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IUE observations of the quasar 3C263 constrain the ionizing photon luminosity of decaying dark matter.
Fabian, A. C.; Naylor, T.; Sciama, D. W.
Dark matter which produces hydrogen-ionizing photons on a time-scale of 2x1023s has been shown by Sciama to explain many problems in astronomy and cosmology. Clusters of galaxies composed of such dark matter will be luminous sources of ionizing photons. The authors report here the results of a search for an otherwise unidentified, exten…
On the Utility of Low Resolution IUE Spectroscopy of the 2800 A MG II Lines as a Stellar Chromosphere Indicator
Smith, Graeme H.; O'Connell, Robert W.; Burstein, David +2 more
Low resolution IUE spectroscopy of the 2800-A Mg II h and k lines is shown to provide a useful means for documenting chromospheric activity among relatively young dwarf stars. An index I(Mg II) has been defined which measures the integrated flux in the region 2784-2814 A relative to the flux interpolated from nearby comparison regions. Values of t…
X-Ray Observations of the Bright Seyfert Galaxy IC 4329A
Singh, K. P.; Rao, A. R.; Vahia, M. N.
We have performed a detailed analysis of the broad-band (0.1-25 keV) EXOSAT observations of the high-luminosity, nearby Seyfert type I galaxy IC 4329A. The observations were carried out on two occasions, 1984 July and 1985 July. The X-ray luminosity decreased by ~35% over one year. A significant short-term variability where the intensity decreased…
Velocity of individual large dust particles ejected from Comet P/Halley
Keller, H. U.; Curdt, W.; Richter, K.
Five discrete events are presented which provide accurate information about the impact locations relative to the comet and lower mass limits of the individual particles. Ejection velocities of about 40 m/s were found for two particles in the 1-mg mass range and of not more than 10 m/s for particles in the 10-mg range for the most probable scenario…
Hubble Space Telescope Wide-Field/Planetary Camera Images of Saturn
Faber, S. M.; Ewald, S. P.; Hester, J. J. +12 more
Saturn was recorded in blue, green, and 'red' light with the Wide-Field/Planetary Camera aboard the Hubble Space Telescope. Owing to relatively high signal levels over most of the planet's image, a dramatic improvement in the visibility of image detail was achieved by deconvolving the raw images, which had suffered severely from the spherical aber…
The chromospheric Lyman-alpha emission of ALTAIR (A7 IV-V).
Catalano, S.; Gouttebroze, P.; Marilli, E. +1 more
The definition of the spectral type along the main sequence where chromospheres appear is of crucial importance for the study of the stellar structure and the chromospheric heating mechanism. Due to the bright UV continuum and the fast rotation typical of early type stars, the Ly-alpha emission core remains the only good chromospheric indicator in…
A Search for Circumstellar Dust around HR 10, a Proposed beta Pictoris Star
Cheng, Kwang-Ping; Grady, C. A.; Bruhweiler, Frederick C.
Archival IRAS data and recent IUE observations of the A shell star HR 10 (HD 256) are presented. HR 10 is detected in the IRAS Faint Source Survey and ADDSCAN data at 12 and 25 microns and marginally detected at 60 microns. The IUE data indicate a spectral type of A2 with 0.1 mag of UV selective extinction following a galactic average extinction l…
Ultraviolet observations of the long-period dwarf nova DX And in outburst.
Woods, J. A.; Drew, J. E.; Hoare, M. G.
Ultraviolet observations of the little-studied dwarf nova, DX And, are presented. The observations were made with the International Ultraviolet Explorer satellite during the late stages of a rise to outburst maximum in November 1989. The spectra indicate a low orbital inclination angle and show clear signs of substantial interstellar reddening. Th…
Twelve years of IUE spectra of the interacting binary VV Cephei.
Stencel, R. E.; Neff, D. H.; Bauer, W. H.
All well-exposed high-resolution IUE spectra obtained of the eclipsing binary system VV Cephei (M2Iabep + B) are examined. High-temperature absorption features attributable to the hot companion were detected, indicating that the companion (or the inner regions of its accretion disk) are not as hot as a B1-B2 star. Doubling of Fe II (UV 1) lines, w…
Studies of symbiotic stars. IV. IUE-optical-IR observations of AS 360.
Munari, U.; Buson, L. M.
Observations of the symbiotic star are reported and compared to similar objects to determine the consistent properties of interacting binaries. Absolute spectrophotometry is conducted at the wavelengths 1200-11,100 A, and UBV photometric observations are also taken. AS 360 is found to be an interacting binary made up of a dust-free M 4.0 III with …