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Star Clusters in M33. III. The Youngest Population
Chandar, Rupali; Bianchi, Luciana; Ford, Holland C. +1 more
We investigate the properties of young (<=10^8 yr) M33 star clusters from the samples presented in the first two papers of this series using far-UV photometry. Previously, UBV colors were used to derive cluster ages, luminosities, and masses, assuming an extinction interpolated from neighboring stars. Fifteen of 44 clusters imaged in the Hubble…
Hubble Space Telescope WFPC2 Imaging of SN 1979C and Its Environment
Filippenko, Alexei V.; Fransson, Claes; Chevalier, Roger A. +6 more
The locations of supernovae in the local stellar and gaseous environment in galaxies contain important clues to their progenitor stars. As part of a program to study the environments of supernovae using Hubble Space Telescope imaging data, we have examined the environment of the Type II-L supernova SN 1979C in NGC 4321 (M100). We place rigorous co…
A Hubble Space Telescope Study of Two HII Regions in NGC 6822
O'Dell, C. R.; Hodge, Paul W.; Kennicutt, Robert C., Jr.
We report on the study of the Hubble V and Hubble X H II regions in NGC 6822 with the Hubble Space Telescope employing emission-line and stellar filters. Calibration was made for both data sets, providing magnitudes for the stars and surface brightnesses for the nebulae. The forms of these H II regions are shown to be decidedly more complex than r…
Multiwavelength Superoutburst Observations of T Leonis
Szkody, Paula; Howell, Steve B.; Ciardi, David R. +5 more
We present results of simultaneous superoutburst observations in the X-ray, EUV, optical, and IR bands of the tremendous outburst amplitude dwarf novae T Leonis. Near peak luminosity, a single blackbody represents a good fit to T Leo's observed continuum in the EUV spectral region, yielding a boundary layer temperature of 71,000-97,000 K. Inclusio…
The Resolved Outer Population of NGC 6822 with WFPC2
Bianchi, L.; Hutchings, J. B.; Cavanagh, B.
We present F336W (U), F439W (B), F555W (V), and F675W (R) Wide Field Planetary Camera 2 (WFPC2) photometry of two outer regions of the Local Group dwarf irregular galaxy NGC 6822. The northeast region is ~13' from the galaxy center, whereas the west region lies 10' out and within the wispy low surface brightness outer regions of the galaxy. The fi…
A Time-Series IUE Archival Study of the White Dwarf in the Ultrashort-Period Dwarf Nova WZ Sagittae
Sion, E. M.; Cheng, F. H.; Slevinsky, R. J. +2 more
The IUE archive offers a series of far-UV spectra of the ultrashort-period dwarf nova WZ Sge over a long time baseline and hence the opportunity to monitor the ongoing accretion, the cooling of the white dwarf, and temporal variations in the line spectra. We have carried out a quantitative analysis of these spectra including model atmosphere simul…
The CaII-M_v Correlation (Wilson-Bappu Effect) Calibrated by HIPPARCOS Parallaxes
Wallerstein, George; Machado-Pelaez, Laura; Gonzalez, Guillermo
We have used Hipparcos parallaxes to derive absolute visual magnitudes of G, K, and M stars with Ca II emission line widths previously measured by O. C. Wilson. A linear relationship similar to the one derived originally by Wilson & Bappu and improved by Lutz & Kelker was found from M_v=+7 to -2. For stars brighter than M_v=-2 a substantia…
A Study of the Time-dependent Background and Continuum Flux Levels in IUE High-Dispersion SWP Images
Smith, Myron A.
The extraction of net spectral fluxes from echellogram images for the creation of the final International Ultraviolet Explorer (IUE) archive was accomplished by the processing system NEWSIPS computing a background surface from unilluminated pixels over a wide area of the image for any given echellogram order. Although this technique facilitates th…
Adaptive Optics Observations of Arcturus using the Mount Wilson 100 Inch Telescope
Mason, Brian D.; ten Brummelaar, Theo A.; Turner, Nils H.
Upon inspection of the multiple-star results in the Hipparcos catalog, the flag for entry number 69673 particularly stands out; it is Arcturus, for which no companion has been reported previously. The Hipparcos companion is reported to be at a separation of 0.255"+/-0.039" with a magnitude difference in a broadband filter (peaked near 460 nm) of 3…
The Early Palomar Program (1950-1955) for the Discovery of Classical Novae in M81: Analysis of the Spatial Distribution, Magnitude Distribution, and Distance Suggestion
Zurek, David R.; Shara, Michael M.; Sandage, Allan
Data obtained in the 1950-1955 Palomar campaign for the discovery of classical novae in M81 are set out in detail. Positions and apparent B magnitudes are listed for the 23 novae that were found. There is modest evidence that the spatial distribution of the novae does not track the B brightness distribution of either the total light or the light b…