J/A+A/661/A141 Kepler-1972 transit timing variations (Leleu+, 2022)
Alleviating the transit timing variations bias in transit surveys.
II. RIVERS: Twin resonant Earth-sized planets around Kepler-1972 recovered from
a Kepler false positive.
Leleu A., Delisle J.-B., Mardling R., Udry S., Chatel G., Alibert Y.,
Eggenberger P.
<Astron. Astrophys. 661, A141 (2022)>
=2022A&A...661A.141L 2022A&A...661A.141L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets
Keywords: planets and satellites: dynamical evolution and stability -
planets and satellites: terrestrial planets -
techniques: photometric - methods: numerical
Abstract:
Transit timing variations (TTVs) can provide useful information for
systems observed in this way, putting constraints on the masses and
eccentricities of the observed planets, and in some cases even
revealing the existence of non- transiting companions. However, TTVs
can also prevent the detection of small planets in transit surveys, or
bias the recovered planetary and transit parameters. Here we show that
Kepler-1972 c, initially the "not transit-like" false positive
KOI-3184.02, is an Earth-sized planet whose orbit is perturbed by
Kepler-1972 b (initially KOI-3184.01). The pair is locked in a 3:2
mean- motion resonance, each planet displaying TTVs of more than 6h of
amplitude over the duration of the Kepler mission. The two planets
have similar masses mb/mc=0.956-0.051+0.056 and radii
Rb=0.802-0.041+0.042R⊕,
Rc=0.868-0.050+0.051R⊕, and the whole system, including
the inner candidate KOI-3184.03, appears to be coplanar. Despite the
faintness of the signals (signal-to-noise ratio (S/N) of 1.35 for each
transit of Kepler-1972 b and 1.10 for Kepler-1972 c), we recovered the
transits of the planets using the RIVERS method, which is based on
recognition of the tracks of planets in river diagrams using machine
learning, and a photo-dynamic fit of the light curve. Recovering the
correct ephemerides of the planets is essential to obtaining a
complete picture of the observed planetary systems. In particular, we
show that in Kepler-1972, not taking into account planet-planet
interactions yields an error of ∼30% on the radii of planets b and c,
in addition to generating in-transit scatter, which is why KOI3184.02
was mistaken for a false positive. Alleviating this bias is essential
for an unbiased view of Kepler systems,some of the TESS stars, and the
upcoming PLATO mission.
Description:
We apply the RIVERS method to KIC 4725681, which have 3 KOIs announced
on the Kepler database1, the candidates KOI3184.01 and .03 with
orbital periods of 7.54 and 4.02 days, respectively, and the
False-positive KOI3184.02 at a period of 11.32 day, flagged as
"Not transit-like".
Objects:
--------------------------------------------------
RA (2000) DE Designation(s)
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19 13 34.87 +39 52 21.5 Kepler 1972 = KOI-3184
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
timingsb.dat 59 198 Transit timings of Kepler-1972 b
timingsc.dat 59 131 Transit timings of Kepler-1972 c
samples.dat 497 300 Samples of the photodynamic fit of Kepler-1972
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Byte-by-byte Description of file: timingsb.dat timingsc.dat
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Bytes Format Units Label Explanations
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1- 19 F19.14 d Date [111.9/1598.78] Median transit date, BJD-2454833.0
21- 39 F19.14 d b_Date [111.89/1598.77] Date 0.15865 quantile,
BJD-2454833.0
41- 59 F19.14 d B_Date [111.91/1598.79] Date 0.84135 quantile,
BJD-2454833.0
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Byte-by-byte Description of file: samples.dat
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Bytes Format Units Label Explanations
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1- 18 F18.15 deg lambda1 [3.24/59.44] Mean longitude for planet b
20- 37 F18.16 d P1 [7.54/7.55] Orbital period for planet b
39- 60 E22.16 --- ecw1 [-0.3/0.2] eccb*cos(long of pericenter b)
62- 84 F23.20 --- esw1 [-0.16/0.22] eccb*sin(long of pericenter b)
86-104 F19.16 --- logmu [-5.45/-4.72] log10((mb+mc)/m*) magnitude
ratio
106-123 F18.14 deg lambda2 [140.23/187.41] Mean longitude for planet c
125-142 F18.15 d P2 [11.32/11.34] Orbital period for planet c
144-166 E23.17 --- ecw2 [-0.27/0.14] eccc*cos(long of pericenter c)
168-190 E23.17 --- esw2 [-0.19/0.14] eccc*sin(long of pericenter c)
192-210 F19.17 [-] logdelta [0.44/0.54] mb/(mb+mc) magnitude ratio
212-232 F21.19 --- R1 [0.0/0.01] Radius of planet b in R* units
234-254 F21.19 --- R2 [0.0/0.01] Radius of planet c in R* units
256-275 F20.18 --- Impact1 [0.0/0.72] Impact parameter for planet b
277-294 F18.16 --- Impact2 [0.72/0.9] Impact parameter for planet c
296-313 F18.14 d t0-03 [134.81/134.87] Time of transit for 03
(BJD-2454833.0)
315-332 F18.16 d P03 [4.02/4.03] Period for 03
334-354 F21.19 --- R03 [0.0/0.01] Radius for 03 in R* units
356-376 F21.19 --- Impact03 [0.0/0.64] Impact parameter for 03
378-396 F19.16 [-] logsigjitt0 [-4.41/-4.38] Light curve jitter
398-416 F19.16 [-] logsigGP0 [-9.98/-6.16] Gaussian process amplitude
418-437 F20.18 [d] logtauGP0 [0.01/3.0] Gaussian process timescale
439-457 F19.17 Sun rho* [0.31/0.56] Stellar density in
Sun density units
459-477 F19.17 --- limbdarku1 [0.37/0.54] Limb darkening coefficient u1
479-497 F19.17 --- limbdarku2 [0.15/0.34] Limb darkening coefficient u2
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Acknowledgements:
Adrien Leleu, Adrien.Leleu(at)unige.ch
(End) Patricia Vannier [CDS] 24-Mar-2022