Search Publications
The Abundance of Interstellar Krypton
Meyer, David M.; Cardelli, Jason A.
We present high signal-to-noise ratio HST Goddard High Resolution Spectrograph (GHRS) observations of the weak interstellar Kr I λ1236 absorption toward the stars τ CMa, κ Ori, ɛ Ori, λ Ori, δ Sco, ω1 Sco, ɛ Per, and ζ Per. In combination with previous GHRS measurements of Kr I in two other sight lines (ζ Oph and 1 Sco), these new obser…
Doppler Shifts and Nonthermal Broadening in the Quiet Solar Transition Region: O VI
Wilhelm, K.; Lemaire, P.; Mariska, J. T. +1 more
Using observations from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) experiment flown on the Solar and Heliospheric Observatory (SOHO) spacecraft, we have measured Doppler wavelength shifts and nonthermal broadening in the 1032 and 1038 Å emission lines of O VI and the 1036 and 1037 Å emission lines of C II. Near Sun center the …
New Wavelength Determinations of Mid-Infrared Fine-structure Lines by Infrared Space Observatory Short Wavelength Spectrometer
Lutz, D.; Heras, A. M.; Beintema, D. A. +18 more
We report accurate new wavelengths for 29 mid-infrared ionic fine-structure lines, based on observations with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Our results originate from observations of NGC 7027, NGC 6543, NGC 6302, the Circinus galaxy, Sgr A West, and W51 IRS 2. The obtained accuracies (λ/Δλ) …
High-Resolution Ultraviolet Observations of the Highly Ionized Interstellar Gas toward Radio Loops I and IV
Tripp, Todd M.; Sembach, Kenneth R.; Savage, Blair D.
We present new Goddard High-Resolution Spectrograph (GHRS) echelle observations of the high ionization lines of Si IV, C IV, and N V toward HD 119608, a halo star at d = 4.1 kpc behind the Loop I and IV supernova remnants. Absorption along the path to HD 119608 makes it possible to study energetic processes that may result in the flow of gas into …
A starburst origin of the OH-megamaser emission from the galaxy Arp220
Sturm, E.; Barlow, M. J.; Stacey, G. J. +3 more
Ultraluminous infrared galaxies have been known for more than a decade, but the source of their very large far-infrared luminosities remains controversial. It may reflect a quasar-like active nucleus surrounded by a torus of dense gas and dust, the latter absorbing the energetic photons from the nuclear region and re-emitting at infrared wavelengt…
The CO2/CO Abundance Ratio in 1P/Halley and Several Other Comets Observed by IUE and HST
Weaver, Harold A.; Feldman, Paul D.; Tozzi, Paolo +1 more
We report the detection of CO Cameron band emission in the ultraviolet spectra of four moderately active comets (including 1P/Halley) obtained by the International Ultraviolet Explorer (IUE) satellite. The motivation was the observation of Cameron band emission, a tracer of the CO2 production rate, in the spectra of two comets observed …
The Hipparcos distance determination of the Wolf-Rayet system γ2 Velorum (WC8+O) and its ramifications
van der Hucht, K. A.; Moffat, A. F. J.; van den Heuvel, E. P. J. +9 more
Hipparcos parallax measurements give a distance to the Wolf-Rayet WC8+O spectroscopic binary γ2 Vel of d = 258 -31+41 pc and a distance to the O4I(n)f star ξ Pup of d = 429 -77+120pc. Adopting for γ2 Vel an interstellar extinction of Aν = 0.06 mag, this implies an absolut…
GX17+2: X-ray spectral and timing behaviour of a bursting Z source
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +2 more
We have investigated the properties of the Z pattern of the low-mass X-ray binary GX17+2 in the X-ray colour-colour diagrams (CDs) and hardness-intensity diagrams (HIDs), and of the power spectra as a function of position in the Z. We used all EXOSAT ME data on GX17+2, a total of six observations during 1983-86. We find that the Z pattern in the C…
Thermal Emission From The Dust Coma Of Comet Hale-Bopp And The Composition Of The Silicate Grains
Hayward, T. L.; Gehrz, R. D.; Hanner, M. S. +7 more
The dust coma of comet Hale-Bopp was observed in the thermal infrared over a wide range in solar heating (R = 4.9–0.9 AU) and over the full wavelength range from 3 µm to 160 µm. Unusual early activity produced an extensive coma containing small warm refractory grains; already at 4.9 AU, the 10 µm silicate emission feature was str…
Hipparcos, VLA, and CCD Observations of Cygnus OB2 No. 5: Solving the Mysteryof the Radio ``Companion''
Badiali, M.; Cardini, D.; Emanuele, A. +4 more
We present accurate optical and radio astrometry for the unresolved contact binary system Cyg OB2 No. 5 and its weaker component to the northeast. While the radio and optical positions of the primary component (taken to be the unresolved contact binary) agree within observational error (~70 mas), we find that the weaker radio component does not ag…