Long Period Unlisted Eclipsing Binary - KID 7971363

KID 7971363 is an unlisted eclipsing binary star system flagged by Planet Hunters forum Talk members in Q7.

Kian Jek:

If the primary stellar data is accurate, we're looking at a 0.24x Sol companion, 26x RE, too large to be a brown dwarf. Let's hope we see a primary eclipse soon, but the eclipse duration of ~37.75 hr means a very long period > 10 years!

 You can follow this eclipsing binary here.

Known Eclipsing Binary with Unknown Third Body KID 11519226

Planet Hunters forum Talk member troyw has identified transit timing variations (TTVs) in a known eclipsing binary star system KID 11519226 using his Amateur Kepler Obvservatory (AKO) program. The TTVs indicate a third orbiting body associated with this system.

troyw:

This star system shows TTVs for both the primary and secondary sets of transits. The published period is 22.1745d, but the data started being collected during a prominent swing in the TTVs, throwing off the period slightly. A more accurate period looks like 22.162d.
image link




Note the change in the black horizontal line indicating the TTVs.

Kian Jek:

Nice find, Troy! The profile of the TTVs for the primary and the secondary eclipses are not quite the inverse of each other, as the curve-fits are slightly different in the O-C plot:




You can follow this eclipsing star system with an unknown third orbiting body here.

Those Tricky Unlisted Eclipsing Binary Stars

One would think it would be easy finding unlisted eclipsing binary (UEB) star systems by visually examining the Kepler light curves at Planet Hunters and then comparing the star data with a published eclipsing binary stars catalog. Here is an example of a detached eclipsing binary that was flagged by Planet Hunters forum Talk members back in December of 2011 for KID 4586468:

In order to be placed with Planet Hunters UEB candidates three transits drops must be observed through the quarters. The third transit drop was identified in Q9. All looks well except that this star is not part of an eclipsing binary star system. The real UEB is associated with KID 4586482.

Kian Jek:

APOs seen and vector plotted below. Contaminated by star #2, KID 4586482, which is the actual eclipsing binary  (an unlisted eclipsing binary) with a period of 623d.






You can follow the real eclipsing binary star system here.


Often light curve contamination of stars by background eclipsing binaries (BGEB) form strange patterns that cue Planet Hunters members to dig deeper. This is the light curve for KID 5791875 posted in October of 2011:

Click here for more detailed view of visual cue- the vertical and spaced light bars.

The next step is to run a phased curve for the light curve looking for the tell that it is an EB. In this case the phased curve shows a rough, but good image for an over contact eclipsing binary (OCEB):

Data from NASA Exoplanet Archive.

Kian Jek:

This curve is extremely noisy and the eclipses are very shallow - after some processing and detrending, this is the best I can do:




With the rounded tops and sharper alternating minimas it certainly looks like an OC EB, but the depths of the minimas are just 0.04%. It's possible that this is due to flux dilution. There is a brighter star nearby which has no periodicity, in fact it is a pulsating giant:


 

Data from NASA SkyView

Veteran forum Talk member Daryll LaCourse completed the analysis using PYKE and identified the real OCEB as star #2:


Source appears to lie in the direction of star #2 (KIC 5791886):



FULL
Flipped and rotated:


KIC 5791886 has a Q4-Q9 light curve on record and is obviously an EB but does not appear to be slated for inclusion in the Prsa catalog as yet:

Kian Jek:

Wow, that's a nice find, Daryll. 5791886 is definitely the real EB here, it's not even in v3, so it must be a new UEB:



Very nice, clean phased curve with deep eclipses. Note how the period matches that of KID 5791875.

You can follow the UEB here.

KIC 5640750 - Long Period Giant Eclipsing Binary

Kian Jek:

The eclipse seen is truly humongous - we are looking at a 6.7 day eclipse (or approx. 160 hours) with a depth of 6.6%! There appears to be another eclipse right at the end of Q11, with a depth of about 1.8%. Just catching a glimpse of this other eclipse is fortuitous because it allows us to get an estimate of the stellar parameters of this EB.

For a giant EB with a total or annular eclipse, the flat-bottomed eclipse is generally the secondary eclipse, where the secondary is occulted by the giant primary. Since it is deeper than the primary eclipse (the one at the end of the data), we can surmise that the secondary must be brighter than the primary. We don't know what the period is, but it must be >1098 days. A reasonable estimate would be approx. 1300 days or longer, and if the primary is 10.365x Sol, then the secondary could be a 1.45x Rsol, Type F star with a Teff of 6300, with an orbit whose semi-major axis is ~ 3 to 3.5 AU. A binary with this configuration will give the observed depths of 6.67% and 1.8% for the secondary and primary eclipses.

You can track the progress of this eclipsing binary star system here.

KIC 11869052 - Disappearing Eclipsing Binary

Kian Jek posted this detrended, combined light curve for KIC 11869052 above showing that the eclipsing binary star system has an evolving orbit with its transit drops diminishing over time. No secondary transits are visible which may indicated that they have already disappeared. This is a published eclipsing binary.

 

Kian Jek:

Here's the OC-plot. The TTVs aren't that marked, about 20 minutes at maximum and they tend to vary a bit, but the curve fits look good. Probably a long period tertiary in there somewhere. The eclipses are very shallow, this EB probably has been eclipsing for quite some time, and I guess we're very lucky to catch this just as it disappears (just what are the odds of this happening?)

Planet Hunters forum Talk member troyw spotted the evolving orbit using the Amateur Kepler Observatory program (AKO). Notice how the horizontal signal indicating a transit is fading out from left to right.

This system has a fading set of primary transits with a slight wobble (TTVs) in the transit line. No secondary transits (that I could see).
p = 20.5469d

 You can follow this eclipsing star system on the Planet Hunters Talk thread here.

Disappearing Eclipsing Binary Stars - Evolving Orbits

The strange story of the disappearing eclipsing binary star systems begins with forum Talk members troyw and Kian Jek's comments on KIC 7955301. Here is what Troy had to say:

KIC  7955301 was added by request to AKO (Amateur Kepler Observatory) and also referenced here in another TTV/EB thread. An incredible image is produced for this star. ~15.34 days you can see the primary eclipses, secondary eclipses, TTVs and an evolving orbit all in one. Have a look at the TTVs in particular. You can see how the sine wave nature of the primary and secondary eclipses are slightly offset. I thought a secondary eclipse would show either the same phase of sine wave, or 180 degrees out of phase. This seems to be out of phase by 15 or 20 degrees. Not only that, but there is trend in primary eclipse line that is different than the secondary. I am not sure how to describe it, other than overall angle of the primary transit line is different than the overall angle of the secondary eclipse transit line.

The blue lines show the difference in transit line angles. Is this an effect of the evolving orbit? Or a larger TTV mixed with the smaller ones? Here is the star on AKO, lined up to 15.34
http://www.extrasolar.us/AKO/Kepler.php?KID=7955301&period=15.34

Here are Kian Jek's comments:

I had meant to take a good look at this star for some time now ever since it was mentioned in Slawson et al:

At the time of this writing, about half of the sample has been completed. The O-C diagrams were inspected visually, and eight cases where the O-C diagram has a significant signal through Q2 were identified, see Figs. 4 and 5. KID5771589 and KID7955301 have changes in their O-C diagrams of more than 100 minutes. Most of the others have changes of 20 to 40 minutes. It seems unlikely that such large changes in the O-C diagram over such short times (≈ 125 days) can be caused only by light travel time effects. We also note that the timescale for apsidal motion is much longer than the variations seen here. Hence, each of these EBs is most likely interacting with a third body.

As we now have up to Q11 data for this star, the change is much greater than 100 minutes. But there are more interesting things here. A plot of the combined light curve shows that the orbit is evolving in inclination:






The red and blue dots mark the extrema of the primary and secondary eclipses respectively, and curves fitted. The curve-fits seem to indicate that the eclipse depths could have maxed out and perhaps in future quarters we might see the depths recede again? A phased plot of the detrended light curve using Prsa v3's period of 15.32634, shows a clean fold:

It's when you zoom into the primary and secondary eclipses that you see the effect of TTVs clearly:





An O-C plot made of the primary and secondary eclipses show very regular periodicities, the red plots are the primary eclipses and the blue, the secondary eclipses:





Here are curve fits to both of them:





The primary eclipse O-C was fitted with a sine curve.







For the secondary eclipses, a cubic-spline fit does a better job. There is a kink just past each local maxima. a similar kink can also be seen in the primary eclipse O-C.




 Now on to KIC 5771589:

Comment by troyw:

Yet another beauty of a system full of TTVs, transit depth variations and mystery! These two transit lines are in phase with each other for the smaller transit shifts, but seems to show a much larger trend of being out of phase. (The primary transit line angles slightly down from left to right, and the secondary transit line angles slightly up from left to right.)

Kian Jek's comments:

This is a very interesting system. There are no APOs, the shallowness of the eclipses are due to the low inclination of the plane of the orbit of the two stars, resulting in grazing, partial eclipses. However, there's much more. I detrended the entire LC and what emerges appears to be decreasing eclipse depths. This suggests an evolving orbit with the inclination changing with time:

In fact, if one extrapolates the slope of the eclipse line, we find that the eclipses may well disappear by Q12, 346 days away!

There are obvious TTVs (or ETVs if one wants to be pedantic) - if I take the published period and fold the LC to see the primary and secondary eclipses, here's what you get:

There appears to be something perturbing the orbits of the components of this eclipsing binary. Perhaps a third stellar object, fairly massive but not in our line of sight.Plotted the O-C for the secondary eclipses, overlaid on the O-C for the primary eclipses. The Secondary O-C is skewed, but has the same periodicity as the primary.

If the precession of the plane of the orbits is due to a third body, the shape of the evolution of the eclipse depths may not not be linear but follow a sinusoidal curve. The eclipses may not disappear, but instead decrease to a minimum and then start increasing again. Or something like that.

troyw:

 

Will this star system continue on its course and complete a disappearing act?
Or.. will a hidden body fling this dancing duo back into the spot light for another chance to be seen?!

Tune in next quarter. Same bat time. Same bat channel.

  KIC 10319590 by Kian Jek:

First mentioned in Slawson et al, KIC 10319590 was noted to have ETVs in excess of 20 minutes. But that was many quarters ago and the data they had was from Q0 to Q2. So out of curiosity I downloaded the light curve and took a look and this is what I found:

Not only is this an evolving orbit, but what's remarkable is that due to precession it is changing in inclination at different rates, including bursts of rapid change, so by the middle of Q6, the two stars finally left our line of sight and stopped eclipsing each other. The O-C plot shows interesting periodicities that appear to be correlated with these inclination changes - the inclination (and eclipse depth) changes faster when the ETVs (Eclipsing Timing Variations) appear greatest:

The period of the ETV variation is approximately 383 days. Will the eclipses reappear? If I'm assuming that the precession will lead to a complete rotation of the plane of the orbit, then yes. But when? A simple model of this system shows that with a period of 21.3d, the separation and relative sizes of the two stars will cause it to disappear from line of sight at an inclination of 87.5°. Since we are not sure what the inclination was at the start of the observed light curve, let us assume that it starts at 90°. So the rate of the precession will be roughly 2.5° every 400 days.

The plane of the orbit will have to return to 87.5° in the opposite direction for eclipses to reappear, i.e. it will have to rotate 175°. So 175/2.5 = 70 * 400 = 28000 days or approximately 76.6 years. Also, 400 days is a lower bound, so it's probably longer than that. I don't think we'll be around to see the eclipses reappear unfortunately. However, since the orbit of the third object is also being perturbed by presence of the close binary, it's possible that at some point its own precession will bring it into eclipse with one or the other of the binary stars.

Did you read that correctly? An eclipse return date of approximately 76.6 years!






And finally KIC 5653126, the reappearing eclipsing binary star system:

Kian Jek:

I thought I'd just download the new Q7-9 data for 5653126 to see how it's turning out and just as Robin said, secondary eclipses have started appearing in Q8 - the inclination of the eccentric orbit has continued to shift so the secondary is finally being occulted by the primary:

Updated O-C plot for the eclipses. The blue plots are the newly visible secondary eclipses:

trow's AKO graph (left column on Kian Jek's chart:






 

 You can track these stars at the Planet Hunters Talk thread here, here, here and here.

KIC10024862 - 600 day Eclipsing Binary or Planet?

This transit occurred in the fourth quarter of the Kepler data release in 2011. Now in Q9, another significant drop has occurred.

Here is the analysis from forum Talk member Kian Jek:

Very nice 17hr drop. Could be a 0.84x RJ planet from the transit profile. However, the Q4 transit appears to have a similar duration, so it's possible that this is a long period, P > 600d, EB and with the secondary eclipse in Q4 and the primary in Q9.

More information here and here.

KIC 10074700 Unlisted Eclipsing Binary with One Year Period

KIC 10074700 is an unlisted detached eclipsing binary star system identified by Planet Hunters forum Talk members with a one year period.