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…
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…
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 NICMOS Polarimetric Calibration
Axon, D.; Batcheldor, D.; Sparks, W. +3 more
An accurate knowledge of the absolute calibration of the polarizing elements in the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) becomes especially important when conducting studies that require measuring degrees of polarization of close to 1% in the near-infrared. We present a comprehensive study of all previously observed polarime…
Variable Unidentified Emission near 6307 Å in η Carinae
Weis, K.; Stahl, O.; Davidson, K. +2 more
We have discovered a conspicuous unidentified variable feature near 6307 Å in the spectrum of η Carinae that is spatially unresolved from the central star and its wind (r<~200-300 AU). It is significant for two reasons: first, such prominent unidentified lines are now rare in this object, and second, this feature varies strongly and systematica…
DDO 44 and UGC 4998: Distances, Metallicities, and Star Formation Histories
Mateo, Mario; Aparicio, Antonio; Alonso-García, Javier
We have obtained deep HST imaging of two candidate dwarf systems in the nearby M81 Group, DDO 44 and UGC 4998. Both are isolated, low surface brightness systems, but with likely very different star formation histories based on their mean colors and color fluctuations. The color-magnitude diagrams of these galaxies have been used to estimate their …