Search Publications
White Dwarfs and Mass Segregation in the Core of 47 Tucanae
Paresce, Francesco; de Marchi, Guido; Jedrzejewski, Robert
The core of the galactic globular cluster (GC) 47 Tucanae was observed by the Faint Object Camera (FOC) on the refurbished Hubble Space Telescope (HST) for the first time through medium-band F253M and F346M filters centered at 255 and 348 nm. A total of 442 stars down to the detection limit at m346 approximately equal to 24 in the 7 sec…
An Archival Study of Hubble Space Telescope Observations of Hercules X-1/HZ Herculis
Raymond, John C.; Cheng, F. H.; Vrtilek, S. D.
We present an archival study of observations of Her X-1/HZ Her obtained by the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST). The optical light curve of HZ Her has previously been modeled as an X-ray heated star (e.g., Bahcall & Bahcall 1972) or an X-ray heated star plus disk (e.g., Gerend & Boynton 1976; Howarth &…
Spectroscopy of Candidate Young Globular Clusters in NGC 1275
Zepf, Stephen E.; Sharples, Ray M.; Carter, Dave +1 more
We present spectra of the brightest member of the population of compact blue objects discovered in the peculiar galaxy NGC 1275 by Holtzman et al. (1992) using Hubble Space Telescope images. These spectra show strong Balmer absorption lines like those observed in A-type stars, as expected if the object is a young globular cluster. The age estimate…
A Search for Microflaring Activity on dMe Flare Stars. I. Observations of the dM8e Star CN Leonis
Carpenter, K. G.; Robinson, R. D.; Percival, J. W. +1 more
Microflares are frequent, short-duration, energetically weak disturbances occurring in the nonradiatively heated regions of the Sun and other magnetically active stars. They are thought to be the low-energy extension of flares commonly seen on active dMe stars and may be a major source of heating the chromosphere and corona of cool stars in genera…
Hubble Space Telescope Observations of Gravitationally Lensed Features in the Rich Cluster AC 114
Smail, Ian; Ellis, Richard S.; Sharples, Ray M. +1 more
Deep Hubble Space Telescope (HST) images of superlative resolution obtained for the distant rich cluster AC 114 (z = 0.31) reveal a variety of gravitational lensing phenomena for which ground-based spectroscopy is available. We present a luminous arc which is clearly resolved by HST and appears to be a lensed z = 0.64 sub-L* spiral gala…
Testing Models for the Quasar Big Blue Bump via Color-Color Diagrams
Elvis, Martin; Wilkes, Belinda J.; Fiore, Fabrizio +3 more
We discuss several models of quasar big blue bump emission in color-color and color-luminosity diagrams. We define several broad passbands: IR (0.8-1.6 µm), VIS (4000-8000 Å), UV (1000-2000 Å), UV1 (1400-2000 Å) and UV2 (1000-1400 Å), and SX (0.2-0.4 keV). The colors have been chosen to investigate characteristics of the big blue bump: (1) I…
Observations of evolving turbulence in the polar solar wind
Balogh, A.; Horbury, T. S.; Forsyth, R. J. +1 more
The Ulysses magnetic field experiment has measured the heliospheric magnetic field in solar wind flows from the Sun's Southern polar coronal hole over a wide range of heliolatitudes and distances. We present an analysis of more than one year of data, covering a latitude range of 40° to 80°S and a distance range of 4.0 to 1.7 AU. We extend an earli…
Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304. III. Ground-based Observations in 1991 November
Glass, I. S.; Bouchet, P.; Filippenko, A. V. +16 more
We present ground-based observations of the BL Lac object PKS 2155-304 during 1991 November. These data were obtained as part of a large international campaign of observations spanning the electro-magnetic spectrum from the radio waves to the X-rays. The data presented here include radio, and UBVRI fluxes, as well as optical polarimetry. The U to …
Hubble Space Telescope Observations of the Dwarf Nova Z Chamaeleontis through Two Eruption Cycles
Clemens, J. C.; Wood, Janet H.; Dolan, J. F. +8 more
We have obtained the first high-speed photometry of the eclipsing dwarf nova Z Cha at ultraviolet wavelengths with the Hubble Space Telescope (HST). We observed the eclipse roughly every 4 days over two cycles of the normal eruptions of Z Cha, giving a uniquely complete coverage of its outburst cycle. The accretion disk dominated the ultraviolet l…
Tomographic Separation of Composite Spectra. III. Ultraviolet Detection of the Hot Companion of phi Persei
Gies, Douglas R.; Penny, Laura R.; Bagnuolo, William G., Jr. +1 more
We have used archival lUE high-dispersion UV spectra of the Be binary φ Per and published spectroscopic radial velocity curves to reconstruct the individual primary and secondary spectra using Doppler tomography. The primary's spectrum has rotationally broadened photospheric lines (consistent with a spectral type B0.5 III-Ve) and narrow "shell" li…