J/A+A/655/A66 Transit Timing Variations bias in transit surveys (Leleu+, 2021)
Alleviating the transit timing variations bias in transit surveys.
I. RIVERS: Method and detection of a pair of resonant super-Earths around
Kepler-1705.
Leleu A., Chatel G., Udry S., Alibert Y., Delisle J.-B., Mardling R.
<Astron. Astrophys. 655, A66 (2021)>
=2021A&A...655A..66L 2021A&A...655A..66L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets
Keywords: planets and satellites: detection -
planets and satellites: dynamical evolution and stability -
methods: data analysis - techniques: photometric
Abstract:
Transit Timing Variations (TTVs) can provide useful information for
systems observed by transit, by putting constraints on the masses and
eccentricities of the observed planets, or even constrain the
existence of non-transiting companions. However, TTVs can also act as
a detection bias that can prevent the detection of small planets in
transit surveys, that would otherwise be detected by standard
algorithm such as the Boxed Least Square algorithm (BLS) if their
orbit was not perturbed. This bias is especially present for surveys
with long baseline, such as Kepler, some of the TESS sectors, and the
upcoming PLATO mission. Here we introduce a detection method that is
robust to large TTVs, and illustrate it by recovering and confirming a
pair of resonant super-Earths with 10 hour TTVs around Kepler-1705
(prev. KOI-4772). The method is based on a neural network trained to
recover the tracks of low-SNR perturbed planets in river diagrams.
We then recover the transit parameters of these candidates by fitting
the lightcurve. The individual transit signal-to-noise of Kepler-1705b
and c are about three time smaller than all the previously-known
planets with TTVs of 3 hours or more, pushing the boundary in the
recovering of these small, dynamically active planets. Recovering this
type of object is essential to have a complete picture of the observed
planetary systems, solving for a bias not often taken into account in
statistical studies of exoplanet populations. In addition, TTVs are a
means of obtaining mass estimates which can be essential to studying
the internal structure of planets discovered by transit surveys.
Finally, we show that due to the strong orbital perturbations, it is
possible that the spin of the outer resonant planet of Kepler-1705 is
trapped in a sub or super-synchronous spin-orbit resonance. This would
have important consequences on the climate of the planet since a
non-synchronous spin implies that the flux of the star is spread over
the whole planetary surface.
Description:
Transit timings for Kepler-1705b and Kepler-1705c. All dates are in
BJD-2454833.0, the first column is the median transit dates, the
second column is the 0.15865 quantile, and the third column is the
0.84135 quantile. The fourth column is the difference between the
third and second column, in days.
Objects:
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RA (2000) DE Designation(s)
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20 06 18.85 +44 18 43.8 Kepler-1705 = KOI-4772 = KIC 8397947
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
kep1705b.dat 59 135 Transit timings and uncertainties Kep1705b (table 3)
kep1705c.dat 59 107 Transit timings and uncertainties Kep1705c (table 3)
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Byte-by-byte Description of file: kep1705b.dat kep1705c.dat
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Bytes Format Units Label Explanations
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1- 19 F19.14 d Date Median transit date, BJD-2454833.0
21- 39 F19.14 d b_Date Date 0.15865 quantile, BJD-2454833.0
41- 59 F19.14 d B_Date Date 0.84135 quantile, BJD-2454833.0
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Acknowledgements:
Adiren Leleu, Adrien.Leleu(at)unige.ch
(End) Patricia Vannier [CDS] 22-Oct-2021