Search Publications
An Explanation of the ROSAT High-Resolution Imager Ultraviolet Sensitivity
Murray, S. S.; Barbera, M.; Collura, A. +1 more
The UV sensitivity to bright stars observed during operations of the high-resolution imager (HRI) on the X-ray-XUV Roentgen Satellite (ROSAT) has been commonly interpreted as a result of enhanced transmission solely in the wavelength range 1500-1700 Å of the HRI's UV/ion shield. We report on recent laboratory UV transmission measurements of HRI fl…
Infrared Space Observatory Mapping of 60 Micron Dust Emission around Vega-Type Systems
Stencel, R. E.; Backman, D. E.; Fajardo-Acosta, S. B.
We mapped 60 µm emission around five Vega-type systems. We utilized the PHOT-C100 far-infrared array camera on board the Infrared Space Observatory. The spatial resolution of the maps is ~30". The maps of three sources (α CrB, σ Her, and α Cen) do not show any evidence of extended emission. The map of γ Oph shows marginal hints of extended e…
Hubble Space Telescope GHRS Spectroscopy of U Geminorum during Two Outbursts
Szkody, Paula; Sion, Edward M.; Cheng, Fuhua +7 more
We obtained Hubble Space Telescope Goddard High-Resolution Spectrograph medium-resolution (G160M grating) phase-resolved spectroscopic observations of the prototype dwarf nova U Geminorum during different stages of two different outbursts. The spectral wavelength ranges were centered on three different line regions: N V (1238 Å, 1242 Å), Si III (1…
The Age of the Large Magellanic Cloud Cluster NGC 1651
Stetson, Peter B.; Graham, John A.; Mould, Jeremy R. +5 more
The age of NGC 1651 is 1.6 +/- 0.4 billion yr. This letter shows that accurate age determinations of young LMC clusters are achievable with aperture photometry of Wide Field Planetary Camera 2 (WFPC2) images taken in a single orbit of the HST.
Based on observations with the NASA/ESA Hubble Space Telescope.A Method for Determining the Photospheric 4He Abundance
Share, Gerald H.; Murphy, Ronald J.
The photospheric 4He/H ratio is not measured directly but is inferred from stellar evolution models, helioseismology, and coronal observations. We suggest a procedure for determining the photospheric ratio on the basis of solar wind isotopic He abundances and γ-ray line measurements. Recent Ulysses measurements of the 4He/
A Laboratory for Magnetized Accretion Disk Model: Ultraviolet and X-Ray Emission from Cataclysmic Variable GK Persei
Kenyon, Scott J.; Yi, Insu
We analyze the ultraviolet spectrum of the cataclysmic variable GK Per at maximum light. The flat ultraviolet spectrum in this system requires a truncated inner accretion disk and an unusually flat radial temperature profile. This requirement is not satisfied by any nonmagnetic steady or nonsteady disk model.
We consider a magnetized accretio…Lateral Shock of the R Aquarii Jet
Hollis, J. M.; Pedelty, J. A.; Kafatos, M.
The R Aqr jet was observed with the VLA B-configuration at two epochs separated by ~13.2 yr. Comparison of the resulting 6 cm continuum images show that the radio jet has undergone a lateral counterclockwise rotation of ~6°-12° on the plane of the sky. The model of jet parcels on independent trajectories is difficult to reconcile with these observ…
Circumstellar Gas in the Wide Binary HD 188037
Jura, M.; Kahane, C.; Fischer, D. +1 more
We report radio, optical, and ultraviolet studies of the wide binary HD 188037 (=IRC +20439). We detect the CO (2-1) and (1-0) rotational lines from the circumstellar envelope in this system, which consists of a luminous (~7000 L⊙) mass-losing M-type star and, at a separation of 0.75", a main-sequence A-type star. The strong (2-1) line …
Self-consistent and Time-dependent Solar Wind Models
Rosner, R.; Suess, S. T.; Musielak, Z. E. +2 more
We describe the first results from a self-consistent study of Alfvén waves for the time-dependent, single-fluid magnetohydrodynamic (MHD) solar wind equations, using a modified version of the ZEUS MHD code. The wind models we examine are radially symmetrical and magnetized; the initial outflow is described by the standard Parker wind solution. Our…
The Ultraviolet Spectrum of the Magnetic Cataclysmic Variable RX J1802.1+1804
Singh, K. P.; Shrader, C. R.; Barrett, P.
We observed the counterpart to the X-ray source RX J1802.1+1804, an object recently discovered as part of a survey to identify the optical counterparts to ultrasoft X-ray sources in the ROSAT point-source catalog that was subsequently identified as a magnetic cataclysmic variable, with the ultraviolet spectrometers on IUE in low dispersion mode. W…