the quiescent and outburst stages are presented and discussed, correlating them to observations made in the optical region. It is concluded that the object is a symbiotic nova, in which…