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Paper: Long-Term Studies of Hitherto Unexplored Variables on Sonneberg Patrol Plates: O - C Aspects
Volume: 335, The Light-Time Effect in Astrophysics: Causes and Cures of the O - C diagram
Page: 119
Authors: Vogt, N.; Kroll, P.
Abstract: The light curves of 216 arbitrarly chosen field stars and of 23 known variables in the Auriga–Taurus–Orion region were derived from scanned, blue-sensitive archival patrol plates, covering a total of 34 years (1961–1995). We achieved a photometric accuracy of 0.07–0.12 mag. 17 field stars turned out to be variables, most of them with time scales of 1000–8000 days in the form of slow waves with amplitudes between 0.1 and 0.3 mag, i.e. below the threshold of traditional variable searches on photographic plates. About 50% of these new long-term variables exhibit drifts indicating periodic or erratic variability at much longer time scales than covered here. In addition, we detected long-term variations in 50% of the known variables. The above fraction of low-amplitude long-term variables among field stars implies that a total of about 45000 new variables should be detectable in the Sonneberg patrol plate archive. They will represent a new, hitherto not investigated population of variable stars with a possibly significant impact on our understanding of the stellar interior and evolution. We discuss implications for the O – C analysis of long-term periodic phenomena which can be extracted from sky patrol achives. An extensive report on these results is in press.
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