Search Publications
The optical counterpart of the isolated neutron star RX J185635-3754
Walter, Frederick M.; Matthews, Lynn D.
The extreme densities of neutron stars make them an ideal system in which to investigate the equation of state of nuclear matter; accurate determinations of neutron star masses and radii are crucial for this. Current observations of neutron stars in binary systems yield masses that are generally consistent with theory. But measurements of radii ar…
First results of ISO-SWS observations of Saturn: detection of CO_2_, CH_3_C_2_H, C_4_H_2_ and tropospheric H_2_O.
Beintema, D. A.; Lellouch, E.; Encrenaz, T. +16 more
The spectrum of Saturn has been recorded between 4.5 and 16.0µm with the grating mode of the Short-Wavelength Spectrometer (SWS) of ISO. The resolving power is 1500. The main results of this observation are (1) the detection of CO_2_, CH_3_C_2_H and C_4_H_2_ in the stratosphere and (2) the detection of H_2_O in the troposphere. In the 4.5-5.…
High Spatial Resolution Imaging of Pre-Main-Sequence Binary Stars: Resolving the Relationship between Disks and Close Companions
Ghez, A. M.; White, Russel J.; Simon, M.
In order to study the passive and active effects of young close companion stars and to constrain possible multiple star formation mechanisms, we have carried out a high-resolution imaging program of six multiple T Tauri star systems using the Hubble Space Telescope from 0.3 to 0.9 µm and ground-based speckle imaging from 1 to 2 µm. Eac…
Determining the Hubble Constant from the Gravitational Lens PG 1115+080
Keeton, C. R.; Kochanek, C. S.
For the quadruple gravitational lens PG 1115+080, we combine recent measurements of the time delays with new lens models to determine the Hubble constant H0. We explore the effects of systematic uncertainties in the lens models on the estimates of H0, and we discuss how the uncertainties can be reduced by future observations.…
Cepheid Calibration of the Peak Brightness of Type Ia Supernovae. VIII. SN 1990N in NGC 4639
Panagia, N.; Saha, A.; Labhardt, Lukas +3 more
Repeated imaging observations have been made of NGC 4639 with the Hubble Space Telescope between 1995 April and July over an interval of 71 days. Images were obtained on 12 epochs in the F555W band and on two epochs in the F814W band. The galaxy is parent to the prototypical Type Ia supernova SN 1990N. A total of 18 definite and six likely Cepheid…
Origins of the Slow and the Ubiquitous Fast Solar Wind
Fineschi, S.; O'Neal, R.; Kohl, J. +4 more
We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5Rs, obtained during the Galileo solar conjunction in 1997 January, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scatte…
Extraplanar Dust in the Edge-On Spiral NGC 891
Savage, Blair D.; Howk, J. Christopher
We present high-resolution (0.6"-0.65") optical broad-band images of the edge-on Sb galaxy NGC 891 obtained with the WIYN 3.5-m telescope. These BVR images reveal a complex network of hundreds of dust absorbing structures far from the mid-plane of the galaxy. The dust structures have a wide range of morphologies and are clearly visible to [ζ]≤1.5 …
Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304 in 1994 May. III. Probing the Inner Jet through Multiwavelength Correlations
Shull, J. M.; Takahashi, T.; Urry, C. Megan +16 more
In 1994 May, the BL Lac object PKS 2155-304 was observed continuously for ~10 days with the International Ultraviolet Explorer and the Extreme Ultraviolet Explorer and for 2 days with ASCA, as well as with ROSAT and with ground-based radio, infrared, and optical telescopes. The light curves show a well-defined X-ray flare followed by a broader, lo…
EUVE J0317-855: a rapidly rotating, high-field magnetic white dwarf
Christian, D. J.; Wickramasinghe, D. T.; Vennes, S. +2 more
Spectropolarimetric observations of the extreme-ultraviolet (EUV) source and high-field magnetic white dwarf EUVE J0317-855 (=RE J0317-853) in the wavelength range 4200-7200 A reveal a strongly structured circular polarization spectrum with a peak polarization of 8 per cent. The strongest features in the polarization spectrum are attributed to Hα …
Coordinated ultraviolet and Hα spectroscopy of bright O-type stars.
Kaper, L.; Kambe, E.; Fullerton, A. W. +7 more
As part of our search for the origin of stellar-wind variability, we have conducted simultaneous ultraviolet and Hα spectroscopy of a number of bright O stars. The observed changes in the Hα line occur at low velocity (0-0.2vinfinity_) on timescales that are characteristic of the development and evolution of discrete absorption componen…