Search Publications
The mass distribution of CL0939+4713 obtained from a `weak' lensing analysis of a WFPC2 image.
Kneib, J. -P.; Schneider, P.; Seitz, S. +1 more
The image distortions of high-redshift galaxies caused by gravitational light deflection of foreground clusters of galaxies can be used to reconstruct the two-dimensional surface mass density of these clusters. We apply an unbiased parameter-free reconstruction technique to the cluster CL0939+4713 (Abell 851), observed with the WFPC2 on board of t…
The ISO LWS grating spectrum of NGC 7027.
Walker, H. J.; Omont, A.; Ade, P. A. R. +39 more
We present a high signal-to-noise ISO Long Wavelength Spectrometer (LWS) grating spectrum of the planetary nebula NGC 7027 from 43-194µm. In total 40 emission lines have been detected, with 30 identified. From the ionized region, we observe fine-structure lines from [N II], [N III] and [O III]. The [O I] and [C II] fine-structure lines from …
Highly Ionized Interstellar Atoms--Heated, Cooled, or Mixed?
Spitzer, Lyman, Jr.
Recent observations with the Goddard High Resolution Spectrograph on the Hubble Space Telescope, combined with Copernicus results, make possible a comparison between C+3 and O+5 interstellar column densities in both the halo and the disk of our Galaxy. The ratio N(C+3)/N(O+5) for six lines of sight in the disk is about an order of magnitude less t…
Detection of hot, abundant water toward AFGL 2591.
Heras, A. M.; Beintema, D. A.; de Graauw, T. +6 more
We present the first detection of absorption lines within the bending vibration of water in the interstellar medium using the ISO-SWS. More than 30 lines between 5.5 and 6.6µm are detected toward the bright infrared source GL 2591, which arise most likely in the dense molecular cloud core surrounding the young stellar object. Comparison with…
Interplanetary discontinuities and Alfvén waves at high heliographic latitudes: Ulysses
Balogh, A.; Goldstein, B. E.; Neugebauer, M. +5 more
This paper presents the results of the first statistical study of interplanetary directional discontinuities at both low and high heliographic latitudes measured by the Ulysses magnetometer. There is a gradual decrease in the rate of occurrence of interplanetary discontinuities (ROIDs) with increasing radial distance. From 1 to 5 AU, an e-(r-…
A Self-consistent Optical, Ultraviolet, and Extreme-Ultraviolet Model for the Spectrum of the Hot White Dwarf G191-B2B
Barstow, M. A.; Holberg, J. B.; Lanz, T. +1 more
The star G191-B2B is one of a number of hot DA white dwarfs whose atmospheres have been found to contain significant quantities of heavy elements, including C, N, 0, Si, Fe, and Ni. Several earlier studies have measured their abundances using IUE echelle data in conjunction with synthetic spectra derived from theoretical model atmosphere calculati…
AR Ursae Majoris: The First High-Field Magnetic Cataclysmic Variable
Gänsicke, B. T.; de Martino, D.; Szkody, Paula +5 more
We identify the luminous soft X-ray source AR UMa as a magnetic cataclysmic variable containing a white dwarf with the highest field yet detected in an accreting binary. lUE and optical spectroscopy, optical photometry, and circular polarimetry and spectropolarimetry define remarkably distinct accretion states of this binary. Circular polarization…
The wavelength calibration and resolution of the SWS.
Lutz, D.; Heras, A. M.; Beintema, D. A. +21 more
The laboratory wavelength calibration of the SWS has been succesfully transferred to the in orbit situation. The achieved accuracies for the grating sections are λ/δλ~10000. Any remaining errors in the wavelength scale are dominated by uncertainties of the relative position of the target in the 14"-20" wide slits. The grating spectral profile is v…
Periodic UV modulation of X1850-087: a double degenerate binary in the globular cluster NGC 6712?
van Paradijs, J.; Charles, P. A.; Naylor, T. +3 more
We report the discovery with the Hubble Space Telescope (HST) of a short-period (20.6 min) UV modulation in X1850-087, the luminous X-ray source in the globular cluster NGC 6712. The low-amplitude modulation (0.044+/-0.007 mag) is not detected in archival X-ray observations with EXOSAT. We compare the properties of X1850-087 with the 11-min binary…
Solar cycle variation in the heliosphere
Gazis, P. R.
Variations in interplanetary plasma and magnetic field parameters over the course of a solar cycle affect a broad range of physical phenomena, such as planetary magnetospheres, cosmic ray modulation, and the interaction of the solar wind with the local interstellar medium. For more than 3 decades a succession of spacecraft have provided in situ me…