Periods and Lights-Ranges of Long-Period Variable Stars.

The General of Variable Stars (2d ed ; Moscow, 1938) includes data for 3196 Mira and SRa variables, of which 35 per cent have spectroscopic classifications Of classified stars, 89 per cent are of type M, 4 per cent of type S, and 7 per cent of types N, R, or C Of the better-observed M-type Mira variables, 96 per cent have bright lines The frequency-curve for variables of spectral type M shows a broad maximum at a period near 300 days, with a shoulder near 160 days. The maximum frequency for S-type variables lies near 360 days, that for carbon variables near 400 days For variables without spectral classification the maximum frequency lies near period 255 days; the difference is probably somehow connected with the fact that these variables are fainter than the others The average light-range shows a substantial increase with period from 140 to 260 days but remains nearly constant for longer periods. The average photographic light-range is smaller than the visual The average range for S-type variables is greater than that for M types, while that for the carbon variables is less