Search Publications
A Weak Diffuse Interstellar Band in the Far-Ultraviolet Spectrum of zeta Ophiuchi
Savage, B. D.; Tripp, T. M.; Cardelli, J. A.
Goddard High Resolution Spectrograph (GHRS) observations at 3.5 km/s resolution reveal several new weak unidentified interstellar absorption lines in the ultraviolet spectrum of zeta Ophiuchi. The unidentified line at 1369.13 A has the appearance and characteristics of a weak diffuse interstellar band (DIB). The line has a smooth profile similar t…
Gradients in Giant Branch Morphology in the Core of 47 Tucanae
Bailyn, Charles D.
I describe an algorithm which uses the high spatial resolution of the Hubble Space Telescope to complement the high spatial-to-noise, approximately symmetric point response function, relatively large spatial coverage, and standard filters available from ground based images of crowded fields. Applying this technique to the central regions of the gl…
A Model for the Spectroscopic Variations of the Peculiar Symbiotic Star MWC 560
Michalitsianos, A. G.; Shore, Steven N.; Aufdenberg, Jason P.
In this note, we show that the ultraviolet and optical spectroscopic variability of this unique symbiotic star can be understood in terms of a time variable collimated stellar wind with a rapid acceleration near the source. Using the radial velocities observed during the ultraviolet bright phase, we find that a variation in the mass loss rate of a…
Optical and Ultraviolet Observations of 3C 279 During Outburst
McCollum, B.; Shrader, C. R.; Smith, A. G. +6 more
An ongoing program of photometric monitoring of selected active galactic nuclei has revealed a significant outburst in the optically violently variable QSO 3C 279. The event occurred during May and June of 1992, and was characterized by a peak amplitude of 2.3 mag in the R band. We obtained nearly simultaneous optical and ultraviolet spectroscopy …
High- Speed Hubble Space Telescope Ultraviolet Photometry of Two DB White Dwarfs: NonRadial and Radial Pulsation
Bond, Howard E.; Kawaler, Steven D.; Sherbert, Lisa E. +1 more
We observed two DB white dwarf stars with the High Speed Photometer aboard the Hubble Space Telescope. The two targets, the nonradial pulsator GD 358, and PG 0112+104, a non-pulsating white dwarf with similar temperature, were each observed for 1800 s with a time resolution of 10 ms. We used the F140LP configuration, which gives a broadband respon…
Calibration of HST Wide Field Camera for Quantitative Analysis of Faint Galaxy Images
Casertano, Stefano; Griffiths, Richard E.; Ratnatunga, Kavan U. +2 more
We present the methods adopted to optimize the calibration of images obtained with the Hubble Space Telescope Wide Field Camera (1991-1993). Our main goal is to improve quantitative measurement of faint images, with special emphasis on the faint (I ~ 20-24 mag) stars and galaxies observed as a part of the Medium-Deep Survey. Several modifications …
Metal-Line Absorption at Z/abs - Z/em From Associated Galaxies
Bechtold, Jill; Yee, H. K. C.; Dobrzycki, Adam +1 more
For a preliminary study of whether C IV absorption at z_abs_~z_em_ is related to associated galaxy companions, we have collected data from a sample of 10 quasars with 0.15< z <0.65 for which high-resolution optical and UV spectroscopy is available from the literature, and for which we have deep optical images and limited spectroscopy. We als…
The 1992/93 Eclipse of 31 Cygni
Eaton, Joel A.; Bell, Coretta
Extensive new ultraviolet and optical spectra of an atmospheric eclipse define the physical properties throughout the wind and chromosphere of 31 Cyg. These data require mass loss of approximately 3 x 10-8 solar masses/yr in a wind that may merge smoothly into the chromosphere. Considerations of how energy is injected into the wind, how…
Planetary Camera Imaging of the Counter-Rotating Core Galaxy NGC 4365
Forbes, Duncan A.
We analyze F555 W(V) band Planetary Camera images of NGC 4365, for which ground-based spectroscopy has revealed a misaligned, counter-rotating core. Line profile analysis by Surma indicates that the counter-rotating component has a disk structure. After deconvolution and galaxy modeling, we find photometric evidence, at small radii to support this…
Independent Distance Determinations to Milky Way Cepheids in Open Clusters and Associations. I. The Binary Cepheid DL CAS in NGC 129
Welch, Douglas L.; Matthews, Jaymie M.; Gieren, Wolfgang P. +2 more
As an eight-day Cepheid which is both a component of a spectroscopic binary and a member of the open cluster NGC 129, DL Cas is potentially a very accurate calibrator of the period-luminosity (PL) relation and Cepheid mass. From 160 high-precision (sigma less than 1.5 km/s) radial velocity observations made with the CORAVEL and DAO spectrometers -…