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Variable stars with companions

In the April 2014 Newsletter we published an article on variable stars with close companion causing problems with their photometry.

In this page we give more information and updated tables so you can be aware of the stars that are causing problems or have caused problems in the past.

We will be updating this information with more stars in the future.
If you find a problem similar to those described in the Newsletter article, please let us know.

VARIABLE STARS WITH COMPANIONS spreadsheet (version June 15, 2016)

We have made a spreadsheet containing all of the stars and several more that still have no observations reported to the AID. All of them have remarks in VSX that will be displayed on the charts you download using the AAVSO's Variable Star Plotter (VSP).
You'll be able to customize the spreadsheet according to your needs. The complete VSP notes are included there along with the relevant information on the variable and its companion(s).
The columns are self-explanatory.

The stars are divided in two groups (the stars in each group are sorted by RA):

Group 1 (yellow cells) = stars with well-known documented problems or with companions close enough to be a source of potential contamination if proper care is not taken. These include the Top 10 in the Newsletter article. These stars are the most problematic ones.

Group 2 (white cells) = stars that have a VSP note to warn observers but the companions are not so close or not so bright to cause problems to the average observer. They may or may not have observations. Check them out anyway!

The stars with names highlighted in blue are the ones that have been added in the most recent version of the spreadsheet.

We also identify stars that have possible variable companions and we encourage you to observe them to confirm/disprove that.

HQ POLICY for stars with companions:

HQ strongly suggests that, if you can only report a blended magnitude on some target, you delete this target from your observing program. Focus on the stars that can be cleanly observed with your equipment. Also, be careful with the variable identification when it is at minimum. Maybe you can cleanly measure the stars if you identified them by hand, but if the variable gets so faint that it becomes invisible, you (or your software) might confuse it with the companion. Be sure you use a chart that shows the field in detail that is suitable for the variable’s brightness – you need more detail when the star is faint than when it is bright. Also, do not push your observing equipment further than it can go, a problem easy to happen for visual observers with smaller telescopes.

If you have already submitted data for any of these objects to the AID, double-check to see if you reported the correct star or that your results are not blended. If you did observe the wrong object, please delete the observations. If your observations are blended, you can add a comment in your report mentioning that fact (something like "The 14th mag companion to the NE is included in the aperture"). We also are updating WebObs so that you can include a "blended" comment code to further mark the submitted measure as a blend.

 

Related links:

Tom Cragg's paper on miras with flat-bottomed minima

LPV Double-Trouble Campaign

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484