More star info…

Thanks again for your amazing work and feedback.  We are working to keep up with you! There is now a data-download button (thanks to Chris, Arfon, Michael, and Stuart!) on the star pages. We are also integrating information about stars that are known eclipsing binaries (EB), Kepler planet candidates (PC) and false positives (FP). Here is an ascii list of light curves with this information. On this list, the APH number is given, followed by the Kepler ID and a flag (EB, PC, FP). For EB objects, D indicates detached binaries, SD is semi-detached, OC is an overcontact binary. Kepler PC stars include columns with the prospective period and planet radius (in Jupiter radii units).

One note about false positives: There are light curves that masquerade as transiting planets. For example, light from a bright foreground star is spread out over several pixels on the CCD detector.  The halo of starlight is swept up into a single brightness measurement by the Kepler team’s software. However, in some cases a more distant eclipsing binary (EB) star system blends into the edges of the foreground star.  Since the EB is more distant, it is fainter and contributes a smaller fraction of the light. In this case, the background eclipse produces a diluted signal that looks very much like a transiting planet.  There are a couple of ways to eliminate these imposters:

  1. the Kepler team has software that looks for pixel contamination and identifies the star as a false positive (FP). When available, we are listing this information on the light curve and star pages.
  2. Follow up radial velocity measurements of the bright star will also include the background blended eclipsing binary.  A large velocity signal can be a give away sign that the light curve does not arise from a transiting planet.

This follow-up is a critical effort, required to move an object from a transit candidate to a planet.


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6 responses to “More star info…”

  1. Constantine Thomas (EDG) says :

    OK, confused here. The ASCII list shows the APH, Kepler ID, and then the flag for the star, but then for the Binaries what are the next two columns that have numbers in them?

    For the Binaries, I think the next column is probably the period in days, but what’s the last one? It seems to be between 0 and 1 for D binaries, but it’s 0 for SD and OC ones. Is that the orbital eccentricity?

    And then for the planets those columns are period in days and size in Rj?

  2. Constantine Thomas (EDG) says :

    Also, have *all* of the EBs in the dataset been previously identified (there were 1832 in the Prsa et al 2010 paper)? Or could there still be a few in there that haven’t been officially determined yet?

  3. Derek N says :

    Costonovich has a complete list of all the duplicated systems here:

    In each case, I believe the first entry is correct, and the successive entries are supposed to have a different APH number. It doesn’t appear to affect the document on the whole, only the cases where information has been duplicated appear to be wrong.

  4. debrafischer says :

    The two columns for the EB’s are orbital period and eccentricity – I’ll have a look at the list and cull out any of the duplicated systems later today.

  5. Jens Ulrik says :

    Excellent decision to publish this data! It is now possible to know instantly (due to Goryus at PH) whether a light curve I have classified as a possible transit, has already been classified as such by the Kepler team or …. tadah! …whether it is a possible transit their algorithms overlooked. Nice!

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