22 citations · 70 across the 13 of their papers we have counts for
13 papers
Effects of correlated turbulent velocity fields on the formation of maser lines
R. Boeger, W. H. Kegel, M. Hegmann
The microturbulent approximation of turbulent motions is widely used in radiative transfer calculations. Mainly motivated by its simple computational application it is probably in…
Argon and Silicon abundances in the damped Ly-alpha system I Zw 18
S. A. Levshakov, W. H. Kegel, I. I. Agafonova
We show that the difference between the Ar and Si relative abundance ratio derived from FUSE absorption spectra and from the HII regions of I Zw 18 is a consequence of the microtur…
Monte Carlo inversion of hydrogen and metal lines from QSO absorption spectra
Sergei A. Levshakov, Irina I. Agafonova, Wilhelm H. Kegel
A new method, based on the simulated annealing algorithm and aimed at the inverse problem in the analysis of intergalactic (interstellar) complex spectra of hydrogen and metal line…
On the deuterium abundance at z_a = 3.514 towards APM 08279+5255
S. A. Levshakov, I. I. Agafonova, W. H. Kegel
A very low primordial deuterium abundance of D/H = 1.5 10^{-5} has recently been proposed by Molaro et al. in the Lyman limit system with log(N_HI) = 18.1 cm^{-2} at z_a = 3.514 to…
The D/H ratio at z = 3.57 toward Q 1937-1009
Sergei A. Levshakov, Wilhelm H. Kegel, Fumio Takahara
Deuterium abundance re-measurements by Burles and Tytler (1998; hereafter BT) yielded D/H = (3.3 +/- 0.3) 10^{-5} and the robust upper limit D/H < 3.9 10^{-5} from the z_a = 3.572…
The D/H ratio at z=0.7 toward Q 1718+4807
Sergei A. Levshakov, Wilhelm H. Kegel, Fumio Takahara
The apparent discrepancy between low and high D abundances derived from QSO spectra may be caused by spatial correlations in the stochastic velocity field. If one accounts for such…