Search Publications
The EUV spectrum of κ Ceti: an active Sun.
Landini, M.; Del Zanna, G.; Landi, E.
The spectrum of κ Cet in the region 80-370Å observed by EUVE Spectrometers is analyzed to investigate the transition region and the corona of the star. The star appears to be in a rather quiet condition and no evidence exists of flare-like lines observed in many active stars. Several emission lines of moderately ionized iron (from Fe IX to Fe XVII…
Measurement of the propagation speed of plasma inhomogeneities in the solar corona using an uplink/downlink cross-correlation method
Pätzold, Martin; Bird, Michael K.; Plettemeier, Dirk +3 more
Radio sounding investigations were performed over a period of about 30 days during the 1991 solar occultation of the Ulysses spacecraft (August and September 1991). Dual-frequency Doppler and ranging measurements were obtained using the NASA Deep Space Network. For this experiment the radio ray path from Ulysses to Earth moved essentially parallel…
Classification of Population II Stars in the Vilnius Photometric System. II. Results
Bartkevicius, A.; Lazauskaite, R.
The results of photometric classification of 848 true and suspected Population II stars, some of which were found to belong to Population I, are presented. The stars were classified using a new calibration described in Paper I (Bartkevicius & Lazauskaite 1996). We combine these results with our results from Paper I and discuss in greater detai…
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.The IUE Spectrum of the ``O VI Sequence'' Planetary Nebula IC 2003
Feibelman, Walter A.
We present archival low- and high-dispersion, as well as new SWP high-dispersion, IUE data of the ``O VI sequence'' planetary nebula IC 2003 that has not been studied extensively in the UV. Contrary to earlier UV studies, IC 2003 shows a rich spectrum of stellar and nebular emission lines. Nearly 60 new emission line fluxes are presented for He II…
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/
An Ultraviolet View of Massive Star Formation in Seyfert Host Galaxies.
O'Connell, Robert W.; Bohlin, Ralph C.; Smith, Andrew M. +5 more
We present deep vacuum ultraviolet (λλ 1200-3300 Å) imagery of four Seyfert galaxies observed by the Ultraviolet Imaging Telescope (UIT): NGC 1068, NGC 2992, NGC 4151, and Mrk 335. These data have a spatial resolution of ∼3" and a limiting surface brightness of ∼24.5 mag arcsec-2 The host galaxies display a diverse range in ultraviolet …
The HST Medium Deep Survey: Light Profiles and Redshifts for Field Galaxies with z<~0.6
Griffiths, R. E.; Windhorst, R. A.; Schmidtke, P. C. +3 more
High-resolution isophotal light profiles have been determined for 36 field galaxies in images taken for the Hubble Space Telescope Medium Deep Survey prior to HST's refurbishment mission. The images were obtained with the Wide Field Camera in "parallel mode" and deconvolved using the Lucy-Richardson image-restoration algorithm with a large library…
Three-dimensional nature of interaction regions: Pioneer, Voyager, and Ulysses solar cycle variations from 1 to 5 AU
Smith, Edward J.; González-Esparza, J. Américo
We combined in-ecliptic observations of interaction regions from 1 to 5 AU by four spacecraft that traveled to Jupiter at different phases of the solar cycle: Pioneer 11 (declining phase of cycle 20), Voyager 1 and 2 (ascending phase of cycle 21), and Ulysses (just after solar maximum 22). We used this set of 97 interaction regions to study two di…
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…