Search Publications
A Circumstellar Disk in a Pre-main-sequence Binary Star
Koresko, Chris D.
New high-resolution images of HK T Tauri B, the companion to the 106 yr old classical T Tauri star HK Tauri A, show it to be surrounded by an optically thick, edge-on circumstellar disk that extends to a radius of at least 50 AU. The images were taken using a modified speckle technique to achieve a linear resolution of 8 AU. The disk is…
Sirius B: A New, More Accurate View
Barstow, M. A.; Bruhweiler, F. C.; Holberg, J. B. +2 more
Long-standing questions regarding the temperature, gravity, mass, and radius of the well-known white dwarf Sirius B are considered in light of new data. Recently obtained Extreme Ultraviolet Explorer (EUVE) observations and reprocessed IUE NEWSIPS data have produced a new, well-defined effective temperature of 24,790 +/- 100 K and a surface gravit…
Do the Infrared Emission Features Need Ultraviolet Excitation?
Werner, M.; Sellgren, K.; Uchida, K. I.
We present the results of imaging spectroscopy of the reflection nebula vdB 133, obtained with the infrared camera and circular variable filter wheel on the Infrared Space Observatory. Our observations reveal the infrared emission features (IEFs), at 6.2, 7.7, 8.7, 11.3, and 12.7 µm, and associated 5-15 µm continuum emission. The stell…
Neutral Hydrogen Column Depths in Prominences Using EUV Absorption Features
Andretta, V.; Kucera, T. A.; Poland, A. I.
Observations of prominence regions in hot coronal lines (≳106 K) at wavelengths below the hydrogen Lyman absorption limit show what appear to be absorption features. Other authors have suggested that these observed features may be due to H and He continuum absorption. But there has, as yet, been no conclusive evidence that this is indeed the case.…
Cradle to grave tracking of the January 6-11,1997 Sun-Earth connection event
Thompson, B. J.; Fox, N. J.; Peredo, M.
During the interval January 6-11, 1997, the satellites and ground facilities of the International Solar-Terrestrial Physics (ISTP) “Observatory” tracked a solar eruption from the Sun to the Earth. The resulting Coronal Mass Ejection (CME) took four days to travel through interplanetary space before arriving at Earth, where it caused electromagneti…
Cataclysmic Variables and a New Class of Faint Ultraviolet Stars in the Globular Cluster NGC 6397
Bailyn, Charles D.; Cool, Adrienne M.; Cohn, Haldan N. +2 more
We present evidence that the globular cluster NGC 6397 contains two distinct classes of centrally concentrated UV-bright stars. Color-magnitude diagrams constructed from U336, B439, V555, and I814 data obtained with the Hubble Space Telescope Wide Field Planetary Camera 2 reveal seven UV-bright stars fai…
HIPPARCOS Period-Luminosity Relations for Mira and Semiregular variables
Bedding, Timothy R.; Zijlstra, Albert A.
We present period-luminosity (P-L) diagrams for nearby Mira and semiregular variables, selecting stars with parallaxes better than 20% and well-determined periods. Using K-band magnitudes, we find two well-defined P-L sequences, one corresponding to the standard Mira P-L relation and the second shifted to shorter periods by a factor of about 1.9. …
Gas Cloud Kinematics near the Nucleus of NGC 4151
Gull, T. R.; Kraemer, S. B.; Crenshaw, D. M. +10 more
We report early observations with Space Telescope Imaging Spectrometer (STIS) of the nuclear region of NGC 4151. Direct images in [O II] and [O III] and slitless medium-dispersion spectral images of the Hβ to [O III] region were obtained. A slitless UV spectral image was taken of the C IV 1550 Å region. We present radial velocities and line ratios…
Detection of 55-80 keV Hydrogen Atoms of Heliospheric Origin by CELIAS/HSTOF on SOHO
Livi, S.; Hsieh, K. C.; Wurz, P. +29 more
The High-Energy Suprathermal Time-of-Flight sensor (HSTOF) of the Charge, Element, and Isotope Analysis System (CELIAS) on the Solar and Heliospheric Observatory (SOHO) near the Lagrangian point L1 is capable of identifying energetic hydrogen atoms (EHAs) between 55 and 80 keV. Between 1996 February 13 and 1997 August 31, near solar minimum, there…
An Empirical Isochrone of Very Massive Stars in R136a
Hubeny, Ivan; Heap, Sara R.; de Koter, Alex
We report on a detailed spectroscopic study of 12 very massive and luminous stars (M >~ 35M⊙) in the core of the compact cluster R136a, near the center of the 30 Doradus complex. The three brightest stars of the cluster, R136a1, R136a2, and R136a3, have been investigated earlier by de Koter, Heap, & Hubeny. Low-resolution spectra…