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The mass, temperature and distance of the white dwarf in V471 Tauri
Barstow, M. A.; Holberg, J. B.; Cruise, A. M. +1 more
We present an analysis of far-UV observations of V471 Tauri made during the first ORFEUS mission. Combining this spectrum with archival data from IUE allows a first unambiguous measurement of the effective temperature and surface gravity of the white dwarf by matching the observed Lyman line profiles to the predictions of stellar model atmosphere …
Hubble Space Telescope Observations of the Gravitationally Lensed Cloverleaf Broad Absorption Line QSO H1413+1143: Imaging
Turnshek, David A.; Rao, Sandhya M.; Espey, Brian R. +2 more
An analysis of Hubble Space Telescope (HST) Wide Field Planetary Camera (WFPC) and Wide Field Planetary Camera 2 (WFPC2) images of the gravitationally lensed Cloverleaf broad absorption line quasi-stellar object (QSO) H1413+1143 is presented. Astrometric and photometric measurements are derived for the four components of the lensed QSO for five di…
New Experimental Data and What It Tells Us About the Sources and Acceleration of Cosmic Rays
Webber, W. R.
This paper summarizes new data in several fields of astronomy that relate to the origin and acceleration of cosmic rays in our galaxy and similar nearby galaxies. Data from radio astronomy shows that SNRs, both in our Galaxy and neighboring galaxies, appear to be the sources of most of the accelerated electrons observed in these galaxies. Gamma-ra…
Venus tail ray observation near Earth
Livi, S.; Hsieh, K. C.; Wurz, P. +23 more
In June, 1996, Venus passed through a very close inferior conjunction with the Sun. At that time the CTOF detector of the CELIAS mass spectrometer experiment on the SOHO spacecraft near Earth's L1 Lagrangian point was measuring heavy ions in the solar wind ∼4.5 × 107 km downstream of Venus. Close to the time predicted by simple geometri…
Principles of statistical astrometry
Wielen, R.
We present a coherent scheme of `statistical astrometry' for high-precision measurements. Statistical astrometry provides methods and tools for treating quantitatively the overall statistical effect of the presence of many individually unresolved or unmodelled astrometric binaries in a stellar ensemble. The non-linear motions of the photo-centers …
Soho Cds nis in-flight intensity calibration using a plasma diagnostic method
Mason, H. E.; Landini, M.; Landi, E. +1 more
The internal intensity calibration of the Coronal Diagnostic Spectrometer (CDS) - Normal Incidence Spectrometer (NIS) is studied using the Arcetri diagnostic method. A large number of spectral lines observed by the CDS-NIS 1 and NIS 2 windows in a solar active region is analysed in order to determine the intensity calibration curve for both channe…
On the evolutionary status of λ Bootis stars using HIPPARCOS data.
Paunzen, E.
We have used the Hipparcos data to derive absolute magnitudes and thus the evolutionary status for the group of λ Bootis stars. The origin for this small group of nonmagnetic, chemically peculiar stars, still remains a matter of debate. Using new evolutionary tracks, we are able to provide an age determination to distinguish between the two propos…
On the Relationship between the Periodic and Aperiodic Variability of Accreting X-Ray Pulsars
Stella, Luigi; Lazzati, Davide
Besides the narrow peaks originating from the periodic signal, the power spectra of accreting X-ray pulsars display continuum components usually increasing toward low frequencies; these arise from the source aperiodic variability. Most studies up to the present have adopted the view that the periodic and aperiodic variations are independent. Howev…
The Spectrum of the Large Magellanic Cloud Pulsar B0540-69
Boyd, Patricia T.; van Citters, G. W.; Taylor, M. J. +4 more
A prism spectrum of PSR B0540-69, the 50 ms pulsar in the Large Magellanic Cloud, was obtained with the Faint Object Spectrograph on the Hubble Space Telescope. This is only the second pulsar spectrum that has been observed in the optical. The 2500-5500 Å spectrum shows a smooth continuum with several broad emission lines. The lines are emitted by…
Ulysses observations of the northward extension of the heliospheric current sheet
Balogh, A.; Forsyth, R. J.; Smith, E. J. +1 more
After passing through the northern polar regions of the heliosphere during the summer of 1995, the Ulysses spacecraft has been gradually returning towards lower equatorial latitudes, reaching 30°N in August 1996 at about which time low speed solar wind from the streamer belt was once again observed. This paper reports on the Ulysses magnetic field…