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Two Stars in Sagittarius with Changing Periods

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Pamela Knight

Maria Mitchell Observatory, Nantucket, Massachusetts

Abstract

My work at The Maria Mitchell Observatory during the summer of 1972 was done on stars in VSF 193 in Sagittarius. In this paper I would like to discuss two stars which were found to have changing periods - one a long period Mira type and the other a short period RR Lyrae type. The first of these stars temporarily designtated as B15, (RA 18h 20m 52s, Dec. -28¡ 27:8, 1900, mag. range 12.6-14.5pg), was discovered at Nantucket during the summer of 1971 by Karen Kwitter. I re-estimated it on approximately 500 NA plates and about 200 MF and B plates by comparing its brightness on each plate to standard comparison stars. Next the magnitude estimates were plotted against Julian day on a scale of 100 days to the inch, and some pieces of light curves began to be visible.