V and Rc light curves of medium-bright PPNe

The other two are found to be giant stars. IRAS09296+1159 pulsates with a period of only 47 days but reaches pulsational light variations of 0.5mag. Supplemental spectroscopy reveals the spectrum of a CH carbon star.

IRAS08359-1644 is a G1III star that does not display pulsational variability; rather, it shows nonperiodic decreases of brightness of up to 0.5mag over this 10 year interval. These drops in brightness are reminiscent of the light curves of R Corona Borealis variables, but with much smaller decreases in brightness and are likely due to transient dust obscuration. Its spectral energy distribution is very similar to that of the unusual oxygen-rich giant star HDE233517, which possesses mid-infrared hydrocarbon emission features.

These two non-PPNe turn out to be members of the rare group of giant stars with large mid-infrared excesses due to dust, objects which presumably have interesting evolutionary histories.