Search Publications
Modulation of Anomalous Cosmic-Ray Ions by the Interplanetary Medium
Simnett, G. M.; Tappin, S. J.
Far-UV Spectral Variability in the Gravitational Lens Candidate UM 425
Michalitsianos, A. G.; Maran, S. P.; Oliversen, R. J.
A comparison of recently acquired far-UV spectra with data obtained nearly 10 months earlier indicates changes have occurred in both absorption and ionization levels associated with Broad Absorption Line (BAL) structure in the QSO UM 425, a candidate gravitationally lensed system. These observations are compared with the initial discovery of O VI …
Far-Ultraviolet Imaging of the Globular Cluster NGC 7099 with the Second Wide-Field and Planetary Camera
Casertano, Stefano; Ballester, Gilda E.; Crisp, David +13 more
We have imaged the globular cluster NGC 7099 in the far-UV and visible with WFPC2 on the Hubble Space Telescope. Our far-UV images show a sparsely populated and fully resolved central region. The far-UV to visible color-magnitude diagram of these stars shows a well-defined horizontal branch with no evidence for hot, more evolved descendants. We fi…
Short-Term Chromospheric Variability in alpha Tauri (K5 III): Results from IUE Time Series Observations
Brown, Alexander; Cuntz, Manfred; Deeney, Bryan D. +1 more
We evaluate time series observations of chromospheric lines (Mg II, Mg I, and C II) for the K giant α Tau obtained using the IUE LWP camera at high dispersion. These observations cover a time span of about 2 weeks in 1994 February-March and were designed to resolve variations occurring within hours, days, and weeks. We consider the observational r…
Requirements for Investigating the Connection between Lyman-α Absorption Clouds and the Large-Scale Distribution of Galaxies
Green, Richard F.; Jannuzi, Buell T.; Sarajedini, Vicki L.
We model the requirements on observational data that would allow an accurate determination of the degree of association between Lyman-alpha absorbers and peaks in the redshift distribution of galaxies (large-scale structures like clusters of galaxies). We compare simulated distributions of low-redshift Lyman-alpha absorption systems, constrained t…
Simultaneous Multiwavelength Observations of Dwarf Novae. I. SU Ursae Majoris: Minihumps at a Minioutburst?
Vogt, N.; Szkody, P.; Roth, M. +19 more
SU Ursae Majoris the prototype of a subgroup of dwarf novae that display superhumps in super- outbursts has been observed during an international campaign dedicated to the observation of the first day of outburst of dwarf novae during 1986 February. After the start of a brightening was reported, the star was monitored by IUE, ground-based photomet…
Helioradius Dependence of Interplanetary Carbon and Oxygen Abundances during 1991 Solar Activity
Krimigis, S. M.; Lanzerotti, L. J.; Maclennan, C. G. +3 more
A comparison of the heliocentric dependence of the relative abundance of low energy (~1 MeV nucleon-1) carbon and oxygen on the Ulysses (~3--4 AU) and Voyager 1 and 2 (~35 and ~47 AU) spacecraft shows that the C/O abundance ratio is significantly smaller at the larger radial distances. This finding is attributed to a more abundant seed population …
The Weak Blue Bump of H2106-099 and Active Galactic Nuclei Dereddening
Ohashi, T.; Sakao, T.; Remillard, R. A. +3 more
We present multifrequency spectra of the Seyfert 1 galaxy H2106-099, from radio to hard X-rays, spanning over a decade of observations. The hard X-ray (2-20 keV) spectrum measured with Ginga was not unusual, with a log slope (Fυ ∝ Eα), of -0.80±0.02 on 1988 May 18 and -1.02±0.10 on 1988 May 22/23 UT, and with no significant o…
Enhancing the Spatial Resolution of Solar Coronagraph Observations Using Dynamic Imaging
Schwenn, R.; Howard, R. A.; Karovska, M. +4 more
The Large Angle Spectrometric Coronagraph (LASCO) Cl coronagraph on board the Solar and Heliospheric Observatory (SOHO) is designed to image the corona from 1.1 to 3.0 Rsun. The resolution of C1 is defined by the size of its CCD pixels, which correspond to 5".6, and not by the diffraction limit of the optical system, which may be as sma…