Stars we call Double Trouble are stars that have close companions that create difficulties for visual and CCD observers alike.
Observers reporting the combined magnitude of both members of a pair are over estimating the brightness of the variable.
Observers reporting the magnitude of the close companion, when in fact, the variable has faded below the brightness of its insidious partner, create flat bottom curves, which do not represent the actual behavioral characteristics of these stars. At the Spring 1963 Meeting, Tom Cragg presented a paper entitled "Sanctum Observers and the Minima of the Mira Stars", which discussed the observational status of Mira light curves with flat bottoms. At the time he (correctly) ascribed them to Miras with nearby companions that are brighter than the variable at minimum. You can find the article here.
A list of all different types of variable stars with close companions is included at the Variable Stars with Companions web page. However we propose here, a long-term campaign specifically on relatively well observed LPVs that are Double Trouble.
The initial goals of the campaign are as follows:
1- To raise awareness of the trouble they cause, and the affect it has on AAVSO data. We hope that bringing attention to these stars will cause observers to submit more accurate data. A side project in this campaign is to have a note regarding these special situations appear in the footer of every AAVSO chart plotted for them to assist in bringing these devils into the light.
2- Determine true minima of the variable members of these close pairs. Not all of these characteristics are well-known, or correctly listed in various catalogs.
3- Increase the density of coverage in hopes of characterizing these stars throughout their light cycles, not just at minimum.
4- We also hope to create a program that utilizes the strengths of both visual and CCD observers working together. Visual observers providing intense coverage in the bright range of the stars, with occasional data provided by CCD observers, and CCD observers picking up the coverage when these stars get below the typical threshold for visual observations (<13.5).
5- Provide an observing challenge that is as much fun for the challenge as it is for the potential scientific payoff. Observing and splitting close double stars has been enjoyed as part of the traditional hobby space of observational astronomy for hundreds of years. These close pairs have the added advantage of never looking the same way twice, since at least one of the members is variable!
As we learn more about these stars we may expand the goals of the campaign to include any serendipitous discoveries made along the way, and we will certainly expand the list of stars as more are brought to our attention, particularly in the southern hemisphere. If you know of any LPVs (or other types of stars) with close companions that may affect the accuracy of the data submitted to the AAVSO please contact the Section Administrator, Andrew Pearce.
The campaign list (sorted by RA) as at June 2016 is as follows: