Proposal #243

Since 2011 I have been studying microvariability in the central stars of planetary nebula. My first interest was in the CSPN of M 57 but this study has spilled over into a study of microvariability in white dwarfs in general. Though this variability was discovered by others (Grauer, Bond, Landolt) it is not well known among the amateur or professional community as a whole.

Most (non-white dwarf specialists) speculation was that this variability was a result of "sunspots" on the surface of the star. Grauer and Bond thought these might be pulsations in the thin atmosphere of the star. Current thought leans toward "Gravity Waves." Part of the issue to determine the cause of these variations is a lack of telescope time. This study has fallen into the crack where a small amateur telescope is too small to achieve the required data and the larger telescopes are all booked up.

TMO61 - Tortugas Mountains Observatory at 0.61 meters is an ideal size to complete this study. Data runs of 1+ hours with a 10-15 second exposure through a Johnson-Cousins I filter should be the most efficient. The I filter negates most of the "noise" of the surrounding nebula but makes a larger telescope necessary. The estimated period of the variability is around 2.5 minutes so keeping exposures short will help determine a smooth light curve.

I propose to have a short trial run as soon as possible this fall, before the star sets for the season.

Run 1 .5 hour run with 10 second exposures using the I filter
Run 2 .5 hour run with 15 second exposures using the I filter

These would be preliminary runs before requesting time in the late spring. The two different exposures would be to help determine the optimum exposure for the later run.

I would like to be able to view and measure the results of this first run but would also like to see if it will present smooth data in Vphot. If Vphot can handle a star embedded in nebula that would save a lot of later analyzing!

Thank you for your consideration

Paul Temple
TPV