On absorption by hot interstellar gas. I. lambda 6375.
Abstract
The spectra of 32 stars have been observed in the region of the coronal forbidden Fe X 6375 line at detection limits near an equivalent width of 1 mA in the best cases. No absorption which can be attributed to Fe X ions in hot interstellar gas is seen in any of these spectra except one, in general agreement with predictions based on a three-phase model of the interstellar medium. Toward Cephei an absorption line is measured with an equivalent width of 8.1 + or - 2 mA, a width corresponding to 20 + or - 5 km/s or a temperature not greater than about (0.5 + or - 0.25) x 10 to the 6th K, and, if it is caused by Fe X ions, a radial velocity of -355 km/s. On that hypothesis, the hot interstellar gas constitutes at least 30 percent of the column density of gas along this light path. Six new telluric lines also are detected, and the 6376, 6379 A diffuse interstellar bands are observed toward all six appreciably reddened stars and one high-latitude star.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1984
- DOI:
- 10.1086/161976
- Bibcode:
- 1984ApJ...280..132H
- Keywords:
-
- Absorption Spectra;
- Astronomical Spectroscopy;
- Forbidden Transitions;
- High Temperature Gases;
- Interstellar Gas;
- Stellar Spectra;
- Interstellar Radiation;
- Iron;
- Spectral Line Width;
- Telluric Lines;
- Astrophysics