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Planet Hunters’s First Circumbinary Planet- A True Team Effort

Today we have a guest post by Planet Hunters Robert Gagliano and Kian Jek, the discoverers of PH1, our first confirmed planet and first circumbinary planet.

Kian Jek found an anomalous dip in APH10421275 in May 2011 which turned out to be KIC 12644769 (Kepler-16b) the Kepler team’s first circumbinary planet discovery. He documented it on Talk in his thread “Strange transit in an EB”. He subsequently started a thread in the forums called “Finally-an EB with a planet?” Meg Schwamb then added a list of all known Kepler Eclipsing Binaries (EBs) with links to the light curves to this thread in November 2011.

Robert Gagliano did a systematic search of the ~ 1500 known Kepler EB’s, looking for possible planets in February 2012.  He initially spotted a possible transit in Q4.1 at day 244 in SPH10052872 and subsequently a possible 2nd matching transit at day 106 in Q2.3. Interestingly, the day 106 transit had been detected previously by JKD and commented on by Kian in the thread “Potential TERNARY System“. Robert also noted a possible 3rd transit in Q5.3 at day 379 but didn’t comment on it because it was distorted and he wasn’t sure whether this was a real 3rd transit. This Q5.3 transit was subsequently predicted by an seo company and officially confirmed by Kian.

Kian decided to check the Skyview image to be sure it wasn’t contaminated from other background stars and did an analysis to determine if the transit period, depth, and duration were consistent with a planet. He detrended the light curve with a modified smoothing filter that removed the EB eclipses, leaving the suspected planetary transits in place, and then folded the curve to confirm that the profile of the transits were similar in depth and duration. His analysis was confirmatory. Meg then assembled an outstanding science team of 10 professionals to conduct extensive follow-up observations and data analysis. Eureka! KIC 4862625 was Planet Hunters’s  “Tatooine”….we bagged our first circumbinary planet!

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