Search Publications
28. Tycho transit detection.
Wagner, K.; Hog, E.; Wicenec, A. +3 more
By means of some extracted parts of the raw countrates of the Tycho photomultipliers the method of detecting signals of stars and estimating their amplitudes and transit positions is described. The elimination of disturbances due to spikes with the help of sophisticated folding and background determination methods is presented.
Expected accuracy of the 1900-1990 earth orientation parameters in the HIPPARCOS reference frame
Vondrak, Jan; Feissel, Martine; Essaifi, Najat
Based on the space and time distribution of observations available over 1900-1990 for estimating the motion of the earth rotation axis in space and relative to the earth's crust, and universal time, we evaluate the accuracy of the earth orientation parameters in the framework of their global analysis in the Hipparcos reference frame currently unde…
The coronal-sounding experiment
Bird, M. K.; Asmar, S. W.; Volland, H. +3 more
The main science objective of the Ulysses Solar Corona Experiment is to derive the plasma parameters of the solar atmosphere using established coronal-sounding techniques. Applying appropriate model assumptions, the 3D electron density distribution will be determined from dual-frequency ranging and Doppler measurements recorded at the NASA Deep Sp…
Photospheric velocity gradients in B1 supergiants.
Massa, D.; Shore, S. N.; Wynne, D.
We present IUE spectra for a set of B1 supergiants. These data clearly demonstrate that the Si III 1300A multiplet (lower level 6.6 ev above ground) becomes progressively more asymmetric with increasing luminosity or, equivalently, mass loss. In the most luminous supergiants, the cores of the 1300A multiplets become displaced by up to -150 km/s re…
The Sun as a Star: High Spectral Resolution Solar Data Degraded to Low-Dispersion IUE Resolution
Doyle, J. G.; Cook, J. W.
High spectral resolution (about 0.06 A) solar data for an active region and a large two-ribbon flare degraded to the typical resolution of low-dispersion (about 5 A) spectra of the IUE satellite are presented. This clearly shows the amount of detail yet to be acquired in stellar spectra and indicates the main spectral regions where line blending i…
Faint Object Spectrograph Observations of the Large-Redshift Gravitational Lens Candidate 1208+1011
Maoz, Dan; Schneider, Donald P.; Jannuzi, Buell T. +2 more
We report HST spectroscopic observations of the z = 3.8 gravitational lens candidate 1208+1011. Low-dispersion (R = 200) Faint Object Spectrograph data, covering the wavelength range 3700-7800 A, were obtained for each of the two components (V ~18.3 and 19.8 mag) and for a comparison (blank) field; the fainter component and the blank field are bot…
X-Ray Observations of Planetary Nebulae with Binary Nuclei
Nousek, J. A.; Apparao, K. M. V.; Berthiaume, G. D.
Einstein and EXOSAT satellite observations of X-ray emission from the planetary nebulae A63 and LoTr 5 are reviewed. Both of these systems contain binary central stars. No flux was detected from A63 (central star UU Sge). LoTr 5 (central star IN Com) is a previously unreported X-ray emitter; it showed no statistically significant X-ray variability…
Double star CCD astrometry and photometry
Irwin, M. J.; Argue, A. N.; Bunclark, P. S. +3 more
Results are presented for angular separation, position angle and V and R photometry for 2373 binary stars, obtained with the CCD camera on the 1-m Jacobus Kapteyn Telescope at La Palma. The stars are part of the Input Catalogue of the Hipparcos Astrometric Satellite launched in 1989 August, and the purpose of our measurements is to assist in the s…
Energy structure of the accretion disc corona in X 1822-371.
Hellier, Coel; Mason, Keith O.; Williams, O. R.
Ginga observations of the LMXB X 1822-371 show that the broad orbital modulation and the eclipse are deeper at higher energies. This is explained if the X-ray emitting corona produces softer emission at greater heights from the disc plane, which suggests that either the corona is optically thick, or that the illuminating X-rays are anisotropic. Fu…
Highly Ionized Gas in the GUM Nebula and Elsewhere: A Comparison of IUE and Copernicus Satellite Results
Savage, Blair D.; Edgar, Richard J.
The data from six high-dispersion IUE echelle spectra are averaged in order to obtain an interstellar absorption line spectrum with an S/N of about 30 and a resolution of about 25 km/s. The interstellar lines of C IV and Si IV are very strong and broad and N V is detected. The profiles for these species and Al III are compared to the Copernicus sa…