Search Publications
A differential analysis of UV photospheric lines of OBN and OBC stars.
Lamers, H. J. G. L. M.; de Jager, C.; Wollaert, J. P. M.
The paper presents measurements of the equivalent widths of several photospheric C, N, O, He, Si and Fe lines in the ultra-violet spectra of 55 OBN, OBC and normal supergiants and main-sequence stars. Seventy-two short-wavelength, high-resolution spectrograms obtained with IUE were used. The differences in equivalent widths of OBN and OBC stars re…
High resolution cluster method for topological studies of the light curves of gamma-ray pulsars.
Buccheri, R.; Sacco, B.; di Gesu, V. +1 more
The authors describe a non-parametric, binning-free, adaptive method for the detection and the analysis of structures in the light curves of gamma-ray pulsars, based on a clustering technique. They use computer simulated data and a sample of COS-B data relative to the Vela pulsar to show its behavior and robustness. As a main result they find that…
The Spacelab-1 very wide field survey of UV-excess objects. I. CPD -71 172 AB, a new binary with a hot subdwarf.
Burgarella, D.; Cassatella, A.; Prevot, L. +1 more
The images taken with the Very Wide Field Camera aboard Spacelab-1 have revealed a variety of stellar objects with strong UV excess. UV(IUE) and ground-based observations of the first object identified (CPD -71°172) have demonstrated a binary system comprising a cool, moderately-evolved star (F3-F4 IV), and a hot OB subdwarf with Teff ≈…
Ultraviolet emission lines and optical photometry of the flare star AT Microscopii.
Linsky, J. L.; Marang, F.; Ayres, T. R. +8 more
Ultraviolet spectra of the dwarf flare star binary AT Mic (dM 4.5e+dM 4.5e) were obtained with the IUE spacecraft on three days in September 1985. A high-resolution short-wavelength spectrum was exposed for 25 hours. Simultaneous optical monitoring in the U-band was performed during part of the IUE observations. At the time of observation AT Mic w…
The unusual carbon star HD 59643 : alternative models.
Querci, M.; Johnson, H. R.; Eaton, J. A. +2 more
The authors discuss a binary model for the star in which the secondary spectrum is formed in an accretion disk. If this hot, ultraviolet-emitting disk radiates like a 20,000K black-body, it must be ≤0.03 R_sun; across at minimum emission. Large widths of C IV multiplet UV1 on high-resolution spectra indicate its formation in the inner parts of a d…
The vanishing shell phase of PLEIONE in the far UV in 1988.
Doazan, V.; Thomas, R. N.; Bourdonneau, B.
Far UV observations made with the IUE in 1988, when the shell spectrum of Pleione was vanishing in the visible region, are compared with previous IUE observations made when the shell was strong (1979) and when it began to weaken (1985). Between the epochs of strong shell and vanishing shell: (1) the apparent continuum level increases in all the ob…
Are tides responsible for enhanced MG II emission in late-type binaries ?
Glebocki, R.; Stawikowski, A.
Mg II h and k fluxes are measured for a homogeneous sample of 30 G III and K III binaries. The spectra have been obtained from the IUE archive and calibrated in absolute units (erg cm-2s-1). Contrary to the generally accepted view that the rate of rotation is responsible for the enhanced chromospheric activity, the Mg II h an…
Analysis of C II resonance lines in some main sequence early-type stars.
Cugier, H.; Hardorp, J.
An analysis of C II resonance lines at 1335 Å in eight main-sequence stars of spectral types A0 to B3 is performed using IUE archival data released for general use. In order to interpret the observed spectra, both LTE and non-LTE line profiles were computed. In stars with low rotational velocities (Vega, π Cet, τ Her and ι Her) the authors obtaine…
A sudy of the continuum flux and the line structure in the IUE spectrum of beta Lyrae.
Sahade, J.; Hack, M.; Engin, S. +5 more
A study of the available archival IUE images of Beta Lyrae has led to the following results: (1) for lambda in the range of 1250 - 1500 A, the eclipse depth at second conjunction is slightly larger than the eclipse depth at primary conjunction; they are equal at about 1670 A; (2) the profiles of the resonance lines of SiIV (and the same seems to b…
Electron densities in late-type stars.
Dufton, P. L.; Lennon, D. J.; Byrne, P. B. +2 more
Recently published atomic calculations for the C II UV 0.01 intersystem multiplet at 2325 Å are combined with dearchived IUE data on a number of late-type giants and supergiants to derive the electron densities in these stars' upper chromospheres/lower transition regions. The results represent a substantial change from previously derived values. T…