Search Publications
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 …
The Properties of OB Supergiants in the Large Magellanic Cloud. I. Energy Distributions of 10 B Supergiants
Fitzpatrick, Edward L.
It is demonstrated here that line-blanketed, LTE plane-parallel model atmosphere calculations provide excellent fits to the energy distributions from the ultraviolet through the visual ranges of B supergiants in the LMC. The models are computed using the atmosphere program of Kurucz (1979) but have been constructed with lower gravities than were c…
Simultaneous Multifrequency Observations of Markarian 421
Brodie, Jean; Bowyer, Stuart; Tennant, Allyn
The highly variable BL Lacertae object Mrk 421 has been observed simultaneously in the radio, optical, ultraviolet, and X-ray bands over a period of 4 days in early 1984 December and once again in early 1985 January. Using the EXOSAT observatory, the authors found that during this time the 2 - 10 keV flux dropped by a factor of 8, whereas the 0.1 …
Spectropscopic Observations of the Symbiotic Binary RW Hydrae
Fernandez-Castro, Telmo; Kenyon, Scott J.
Ultraviolet/optical spectrophotometry and infrared photometry show that the symbiotic binary RW Hya is comprised of an M giant (with L of about 1000 solar luminosities) and a compact object (with L of about 200 solar luminosities) which resembles the central star of a planetary nebula. The luminosity of the hot component is produced by a nuclear s…
EXOSAT and Einstein Observations of the X-Ray Pulsar 4U 1145-619
Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +1 more
Results are presented of several Einstein and Exosat X-ray observations of 4U 1145 - 619, an X-ray pulsar orbiting the Be star HD 102567/Hen 715 with marked transient behavior. Pulse-timing analysis of data from imaging instruments on both missions was performed using a period-folding technique, which showed an interesting variation of the light c…