Abstract
Radial Velocities of Variable Stars. Dr. P. W. Merrill contributes an article on this subject to Popular Astronomy for April. He refers to the former idea that these were dwarf stars approaching extinction; a study of their proper motions showed that the variables are in most cases remote, so that they are now reckoned as giants, not as dwarfs. The radial velocities are important for giving an estimate of their true speeds, since the thwart velocities are generally too small to determine accurately. It has been observed in many cases that the bright lines visible at maximum show a velocity of approach of about 15 km./sec. relatively to the dark lines. It is concluded in the article that the latter give the true speed of the star, and that the difference arises from an outward motion of heated gases. A strong argument for this is afforded by the close double star X Ophiuchi; one component is variable, the other of constant light; at maximum the spectrum of the former is observable, at minimum that of the latter; the dark lines in both stars give the same radial velocity,—70¾ km./sec., while the bright lines in the variable give—83½ J. A similar argument is drawn from R Aquarii and its companion nebula. In some faint variables the bright lines only are measurable. A correction is applied to these to deduce the true velocity of the star. A statistical study then shows that the variables, as a whole, have a mean speed of 37 km./sec. relatively to the other stars, this speed being towards a point in the southern hemisphere nearly opposite the solar apex.
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Astronomical Topics. Nature 131, 917 (1933). https://doi.org/10.1038/131917a0
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DOI: https://doi.org/10.1038/131917a0