CBA Center for Backyard Astrophysics

PX Andromedae: World's Most
Famous SW Sex Star (The 1996 - 1997 Campaign)

PX And figure

We just finished a two-year campaign on PX And, perhaps the most famous of the "SW Sex" stars. This star always shows eclipses at 0.14635 d, and has another variation at 4.2 - 5.1 days. The 1996 power spectrum near the orbital frequency is shown in the lower frame. It's dominated by a signal at 7.068 c/d, a "negative superhump" since its period is slightly less than Porb. The upper frame shows the power spectrum of an artificial time series constructed with this signal alone. As you can see, the real power spectrum contains an additional signal at the orbital frequency (6.833 c/d), and possibly another at 6.27 c/d. Because the star eclipses and we have ~ 100 eclipses covered, we can study the variation of eclipse shape with superhump phase, and thereby learn where the superhump originates!

The non-orbital periods wander slightly, and we'll track that wander through the rest of the year.