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4 Draconis : a unique triple system containing an M3 giant and a cataclysmic binary.
Reimers, D.; Brown, A.; Griffin, R. F.
The M3 III giant 4 Dra has a UV bright companion discovered with IUE as a probable cataclysmic variable (CV). The authors determine the orbit of the M giant around the centre of gravity of the system that it forms with the cataclysmic binary and find P = 1703 d, e = 0.30, a1msin i = 82 Gm, and f(m) = 0.0076 M_sun;. They find that 4 Dra …
High-resolution spectroscopy of central stars of planetary nebulae : LSS 1362.
Werner, K.; Heber, U.; Drilling, J. S.
High resolution spectra of the hot sdO star LSS 1362, a central star of a planetary nebula, are analyzed by means of model atmosphere techniques. Improved NLTE model atmospheres based on the newly developed 'accelerated lambda iteration' method are used. The very high effective temperature (100000 K) derived previously from the UV energy distribut…
The recurrence behaviour of X-ray bursts from 4U/MXB 1735-44.
van Paradijs, J.; Lewin, W. H. G.; Sztajno, M. +2 more
During about 80 h of uninterrupted observations of the X-ray burst source 4 U/MXB 1735-44, made in August 1985 with Exosat, five bursts were observed. The bursts occur at irregular intervals, ranging between 30 min and 36 h. The burst sizes do not scale with the intervals preceding the bursts; in particular the energy in a burst which occurred aft…
IUE observations of high galactic latitude F supergiants HD 161796 and HD 187885.
Pottasch, S. R.; Wamsteker, W.; Parthasarathy, M.
Low resolution (6 A) IUE ultraviolet spectra of the high galactic latitude F supergiants HD 161796 (F3 Ib) and HD 187885 (F2-3I) are analyzed. The UV spectrum (1250 A to 3250 A) of HD 161796 shows no excess UV flux attributable to a hot degenerate companion. From the UV spectrum the temperature is found to be 6300 K. There is no evidence for signi…
Far-ultraviolet and X-ray emission of the long period RS CVn star sigma Geminorum.
Linsky, J. L.; Kjeldseth-Moe, O.; Westergaard, N. J. +6 more
The new UV and X-ray observations of σ Gem support the theory that large active regions associated with starspots are responsible for the enhanced line emission commonly seen in RS CVn systems. The rotational modulation of the UV line fluxes increases with temperature of the line-forming region. The X-ray emission from the stellar corona, on the o…
Variations of the ultraviolet spectrum of 3C 273 : 9 years of IUE data.
Wamsteker, W.; Ulrich, M. -H.; Courvoisier, T. J. -L.
The quasar 3C 273 has been observed with the IUE satellite in the range 1200-3000 A every two weeks from 29 November 1986 to 18 February 1987, with additional observations in May 1986 and 1 June and 17 July 1987. These recent observations are analyzed together with the archived IUE spectra from 1978 to 1985. The flux at 1275 A undergoes variations…
High-energy gamma rays as a probe of cosmic-ray spectral differences throughout the Galaxy. II - A comparison with radio synchrotron emission
Schlickeiser, R.; Bloemen, J. B. G. M.; Reich, W. +1 more
A spectral analysis of the galactic high-energy γ-ray emission (300 MeV-6 GeV) is presented using the observations obtained with the COS-B satellite. Large-scale spectral variations are found and compared with recent results from a study of the galatic radio-continuum emission at 408 and 1420 MHz. The combination of the radio and γ-ray findings es…
Variable C : an S Doradus-type variable in M 33.
Stahl, O.; Humphreys, R. M.; Leitherer, C. +2 more
Variable C is one of the Hubble-Sandage variables in M 33. Our photometric and spectroscopic observations obtained during one of its rare maxima show that Variable C's variations are typical of luminous blue variables especially those of the S Doradus type. Its spectrum at maximum light suggests a temperature of 7500 K for its expanding optically …
AG Carinae. II. IUE observations of the ring nebula.
The, P. S.; Viotti, R.; Cassatella, A. +1 more
The authors describe the first ultraviolet observations of the ring nebula surrounding the P Cyg superluminous star AG Car. The spectrum of the nebula resembles that of the central star with strong Fe II and Mg II emission lines. The nebular/stellar continuum ratio is nearly constant from 2000 to 3200 Å. This result and the derived surface brightn…
EXOSAT observations of M dwarf stars in the solar neighborhood.
Schmitt, J. H. M. M.; Rosso, C.
The authors present EXOSAT observations of a sample of nearby (d < 6 pc) M dwarf stars most of which have not previously been observed in X-rays. All the target stars were detected except one (Gl 754, spectral type M7). The X-ray luminosities derived are in the typical range of M dwarf X-ray luminosities derived from Einstein Observatory data, …