Search Publications
Detection of β Pictoris-like Gaseous Infall in 2 Andromedae
Neff, James E.; Cheng, K. -P.; Bruhweiler, Fred C.
Ultraviolet observations of 2 Andromedae with the Goddard High Resolution Spectrograph on board the Hubble Space Telescope (HST) clearly reveal the existence of circumstellar gas, in addition to previously known anomalous interstellar features, in the line of sight toward this nearby star. We also detect varying, redshifted Ca II absorptions, whic…
An Analysis of the Statistics of the Hubble Space Telescope Kuiper Belt Object Search
Brown, Michael E.; Kulkarni, Shrinivas R.; Liggett, Timothy J.
We calculate statistical limits to the detection of Kuiper belt objects in the Hubble Space Telescope (HST) data of Cochran et al., in which they report the discovery of a population of Halley-sized objects in Pluto-like orbits. Detection of a population of faint objects in these data is limited by the number of false objects that appear owing onl…
Restoration of Long-Exposure Full-Disk Solar Intensity Images
Duvall, T. L.; Jefferies, S. M.; Toner, C. G.
We describe an algorithm for restoring full-disk solar intensity images blurred by a smooth, quasi-stationary point-spread function (PSF). For Earth-based observations, this type of data can be obtained by using exposure times that are much longer than the redistribution time of the atmosphere. Using simulated data for a wide range of observing co…
The Age of the Globular Cluster M68
Castellani, V.; Brocato, E.; Piersimoni, A.
Relying on the accurate color-magnitude diagram (CMD) presented by Walker in 1994, we use the fitting of moderately hot horizontal-branch models to the observed CMD to derive suitable information regarding both cluster reddening and distance modulus and to discuss theoretical predictions constraining the absolute age of the metal-poor Galactic glo…
The Distance to the Hyades Cluster Based on Hubble Space Telescope Fine Guidance Sensor Parallaxes
Kozhurina-Platais, V.; Benedict, G. F.; Franz, O. G. +24 more
Trigonometric parallax observations made with the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) 3 of seven Hyades members in six fields of view have been analyzed along with their proper motions to determine the distance to the cluster. Knowledge of the convergent point and mean proper motion of the Hyades is critical to the derivation o…
Astronomical Search and Laboratory Spectroscopy of the FeCO Radical
Kagi, Eriko; Kasai, Yasuko; Ungerechts, Hans +1 more
The millimeter and submillimeter spectrum of the FeCO radical in the 3Σ- ground electronic state has been observed in the laboratory. The radical was generated by a DC glow discharge in a mixture of Fe(CO)5 and argon. A total of 33 rotational transitions in the three spin sublevels with Ω = 1, 0 were observed in th…
Statistical Properties of the Big Blue Bump in Active Galactic Nuclei
Wang, J. M.; Zhou, Y. Y.; Yu, K. N. +2 more
The shape is the most important characteristic of the big blue bump (bbb). By employing the sample from Walter & Fink, and supplementing it with medium energy X-ray data, we have been successful in separating the bbb component from the nonthermal component for the soft X-ray region and thus obtaining the cutoff energy Ecut of the bi…
The Surface Brightness Fluctuations and Globular Cluster Population of NGC 4478
Ford, Holland C.; Tsvetanov, Zlatan I.; Neilsen, Eric H., Jr.
We calculate the distance to NGC 4478, a neighbor of the giant Virgo elliptical M87, using the surface brightness fluctuations method on parallel data from the HST WFPC2 camera. The exposures considered were taken through the F814W filter, which approximates the Johnson I, and through the F606W filter, which is effectively a broad V filter. We des…
Detectability of High-Redshift Elliptical Galaxies in the Hubble Deep Field
Maoz, Dan
Relatively few intensively star-forming galaxies at redshifts of z>2.5 have been found in the Hubble Deep Field (HDF). This has been interpreted to imply a low space density of elliptical galaxies at high z, possibly due to a late (z<2.5) epoch of formation or to dust obscuration of the ellipticals that are forming at z~3. I use Hubble Space…
Abundances and Depletions toward the Orion Nebula
Snow, Theodore P.; Shuping, R. Young
This paper presents an absorption-line study of θ1 C Orionis (HD 37022), based on IUE data. The line of sight, as determined by O'Dell et al. (1993), is thought to consist of two major cloud complexes: the ``neutral lid'' and some foreground material. A key challenge was to improve the S/N for IUE spectra, and this is discussed in some …