Search Publications
X-ray and ultraviolet observations of extragalactic HII regions.
Panagia, N.; Fabbiano, G.
The dwarf galaxies NGC 5204, NGC 5474, and NGC 5585 have been shown by Sandage and Tammann (1974) to be physically associated with M101 (distance 7.2 Mpc). The present investigation is concerned with observations of the dwarf galaxies in the M101 group conducted with the aid of the Einstein satellite. Upon detection of X-ray emission from NGC 5204…
The Seyfert 1 galaxy NGC 4593- II. The pattern of variability of theUV spectrum.
Clavel, J.
IUE observations of NGC 4593 are found to show approximately 30 percent variations in the intensities of the emission lines and UV continuum in nine days, which set upper limits to the dimension of the UV continuum and broad line emitting regions comparable to that found for NGC 4151 and 3783. UV observations at six different epochs show the exist…
Optical and ultraviolet line profiles and ultraviolet line intensities in the T Tauri star LHα 332-21.
Penston, M. V.; Lago, M. T. V. T.
The ultraviolet spectrum of the T Tauri star LHα 332-21 is presented. This shows emission lines of chromospheric origin. Optical and ultraviolet line profiles for this star are compared: in LHα 332-21 the Mg II lines show blue-displaced absorption and outflow is therefore demonstrated. It is argued that the general similarities of the Mg II line p…
Discovery of a nitrogen-rich uv-bright star in the globular cluster M5.
Bohlin, R. C.; Stecher, T. P.; Cornett, R. H. +3 more
Ultraviolet images of the globular cluster M5 (NGC 5904) obtained with a rocket-borne telescope show a hot and luminous star ≡20arcsec from the cluster center. Spectra of this UV-bright star, obtained with the IUE satellite in the low-resolution mode, reveal an energy distribution very similar to that of µ Col, a Population I O9.5 IV star. A…
Observations of ultraviolet carbon lines in the spectra of three DC white dwarfs.
Wegner, G.
Ultraviolet spectra of three DC white dwarfs have been obtained using the International Ultraviolet Explorer satellite (IUE). These objects are LDS 275A (= EG 66 = 0935-37), G187-15 (=LTT16151 = EG262 = 2059+31), and L791-40 (=LTT9491 = EG264 = 2317-17). All three show the strong ultraviolet lines of neutral carbon recently found in the spectra of…
The narrow ultraviolet emission lines of the red dwarf AU Microscopii(dM1.6e).
Eriksson, K.; Stencel, R. E.; Linsky, J. L. +1 more
It is pointed out that the red dwarfs are the smallest, coolest, faintest, least massive, but most common of normal main-sequence stars. The dMe (H-alpha emission) subclass of the red dwarfs exhibits the largest median soft X-ray to bolometric luminosity ratio of any group of late-type stars. In connection with the present investigation, attention…
Envelope structure of the cyclic V/R variable shell stars.
Baade, D.; Hubert, H.; Hirata, R. +4 more
The radial velocity measurement in the far ultraviolet and visual spectra of two V/R variable shell stars, ζ Tau and 48 Lib, has been performed. The radial velocities of once and twice ionized elements in the far ultraviolet region coincide with those of the visual shell lines, while the radial velocities of more ionized elements, such as Si IV an…
The O IV infrared and ultraviolet flux ratios as temperature and density diagnostics.
Nussbaumer, H.; Hayes, M. A.
New fine-structure collision strengths for transitions among the levels of the first two terms of O+3 are presented. The density sensitivity of the intensity ratios of the components of the intercombination multiplet at 1401 Å is re-evaluated for densities and temperatures applicable to planetary nebulae. The authors also show that the …
Epsilon Aurigae in eclipse. I. Ultraviolet spectroscopy during INGRESS and totality.
Lambert, D. L.; Parthasarathy, M.
Epsilon Aurigae is a long-period eclipsing system containing a F0 Ia supergiant and an unseen slightly less-massive secondary. A primary eclipse began in mid-1982 with the unseen companion passing in front of the supergiant. Low-resolution ultraviolet (IUE) spectra of Epsilon Aur in 1982 and early 1983 provide eclipse light curves extending into t…
The cool DC white dwarf Stein 2051B.
Wegner, G.; Yackovich, F. H.
Visual scans from the Kitt-Peak 2.1-m telescope and UV spectra from the IUE satellite are combined in a spectroscopic study of the bright DC white dwarf, Stein 2051B. With a cooling age near 2 billion years, and a resulting atmospheric mass of hydrogen of the order of 6 x 10 to the 17th g, the accretion rate over the star's lifetime is less than 2…