Search Publications
White Dwarfs in Cataclysmic Variables
Sion, E. M.
Prior to the last 15 years, the literature on cataclysmic variables (CVs) contained little on the properties of the underlying white dwarf accreter other than estimates of their masses. They were regarded simply as nondescript potential wells for studies of accretion disk structure and stability. Estimates of their masses and associated core compo…
Calibration of the MACHO Photometry Database
Alcock, C.; Allsman, R. A.; Alves, D. R. +22 more
The MACHO Project is a microlensing survey that monitors the brightnesses of ~60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. Our database presently contains about 80 billion photometric measurements, a significant fraction of all astronomical photometry. We describe the calibration of MACHO two-co…
Charge-Transfer Efficiency of WFPC2
Casertano, Stefano; Heyer, Inge; Whitmore, Bradley
Observations of ω Centauri have been used to characterize the charge-transfer efficiency (CTE) of the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope. A set of formulae has been developed to correct aperture photometry for CTE loss with dependencies on the X- and Y-positions, the background counts, the brightness of t…
The Detection and Photometric Redshift Determination of Distant Galaxies Using SIRTF's Infrared Array Camera
Simpson, Chris; Eisenhardt, Peter
We investigate the ability of the Space Infrared Telescope Facility's Infrared Array Camera to detect distant (z~3) galaxies and measure their photometric redshifts. Our analysis shows that changing the original long-wavelength filter specifications provides significant improvements in performance in this and other areas.
The Photometry of Undersampled Point-Spread Functions
Lauer, Tod R.
An undersampled point-spread function (PSF) may interact with the microstructure of a solid-state detector such that the total flux detected can depend sensitively on where the PSF center falls within a pixel. Such intrapixel sensitivity variations will not be corrected by flat-field calibration and may limit the accuracy of stellar photometry con…
The Age of the Sculptor Dwarf Spheroidal Galaxy from Imaging with WFPC2
Ballester, Gilda E.; Grillmair, Carl; Krist, John E. +17 more
From images taken with the Hubble Space Telescope's WFPC2, we have obtained photometry of a field in the Sculptor dwarf spheroidal galaxy to 3 mag below the main-sequence turnoff. We determine an age equal to that of the earliest globular clusters for the bulk of the stars in our field of view. We attempt to constrain the star formation history of…
Calibration of Hubble Space Telescope WFPC2 Emission-Line Filters
O'Dell, C. R.; Doi, Takao
The results of calibration of the primary emission-line filters of the Hubble Space Telescope WFPC2 are presented in a form which allows observers to easily calculate emission-line surface brightnesses for Hα, Hβ, [O III] λ5007, and [N II] λ6583. The Hα and [N II] filters pass both lines in such a way that observations in both are necessary to obt…
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…