THE INTERSTELLAR DEUTERIUM-TO-HYDROGEN RATIO - A REEVALUATION OF LYMAN ABSORPTION-LINE MEASUREMENTS

The D/H ratio in the local interstellar medium is evaluated based upon previously published measurements of Lyman absorption lines together with the hypothesis that the D/H ratio is constant. A unique value for the D/H ratio of 1.5(+/- 0.2) x 10(-5) by number is shown to be consistent with all published determinations made with the Copernicus and the International Ultraviolet Explorer satellites. The possibility that the D/H ratio may vary substantially in the local interstellar medium is considered and found to be unnecessary.