Planet Hunters Talk

KID 201338508 - APHC0110955

  • zoo3hans by zoo3hans

    KID 201338508 seems to have interesting dips in all quarters. Since the duration is sometimes different, there must be more than one object present (if real). I get one possible period of about 10.93 days, at BKJD 1981.63, 1992.55, 2003.44, 2014.37, 2025.34, 2036.25, 2047.18.

    For the data and a picture see https://www.cfa.harvard.edu/~avanderb/k2c1/ep201338508.html

    Posted

  • zoo3hans by zoo3hans

    Slightly detrended lightcurve:

    enter image description here

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  • ajamyajax by ajamyajax

    201338508: already has two planets as designated in this paper, so my take is they are fairly confident of this disposition. And maybe there is not much we can help with past this. ? (Edit: Shellface suggested this also on another thread)

    "Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 18 Systems, Including a Planet Receiving Earth-like Insolation"

    Benjamin T. Montet, Timothy D. Morton, Daniel Foreman-Mackey, John Asher Johnson, David W. Hogg, Brendan P. Bowler, David W. Latham, Allyson Bieryla, Andrew W. Mann

    http://arxiv.org/abs/1503.07866

    "We do not detect any significant transit timing variations (TTVs) in any of these systems from the K2 data alone. EPIC 201338508 would be expected to have a TTV period of 117 days, but is likely too far from commensurability to have an observable TTV signal."

    201338508 169.303502 -1.877976 10:9328+0:0022 (p1=10.9328)

    201338508 169.303502 -1.877976 5:7350+0:0006 (p2=5.735)

    Posted

  • zoo3hans by zoo3hans

    Ah thanks Mark. It's still a good feeling that it is possible to recover such a fine candidate "by eye" in the PH interface.

    And by the way, at least one signal (around BKJD 1994.6) has definitely a longer duration than the 10.93 days period object, so its period must be longer, i.e there is at least a third object in this system.

    Posted

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

    Hans Martin, that is interesting. If the transit depth is greater there and there aren’t any known glitches, you might have a good case for a longer period transit -- and planet #3. Too bad there isn’t any visible TTV in the K2 data (per their paper) or that could be used to help ID this also, as you know. Nice spotting on PH all the way around.

    Posted

  • zoo3hans by zoo3hans

    AKO images

    P=5.735 days

    enter image description here

    P=10.9328 days

    enter image description here

    Single transit at BKJD 1994.6

    (AKO image makes no sense with just one dip)

    Posted

  • ajamyajax by ajamyajax

    Hans Martin, took a closer look and see a possible repeat that might support your third planet. I used your BKJD observation as the epoch and a period of 24.6x. Pls see chart for fit. One of three possible transits is partially blended, but the other two are about the same duration and depth. As you can see from the charts of the other two planets this is a blended LC anyway, so one less distinct transit could be ok. Good luck and hope it helps.

    s1=1981.59 p1=10.935 d1=0.12 (2.88 hours)

    s2=1987.335 p2=5.7365 d2=0.10 (2.40 hours)

    s3=1994.585 p3=24.634 d3=0.17 (4.08 hours)

    F3

    T1
    T2

    F1
    F2

    Posted

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

    Dear Mark,

    marvellous. I think your period of 24.634 days for the third object looks very good!

    Thank you very much for your help,

    Cheers, Hans Martin

    Posted

  • Shellface by Shellface

    Alright. For two planets transiting the same star, T(out)/T(in) ≈ (P(out)/P(in))^(1/3), where "T" refers to transit duration, "P" refers to orbital period, and "in" and "out" refer to the shorter period and longer period planets, respectively. This is an approximation rather than an identity because there are other, unaccounted parameters that can affect the transit duration, such as differing impact parameters and/or eccentricities. However, it should be within a moderate margin of the truth for a typical system.

    For example, the implied period ratio for the validated planets derived from aja's transit lengths is ~1.73, compared to the actual ~1.91. This is a~10% discrepancy, which is fairly reasonable.

    For the suggested third transiting body, the implied period ratio with the 11-day planet is ~2.84. For an error margin of, say, 20%, the implied third orbital period is ~31 ± 6 days, which is marginally compatible with a 24.6-day orbital period (to a little more than 1σ), and more generally implies the presence of multiple transits in the K2 dataset.

    While I advocate testing of possible longer orbital periods, I must say that the three transits aja has selected show good mutual agreement in depth and spacing, and so it seems quite probable that this is a real signal. So, I must say; excellent work, both of you.

    I estimate the candidate companion radius to be about 2 Rearth, based on comparison with the radii of the validated planets given in the paper. However, my calculations suggest these are, for some reason or other, overestimated slightly. I esimate the candidate's equilibrium temperature to be 400 K, which places it interior to the HZ but still makes it relatively cool.

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  • ajamyajax by ajamyajax

    I was thinking we might be able to constrain the K2 stellar properties further using only period and duration data... So in this experiment those were the baseline values (the periods being the most constant). So how does a 0.6X R_sol star look here to everyone?

    Semi-Major Axis a (A.U.) = 0.0815

    Stellar diameter ratio = 0.605

    Stellar mass ratio = 0.605

    Period ~= 10.93 days

    Duration ~= 2.89 hours

    Semi-Major Axis a (A.U.) = 0.05305

    Stellar diameter ratio = 0.605

    Stellar mass ratio = 0.605

    Period ~= 5.74 days

    Duration ~= 2.33 hours

    Semi-Major Axis a (A.U.) = 0.14015

    Stellar diameter ratio = 0.605

    Stellar mass ratio = 0.605

    Period ~= 24.64 days

    Duration ~= 3.79 hours

    Posted

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

    Update: oops sorry, just remembered to look in the paper and saw they have 0.58 stellar mass and 0.56 stellar radii for this system.
    But since I was oblivious to this before, I'll consider my little experiment a success! 😃

    p.s. anybody want the python source for these calcs? I can clean the routines up a bit and post later, if any interest.

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

    I'm interested.

    Posted

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

    Here it is. Hope the format works in this message space. Good luck.

    #!/usr/bin/env python3

    from math import *

    from numpy import *

    sun_mass = 1.9891 * 10.**30.

    def get_period(a, mass):

     """ "from Kepler's third Law.  Use 24:00:00 hour days, AU, and Earth masses." """

 return 365.25 * sqrt( a*a*a * sun_mass / mass)

    def get_duration(a, stellar_diameter_ratio, stellar_mass_ratio):

     return 13 * stellar_diameter_ratio * math.sqrt(a/stellar_mass_ratio)

    """ input example """

    au = 0.14015

    stellar_diameter_ratio = 0.605

    stellar_mass_ratio = 0.605

    earth_mass = (5.9736 * 10.**24.) * 1. # note changes here have a negligible effect on the period

    transit_period = get_period(au, earth_mass + sun_mass * stellar_mass_ratio)

    transit_duration = get_duration(au, stellar_diameter_ratio, stellar_mass_ratio)

    print("Semi-Major Axis a (A.U.) =", au)

    print("Stellar diameter ratio =", stellar_diameter_ratio)

    print("Stellar mass ratio =", stellar_mass_ratio)

    print("Period ~=", round(transit_period,2), "days")

    print("Duration ~=", round(transit_duration,2), "hours")

    """

    Credit and reference:

    https://www.python.org/

    http://www.numpy.org/

    This python routine uses a code fragment or a calculation or mass data from these sources (thank you):

    http://sjml.spelljammer.org/archive/oracle/201008/10-182240.html

    http://www.smartconversion.com/otherInfo/Mass_of_planets_and_the_Sun.aspx

    http://kepler.nasa.gov/Science/about/characteristicsOfTransits/

    """

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  • zoo3hans by zoo3hans

    Thank you Mark.

    It works.

    Posted

  • ajamyajax by ajamyajax

    201338508 follow-up: think I will post the possible third planet (P=24.6x) we discussed here on CFOP2 because we had a good consensus. The other two PCs in this system are already in a paper, so can't think of any reason not to. Thoughts?

    Posted

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

    Go for it! Try to include as much as possible, maybe look at the HAT reduction.

    I really ought to do more ExoFOP, but it takes forever to format the data. And why are transit depths given in millimagnitudes?

    And I should also really get around to doing more science. I always end up so very drained in the summer, and so I've been thoroughly unenthused for the past few weeks. I hope I can get it together for C3, at least

    Posted

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

    All right, will wait a bit to see if ok with Hans Martin and the science team (don't see any reason for PM's though) and will do what I can. There are probably other PCs like this and even more likely BGEB's just on my list. Will try to corral some of those later.

    Posted

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

    Hey Mark, just go ahead! Of course it's OK with me!

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