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The atmospheric composition, extinction and luminosity of the LBV star R71
Stahl, O.; Lennon, D. J.; Kudritzki, R. -P. +1 more
ESO 3.6m Caspec spectra of the LMC luminous blue variable (LBV) taken at minimum have been analysed using NLTE model atmospheres and line formation calculations to derive atmospheric parameters and chemical composition. Using the silicon ionization balance and the hydrogen Balmer lines we deriveT eff =17250, log g=1.80 and a microturbu…
Doppler tomography of O-type binaries: The physical properties of seven systems
Gies, D. R.; Penny, L. R.; Bagnuolo, W. G.
We have analyzed UV photospheric lines of seven O-type binaries, by means of crosscorrelation and Doppler tomographic methods, with the goal of estimating the physical properties of the individual stars. These systems are HD 1337 (AO Cas), HD 47129 (Plaskett's star), HD 57060 (29 UW CMa), HD 37043 (Iota Ori), HD 215835 (DH Cep), HD 152218, and HD …
Hubble Space Telescope spectroscopy of massive hot stars in the Magellanic Clouds and M31
Lennon, D. J.; Bianchi, L.; Puls, J. +4 more
Using the Hubble Space Telescope (HST) and the Faint Object Spectrograph (FOS) high signal to noise spectrograms were obtained for 15 OB stars in the Magellanic Clouds***, three of which are of spectral type O3. The data cover the spectral region from 1150 A 2300 A with a resolution of Δλ/λ≈1 A. One O8.5 supergiant, OB78#231, in M31
The COS-B X-ray observations of X-ray binaries.
van der Klis, M.
The observational information on X-ray binaries that was collected with the 80 sq cm auxiliary X-ray detector onboard the COS-B gamma-ray satellite is reviewed. The results illustrate that in the study of X-ray binaries observations of long duration are extremely effective, even when using a small instrument.
Massive star distribution in external galaxies and starburst regions
Conti, Peter S.
Counts of hot and luminous stars in a number of associations in the Galaxy and Magellanic Clouds enable one to directly investigate the numbers and types of massive stars. There seems to be little, if any, dependence of the slope of the Intial Mass Function, or theM upper on the initial composition of the stars. Indirect estimates of n…
Line blanketing by iron group elements in non-LTE model atmospheres of hot stars
Dreizler, Stefan; Werner, Klaus
We report on our recent progress in modeling non-LTE atmospheres of O-stars including blanketing by lines from the iron group elements. The numerical method to account for the huge number of atomic levels and line transitions is presented. Results of exploratory model calculations examining the effects on the temperature structure, the hydrogen an…
Stellar winds of massive stars in M31
Hutchings, John; Bianchi, Luciana
We have obtained the first UV high resolution spectra of hot luminous stars in M31 with the FOS onHubble Space Telescope. The spectra, combined with optical spectroscopic and photometric observations, enable us to study their stellar winds and photospheric parameters. We derive mass-loss rates and velocity laws from the wind line profiles, with th…
The population of massive stars in R136 from HST/FOC UV observations
Leitherer, Claus; Nota, Antonella; de Marchi, Guido +2 more
New ultraviolet (λ≃1300 A, λ≃3400 A),HST FOC observations have been used to derive the UV color-magnitude diagram (CMD) of R136, with the main scientific goal of studying the upper end of the stellar mass function at ultraviolet wavelengths where the color degeneracy encountered in visual CMDs is less severe. The CMD has been compared to a set of …