Search Publications
Illumination in Symbiotic Binary Stars: Non-LTE Photoionization Models. II. WIND Case
Raymond, John C.; Kenyon, Scott J.; Proga, Daniel
We describe a non-LTE photoionization code to calculate the wind structure and emergent spectrum of a red giant wind illuminated by the hot component of a symbiotic binary system. We consider spherically symmetric winds with several different velocity and temperature laws and derive predicted line fluxes as a function of the red giant mass-loss ra…
ISOCAM Mid-Infrared Imaging of the Quiescent Spiral Galaxy NGC 7331
Smith, Beverly J.
Using the mid-infrared camera (ISOCAM) on the Infrared Space Observatory (ISO), the Sb LINER galaxy NGC 7331 has been imaged in two broadband and four narrowband filters between 6.75 and 15 µm. These maps show a prominent circumnuclear ring of radius 0.25 arcmin × 0.75 arcmin (1.1 × 3.3 kpc) encircling an extended central source. The 7.7 and…
The Identification and Characterization of Alfvénic Fluctuations in ULYSSES Data at Midlatitudes
Balogh, A.; Lucek, E. A.
Ulysses magnetic field and plasma data recorded during 1992 and 1993 as the spacecraft moved through mid-heliolatitudes, have been used to identify intervals dominated by Alfvénic fluctuations in the presence of corotating interaction regions. A wavelet frame representation of Elsässer variables was used to calculate the Alfvénicity of the fluctua…
The Ultraviolet-Optical Albedo of Broad Emission Line Clouds
Korista, Kirk; Ferland, Gary
We explore the effective UV-optical albedos of a variety of types of broad emission line clouds, as well as their possible effects on the observed spectra of active galactic nuclei (AGNs). An important albedo source in moderately ionized ionization-bounded clouds is that which is due to neutral hydrogen: Rayleigh scattering of continuum photons of…
Below the Lyman Edge: Ultraviolet Polarimetry of Quasars
Antonucci, Robert; Koratkar, Anuradha; Storrs, Alex +1 more
The Lyman edge at 912 Å is an important diagnostic region for studying quasi-stellar objects (QSOs). In particular, it reveals a great deal about the physical conditions within the atmospheres of accretion disks, a ubiquitous component of QSO theories. A robust prediction of accretion disk models is a significant polarization due to electron scatt…
A Search for Ultrarapid Microvariability in the Seyfert Galaxy NGC 7469 with the Hubble Space Telescope
Peterson, B. M.; Koratkar, A. P.; Korista, K. T. +1 more
The Faint Object Spectrograph on the Hubble Space Telescope (HST) was used to obtain spectrophotometric observations of the Seyfert 1 galaxy NGC 7469. The spectra were obtained with a 90 s time resolution in order to resolve the fastest expected variability and to search for rapid characteristic timescales (e.g., quasi-periodic oscillations or bre…
Space Telescope Imaging Spectrograph Near-Ultraviolet Time-tagged Spectra of the Crab Pulsar
Gull, Theodore R.; Lundqvist, Peter; Sonneborn, George +8 more
We present the spectrum and the pulse profile of the Crab Pulsar in the near-ultraviolet (1600-3200 Å) observed with the Space Telescope Imaging Spectrograph (STIS) during the Hubble Space Telescope (HST) second Servicing Mission Orbital Verification (SMOV) period. The two-dimensional near-ultraviolet Multianode Microchannel Array (NUV MAMA) was u…
The Probable Optical Counterpart of the Luminous X-Ray Source in NGC 6441
Anderson, Scott F.; Margon, Bruce; Deutsch, Eric W. +1 more
We report results from Hubble Space Telescope (HST)WFPC2 imaging of the field of the luminous, bursting X-ray source in the globular cluster NGC 6441. Although the X-ray position is known to a precision of a few arcseconds, this source is only ~6" from the cluster center, and the field contains hundreds of stars within the 3" X-ray error circle, m…
Ultraviolet Coronagraph Spectrometer Observations of Density Fluctuations in the Solar Wind
Romoli, M.; Poletto, G.; Noci, G. +2 more
In the Letter ``Ultraviolet Coronagraph Spectrometer Observations of Density Fluctuations in the Solar Wind'' by L. Ofman, M. Romoli, G. Poletto, G. Noci, and J. L. Kohl (ApJ, 491, L111 [1997]), there was an error in the data reduction of the polarized brightness (pB). It was assumed that the cadence of the da…
Hubble Space Telescope Observations of Planetary Nebulae in the Magellanic Clouds. VII. Cycle 3 and Archive Narrowband [O III] 500.7 nanometer Imaging
Ford, H. C.; Harrington, J. P.; Wood, P. R. +6 more
We present the continuation of our analysis of narrowband [O III] images, obtained using the Hubble Space Telescope (HST), of planetary nebulae (PNs) in the Magellanic Clouds. Six objects, five in the Large Magellanic Cloud, are observed as part of the General Observer program. An additional 15 objects are retrieved from the HST archive. The major…