Search Publications
A snapshot of the continuous emission of the active galactic nucleus in NGC 3783 from gamma-ray to radio wavelengths.
Altieri, B.; Glass, I. S.; Malkan, M. A. +21 more
With the aim of better understanding the physical processes that produce the continuous emission in active galactic nuclei (AGNs), a snapshot of the overall continuous energy distribution of NGC 3783, from γ-ray to radio wavelengths, has been obtained within the framework of the World Astronomy Days. The data collected in this campaign are from GR…
The Stellar Content of 30 Doradus Derived from Spatially Integrated Ultraviolet Spectra: A Test of Spectral Synthesis Models
Robert, Carmelle; Leitherer, Claus; Vacca, William D. +1 more
Using the IUE satellite, we have obtained spatially integrated ultraviolet spectra of three areas within the giant H II region 30 Dor in the Large Magellanic Cloud. The spectra correspond to spatial regions with sizes of 20" x 20", 1' x 1', and 3' x 3', all of which are approximately centered on R136. We have performed a spectral synthesis analysi…
Further Studies of Waves Accompanying the Solar Wind Pick-up of Interstellar Hydrogen
Balogh, A.; Tsurutani, B. T.; Smith, E. J. +2 more
Data collected by the magnetometer onboard the Ulysses spacecraft are surveyed for the occurrence of waves generated during the pick-up of interstellar hydrogen. Thirty one wave events were found during a 640 day study period, between March 21, 1992 and December 20, 1993 (after the Ulysses encounter with Jupiter). It is found that observation of t…
Stellar Activity at the End of the Main Sequence: GHRS Observations of the M8 Ve Star VB 10
Brown, Alexander; Giampapa, Mark S.; Wood, Brian E. +2 more
We present Goddard High Resolution Spectrograph observations of the M8 Ve star VB 10 (= Gl 752B), located very near the end of the stellar main sequence, and its dM3.5 binary companion Gl 752A. These coeval stars provide a test bed for studying whether the outer atmospheres of stars respond to changes in internal structure as stars become fully co…
Long-term X-ray variability of NGC 4151
Papadakis, I. E.; McHardy, I. M.
We present a new method of estimating the power spectrum in the case of unevenly sampled data, together with its application to the long X-ray light curve of the Seyfert galaxy NGC 4151. This method is based on the Fourier transform of the observed autocovariance function. The method is simple to use and wisely applicable. The long-term power spec…
Evidence for Elemental Variation in the Ejecta of the TYCHO Supernova Remnant
Hughes, John P.; Gorenstein, P.; Vancura, O.
We present an X-ray study of the Tycho supernova remnant utilizing archival data from the high-resolution imagers (HRIs) on Einstein and ROSAT, the low-energy imaging telescopes (LEITs) on EXOSAT, and spectral data from the Broad Band X-ray Telescope (BBXRT). We have made use of the differing HRI bandpasses to construct images of Tycho in two spec…
First Direct Comparison of High and Low Ionization Line Kinematics in Active Galactic Nuclei
Marziani, P.; Moles, M.; Sulentic, J. W. +2 more
We present first results of a comparison of emission line shift properties for the high (HILs) and low (LILs) ionization lines in 43 low- redshift quasars. We identify a core sample of C IV λ1549 and Hβ profiles with a wide distribution of red- and blueshifts (<= 1000 km s^-1^). We also identify two tails in this distribution: one with large Hβ…
Hubble Space Telescope High-Resolution Spectroscopy of the Exposed White Dwarf in the Dwarf Nova VW Hydri in Quiescence: A Rapidly Rotating White Dwarf
Szkody, Paula; Sion, Edward M.; Cheng, Fu-Hua +1 more
We obtained a far-ultraviolet spectrum of the dwarf nova VW Hyi in quiescence, with the Hubble Space Telescope Goddard High Resolution Spectrograph covering the region of the Si iv lambda(lambda)1393, 1402 resonance doublet. The broad, shallow Si iv doublet feature is fully resolved, has a total equivalent width of 2.8 A, and is the first metal ab…
ULYSSES Out-of-Ecliptic Observations of ``27-day'' Variations in High Energy Cosmic Ray Intensity
Balogh, A.; Simpson, J. A.; McKibben, R. B. +2 more
We report the discovery that for latitudes above ∼40°S, the observed recurring modulation of cosmic rays and anomalous nuclei occurs without the detection byUlysses of the solar wind velocity and magnetic field recurring enhancements that have, heretofore at lower latitudes, defined corotating interaction regions—i.e., the mechanism producing the …
A Critical Analysis of Interstellar Zn and CR as Galactic Abundance Benchmarks for Quasar Absorbers
Steidel, Charles C.; Sembach, Kenneth R.; Meyer, David M. +1 more
We present interstellar gas-phase abundances of zinc and chromium in the Milky Way for comparison with the abundances of these elements in damped Lyα systems at redshifts near z ~ 2. We make use of both IUE and GHRS archival information in deriving the Milky Way values and find that the average difference in [Zn/H] and [Cr/Zn] between the Milky Wa…