Search Publications
The He+/H+ Abundance in the Orion Nebula from Infrared Space Observatory Measurements
Dufour, Reginald J.; Rubin, Robert H.; Colgan, Sean W. J. +1 more
Using the Short Wavelength Spectrometer on the Infrared Space Observatory, we measured in the Orion Nebula several components of the He I Brα transition, the first detections to the best of our knowledge in an H II region, and the H I Brα line. A value of He+/H+=0.085+/-0.003 is inferred from these data and is typical of prev…
On the Reliability of Ring Diagram Analysis
Chou, Dean-Yi; Gonzalez Hernandez, I.; Patron, J. +1 more
A comparison between the results of applying a ring diagram analysis to two data sets is described in order to check the quality of the two sets and the reliability of the method. The series used have been obtained with two different helioseismological instruments with the same spatial resolution. A section of 30 × 30 deg2 about the disk center ha…
The IUE Spectrum, Electron Density, and Terminal Wind Velocity of the ``O VI Sequence'' Planetary Nebula NGC 5315
Feibelman, Walter A.
Extensive archival and new IUE data obtained during the last (19th) year episode of the ``O VI sequence'' planetary nebula NGC 5315 and its central star have been analyzed. A large number of high-excitation emission lines have been identified, and their fluxes were determined. These yield electron densities from C III], Si III], and N III], and te…
A Nearby Galaxy in the Deep-Ultraviolet: Voyager 2 Observations of M33 from Lyα to the Lyman Limit
Keel, William C.
Observations of high-redshift galaxies in the emitted-wavelength regime around Lyα have renewed interest in the appearance of normal galaxies in the deep ultraviolet. This paper presents an analysis of spectrophotometry of the local Sc galaxy Messier 33 (NGC 598) obtained by Voyager 2, covering the range from below the Lyman limit to about 1250 Å.…
No Death Star--For Now
Gould, Andrew; Frogel, Jay A.
A star passing within ~104 AU of the Sun would trigger a comet shower that would reach the inner solar system about 0.18 Myr later. We calculate an a priori probability of ~0.4% that a star has passed this close to the Sun but that the comet shower has not yet reached the Earth. We search the Hipparcos catalogue for such recent close-en…
The Blue Companion of 3C 65: A Star-forming Galaxy with a Probable Redshift of 2.8
Charlot, Stéphane; Dunlop, J. S.; Owen, Frazer +2 more
We present BVRIK images and photometry of the z = 1.175 radio galaxy 3C 65 and its extended blue companion, along with a 6 cm radio map. These data are used to test the hypotheses that the companion is scattering the continuum of a hidden active nucleus within the radio galaxy and/or is undergoing a starburst triggered by interaction with its radi…
New Observations Testing the Adopted HIPPARCOS Link to the International Celestial Reference Frame
Stone, Ronald C.
This paper tests the Hipparcos link to the extragalactic reference frame by using new data obtained after the release of the catalog, thereby providing an external check on the accuracy of the established link process. The new data consist of 689 positions of Hipparcos stars determined in the International Celestial Reference Frame (ICRF) from CCD…
Constraints on Ultraviolet Absorption in the Intracluster Medium of Abell 1030
Koekemoer, Anton M.; Baum, Stefi A.; O'Dea, Christopher P. +3 more
We present results from an extensive Hubble Space Telescope (HST) spectroscopic search for UV absorption lines in the spectrum of the quasar B2 1028+313, which is associated with the central dominant galaxy in the cluster Abell 1030 (z = 0.178). This is one of the brightest known UV continuum sources located in a cluster and therefore provides an …
Spectroscopy of the Cataclysmic Variable UU Aquarii: s-Waves and Bright Spots
Schlegel, Eric M.; Kaitchuck, Ronald H.; White, James C., II +1 more
This paper reports the results of UV and optical spectroscopy of the nova-like variable UU Aqr. There is a decrease in the light flux of both the optical and UV emission lines at phase ~0.95. This appears to be due to an occultation of an asymmetric accretion disk. The emission-line profiles seem to show the first half of the rotational disturbanc…
High-Excitation Emission Lines in the Far-Ultraviolet Spectrum of the Late A Star α Cephei
Ayres, Thomas R.; Simon, Theodore
The A7 V star α Cephei lies in a region of the Hertzsprung-Russell diagram that is generally thought to be devoid of solar-like magnetic activity. The far-ultraviolet spectrum of this star was observed with the Berkeley spectrograph during the 1996 ORFEUS-SPAS II mission. We detected emission lines of Si III, C III, and O VI in the 900-1200 Å inte…