John Toone (BAA VSS, Shropshire) has reported RY Sgr fainter than normal, at visual magnitude 8.0 on Aug 29 (compared to 6.2 on Jul 8) and has suggested that it might be at the start of a fading episode. Several other observers have also reported the star as being fainter of late. Further observations are urgently requested to determine whether this is the beginning of a deep fade or just a deep pulsation minimum.
RY Sgr is a yellow supergiant of the R Coronae Borealis class. As is typical for the class, its light curve is characterised by a sudden drop in brightness from 6th mag to mag 12 to 14 over a few weeks before gradually brightening over the following several months. The interval between these fading episodes is irregular. The fading is due to the presence of dust clouds of carbon obscuring the star.
RY Sgr is also a pulsating variable, with a semiregular period of 38 days, mag
The southerly declination of RY Sgr is a challenge for UK-based observers (
Finer charts are available at the AAVSO VSP: https://app.aavso.org/vsp/chart/?star=R ... east=right
Jeremy Shears
Director, VSS
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