Search Publications
Spatial Variability in the Ratio of Interstellar Atomic Deuterium to Hydrogen. I. Observations toward δ Orionis by the Interstellar Medium Absorption Profile Spectrograph
Tripp, Todd M.; Jenkins, Edward B.; Sofia, Ulysses J. +2 more
Studies of the abundances of deuterium in different astrophysical sites are of fundamental importance to answering the question about how much deuterium was produced during big bang nucleosynthesis and what fraction of it was destroyed later. With this in mind, we used the Interstellar Medium Absorption Profile Spectrograph (IMAPS) on the ORFEUS-S…
An Abundance Analysis for Five Red Horizontal-Branch Stars in the Extremely Metal-rich Globular Cluster NGC 6553
Cohen, Judith G.; Carretta, Eugenio; Gratton, Raffaele G. +1 more
We provide a high-dispersion line-by-line abundance analysis of five red horizontal-branch (HB) stars in the extremely metal-rich Galactic globular cluster NGC 6553. These red HB stars are significantly hotter than the very cool stars near the tip of the giant branch in such a metal-rich globular cluster, and hence their spectra are much more amen…
Comparison between Predicted and Empirical ΔVbumpHB in Galactic Globular Clusters
Salaris, M.; Zoccali, M.; Bono, G. +2 more
We present observational estimates of ΔVbumpHB in a sample of 28 galactic globular clusters (GGCs) observed by the Hubble Space Telescope. The photometric accuracy and the sizable number of stars measured in each cluster allowed us to single out the red giant branch bump both in metal-poor and in metal-rich GGCs. Empirical va…
Detection of the Red Giant Branch Stars in M82 Using the Hubble Space Telescope
Madore, Barry F.; Sakai, Shoko
We present color-magnitude diagrams and luminosity functions of stars in two halo regions of the irregular galaxy in M82, based on F555W and F814W photometry taken with the Hubble Space Telescope (HST) and Wide Field Planetary Camera 2. The I-band luminosity function shows a sudden jump at I~23.95 mag, which is identified as the tip of the red gia…
Calibration of the Thickness of the Solar Tachocline
Gough, D. O.; Elliott, J. R.
Material circulation in the solar tachocline mixes the tachocline material with the convection zone, which causes the sound speed in and immediately beneath the tachocline to exceed what one would expect from current standard solar models. Calibration against a helioseismic determination of the sound speed from SOI/MDI data of a sequence of solar …
Hubble Space Telescope Fine Guidance Sensor Astrometric Parallaxesfor Three Dwarf Novae: SS Aurigae, SS Cygni, and U Geminorum
Harrison, Thomas E.; Benedict, G. F.; Szkody, Paula +4 more
We report astrometric parallaxes for three well-known dwarf novae obtained using the Fine Guidance Sensors on the Hubble Space Telescope (HST). We found a parallax for SS Aurigae of π=5.00+/-0.64 mas, for SS Cygni we found π=6.02+/-0.46 mas, and for U Geminorum we obtained π=10.37+/-0.50 mas. These represent the first true trigonometric parallaxes…
Infrared Spectroscopy of NGC 4151: Probing the Obscured Ionizing Active Galactic Nucleus Continuum
Lutz, Dieter; Netzer, Hagai; Alexander, Tal +3 more
The Infrared Space Observatory (ISO) Short-Wavelength Spectrometer4 (SWS) infrared spectroscopic observations of the nucleus of Seyfert galaxy NGC 4151, which are described in a companion paper, are used in conjunction with a compilation of UV to IR narrow emission line data to determine the spectral shape of the obscured extreme-UV continuum that…
The Host Galaxy of GRB 990123
Piro, L.; Frontera, F.; Harrison, F. A. +20 more
We present deep images of the field of GRB 990123 obtained in a broadband UV/visible bandpass with the Hubble Space Telescope (HST) and deep near-infrared images obtained with the Keck I 10 m telescope. The HST image reveals that the optical transient (OT) is offset by 0.67" (5.8 kpc in projection) from an extended, apparently interacting galaxy. …
Faint, Moving Objects in the Hubble Deep Field: Components of the Dark Halo?
Ibata, Rodrigo A.; Gilliland, Ronald L.; Richer, Harvey B. +1 more
The deepest optical image of the sky, the Hubble Deep Field, obtained with the Hubble Space Telescope in 1995 December, has been compared to a similar image taken in 1997 December. Two very faint, blue, isolated, and unresolved objects are found to display a substantial apparent proper motion, 23+/-5 and 26+/-5 mas yr-1 a further three …
Filament Eruptions near Emerging Bipoles
Sheeley, N. R., Jr.; Wang, Y. -M.
It has been suggested in previous studies that quiescent prominences and filaments erupt preferentially in the vicinity of emerging magnetic flux. We describe three such filament eruptions observed during 1998 with the Extreme-ultraviolet Imaging Telescope on the Solar and Heliospheric Observatory. Comparison with magnetograms and with potential f…