AAVSO: American Association of Variable Star Observers

Studies of R CrB Star Pulsation Using ASAS-SN Photometry

Volume 51 number 1 (2023)

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John R. Percy
Department of Astronomy and Astrophysics, and Dunlap Institute of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto ON M5S 3H4, Canada; john.percy@utoronto.ca


R Coronae Borealis (RCB) stars are low-mass, carbon-rich, hydrogen-poor stars which suddenly and unpredictably fade by up to eight magnitudes or more in visual brightness, then slowly return to maximum. They may also undergo small-amplitude variations, on time scales of weeks, due to pulsation. The present study uses data from the All-Sky Automated Search for Supernovae (ASAS-SN), along with light curve analysis and time-series analysis, to study pulsational variations in 23 stars which were classed as RCB stars in both the ASAS-SN Variable Star Catalog and the General Catalogue of Variable Stars. All show irregular or semiregular variability on time scales of 20 to 100+ days, with semi-amplitudes of 0.05 to 0.3 magnitudes. For 14, some estimate of the period could be derived; the periods cluster between 30 and 50 days and are, on average, about half those of low-mass yellow supergiants with similar luminosity but more normal composition.