Search Publications
On the Progenitor of the Type II-Plateau Supernova 2003gd in M74
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Li, Weidong
Hubble Space Telescope (HST) WFPC2 archival F606W and F300W images obtained within 1 year prior to the explosion of the nearby Type II supernova (SN) 2003gd in M74 (=NGC 628) have been analyzed to isolate the progenitor star. The SN site was located using precise astrometry applied to the HST images. Two plausible candidates are identified within …
A Search for Core-Collapse Supernova Progenitors in Hubble Space Telescope Images
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Li, Weidong
Identifying the massive progenitor stars that give rise to core-collapse supernovae (SNe) is one of the main pursuits of supernova and stellar evolution studies. Using ground-based images of recent, nearby SNe obtained primarily with the Katzman Automatic Imaging Telescope, astrometry from the Two Micron All Sky Survey, and archival images from th…
Ultraviolet and Optical Properties of Narrow-Line Seyfert 1 Galaxies
Shields, Joseph C.; Constantin, Anca
Narrow-line Seyfert 1 galaxies (NLS1s) are remarkable for their extreme continuum and emission-line properties, which are not well understood. New results bearing on the spectroscopic characteristics of these objects are presented here, with the aim of establishing their typical UV and optical spectral behavior. We employ Hubble Space Telescope ob…
Molecular Hydrogen in the Ring Nebula: Clumpy Photodissociation Regions
Knezek, Patricia M.; Meixner, Margaret; Jacoby, George H. +1 more
We present a 0.65" resolution H2 1-0 S(1) 2.122 µm image of the Ring Nebula (NGC 6720), which was taken with the Near Infrared Imager at the WIYN 3.5 m telescope on Kitt Peak. The high resolution of the H2 observation is sufficient to reveal the finer structure of the molecular material in this nebula. The morphology of…
Relative Flux Calibration of Keck HIRES Echelle Spectra
O'Meara, John M.; Tytler, David; Lubin, Dan +2 more
We describe a method to calibrate the relative flux levels in spectra from the High-Resolution Echelle Spectrograph (HIRES) on the Keck I telescope. Standard data reduction techniques that transfer the instrument response between HIRES integrations leave errors in the flux of 5%-10% because the effective response varies during the night. The flux …
On the Progenitor of Supernova 2001du in NGC 1365
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Li, Weidong
Hubble Space Telescope (HST) WFPC2 archival images obtained years prior to the explosion of the Type II-plateau supernova (SN) 2001du in NGC 1365 previously have been analyzed to isolate the progenitor star. The SN site was located using precise astrometry applied to the HST images, with significant uncertainty, leaving three possible progenitor c…
Simultaneous ASCA and Hubble Space Telescope/GHRS Observations of Cygnus X-2/V1341 Cygni
McCray, R.; Raymond, J. C.; Kallman, T. +4 more
We present results from ultraviolet and X-ray observations of the low-mass X-ray binary Cygnus X-2. The simultaneous Hubble Space Telescope/GHRS and ASCA observations took place during the low state of an 82 day cycle. We compare our observations as well as archival IUE and RXTE data with models that predict ultraviolet and optical continuum emiss…
Comparative Absorption and Emission Abundance Analyses of Nebulae: Ion Emission Densities for IC 418
Jenkins, Edward B.; Williams, Robert; Baldwin, Jack A. +1 more
Recent analyses of nebular spectra have resulted in discrepant abundances from CNO forbidden and recombination lines. We consider independent methods of determining ion abundances for emission nebulae, comparing ion emission measures with column densities derived from resonance absorption lines viewed against the central star continuum. Separate a…