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Photometric and UV spectroscopic observations of 22 VUL at eclipse : observational evidence for an extended chromosphere of a solar type G supergiant.
Che-Bohnenstengel, A.; Schroeder, K. -P.
The solar spectral type supergiant (G3 Ib-II) of the 22 Vul binary has been observed photometrically and spectroscopically during its recent eclipse of the B9 V companion. From the new photometric observations the eclipse data given by Parsons and Ake (1984) can be slightly improved (period = 249.21 ± 0.2 days, mideclipse: JD 2446191.6 ± 0.2). The…
The ultraviolet absorption spectrum of NGC 4151.
Tarenghi, M.; Veron, P.; Veron-Cetty, M. P.
The analysis of all available low dispersion, short wavelength, large aperture IUE spectra of NGC 4151 taken prior to March 1982 shows a linear correlation between the depth of the absorption lines and the strength of the underlying emission; the absorption lines vanish while the continuum is still measurable. This is interpreted as being due to a…
Properties of dust in the Orion nebula.
Patriarchi, P.; Perinotto, M.
New observations of the Orion nebula very close to the Trapezium stars have been taken with the IUE satellite in order to improve knowledge of the dust properties in the nebula. The new data have been interpreted together with previous observations using multiscattering models with various distributions of the dust-to-gas ratio. The main result is…
An interpretation of the spectral variations of theta Coronae Borealis.
Underhill, A. B.
Measurements are presented of the strengths and displacements of sharp absorption components of the resonance lines of Si IV, C IV, and Al III in the spectrum of θ CrB. No evidence is found for mass loss at a detectable rate. A qualitative model of a Be star is developed. It is suggested that the spectral variations of θ CrB are the result of chan…
The outer layers of the beta Cephei stars BW VUL and sigma Sco.
Blomme, R.; Hensberge, H.
Mass loss rates for the Beta Cephei stars BW Vul and Sigma Sco have been derived from the C IV and Si IV resonance lines, which are formed in the outflowing layers. Assuming an ionization fraction log q(C IV) = -1.9, mass losses of 1.4 and 1.9 x 10 to the -9th solar mass/yr are predicted for BW Vul and Sigma Sco, respectively. In the case of BW Vu…
M 62 : an RR Lyrae-rich, UV-bright galactic globular cluster.
Tarenghi, M.; Caloi, V.; Castellani, V.
The central region of the globular cluster M62 was observed with IUE. The authors confirm that, in the UV, M62 is the brightest cluster observed up to now in the galaxy. This RR Lyrae-rich system is another example of an UV-bright cluster with a horizontal branch not confined to the blue. The interpretation of UV excesses from spiral nuclei and el…
IUE data analysis : radial velocities from line coincidence statistics.
Bord, D. J.; Davidson, J. P.
The authors have employed the method of wavelength coincidence statistics (WCS) to determine radial velocities from International Ultraviolet Explorer (IUE) satellite data for several chemically peculiar stars. By repeatedly carrying out the entire WCS procedure with a sequence of radial velocities, the authors demonstrate that significance-weight…
The typical interstellar extinction in the Small Magellanic Cloud.
Lequeux, J.; Prevot, L.; Rocca-Volmerange, B. +2 more
The authors give a mean UV extinction curve for the Small Magellanic Cloud which corresponds to the most common case and consequently to the most probable typical extinction law. The curve is almost linear in λ-1 without any evidence of the 2200 Å galactic feature. This is consistent with almost pure silicate interstellar grains and lit…
The nature of magnetic activity in lower main sequence stars.
Vilhu, O.
The chromospheric-coronal emission of lower main sequence single and binary stars is correlated with an activity parameter of the form R = g(B-V)P-1, where P is the rotation period and g(B-V) is a function of the colour resembling the convective turnover time. A more general form of R, including also gravity, is suggested. The functiona…
The atmosphere of sublumious B stars.
Heber, U.; Kudritzki, R. P.; Hunger, K. +1 more
The spectra of eight high galactic latitude B stars, suspected to be subluminous, are analyzed for effective temperature, gravity, and helium to hydrogen ratio. Model atmospheres include (LTE) UV line blanketing (for T/eff/ less than or equal to 30,000 K) and NLTE effects (for T/eff/ greater than 30,000 K). Among the eight confirmed subdwarfs, six…