Search Publications
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 Nuclear Spectral Energy Distribution of NGC 4395, the Least Luminous Type 1 Seyfert Galaxy
Moran, Edward C.; Filippenko, Alexei V.; Ho, Luis C. +5 more
We present X-ray (ROSAT), infrared, and radio observations of NGC 4395, which harbors the optically least luminous type 1 Seyfert nucleus discovered thus far. In combination with published optical and ultraviolet spectra, we have used these data to assemble the broadband spectral energy distribution (SED) of the galaxy's nucleus. Interestingly, th…
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…
The Orbit of 16 Cygni AB
Marcy, Geoffrey W.; Hauser, Heather M.
The high orbital eccentricity of the planet around 16 Cygni B may have been induced by the companion star, 16 Cygni A, but only if the stellar binary has sufficiently small periastron distance. The long period of the stellar binary, ~3x10^4 yr, implies that less than 1% of the orbit has transpired since its first astrometric measurements in 1830. …
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…
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…