Search Publications
Discovery of an Optical Synchrotron Jet in 3C 264
Boksenberg, A.; Barbieri, C.; Weigelt, G. +17 more
Observations with the Faint Object Camera on board the Hubble Space Telescope have revealed a new optical jet in the core of the elliptical galaxy NGC 3862 (3C 264). Morphologically, this jet is similar to the synchrotron jets seen in other galaxies, as it shows knots and bifurcations. The optical spectral index [-d log I(v)/d log v = α = 1.4] is …
The Quasi-periodic Oscillations and Very Low Frequency Noise of Scorpius X-1 as Transient Chaos: A Dripping Handrail?
Scargle, Jeffrey D.; Steiman-Cameron, Thomas; Young, Karl +3 more
We present evidence that the quasi-periodic oscillations (QPO) and very low frequency noise (VLFN) characteristic of many accretion sources are different aspects of the same physical process. We analyzed a long, high time resolution EXOSAT observation of the low-mass X-ray binary (LMXB) Sco X-1. The X-ray luminosity varies stochastically on time s…
GINGA Observations of the Coma Cluster and Studies of the Spatial Distribution of Iron
Hughes, John P.; Tanaka, Yasuo; Butcher, Jackie A. +1 more
The large area counters on the Japanese satellite Ginga have been used to determine the X-ray spectrum from the central region of the Coma cluster of galaxies over the energy range from 1.5 to 20 keV. The spectrum is well represented by an isothermal model of temperature 8.21+/-0.16 keV and a heavy element (iron) abundance of 0.212+/-0.027 relativ…
Observations of the Gaseous Galactic Halo toward 3C 273 with the Goddard High Resolution Spectrograph
Savage, Blair D.; Morris, Simon L.; Gilliland, Ronald L. +2 more
We present an analysis of observations of 24 absorption lines produced zero redshift by Milky Way disk and halo gas along the sight line to 3C 273. The observations were obtained with the intermediate-resolution mode of the Goddard High Resolution Spectrograph (GHRS) using the large entrance aperture. The spectral spread function has FWHM ~20 km s…
The Narrow-Line Region of High-Luminosity Active Galactic Nuclei
Netzer, H.; Ferland, G. J.; Browne, I. W. A. +5 more
The HST's Faint Object Spectrograph and Kitt Peak ground instruments have been used to gather high S/N spectroscopic observations of seven radio-loud quasars; the resolutions obtained allow a separation of emission line broad and narrow components to be made. Attention is given to the relative weakness of the narrow UV lines, in contradiction to t…
Observations of the White Dwarf in the U Geminorum System with the Hopkins Ultraviolet Telescope
Blair, William P.; Sion, Edward M.; Kriss, Gerard A. +4 more
The Hopkins Ultraviolet Telescope was used to obtain an FUV spectrum of U Gem about 10 d after the end of an outburst. Most of the FUV emission from U Gem appears to rise from the white dwarf (WD) in the system. Various possibilities to explain the hot component in the present spectrum are explored. It is most likely due to radiation from the boun…
The Interstellar Abundances of Tin and Four Other Heavy Elements
York, D. G.; Welty, D. E.; Hobbs, L. M. +2 more
Spectra recorded at 1150-1600 A with an instrumental resolution near 16 km/s were obtained with the Goddard High-Resolution Spectrograph on board the HST. The gaseous interstellar abundances of five heavy elements along the light paths to 23 Ori, 15 Mon, 1 Sco, Pi Sco, and Pi Aqr were determined from the observations. The 1400.450 A line of Sn II …
Two New Extremely Iron-rich Hot DA White Dwarfs and the Nature of the EUV Opacity
Werner, K.; Dreizler, S.; Barstow, M. A. +8 more
We have obtained IUE echelle spectra of two bright extreme ultraviolet (EUV) sources discovered by the ROSAT wide field camera all-sky survey. These stars, RE 2214-492 and RE 0623-377, are previously uncataloged hot DA white dwarfs with respective apparent visual magnitudes of 11.71 and 12.09 and exhibit short-wavelength EUV cutoffs steeper than m…
Discovery of a Magnetic/Nonmagnetic Double-degenerate Binary System
Bergeron, P.; Saffer, Rex A.; Liebert, James +1 more
We report the discovery of an unresolved binary system consisting of two degenerate stars: one a polarized object with an inferred magnetic field among the largest yet found on a white dwarf; the other a normal DA with no detectable field. We have deconvolved the composite 1250 Å-2.2 microns energy distribution into individual spectra and find tha…
A Catalog of Stellar Lyman-Alpha Fluxes
Simon, Theodore; Landsman, Wayne
We present a catalog of stellar Ly-alpha emission fluxes, based on new and archival images obtained with the IUE spacecraft. The catalog includes 227 stars with detectable Ly-alpha emission fluxes, and upper limits on the Ly-alpha emission flux for another 48 stars. Multiple flux measurements are given for 52 stars. We present a model for correcti…