Spectralphotometry and quantitative analysis of the hydrogen-deficient stars HD 144941 and CPD -69 2698.
Summary. Wavelengths and equivalent widths are given for absorption lines in the spectra of the hydrogendeficient stars HD 144941 and CPD6902698. The coude-spectrograms are taken with the ESO 152 cm telescope at La Silla. The dispersion is 20 A/mm (HD 144941) and 12.4 A/mm (CPD6902698). Fine analyses have been performed by using a grid of flux constant hydrogen-line blanketed models with varying Teff, logg and e (number fraction of H). The models are adapted to match the following criteria; H-profiles, He i-equivalent widths, the ionization equilibria of Si il/Si ill and Si iv, and also the turbulent velocity. The following models result: HD 144941: Teff=215000K, logg=3.5, =0.062, CPD-6902698: Teff=29000 0K, logg = 4.1, The abundance analysis yields the surprising result that in HD 144941, C and N is underabundant by a factor > 10 with respect to normal B-stars (and drastically underabundant with respect to the Helium-Carbon star BD + 1002179). In CPD-6902698, the metal abundances are approximately normal, except for S which is under- abundant by a factor of 10. The mass of HD 144941 is small (m =2.0 m0.) and the radius comparatively large (R =4.2 R0) which is typical for the extreme subclass of hydrogen-deficient stars. For CPD-6902698 m =4.5 m0 and R =3.1 R0 result, which are both too small for the luminosity (logL/L0 =3.8). Key words: stellar atmospheres - helium stars - spectroscopy - abundances H=0.70, Vt=8km/S
Astronomy and Astrophysics
- Pub Date:
- June 1973