Search Publications
The Properties of Bursts with Short Recurrence Times from the Transient X-Ray Source EXO 0748-676
Haberl, Frank; Parmar, Arvind N.; White, Nick E. +1 more
On January 13/14 1986 Exosat performed a 11.3-hr observation of the transient X-ray burst source EXO 0748-676. The source was in a low state and emitted 11 type I X-ray bursts, of which 10 were analyzed in detail. The properties of the bursts were similar to those found in previous low-state observations reported in Gottwald et al. (1986). The tot…
The X-Ray Spectrum of Markarian 509 Observed by EXOSAT
Molteni, D.; Morini, M.; Lipani, N. A.
Mrk 509 was observed with Exosat at three different epochs during October and November 1983. Variability of about 30 percent was apparent both in the medium-energy (1-10 keV) and in the low-energy (less than 2 kev) X-ray bands between the different observations, on a time scale of 10 days. No correlation between the two energy bands was observed. …
The Ionization Structure of Planetary Nebulae. VII. New Observations of the Ring Nebula
Barker, Timothy
New optical spectrophotometric observations of emission-line intensities have been made in eight positions in the Ring Nebula corresponding to those observed previously with the Ultraviolet Explorer satellite; the total coverage is therefore 1400 to 7200 A. The intensities are in generally good agreement with those found previously in correspondin…
Ultraviolet and Visual Spectroscopy of DB White Dwarfs
Nelan, E. P.; Wegner, G.
Visual wavelength and IUE ultraviolet spectroscopy and model atmospheres of DB white dwarfs are reported. A search for spectral lines due to elements other than helium, and in particular carbon and hydrogen, was made. In no case is there a positive detection of carbon from these data, and upper limits relative to helium by number are derived in th…
Time Variability of Gamma Cassiopeiae in X-Rays
Frontera, F.; Costa, E.; Manzo, G. +3 more
A 22,000 s observation with EXOSAT of the X-ray source 4U 0053+60/Gamma Cassiopeiae reveals oscillations in the X-ray flux with a period of about 6000 s. The source also exhibits chaotic variability with time scales down to a few tens of seconds. This observation strengthens the hypothesis that the X-ray source is a neutron star in a wide orbit ar…
The Ultraviolet and Optical Emission-Line Spectrum of III ZW 77
Ferland, Gary J.; Osterbrock, Donald E.
The high-ionization Seyfert I galaxy III Zw 77 has been simultaneously observed over the satellite ultraviolet to near-IR spectral regions. As in other AGN, the continuous energy distribution shows a roughly power-law decline across much of the optical region and a flatter-than-unity spectral index in the near-UV. The equivalent widths of the Balm…
The Interstellar Medium toward Supernova 1987A
Kirshner, R. P.; Sonneborn, G.; Raymond, J. C. +2 more
High-resolution spectra of SN 1987A obtained with the IUE show absorption features from the disk and halo of our Galaxy and the Large Magellanic Cloud. A rich variety of elements and ionization stages is found, including allowed resonance lines of abundant elements with ionization states ranging from C I and O I to Al III, Si IV and C IV. The Si I…
PG 1411+442: The Nearest Broad Absorption Line Quasar
Green, Richard F.; Hutchings, John B.; Malkan, Matthew A.
IUE observations reveal strong, moderately broad absorption troughs in the blue wings of the C IV and N V emission lines of the quasar PG 1411 + 442. No absorption from weakly ionized gas is detected. The emission-line strengths and overall shape of the ultraviolet/optical/near-infrared/far-infrared continuum of the new broad absorption line quasa…
Ultraviolet Interstellar Extinction toward NGC 6530 and the Intrinsic Energy Distribution of 9 Sagittarii and HD 165052
Torres, Ana V.
The ultraviolet interstellar extinction curve is determined toward 12 early B main-sequence stars and one O8 V star in NGC 6530. The extinction is found to be uniform across the cluster. At short wavelengths, the extinction curve of NGC 6530 falls below the average Galactic curve by a full magnitude, indicating that the population of small grains …
Are There Stellar Winds in the Hot Stars of M31?
Massey, Philip; Bianchi, L.; Hutchings, J. B.
Results are reported of 16 hr exposures with the IUE satellite of two stars in M31. Ground-based spectra indicate these stars to be of type about O6 and WN 7. The UV spectra have good signal but are conspicuously different from Galactic stars of their type. Specifically, no line emission is seen in either star, resonance absorption lines are very …