Search Publications
The Elemental Abundances in Bare Planetary Nebula Central Stars and the Shell Burning in AGB Stars
Werner, Klaus; Herwig, Falk
We review the observed properties of extremely hot, hydrogen-deficient post-asymptotic giant branch (AGB) stars of spectral type [WC] and PG1159. Their H deficiency is probably caused by a (very) late helium-shell flash or an AGB final thermal pulse, laying bare interior stellar regions that are usually kept hidden below the hydrogen envelope. Thu…
The Light Echo around Supernova 2003gd in Messier 74
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Li, Weidong
We confirm the discovery of a light echo around the Type II-plateau supernova 2003gd in Messier 74 (NGC 628), seen in images obtained with the High Resolution Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST) as part of a larger Snapshot program on the late-time emission from supernovae. The analysis of the echo …
Evidence of Orbital Motion in the Binary Brown Dwarf Kelu-1AB
Kulkarni, S. R.; Gelino, Christopher R.; Stephens, Denise C.
We have resolved Kelu-1 into a binary system with a separation of ~290 mas using the Laser Guide Star Adaptive Optics system on the Keck II telescope. We have also reanalyzed a 1998 HST observation of Kelu-1 and find that the observed PSF is best fit by a binary object separated by 45 mas. Observations at multiple epochs confirm that the two objec…
A Cloudy/XSPEC Interface
Turner, T. J.; Kraemer, S. B.; Ferland, G. J. +3 more
We discuss new functionality of the spectral simulation code Cloudy that allows the user to calculate grids with one or more initial parameters varied and formats the predicted spectra in the standard FITS format. These files can then be imported into the X-ray spectral analysis software XSPEC and used as theoretical models for observations. We pr…
An Internet Database of Ultraviolet Continuum Light Curves for Seyfert Galaxies
Dunn, Jay P.; Crenshaw, D. Michael; Farrington, Chris +3 more
Using the Multimission Archive at STScI (MAST), we have extracted spectra and determined continuum light curves for 175 Seyfert galaxies that have been observed with the International Ultraviolet Explorer and the Faint Object Spectrograph on the Hubble Space Telescope. To obtain the light curves as a function of Julian Date, we used fixed bins in …
Astrometry of Saturn's Satellites from the Hubble Space Telescope WFPC2
French, R. G.; Verbiscer, A.; McGhee, C. A. +4 more
Highly accurate astrometric positions of 14 of Saturn's satellites have been obtained from 444 Hubble Space Telescope images taken with the Wide Field Planetary Camera 2 (WFPC2) between 1996 and 2005. In all, 1036 satellite positions were measured in Planetary Camera (PC) frames, with a typical uncertainty of σPC=0.014" (80 km at Saturn…
MK Classification and Dynamical Masses for Late-Type Visual Binaries
Docobo, José A.; Tamazian, Vakhtang S.; Melikian, Norair D. +1 more
On the basis of slit spectra obtained with the SCORPIO spectral camera attached to the 2.6 m telescope of the V. Ambartsumian Byurakan Astrophysical Observatory (Armenia), MK classifications for 30 visual binaries comprising mostly late K and M type stars are presented. Comparison with other determinations shows that this configuration provides a …
The WFPC2 Archival Pure Parallels Project
Casertano, Stefano; Ferguson, Henry; Koekemoer, Anton +4 more
We introduce the WFPC2 Archival Pure Parallels Project, in which the methods and procedures described here are used to obtain a near-automatic combination of WFPC2 images obtained as part of the WFPC2 Archival Parallels Program. Several techniques have been developed or refined to ensure proper alignment, registration, and combination of overlappi…
Slitless Grism Spectroscopy with the Hubble Space Telescope Advanced Camera for Surveys
Larsen, S.; Walsh, J. R.; Kümmel, M. +2 more
The Advanced Camera for Surveys on board the Hubble Space Telescope is equipped with one grism and three prisms for low-resolution, slitless spectroscopy in the range 1150-10500 Å. The G800L grism provides optical spectroscopy between 5500 Å and >1 µm, with a mean dispersion of 39 and 24 Å pixel-1 (in the first spectral order) …
The Concept of a Stare-Mode Astrometric Space Mission
Zacharias, N.; Dorland, B.
In this paper, we introduce the concept of a stare-mode astrometric space mission. The traditionally accepted mode of operation for a mapping astrometric space mission is that of a continuously scanning satellite, such as the successful Hipparcos and planned Gaia missions. With the advent of astrometry missions mapping out stars to 20th magnitude,…