Search Publications
Center-to-Limb Angle Dependence of Phases (v, δ|B|) Observed with the Michelson Doppler Imager
Liu, Y.; Ulrich, R. K.; Norton, A. A.
We test the hypothesis that phases between line-of-sight magnetic and velocity signals depend upon center-to-limb angle if the magnetic response to photospheric velocity perturbations is both magneto-acoustic and Alfvénic. The Michelson Doppler Imager observes two bipolar active regions. Sunspots exhibit the predicted shift toward phase angles of …
Models of the Shoemaker-Levy 9 Impacts. I. Ballistic Monte Carlo Plume
Deming, Drake; Harrington, Joseph
We model the plumes raised by impacting fragments of comet Shoemaker-Levy 9 to calculate synthetic plume views, atmospheric infall fluxes, and debris patterns. Our plume is a swarm of ballistic particles with one of several mass-velocity distributions (MVDs). The swarm is ejected instantaneously and uniformly into a cone from its apex. On falling …
The Host Galaxy and Environment of the z=1.195 Quasar 3C 190
Stockton, Alan; Ridgway, Susan E.
We present deep imaging and spectroscopic observations of the z=1.195 quasar 3C 190 and its immediate environment. The quasar is surrounded by an asymmetric, low surface brightness envelope in which there are also several galaxies with characteristic dimensions of 3-5 kpc. Some of these form a linear structure some 50 kpc long in projection, offse…
Long-Term Multiwavelength Observations of GRS 1758-258 and the Advection-dominated Accretion Flow Model
Hailey, Charles J.; Kahn, Steven M.; Craig, William W. +9 more
We present a long-term multiwavelength light curve of Galactic black hole candidate GRS 1758-258 by combining previously published and archival data from Granat, ROSAT, the Compton Gamma Ray Observatory, the Rossi X-Ray Timing Explorer, BeppoSAX, ASCA, EXOSAT, and the Very Large Array. In addition, we include the first spectral results from the ba…
Extent of Excess Far-Infrared Emission around Luminosity Class III Stars
Zuckerman, B.; Kim, Sungsoo S.; Silverstone, Murray
With the Infrared Space Observatory, we conducted 3×3 pixel imaging photometry of 12 luminosity class III stars, which were previously presumed to have dust particles around them, at far-infrared wavelengths (60 and 90 µm). Eleven out of 12 targets show a peak of excess (above photosphere) far-infrared emission at the location of the star, i…
A Test for the Nature of the Type IA Supernova Explosion Mechanism
Pinto, Philip A.; Eastman, Ronald G.; Rogers, Tamara
Currently, popular models for Type Ia supernovae (SNe Ia) fall into two general classes. The first comprises explosions of nearly pure carbon/oxygen (C/O) white dwarfs (WDs) at the Chandrasekhar limit which ignite near their centers. The second consists of lower mass C/O cores which are ignited by the detonation of an accreted surface helium layer…
A Multivariate Analysis of Galaxies in the Hubble Deep Field-North
Thompson, Rodger I.; Corbin, Michael R.; Stobie, Elizabeth +2 more
We use the ultraviolet and optical WFPC2 and near-infrared NICMOS images of the Hubble Deep Field-North to measure and statistically compare an array of parameters for over 250 of the galaxies it contains. These parameters include redshift, rest-frame visible asymmetry and concentration, bolometric luminosity, and extinction-corrected star formati…
Shocking Clouds in the Cygnus Loop
Graham, James R.; Levenson, N. A.
With Hubble Space Telescope Wide-Field Planetary Camera 2 observations of the Cygnus Loop supernova remnant, we examine the interaction of an interstellar cloud with the blast wave on physical scales of 1015 cm. The shock front is distorted, revealing both edge-on and face-on views of filaments and diffuse emission, similar to those obs…
Far-Ultraviolet Spectra of B Stars near the Ecliptic
Drake, Jeremy J.; Bowyer, Stuart; Edelstein, Jerry +7 more
Spectra of B stars in the wavelength range of 911-1100 Å have been obtained with the Espectrógrafo Ultravioleta de Radiación Difusa (EURD) spectrograph on board the Spanish satellite MINISAT-01 with ~5 Å spectral resolution. International Ultraviolet Explorer (IUE) spectra of the same stars have been used to normalize Kurucz models to the distance…
Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. V. Oscillator Strengths for Neutral Carbon Lines below 1200 Å
Federman, S. R.; Zsargó, J.
We analyzed high-resolution spectra of interstellar C I absorption toward λ Ori, 1 Sco, and δ Sco that were obtained with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. Several multiplets were detected within the wavelength interval 1150-1200 Å, where most C I lines have ill-defined oscillator strength; multiplets at longe…