Search Publications
Theoretical Modeling of ISO Results on Planetary Nebula NGC 7027
Bjorkman, J. E.; Federman, S. R.; Yan, M. +1 more
We present a thermal and chemical model of the neutral envelope of planetary nebula NGC 7027. In our model, the neutral envelope is composed of a thin dense shell of constant density and an outer stellar wind region with the usual inverse-square law density profile. The thermal and chemical structure is calculated with the assumption that the inci…
Ultraviolet and Optical Line Profile Variations in the Spectrum of ɛ Persei
Kambe, E.; Gies, D. R.; Riddle, R. L. +13 more
The rapid variable star, ɛ Per (B0.5 IV-III), displays the largest amplitude profile fluctuations known among the growing number of massive, spectrum-variable stars. Here we present an analysis of a continuous 5 day run of IUE UV spectroscopy, and we show for the first time that the systematic, blue-to-red moving patterns observed in high-quality …
Application of Realistic Model Atmospheres to Eclipse Maps of Accretion Disks: The Effective Temperature and Flare of the Disk in the Dwarf Nova Z Chamaeleontis
Wood, Janet H.; Wade, Richard A.; Robinson, Edward L.
In a previous paper we presented ultraviolet (λeff=1550 Å) high-speed photometry of the eclipsing dwarf nova Z Cha obtained near the peak of a normal eruption, and we derived a maximum-entropy disk map from the eclipse light curve. In the present paper we report a new calculation of the disk map and temperature profile. The calculation …
A Cepheid Distance to NGC 4603 in Centaurus
Zepf, Stephen E.; Davis, Marc; Madore, Barry F. +5 more
In an attempt to use Cepheid variables to determine the distance to the Centaurus cluster, we have obtained images of NGC 4603 with the Hubble Space Telescope for 9 epochs (totalling 24 orbits) over 14 months in the F555W filter and 2 epochs (totalling six orbits) in the F814W filter. This galaxy has been suggested to lie within the ``Cen 30'' por…
Far-Infrared and Submillimeter Observations and Physical Models of the Reflection Nebula Cederblad 201
van Dishoeck, Ewine F.; Hogerheijde, Michiel R.; Tielens, Alexander G. G. M. +3 more
Infrared Space Observatory (ISO) [C II] 158 µm, [O I] 63 µm, and H2 9 and 17 µm observations are presented of the reflection nebula Ced 201, which is a photon-dominated region (PDR) illuminated by a B9.5 star with a color temperature of 10,000 K (a cool PDR). In combination with ground-based [C I] 609 µm, CO,
New Identifications of Si VIII and S X Lines in the Solar Coronal Spectrum Measured by SOHO/SUMER
Feldman, U.; Kink, I.; Engström, L.
This paper reports the identification of 14 lines in the solar coronal spectrum as high-excitation 2s22p23s-2s22p23p and 2s22p23p-2s22p23d transitions in Si VIII and S X (N I isoelectronic sequence). The analysis combines solar spectra, recorded by the SUMER (S…
NICMOS Observations of Interaction-triggered Star Formation in the Luminous Infrared Galaxy NGC 6090
Rieke, Marcia; Evans, Aaron S.; Scoville, Nick Z. +2 more
High-resolution 1.1, 1.6, and 2.2 µm imaging of the luminous infrared galaxy NGC 6090 obtained with NICMOS on the Hubble Space Telescope is presented. These new observations are centered on the two nuclei of the merger and reveal the spiral structure of the eastern galaxy and the amorphous nature of the western galaxy. The nuclear separation…
Sleuthing the Dynamo. II. Hubble Space Telescope Goddard High Resolution Spectrograph Observations of Solar-Type Dwarfs in Young Galactic Clusters
Ayres, Thomas R.
Far-ultraviolet (1150-1670 Å) spectra of three solar-type dwarfs in the young galactic clusters α Persei and the Pleiades were obtained with the Hubble Space Telescope Goddard High-Resolution Spectrograph (G140L mode). Time series of Si IV λ1393 show erratic variability on timescales of tens of minutes. An X-ray/C IV flux-flux diagram displays a p…
Direct Measurement of the Jet Geometry in Seyfert Galaxies
Clarke, C. J.; Pringle, J. E.; Schmitt, H. R. +3 more
We demonstrate that by combining optical, radio, and X-ray observations of a Seyfert galaxy, it is possible to provide a direct measurement of the angle β between the direction of the radio jet and the normal to the plane of the spiral host galaxy. To do so, we make the assumptions that the inner radio jet is perpendicular to the X-ray observed in…
Lifetime Measurements for Ground Term Transitions in TA II, W II, and RE II
Wahlgren, G. M.; Henderson, M.; Brage, T. +4 more
Lifetime measurements have been made for the radiation emitted in the ground term transitions of the nominal form 5s25p65dx6s-5s25p65dx6p in Ta II (x=3), W II (x=4), and Re II (x=5). Supporting theoretical calculations have also been performed to characterize configuration interacti…