Search Publications
Ultraviolet Evidence for a Binary Nucleus of the Planetary Nebula SH 2-71
Feibelman, Walter A.
Archival IUE spectra of the planetary nebula Sh 2-71 show a variable Mg II lambda2800 emission line superposed on a variable stellar continuum. The Mg II feature is thought to be excited in the chromosphere of the cooler component of a binary nucleus, although other causes are also plausible.
Coronal Hole Properties Observed with SUMER
Solanki, S. K.; Wilhelm, K.; Schühle, U. +5 more
We analyze SUMER spectra of 14 lines belonging to 12 ions, obtained on both sides of the boundary of polar coronal holes as well as at other locations along the limb. We compare line intensities, shifts and widths in coronal holes with values obtained in the quiet Sun. We find that with increasing formation temperature, spectral lines show an incr…
Hubble Space Telescope WFPC2 Imaging of Three Low Surface Brightness Dwarf Elliptical Galaxies in the Virgo Cluster
Impey, C. D.; Bothun, G. D.; O'Neil, Karen
Utilizing the F814W and F300W filters, Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images were taken of three low surface brightness dwarf elliptical galaxies in the Virgo Cluster. The intent of the observations was to determine the small-scale structure in these enigmatic galaxies and to attempt to learn something about the natur…
CCD photometry and astrometry for visual double and multiple stars of the HIPPARCOS catalogue. I. Presentation of the large scale project
Cuypers, J.; Lampens, P.; Sinachopoulos, D. +7 more
A description is given of the activities of an international working group created with the aim of obtaining both photometric and astrometric observations of visual double and multiple stars with angular separations in the range of one to fifteen arcseconds, that formed part of the HIPPARCOS Input Catalogue. The scientific aims and realisations of…
Interplanetary Pick-Up Ion Acceleration A Study of Anisotropic Phase-Space Diffusion
Fahr, H. J.; Chalov, S. V.
Interplanetary pick-up ions originate from ionizations of neutral interstellar atoms in the heliosphere. Over the past periods it was generally expected that after pick-up by the frozen-in solar wind magnetic fields these ions quickly isotropize in velocity space by strong pitch- angle scattering, they do, however, not assimilate to the ambient so…
Analyses of the Short-Period Cepheid SU Cassiopeiae
Volk, K.; Milone, E. F.; Wilson, W. J. F.
Baade-Wesselink analyses of this important Galactic classical Cepheid provide new values for the radius, luminosity, distance, and mass and show SU Cas likely to be pulsating in the first overtone. Application of a modified Baade-Wesselink technique and the maximum likelihood method, which we have previously applied to δ Scuti-type variables, yiel…
Radial Velocities of Population II Stars. II.
Bartkevičius, A.; Sperauskas, J.
A program for radial velocity measurements of Population II stars was started in 1988 and was carried out during six observing runs. The program includes metal-deficient stars, components of Population II visual binaries or common proper motion stars, suspected radial velocity variables and the Population II stars from the Hipparcos program. The m…
NOTE: A Visual Spectrum of Triton from the Hubble Space Telescope
Bosh, Amanda S.; Tryka, Kimberly A.
Observations of Triton were made using the Faint Object Spectrograph on the Hubble Space Telescope in August of 1995. We present a visual spectrum of Triton between 3000 and 8500 Å. We compare our measurements with previous observations and find that Triton's color in 1995 is consistent with its color at the time of the Voyager 2 flyby.
Modeling Visual Photometry I: Preliminary Determination of Visual Bandpass
Collins, Peter L.
This paper addresses the issue of spectral sensitivity as part of the overall visual model. A mathematical theory and observational method are presented for the determination of color coefficient with error term for an individual observer.
AAVSO Photoelectric Photometry and Hipparcos Photometry of the Pulsating Red Giant AG Cet
Percy, John R.; Marinova, Margarita
The pulsating red giant AG Ceti was observed by the observers in the AAVSO photoelectric photometry program, and by the Hipparcos satellite. The data have been analyzed using light curves, autocorrelation diagrams, Fourier transforms, and phase diagrams. The AAVSO data show seasonal gaps, and Hipparcos data are also distributed non-uniformly in ti…