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Triple star August tertiary eclipse campaign

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Triple star August tertiary eclipse campaign

Dear All,

I would like to encourage observations of a very odd star, KIC 2856960, which is a triple star composed of a ~6 hour period eclipsing close binary in a 204 day orbit with another star (the latter dominates the light). The system is aligned so that the binary crosses the face of the third star every 204 days leading to odd-looking multiple eclipse events. The peculiar thing about this star is that we have completely failed to come up with a physically consistent model of what should be a simple system: the light curve seems to require the binary to be wider than allowed by Kepler's laws. The star was discovered in Kepler data, and the last observation of the "tertiary eclipses" was by Kepler in 2012. The next such events are well placed for ground-based observation on August 9 to 10 [UT] and I would like to obtain as near to 24-hour photometric coverage as possible of this interval and a bit before and after. Combined with spectroscopy that is also being obtained, I hope we can crack this system. The star has a magnitude of about 15.5 and the tertiary eclipses are predicted to be about 6% deep. For many more details, links to a research paper, finding charts, etc, please see

Tom Marsh

WBY's picture
Results from Central Texas Astronomical Society

I completed 4 PT runs on KIC 02856960 between Aug 8 UT and Aug 13 UT. The one on 8/13 was just to provide a post transit baseline. We obtained reasonably good results using the 0.61 meter telescope at the CTAS Paul and Jane Meyer Observatory near Waco, TX. Data has been submitted to AAVSO and are presented in the attached spreadsheet.

The portion of the long period eclipse that was captured shows very close agreement to the 0.08 magnitude 204-day period eclipse depth mentioned in MNRAS article. We captured almost one complete orbit of the close binary during the transit. The data is a little noisier than I would like, but our guider was down and I limited exposures to two minutes to avoid excessive elongation. I probably should have used a BG40 filter (very wide bandwidth UV and IR blocking) with V mag zero points rather than a V filter to reduce noise, but I was concerned that using an odd filter might cause some difficulty combining our data with others. 

** Spreadsheet with plots attached. **

Brad Walter, WBY

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