Fine analysis of Popper's star HD 124448.
Abstract
Wavelengths and equivalent widths are given for absorption lines in the spectrum of the extremely hydrogen-deficient star HD 124448. The coude-spectrograms have been taken with the ESO 152-cm telescope at La Silla. The dispersion is 20 A/mm. A fine analysis has been performed by using a grid of constant flux continuum model atmospheres with varying effective temperature (Teff), log g, and helium (nHe), carbon (nC), and nitrogen (nN) abundances (number fractions). With these models the following quantities are computed: the equivalent widths and profiles of He I and C II lines, the ionization equilibria of Al II/Al III, Si II/Si III, S II/S III, and the turbulent velocity. The model which represents the observations best has Teff equal to 16,000 K, log g equal to 2.2, nHe equal to 0.99, nC equal to 0.008, nN equal to 0.002, and turbulent velocity equal to 10 km/s. The upper limit of the hydrogen abundance is about 0.0001. Besides carbon and nitrogen, magnesium is overabundant. Oxygen is underabundant. The star's mass is estimated to be equal to that of the sun, its radius is 13 times that of the sun, and its luminosity is 10,000 times that of the sun.-
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 1974
- Bibcode:
- 1974A&A....37...87S
- Keywords:
-
- Absorption Spectra;
- Abundance;
- Fine Structure;
- Line Spectra;
- Stellar Atmospheres;
- Stellar Spectra;
- Astronomical Spectroscopy;
- Atmospheric Models;
- H Lines;
- Hydrogen;
- Spectral Line Width;
- Stellar Evolution;
- Tables (Data);
- Astrophysics