Last week (4th September) I was able to get out and observe the variable star RW Cephei. The conditions weren't that great as the waning gibbous moon (2 days from last quarter) was rising at 20:20 UT and the sky was hazy. Astronomical twilight ended at about 20:40 UT.
Using my 7x50 binoculars I was able to find RW using chart 312.02 from the BAA. At 20:43 UT RW was fainter than both nearby stars P (mag. 6.2) and B (mag. 6.5) on that chart. However, at 20:46 UT I determined it was brighter than star E (mag. 7.3). My estimate was that it was one "point" from B in brightness and two "points" from E, namely B(1)V(2)E which made it magnitude 6.8 (to 1 d.p.). This is in good agreement with other data from the BAA.
As noted before (in December 2022 and January 2023) this star has recently gone through a period of dimming similar to that which occurred to Betelgeuse in 2020. That dimming now seems to be over as its brightness has returned to its normal range of magnitudes as seen by the plot generated from the BAAVSS below:-
My latest data point is the black circle at the extreme right of this light curve (magnitude on the vertical axis, calendar date on the horizontal). In a recent paper in The Astronomical Journal the authors have presented some images of this star obtained through interferometry which show that during the period of dimming the star's surface brightness appeared asymmetric. They suggest that this has been caused by a mass ejection of material that has resulted in a dust cloud that is blocking the light from the stellar photosphere. This is similar to what happened to Betelgeuse.
All text and images © Duncan Hale-Sutton 2023 (except for the image from the BAAVSS)
