Ultraviolet observations of cool stars. V. The local density of interstellar matter.
Abstract
A high-resolution Copernicus observation of the chromospheric Ly-alpha emission line of the nearby (3.3 pc) K dwarf epsilon Eri sets limits on the velocity, the velocity dispersion, and the density of atomic hydrogen in the local interstellar medium. Analysis shows that the interstellar Ly-alpha absorption is on the flat portion of the curve of growth. An upper limit of 0.12 per cu cm is derived for the atomic-hydrogen density. The value of this density is 0.08 (plus or minus 0.04 per cu cm if the velocity-dispersion parameter is 9 km/s, corresponding to a temperature of 5000 K. Also, the interstellar deuterium Ly-alpha line may be present in the spectrum.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1976
- DOI:
- 10.1086/182064
- Bibcode:
- 1976ApJ...204L.103M
- Keywords:
-
- Cool Stars;
- Dwarf Stars;
- Interstellar Gas;
- Late Stars;
- Stellar Spectra;
- Ultraviolet Spectroscopy;
- Doppler Effect;
- Gas Density;
- Hydrogen Atoms;
- K Stars;
- Line Spectra;
- Lyman Alpha Radiation;
- Oao 3;
- Signal To Noise Ratios;
- Spectrum Analysis;
- Astrophysics