Search Publications
Measuring Sizes of Marginally Resolved Young Globular Clusters with the Hubble Space Telescope
Holtzman, Jon A.; Carlson, Matthew N.
We present a method for deriving sizes of marginally resolved star clusters from Hubble Space Telescope/WFPC2 observations by fitting King models to observations. We describe results both on simulated images and on observations of young compact clusters in NGC 3597 and NGC 1275. From the simulations, we find that we can measure King model concentr…
Spectroscopic Observation of the Planetary Nebula IC 4846
Hyung, Siek; Aller, Lawrence H.; Lee, Woo-baik
A high-dispersion optical (3700-10100 Å) spectrum was secured with the Hamilton echelle spectrograph at the coudé focus of the 120 inch (3 m) Shane telescope at Lick Observatory, with the goal of deriving chemical abundances for the compact planetary nebula IC 4846. We also remeasured the UV spectra from the IUE archive. Diagnostics indicate that …
SPIRAL Phase A: A Prototype Integral Field Spectrograph for the Anglo-AustralianTelescope
Kenworthy, Matthew A.; Taylor, Keith; Parry, Ian R.
We present details of a prototype fiber feed for use on the Anglo-Australian Telescope (AAT) that uses a dedicated fiber-fed medium/high-resolution (R~=10,000) visible-band spectrograph to give integral field spectroscopy (IFS) of an extended object. A focal reducer couples light from the telescope to the close-packed lenslet array and fiber feed,…
Markarian 478: A Second Seyfert Galaxy with 1 Micron Fe II Emission Lines
Hamann, F.; Rudy, Richard J.; Puetter, R. C. +3 more
We present infrared spectroscopy of the narrow-line Seyfert 1 galaxy Mrk 478 that shows the 1 µm Fe II lines λ9997, λ10501, λ10863, and λ11126. This is the second active galaxy, after I Zw 1, in which these features have been observed. Like I Zw 1, the 1 µm Fe II lines of Mrk 478 appear to arise from collisional excitation of their com…
Astrophysics in 2000
Aschwanden, Markus J.; Trimble, Virginia
It was a year in which some topics selected themselves as important through the sheer numbers of papers published. These include the connection(s) between galaxies with active central engines and galaxies with starbursts, the transition from asymptotic giant branch stars to white dwarfs, gamma-ray bursters, solar data from three major satellite mi…
The Accretion Disk and White Dwarf in the Short-Period Dwarf Novae TY Piscium and V436 Centauri during Quiescence
Sion, Edward M.; Nadalin, Ira
The short-period dwarf novae TY Psc and V436 Cen are SU UMa systems with very similar orbital periods, similar recurrence times for normal outbursts (~23 days) and superoutbursts (~340 days), and nearly identical outburst amplitudes. We have carried out high-gravity model atmosphere and accretion disk synthetic spectra from the grid of Wade & …
Dying Pulse Trains in Cygnus XR-1: Evidence for an Event Horizon?
Dolan, Joseph F.
The X-ray-emitting component in the Cyg XR-1/HDE 226868 system is a leading candidate for identification as a stellar-mass-sized black hole. The detection of an event horizon surrounding the point singularity in such a system would constitute a positive identification of a black hole as predicted by general relativity. One signature of such an eve…
Spectroscopy of Massive Stars in NGC 6822 and M33
Bianchi, Luciana; Hutchings, John B.; Scuderi, Salvatore +1 more
We present blue spectra of massive stars in the Local Group galaxies NGC 6822 and M33. For all the targets, selected from our previous Hubble Space Telescope WFPC2 photometry, no previous spectroscopic studies exist, to our knowledge, except for a bright Wolf-Rayet star in NGC 6822. Photospheric parameters Teff and gravity are derived b…
Hubble Space Telescope Photometry of Clusters of Galaxies behind the Dwarf Irregular Galaxies DDO 216 and IC 1613 and the Small Magellanic Cloud
Hodge, Paul W.; Krienke, Karl
We have measured the integrated colors of galaxies in clusters located behind the dwarf irregular galaxies DDO 216 (Pegasus) and IC 1613 and a position in the Small Magellanic Cloud (SMC) near the cluster Lindsey 31. We examine limits on the accuracy of using these for studying the total extinction in galaxies. We show that the method is feasible …
Hubble Space Telescope Color-Magnitude Data for Globular Clusters. I. Transformations between STIS LP Magnitudes and WFPC2 F606W and F814W Magnitudes
Wyse, Rosemary F. G.; Gilmore, Gerard; Houdashelt, Mark L.
We present deep Hubble Space Telescope optical imaging observations of two Galactic globular clusters, 47 Tucanae and M15, using the Space Telescope Imaging Spectrograph (STIS) longpass (LP) filter and the Wide Field and Planetary Camera 2 (WFPC2) F606W and F814W filters. These globular clusters have very different metallicities ([Fe/H]~-0.7 dex f…