Search Publications
The ultraviolet excess of luminous quasars. II. Evidence for massive accretion disks.
Malkan, M. A.
This paper presents new infrared, optical, and ultraviolet spectra of three high-redshift quasars. They are analyzed along with three published quasar spectra. After accounting for other sources of radiation, the continua are fitted with spectra predicted for optically thick steady-state accretion disks which include the effects of general relativ…
Peculiar ultraviolet interstellar extinction.
Savage, B. D.; Fitzpatrick, E. L.; Massa, D.
In connection with investigations of the physical characteristics of interstellar dust, a study of objects with peculiar extinction might provide new insights about the composition, size distribution, formation, and destruction of the particulate matter. Meyer and Savage (1981) have found that the dust toward many stars exhibits peculiar UV extinc…
Prominent ultraviolet emission lines from type 1 Seyfert galaxies.
Gull, T. R.; Boggess, A.; Wu, C. -C.
IUE Explorer data with a 6-A resolution are reported for Ly-alpha, C IV 1550 A, C III semiforbidden line 1909 A, and Mg II 2800 A, as well as the continuum at 1450 A, for 20 Seyfert galaxies and one quasar. Good correlation is found between the continuum and the line fluxes, indicating that photoionization is the dominant heating mechanism for the…
Coordinated Einstein and IUE observations of a disparitions brusques type flare event and quiescent emission from Proxima Centauri.
Golub, L.; Stencel, R. E.; Linsky, J. L. +4 more
The Einstein Imaging Particle Counter observed a major X-ray flare in its entirety during a 5-hr period of simultaneous observations, with the IUE, of the dM5e flare star Proxima Centauri in August, 1980. The detailed X-ray light curve, temperature determinations during various intervals, and UV line fluxes obtained before, during, and after the f…
A far Ultraviolet extinction law : what does it mean ?
Greenberg, J. M.; Chlewicki, G.
The dust grains in the diffuse cloud medium are characterized by a far-ultraviolet (FUV) extinction "law" so that all curves have the same functional form for inverse wavelengths λ-1 ⪆ 6 µm-1. A direct theoretical consequence of this fact is that there is very little scattering by either the particles responsible for th…
Gamma-rays from atomic and molecular gas in the first galactic quadrant
Caraveo, P. A.; Bignami, G. F.; Strong, A. W. +15 more
The fully sampled Columbia 1 deg CO survey and the Berkeley H I survey are compared with the COS B gamma-ray survey. As a first step, the study is limited to the high-energy gamma-rays (E greater than 300 MeV). It is found that a simple model, in which uniformly distributed cosmic rays interact with the interstellar gas, as traced by H I and CO, c…
The discovery of S2 in comet IRAS-Araki-Alcock 1983d
Feldman, P. D.; A'Hearn, M. F.; Schleicher, D. G.
Ultraviolet spectra of comet IRAS-Araki-Alcock 1983d, obtained with the International Ultraviolet Explorer spacecraft when the comet was only 0.032 AU from earth, show strong emission bands due to S2, the first detection of this species in an astronomical object. The spatial profiles imply that the S2 is released directly from the nucleus and has …
First observations of stellar coronal structure : the coronae of AR Lacertae.
Basri, G. S.; Walter, F. M.; Gibson, D. M.
In connection with the present investigation, X-ray, radio, and ultraviolet observations of AR Lacertae over one orbital cycle have been obtained. The X-ray light curve shows a deep primary minimum and a broad, shallow secondary minimum. The quiescent corona of the G2 IV component is small and asymmetric. This corona extends some 0.02 stellar radi…
The structure and emission spectrum of a nonradiative shock wave in the Cygnus Loop.
Gull, T. R.; Raymond, J. C.; Fesen, R. A. +1 more
The ultraviolet spectrum of a Balmer-line filament located just outside the main body of optical filaments in the Cygnus Loop confirms the nonradiative shock wave theory for its origin. This theory is extended to include the hydrogen two-photon continuum, and the possibility of slow electron-ion equilibration in the postshock gas is considered. Th…
A multifrequency study of star formation in the blue compact dwarf galaxy I ZW 36.
Thuan, T. X.; Viallefond, F.
Radio, near IR, optical, and UV observations of I Zw 36 = Mrk 209 = Haro 29 are reported. The H I distribution shows a core-halo structure, the core containing half of the mass and showing systematic motions; the halo is diffuse and contains several H I clumps. The visible star formation region is associated with the core but is shifted slightly w…