RR Lyrae stars in the small Magellanic Cloud

A field covering an area 10 x 1.30 in an outlying region of the Small Magellanic Cloud (SMC) is searched for variable stars. Ninety-two variables were identified and periods were determined for 77 of these. Seventy-six stars have periods less than a day and amplitudes of several tenths of a magnitude, and are probably variables of the RR Lyrae type. Ten yellow and red variables with periods longer than a day are briefly described. Multiple discovery statistics suggest a completeness of 93 percent for variables of Bailey class ab and 50 percent for those of Bailey class c. Approximately 30 percent of the RR Lyrae variables show variations in amplitude and/or phase of maximum or minimum light. The period distribution is unlike that found anywhere in the Galaxy, and resembles most closely that of the variables in the Leo II dwarf galaxy. There is some evidence that, for a given period, the SMC variables tend to have smaller amplitudes than Galactic RR Lyrae stars. The mean blue magnitudes of the SMC variables peak sharply at (B) = 20.0 m. The mean, (anti B), for all RR Lyrae variables with known periods and with (B) greater than 19.0 m is 19.95 m. Measurements of three yellow plates give a similar mean, (anti V), = 19.57 m for this same group. For a distance modulus of 19.0 m for the SMC, a mean absolute visual magnitude of +0.6 m +- 0.25 m is found for the RR Lyrae stars in the SMC. It is suggested that the RR Lyrae stars are distributed rather evenly over the SMC and concentrate neither toward the central bar nor towards the center of the SMC system adopted by Westerlund