Search Publications
Ultraviolet Absorption Lines from High-Velocity Gas in the VELA Supernova Remnant: New Insights from Space Telescope Imaging Spectrograph Echelle Observations of HD 72089
Kaiser, Mary Elizabeth; Tripp, Todd M.; Jenkins, Edward B. +12 more
The star HD 72089 is located behind the Vela supernova remnant and shows a complex array of high- and low-velocity interstellar absorption features arising from shocked clouds. A spectrum of this star was recorded over the wavelength range 1196.4-1397.2 Å at a resolving power of λ/Δλ = 110,000 and a signal-to-noise ratio of 32 by the Space Telesco…
Very low frequency waves in the heliosphere: Ulysses observations
Balogh, A.; McComas, D. J.; Forsyth, R. J. +5 more
An overall profile of plasma wave activity in a frequency range of 0.2 to 448 Hz in the solar wind is presented using 6 years of Ulysses data which cover a large range of heliographic latitudes (0° to +/-80°) at distances from 1 to 5 AU from the Sun. The spacecraft has continuously observed wave activity with peak power below the local electron cy…
The nature of some doubtful open clusters as revealed by HIPPARCOS
Baumgardt, H.
We discuss the nature of some galactic open clusters by using proper motions and parallaxes from the Hipparcos and ACT catalogues. We show that the clusters Collinder 399, Upgren 1, NGC 1252 and Melotte 227 do not exist. Collinder 132 is found to be mainly composed out of members of an OB association, but there may be a star cluster present in thi…
High-Temperature Lines in SUMER Spectra Recorded Above a Bright Solar Active Region
Wilhelm, K.; Curdt, W.; Schühle, U. +3 more
We identify spectral lines emitted by solar abundant elements due primarily to transitions within the 2s22pk and 3s23pk (where k = 1, 5) ground configurations of ions that are formed in ionization equilibrium between 2 × 106 and 8 × 106 K. The transitions were identified in spectra …
Radio jet interactions in the radio galaxy PKS 2152-699
di Serego Alighieri, S.; Fosbury, R. A. E.; Morganti, R. +3 more
We present radio observations of the radio galaxy PKS 2152-699 obtained with the Australia Telescope Compact Array. The much higher resolution and signal-to-noise ratio of the new radio maps reveal the presence of a bright radio component about 10 arcsec north-east of the nucleus. This lies close to the highly ionized cloud previously studied in t…
Atomic Carbon in ARP 220
Gerin, Maryvonne; Phillips, Thomas G.
We present detections of the 3P1-3P0 fine-structure line of neutral carbon and of the J=3-2 rotational line of carbon monoxide in the ultraluminous infrared galaxy Arp 220, obtained at the Caltech Submillimeter Observatory. C I emission in Arp 220 is found to be at the expected level in relation to the s…
ROSAT and HIPPARCOS Observations of Isolated Pre-Main-Sequence Stars near HD 98800
Cohen, David H.; Jensen, Eric L. N.; Neuhäuser, Ralph
We present new observations of the isolated young stars HD 98800 and CD -33 deg7795. Pointed ROSAT observations show that their X-ray properties, including X-ray luminosity and variability, are consistent with those of pre-main-sequence (PMS) stars. These observations do not reveal any additional PMS candidates in 40' fields centered on HD 98800 a…
Broad Emission Line Variability as a Constraint upon the Physical Conditions within the Broad Emission Line Region of NGC 5548
Goad, Mike; Koratkar, Anuradha
Using a Gaussian fitting procedure, we have constructed an accurate UV narrow emission line template spectrum for the Seyfert 1 galaxy NGC 5548, from the low-state Hubble Space Telescope/Faint Object Spectrograph UV spectrum taken on 1982 July 5 with the 1.0" circular aperture. This template spectrum is similar in form to that determined for the p…
Hubble Space Telescope ultraviolet spectroscopy of the supersoft X-ray binaries CAL83 and RXJ0513.9-6951
Gänsicke, B. T.; Beuermann, K.; de Martino, D. +1 more
We present Hubble Space Telescope ultraviolet observations with the Goddard High Resolution Spectrograph of the supersoft X-ray binaries CAL83 and RXJ0513.9-6951 in the Large Magellanic Cloud. Both sources show a remarkably similar spectrum with an almost flat continuum and weak \N V and \O V emission lines. The neutral hydrogen column densities d…
The Si/Ne Abundance Ratio in Polar Coronal Hole and Quiet-Sun Coronal Regions
Wilhelm, K.; Schühle, U.; Lemaire, P. +4 more
Using spectra obtained from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory (SOHO) spacecraft, we determine the Si/Ne abundance ratio in diffuse, interplume polar coronal hole regions, as well as the ratio relative to quiet-Sun coronal regions. Ne has the second highest f…