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Large photometric variations on II Peg in Sept/Nov 1986 : implications for the starspot hypothesis.
Doyle, J. G.; Butler, C. J.; Morrison, L. V. +1 more
Large cyclic photometric variations of ΔV= 0.5 mag are observed on II Peg in late 1986. Modelled in terms of starspots, this implies a large spot group covering at least 40% (and perhaps as much as 55%) of the projected area of one hemisphere.
A correction method for the sensitivity loss of the LWR camera on board the IUE satellite.
Clavel, J.; Gilmozzi, R.; Prieto, A.
The loss of sensitivity of the IUE LWR camera (1950-3300 A) is analyzed. A total of 308 low-resolution spectra of the five UV standard stars BD + 75 325, BD + 28 4211, BD + 33 2642, HD 93521, and HD 60753, obtained from 1978 to October 1983, are compared. The loss of sensitivity is found to vary rapidly with wavelength, reaching a maximum of 3 per…
Coordinated X-ray and optical observations of the pulsating X-ray transient A 1118-61.
Motch, C.; Janot-Pacheco, E.; Pakull, M. W. +1 more
An EXOSAT observation of the field of the X-ray transient A 1118-61 reveals the presence of a weak hard X-ray source in the detectors of the medium energy experiment (ME). The detection by the Einstein IPC instrument of a similar hard X-ray source at a position consistent with that of the Be star He3-640, the proposed optical counterpart of A 1118…
Singly ionized iron as a diagnostic of stellar envelopes. II The structure of the envelopes of six luminous blue stars.
Friedjung, M.; Muratorio, G.
The methods described in Friedjung and Muratorio (1987), involving the self-absorption curve for the Fe II optical emission lines and spectral synthesis for the UV, are applied to study the surroundings of the galactic P Cygni star AG Car and of five luminous Magellanic Cloud stars. Their Fe II emission and absorption spectra are interpreted by li…
Time-dependent heating phenomena in coronal loops.
Barstow, M. A.; van den Oord, G. H. J.
The authors have investigated the behaviour of coronal loops subject to flare-like heating. They pay attention to the conflicting results obtained by Kuin and Martens (1982) and Craig and Schulkes (1985). They show that the description of Kuin and Martens is correct and extend it for a larger range of loop temperatures. Further, they show that the…
Carbon abundance in beta Persei and lambda Tauri.
Cugier, H.; Hardorp, J.
A carbon abundance analysis of two Algol-type stars is performed using IUE archival data released for general use. The primaries of Beta Per and Lambda Tau show carbon abundances equal to log N(C/H) = -3.87 + or - 0.20 and 3.88 + or - 0.20, respectively. The results should be compared with the cosmic value of -3.48 given by Allen (1973). A C-defic…
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…