Search Publications

LASCO Observations of Disconnected Magnetic Structures Out to Beyond 28 Solar Radii During Coronal Mass Ejections

Llebaria, A.; St. Cyr, O. C.; Plunkett, S. P. +16 more

Two coronal mass ejections have been well observed by the LASCO coronagraphs to move out into the interplanetary medium as disconnected plasmoids. The first, on July 28, 1996, left the Sun above the west limb around 18:00 UT. As it moved out, a bright V-shaped structure was visible in the C2 coronagraph which moved into the field-of-view of C3 and…

Galaxy Morphology without Classification: Self-organizing Maps

Griffiths, Richard E.; Ratnatunga, Kavan U.; Naim, Avi

We examine a general framework for visualizing data sets of high (greater than 2) dimensionality and demonstrate the framework by taking the morphology of galaxies at moderate redshifts as an example. The distributions of various populations of such galaxies are examined in a space spanned by four purely morphological parameters. Galaxy images are…

Deep WFPC2 and Ground-Based Imaging of a Complete Sample of 3C Quasars and Galaxies.

Stockton, Alan; Ridgway, Susan E.

\tighten We present the results of an HST and ground-based imaging study of a complete 3C sample of z ~ 1 sources, comprising 5 quasars and 5 radio galaxies. We have observed all of the sample in essentially line-free bands at rest-frame 0.33 mu m with WFPC2 and in rest-frame 1 \micron\ images from the ground; we have also observed most of the sam…

The HIPPARCOS Mission

van Leeuwen, Floor

Coronal streamer belt asymmetries and seasonal solar wind variations deduced from Wind and Ulysses data

Steinberg, J. T.; Crooker, N. U.; Smith, E. J. +4 more

Solar wind measurements from Wind during March 1995 are combined with those from Ulysses' fast latitude scan to construct a map of the streamer belt. On the timescale of coronal change, the map is nearly a snapshot view of solar wind speed contours threaded by the trace of the heliospheric current sheet (HCS) in the +/-30° heliolatitude range. The…

Elemental abundances for Nova V693 Coronae Austrinae 1981

Shore, Steven N.; Starrfield, Sumner; Vanlandingham, Karen M.

We present an analysis of the UV spectra of the fast ONeMg nova V693 Coronae Austrinae 1981. Observations with IUE began on 1981 April 10 and continued until 1981 November 14. We find the reddening for the nova to be E(B-V)~=0.2+/-0.1. Using the photoionization code cloudy90.02 and the minimization routine minuit, we derive elemental abundances fo…

Hubble Space Telescope Imaging of the Central 1 Kiloparsec of M81

Ford, Holland; Devereux, Nick; Jacoby, George

M81 is the closest example of a galaxy that exhibits both LINER and Seyfert 1 characteristics. New, postrepair (cycle 5), Hubble Space Telescope imaging observations of the central kpc of M81 are presented, specifically, WFPC2 Hα and continuum images, a WFPC2 UV continuum (1500 Å) image, and a V-band faint object camera (FOC) image. The continuum …

The Relationship of Green-Line Transients to White-Light Coronal Mass Ejections

Llebaria, A.; St. Cyr, O. C.; Plunkett, S. P. +18 more

We report observations by the Large Angle Spectrometric Coronagraph (LASCO) on the SOHO spacecraft of three coronal green-line transients that could be clearly associated with coronal mass ejections (CMEs) detected in Thomson-scattered white light. Two of these events, with speeds >25 km s^-1, may be classified as `whip-like' transien…

Interferometric Angular Diameters of Mira Variables with the Hubble Space Telescope

Munari, Ulisse; Whitelock, Patricia A.; Feast, Michael W. +1 more

This paper presents the first successful interferometric observations of angular diameters with the astrometer Fine Guidance Sensor (FGS) aboard the Hubble Space Telescope, the only optical interferometer operating in space. We report single-epoch angular diameters in visible light for the two Mira-type variables, R Leonis and W Hydrae, along two …

Experimental constraints on pulsed and steady state models of the solar wind near the Sun

Habbal, S. R.; Wang, Y. -M.; Feldman, W. C. +1 more

Ulysses observations of the high-latitude solar wind were combined with Spartan 201 observations of the corona to investigate the nature and extent of uncertainties in our knowledge of solar wind structure near the Sun. In addition to uncertainties stemming from the propagation of errors in density profiles inferred from coronagraph observations […