Abstract
The era of large-scale photometric variability surveys began a quarter of a century ago, when three microlensing projects - EROS, MACHO, and OGLE - started their operation. These surveys initiated a revolution in the field of variable stars and in the next years they inspired many new observational projects. Large-scale optical surveys multiplied the number of variable stars known in the Universe. The huge, homogeneous and complete catalogs of pulsating stars, such as Cepheids, RR Lyrae stars, or long-period variables, offer an unprecedented opportunity to calibrate and test the accuracy of various distance indicators, to trace the three-dimensional structure of the Milky Way and other galaxies, to discover exotic types of intrinsically variable stars, or to study previously unknown features and behaviors of pulsators. We present historical and recent findings on various types of pulsating stars obtained from the optical large-scale surveys, with particular emphasis on the OGLE project which currently offers the largest photometric database among surveys for stellar variability.
Highlights
Over the past quarter century, our knowledge of the pulsating stars has made a dramatic step forward and the lion’s share of this progress came from large-scale optical surveys for stellar variability. The first such surveys were initiated in the early 1990s as a response to the suggestion of Bohdan Paczynski ([23]), who pointed out the possibility of using gravitational microlensing effects to detect massive compact objects in the Galactic halo
In the last sentence of his seminal paper Paczynski stated: “It is clear that the observational project is not simple, but one of its by-products, a systematic discovery of a large number of variable stars in a nearby galaxy, is attractive, even if no lensing events are discovered”
From left to right and from top to bottom we present here the historically first PL diagram plotted in 1912 by Leavitt ([19]) for 25 Cepheids in the SMC, the period–Wesenheit index diagram obtained by Barry Madore in 1982 ([20]) containing all LMC Cepheids with high-quality photoelectric observations published in those days, the PL diagram with 1800 LMC Cepheids observed by the MACHO team ([5]), and the newest PL diagram with 4620 LMC classical Cepheids cataloged by the OGLE
Summary
Over the past quarter century, our knowledge of the pulsating stars has made a dramatic step forward and the lion’s share of this progress came from large-scale optical surveys for stellar variability. The first such surveys were initiated in the early 1990s as a response to the suggestion of Bohdan Paczynski ([23]), who pointed out the possibility of using gravitational microlensing effects to detect massive compact objects in the Galactic halo. Paczynski predicted that photometric monitoring of a few million stars in the Magellanic Clouds over a time scale of two years should lead to a discovery of the first microlensing events (which in those days were hypothetical phenomena) and shed light on the nature of dark matter. The total number of classical Cepheids in both Clouds is about 10 000
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