Search Publications
Spatiotemporal Correlations and Turbulent Photospheric Flows from SOHO/MDI Velocity Data
Tarbell, T.; Lawrence, J. K.; Cadavid, A. C. +2 more
Time series of high-resolution and full-disk velocity images obtained with the Michelson Doppler Imager (MDI) instrument on board SOHO have been used to calculate the spacetime spectrum of photospheric velocity flow. The effects of different methods for filtering acoustic oscillations have been carefully studied. It is found that the spectra show …
The HIPPARCOS proper motion link to the extragalactic reference system using NPM and SPM
Kozhurina-Platais, V.; Lindegren, L.; Platais, I. +9 more
We describe the use of the Lick Northern Proper Motion (NPM) program and its southern-sky complement, the Yale/San Juan Southern Proper Motion (SPM) program, to determine the Hipparcos proper motion link to the extragalactic reference system defined by galaxies. In total ~ 9,100 Hipparcos stars were chosen for the NPM link solution and ~ 4,100 for…
Hubble Space Telescope Wide Field Planetary Camera 2 Imaging of UGC 12695: A Remarkably Unevolved Galaxy at Low Redshift
Impey, C. D.; Bothun, G. D.; O'Neil, Karen +1 more
Utilizing the F814W and F300W filters, short-exposure Hubble Space Telescope Wide Field Planetary Camera 2 images were taken of UGC 12695, a nearby (z ~ 0.021) low surface brightness disk galaxy. UGC 12695 has an unusual morphology, consisting of a Y-shaped nucleus surrounded by a faint spiral arm with a number of bright H ii regions interspersed …
The Sirius Supercluster and Missing Mass near the Sun
Eggen, Olin J.
The Hipparcos results confirm some 50 members of the Sirius supercluster in the Bright Star Catalogue. The resulting, well-defined color-luminosity array indicates an age of 4 x 10^8 yr from conventional (no overshoot) models. A comparison of the luminosity function obtained from members in the Bright Star Catalogue, unbiased as to proper motion, …
Large Variations in the Winds of Single Cool Giants: λ Velorum and γ Crucis
Carpenter, K. G.; Mullan, D. J.; Robinson, R. D.
UV spectra of the ``noncoronal'' single K supergiant λ Vel and of the single M giant γ Cru obtained with IUE and the Hubble Space Telescope at various epochs indicate that the profiles of many lines formed in the wind exhibit striking alterations in shape with time. We parameterize the wind profiles in terms of an empirical optical depth τemp…
Discovery of a Luminous White Dwarf in a Young Star Cluster in the Large Magellanic Cloud
Elson, Rebecca A. W.; Sigurdsson, Steinn; Hurley, Jarrod +2 more
We have identified a candidate ~1-2×105 yr old luminous white dwarf in NGC 1818, a young star cluster in the Large Magellanic Cloud. This discovery strongly constrains the boundary mass Mc at which stars stop forming neutron stars and start forming white dwarfs, to Mc>~7.6 Msolar.
Abundance and Isotopic Composition of Platinum in χ Lupi and HR 7775 Derived with the Help of New Laboratory Spectra of Pt II
Johansson, Sveneric; Wahlgren, Glenn M.; Leckrone, David S. +3 more
The platinum isotope anomaly observed in the chemically peculiar HgMn star χ Lupi has been confirmed by analysis with new high-resolution laboratory spectra recorded with the VUV Fourier transform spectrometer at Lund University. The χ Lupi platinum composition is shown to be a mixture of isotopes 196 and 198. Recent observations made with the Hub…
Asteroid Trails in Hubble Space TelescopeWFPC2 Images: First Results
Ballester, Gilda E.; Grillmair, Carl; Crisp, David +21 more
Careful examination of 28,460 selected Wide Field and Planetary Camera 2 (WFPC2) long exposures from 1994, 1995, and early 1996 has revealed trails of 96 distinct moving objects. They have been reported to the International Astronomical Union's (IAU) Minor Planet Center for their asteroid database and a few have been identified with known asteroid…
Extreme Infrared Stars Discovered in Magellanic Cloud Globular Clusters
Glass, I. S.; Sauvage, M.; Onaka, T. +3 more
We report preliminary results of our systematic survey for infrared stars in the globular clusters of the Magellanic Clouds. In the course of an ISOCAM survey for AGB stars in the intermediate-age clusters, we have discovered extremely red AGB stars in NGC 419 and NGC 1978. From their colours and luminosities, they are thought to be experiencing i…
TRIFFID Photometry of Globular Cluster Cores - I. Photometric Techniques and Variable Stars in M15
Morris, P. W.; Shearer, A.; Butler, R. F. +6 more
The Galway/DIAS Image Sharpening Camera, TRIFFID, has been used to make observations in two colours of the centre of the post-core-collapse globular cluster M15. We present here our analysis of the photometry in B over two seasons. We have combined the complementary qualities of the HST's high astrometric precision and TRIFFID's extended coverage …