Search Publications
High-energy gamma rays as a probe of cosmic-ray spectral differences throughout the Galaxy. II - A comparison with radio synchrotron emission
Schlickeiser, R.; Bloemen, J. B. G. M.; Reich, W. +1 more
A spectral analysis of the galactic high-energy γ-ray emission (300 MeV-6 GeV) is presented using the observations obtained with the COS-B satellite. Large-scale spectral variations are found and compared with recent results from a study of the galatic radio-continuum emission at 408 and 1420 MHz. The combination of the radio and γ-ray findings es…
Variable C : an S Doradus-type variable in M 33.
Stahl, O.; Humphreys, R. M.; Leitherer, C. +2 more
Variable C is one of the Hubble-Sandage variables in M 33. Our photometric and spectroscopic observations obtained during one of its rare maxima show that Variable C's variations are typical of luminous blue variables especially those of the S Doradus type. Its spectrum at maximum light suggests a temperature of 7500 K for its expanding optically …
AG Carinae. II. IUE observations of the ring nebula.
The, P. S.; Viotti, R.; Cassatella, A. +1 more
The authors describe the first ultraviolet observations of the ring nebula surrounding the P Cyg superluminous star AG Car. The spectrum of the nebula resembles that of the central star with strong Fe II and Mg II emission lines. The nebular/stellar continuum ratio is nearly constant from 2000 to 3200 Å. This result and the derived surface brightn…
EXOSAT observations of M dwarf stars in the solar neighborhood.
Schmitt, J. H. M. M.; Rosso, C.
The authors present EXOSAT observations of a sample of nearby (d < 6 pc) M dwarf stars most of which have not previously been observed in X-rays. All the target stars were detected except one (Gl 754, spectral type M7). The X-ray luminosities derived are in the typical range of M dwarf X-ray luminosities derived from Einstein Observatory data, …
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…