Search Publications
Infrared Observations of Comet Austin (1990 V) by the COBE/Diffuse Infrared Background Experiment
Reach, W. T.; Lisse, C. M.; Kelsall, T. +4 more
Comet Austin was observed by the Cosmic Background Explorer (COBE)/Diffuse Infrared Background Experiment (DIRBE) with broadband photometry at 1-240 micrometers during the comet's close passage by Earth in 1990 May. A 6 deg long (6 x 106 km) dust tail was found at 12 and 25 micrometers, with detailed structure due to variations in parti…
Highly Ionized Gas in the Galactic Disk: The L = 295 degrees , B = 0 degrees Interarm Direction
Sembach, Kenneth R.
I present new high-resolution measurements of ultraviolet interstellar absorption lines toward three distant stars in the Galactic disk in the general direction l = 295 deg, b = 0 deg. The high ionization lines of Si IV and C IV toward HD 100276, HD 103779, and HD 104705 show substantial variations on angular scales of less than 1 deg, or about 50…
Ultraviolet Observations of the Accretion Disk in LMC X-3
Hutchings, J. B.; Crampton, D.; Cowley, A. P. +1 more
We report information obtained from a series of IUE low-resolution spectra and two HST UV spectra of LMC X-3. The HST spectra are used to identify disk emission lines and interstellar absorptions as well as to fit continuum models, which indicate the presence of a hot disk component. The IUE observations, mainly taken over ~1.5 years, were intende…
Observations of SN 1987A with the COSTAR-corrected Faint Object Camera
Panagia, N.; Jakobsen, P.; Macchetto, F. +1 more
New near-ultraviolet and visible [O III] observations of SN 1987A obtained 2511 and 2533 days after outburst with the Corrective Optics Space Telescope Axial Replacement (COSTAR) corrected Faint Object Camera on board the Hubble Space Telescope are presented. Even though the supernova is now very faint (m ~ 19), the new data are of dramatically hi…
Evolution of Solitary Density Waves in Stellar Winds of Early-Type Stars: A Simple Explanation of Discrete Absorption Component Behavior
Waldron, Wayne L.; Altner, Bruce; Klein, Larry
We model the evolution of a density shell propagating through the stellar wind of an early-type star, in order to investigate the effects of such shells on UV P Cygni line profiles. Unlike previous treatments, we solve the mass, momentum, and energy conservation equations, using an explicit time-differencing scheme, and present a parametric study …
Toward Unbiased Determination of the Redshift Evolution of Lyman-Alpha Forest Clouds
Lu, Limin; Zuo, Lin
The possibility of using D_A_, the mean depression of a quasar spectrum due to Lyα forest absorption, to study the number density evolution of the Lyα forest clouds is examined in some detail. Current D_A_ measurements are made against a continuum that is a power- law extrapolation from the continuum longward of Lyα emission. Compared to the line-…
Concurrent X-Ray and Optical Observations of Two Dwarf Novae during Eruption
Raymond, J. C.; Vrtilek, S. D.; Silber, A.
The dwarf novae SU UMa and RU Peg were each observed with the ROSAT Observatory during outburst. SU UMa was also observed twice between outbursts. The spectrum of SU UMa during quiescence is well fitted by a 2.1 keV thermal bremsstrahlung model with a Gaussian line at 0.97 keV absorbed by a column density of 1.4 x 1020/sq cm. During the…
Markarian 315: A Test Case for the Active Galactic Nucleus--Merger Hypothesis?
MacKenty, John W.; Wilson, Andrew S.; Griffiths, Richard E. +2 more
Using the Hubble Space Telescope Wide Field/Planetary Camera, we have detected a diffuse continuum knot in the inner regions of the Seyfert galaxy Markarian 315. This knot may be a remnant nucleus. It is associated with a complex, ringlike structure in both the continuum and ionized gas emission. We have measured the kinematics of the ionized gas …
The Linear Polarization of 3C 345 in the Ultraviolet
Boyd, Patricia T.; Impey, C. D.; Nelson, M. J. +9 more
The linear polarization of 3C 345, a superluminal radio source and OVV quasar, was observed in two bandpasses in the ultraviolet (centered at 2160 A and 2770 A) in 1993 April using the High Speed Photometer on the Hubble Space Telescope. The quasar is significantly polarized in the UV (p > 5%). Ground-based polarimetry was obtained 11 days late…
Ultraviolet Observations of the Gamma-Ray Blazar 3C 279 following the Gamma-Ray Flare of 1991 June
Vestrand, W. Thomas; Bonnell, Jerry T.; Stacy, J. Gregory
Ultraviolet observations of the gamma-ray blazar 3C 279 were carried out in 1991 July with the International Ultraviolet Explorer (IUE) satellite, 28 days after the outburst of intense gamma-ray emission detected from this source with the high-energy EGRET instrument aboard the Compton Gamma-Ray Observatory. IUE observations were conducted over th…