Planet Hunters Talk

EPIC 204618782 - APH0000jjp

  • zoo3hans by zoo3hans

    EPIC 204618782 : this looks like an EB with period 62.15 days, but could also be a circumbinary system.

    Eclipses at BKJD 2061.83 and 2123.99, duration about 25.5 hours, depth 0.027. Transit at 1.45 BKJD 2109.95, duration 3.5 hours, depth 0.013.

    Posted

  • ajamyajax by ajamyajax in response to zoo3hans's comment.

    Re 204618782: that's an interesting possible planetary transit, but my guess is the combined mass of both stars would need to be pretty small for a circumbinary to work. The colors anyway seem to show at least one larger star is more likely. But circumbinary orbits are certainly different than single star orbits, so really just a guess with the calcs here. Also my PC transit depth estimate is very approximate with only four data pixels to work with.

    Edit: also listed as an EB with P=62.153 and '2081 (AF Star)' on K2VARCAT. And maybe another possible explanation is the secondary transit of an eccentric EB, but the duration seems kind of short for that.

    s1=2110.239 p1=? d1=0.122 (2.92 hours)

    EPIC, 2MASS, J mag, H mag, K mag, J - H, H - K, (J-H spectral type, stellar mass est) (H-K spectral type, stellar mass est)

    204618782 , 2MASS J15575426-2135268 , 10.068 , 9.726 , 9.638 , 0.342 , 0.088 , ('G6V', 0.97) , ('G9V', 0.91)

    Semi-Major Axis a (A.U.) = 0.0538

    Stellar diameter ratio = 0.94

    Stellar mass ratio = 0.94

    Period ~= 4.7 days

    Duration ~= 2.92 hours

    Semi-Major Axis a (A.U.) = 0.23

    Stellar diameter ratio = 0.22

    Stellar mass ratio = 0.22

    Period ~= 85.89 days

    Duration ~= 2.92 hours

    F1

    Posted

  • zoo3hans by zoo3hans

    Thanks Mark, I did the period calculation wrong, correct is indeed a value around 62.15 days.

    Posted

  • ajamyajax by ajamyajax in response to zoo3hans's comment.

    That's all right, I had to fix my transit depth estimate here also. 😃 This is interesting stuff though. I'm going to experiment with some known circumbinary system data a bit, see what results I can get using similar approximations.

    Update:

    Well, so far so good. In my first test I used published data for circumbinary systems Kepler-16 and 34. AU, combined stellar masses, and the diameter of the larger star are the inputs, while period and duration are the outputs. The calculated period results were very similar to published values and the durations were close to a what my transit program displayed with a clear single transit.

    So this is good news because (as I was experimenting with above), if I know the duration and can guess at AU, and the stellar masses and diameters with color values, I can estimate a period for circumbinary system planets just like single star planets.

    Kepler-16 b, KOI-1611.02, KIC 12644769

    P=228.776, AU=0.7048, 0.6489 R_sol, 0.6897 M_sol

    from: http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=Kepler-16+b&type=CONFIRMED_PLANET

    Star A mass 0.6897, Star B mass 0.20255, P=41.079, AU=0.22431

    from: http://kepler.nasa.gov/Mission/discoveries/kepler16b/

    My Kepler-16 b results:

    Semi-Major Axis a (A.U.) = 0.7048

    Stellar diameter ratio = 0.6489

    Stellar mass ratio = 0.89225

    Period ~= 228.79 days

    Duration ~= 7.5 hours (0.3125 BJD)

    from Wiki:

    "Kepler-16A, is a K-type main-sequence star and the secondary, Kepler-16B, is an M-type red dwarf. They are separated by 0.22 AU, and complete an orbit around a common center of mass every 41 days."

    "Kepler-16b is a gas giant that orbits the two stars in the Kepler-16 system.[2] The planet is a third of Jupiter's mass and slightly smaller than Saturn at 0.7538 Jupiter radii, but is more dense. Kepler-16b completes a nearly circular orbit every 228.776 days."

    https://en.wikipedia.org/wiki/Kepler-16

    ...

    Kepler-34 b, KOI-2459.02, KIC 8572936

    P=288.822, AU=1.0896, 1.1618 R_sol, 1.0479 M_sol

    from: http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=Kepler-34+b&type=CONFIRMED_PLANET

    Star A mass 1.0479, Star B mass 1.0208, P= 27.7958103, AU=0.22882

    from: http://kepler.nasa.gov/Mission/discoveries/kepler34b/

    My Kepler-34 b results:

    Semi-Major Axis a (A.U.) = 1.0896

    Stellar diameter ratio = 1.1618

    Stellar mass ratio = 2.0687

    Period ~= 288.83 days

    Duration ~= 10.96 hours (0.4567 BJD)

    from Wiki:

    "Kepler-34 is an eclipsing binary star system in the constellation of Cygnus. Both stars have roughly the same mass as the Sun, therefore both are spectral class G."

    "Kepler-34b is a gas giant that orbits the two stars in the Kepler-34 system. The planet is just over a fifth of Jupiter's mass and has a radius of 0.764 Jupiter radii. The planet completes a somewhat eccentric orbit every 288.822 days from a semimajor axis of just over 1 AU, the largest of any transiting planets at the time of its discovery."

    https://en.wikipedia.org/wiki/Kepler-34

    So revising my estimate above so that the combined stellar mass might be 0.94X M_sol, I get new results for the observed duration. The period is still inside the EB period unfortunately, but if these stellar estimates are actually too high then perhaps a circumbinary is still possible, like in the small system example on the previous page.

    Semi-Major Axis a (A.U.) = 0.214

    Stellar diameter ratio = 0.47

    Stellar mass ratio = 0.94

    Period ~= 37.29 days

    Duration ~= 2.92 hours

    Posted