J/MNRAS/505/1293 Duration measurements analysis KOIs planets (Shahaf+, 2021)
Systematic search for long-term transit duration changes in Kepler
transiting planets.
Shahaf S., Mazeh T., Zucker S. and Fabrycky D.
<Mon. Not. R. Astron. Soc. 505, 1293-1366 (2021)>
=2021MNRAS.505.1293S 2021MNRAS.505.1293S (SIMBAD/NED BibCode)
ADC_Keywords: Exoplanets ; Stars, double and multiple ; Binaries, orbits
Keywords: planets and satellites: general
Abstract:
Holczer, Mazeh, and collaborators (Holczer et al. 2016ApJS..225....9H 2016ApJS..225....9H,
Cat. J/ApJS/225/9) used the Kepler 4-yr observations to derive a
transit-timing catalog, identifying 260 Kepler objects of interest
(KOI) with significant transit timing variations (TTV). For KOIs with
high enough S/Ns, HM+16 also derived the duration and depth of their
transits. In this work, we use the duration measurements of HM+16 to
systematically study the duration changes of 561 KOIs and identify 15
KOIs with a significant long-term linear change of transit durations
and another 16 KOIs with an intermediate significance. We show that
the observed linear trend is probably caused by a precession of the
orbital plane of the transiting planet, induced in most cases by
another planet. The leading term of the precession rate depends on the
mass and relative inclination of the perturber, and the period ratio
between the two orbits, but not on the mass and period of the
transiting planet itself. Interestingly, our findings indicate that,
as a sample, the detected time derivatives of the durations get larger
as a function of the planetary orbital period, probably because
short-period planetary systems display small relative inclinations.
The results might indicate that short-period planets reside in
relatively flattened planetary systems, suggesting these systems
experienced stronger dissipation either when formed or when migrated
to short orbits. This should be used as a possible clue for the
formation of such systems.
Description:
From the catalogue of HM+16 (Holczer et al. 2016ApJS..225....9H 2016ApJS..225....9H,
Cat. J/ApJS/225/9) including a subset of 561 KOIs with at least 10
transit-duration measurements that had not been tagged as False
Positives by the Kepler team (Twicken et al. 2016AJ....152..158T 2016AJ....152..158T,
Cat. J/AJ/152/158).
We constitute our exoplanet sample properties. First, for each KOI in
the restricted sample, we estimated the scatter of the obtained
transit durations by their median absolute deviation (Hampel et al.
1974, J. Am. Stat. Assoc., 69, 383), and compared it to the median
of the reported duration uncertainty. We expected these two statistics
to have similar values for a transiting planet without a real duration
variation which is indeed the case for most KOIs, except for some
systems that exhibit scatter values larger than expected.
Secondly, we searched for a linear trend of the transit duration of
each KOI by fitting a straight line to its duration measurements as a
function of time. To mitigate the effect of outliers, we performed a
fit that used a robust weighted linear regression, while minimizing
the chi2 under the bi-square weight-function penalty
(e.g. Beaton & Tukey 1974, Technometrics, 16, 147).
Hereafter, to each derived linear trend, we assigned a p-value that
represented the probability that the fitted slope was consistent with
zero, using the t-statistic based on the derived slope divided by its
estimated uncertainty.
Furthermore, transit duration may also display variations on short
time-scales relative to the 4-yr Kepler campaign, introducing an
increased correlated scatter around the long-term linear trend. To
test for the presence of such correlated scatter, we used the Abbe
statistic (e.g. Kendall 1971, Biometrika, 58, 369; Lemeshko
2006, Meas. Tech., 49, 962 see Appendix A) applied to the duration
time-series before and after subtracting the best-fitting linear
trend.
The table1.dat lists the results for all 561 KOIs, along with the
orbital period, impact parameter, and planetary radius reported in the
NASA exoplanet archive KOI table (e.g exoplanetarchive.ipac.caltech.edu).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 561 Transit details and variance analysis of the
duration measurements for the 561 KOIs
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See also:
J/ApJS/218/26 : Parameters of planets orbiting coolest dwarfs (Swift+, 2015)
J/ApJS/225/9 : Kepler TTVs. IX. The full long-cadence data set (Holczer+,2016)
J/AJ/152/158 : Final Kepler transiting planet search (DR25) (Twicken+, 2016)
J/ApJS/234/9 : A spectral approach to transit timing variations (Ofir+, 2018)
J/AJ/165/34 : Habitable Zone Exoplanets from NASA Archive (Hill+, 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 --- KOI KOI number ID (KOI) (1)
9- 17 F9.5 d Period Orbital transit period (Period) (1)
19- 24 F6.3 h Duration Duration time of the measurement (Duration)
(1)
26- 30 F5.3 --- b Impact parameter (b) (1)
32- 38 F7.3 Rgeo Rp Planetary radius (Rp) (1)
40- 45 F6.4 min sigma Median absolute deviation of the transit
durations (sigma)
47- 52 F6.4 min Delta Median of the reported duration uncertainty
of the transit durations (delta)
54- 60 F7.3 min/yr dT/dt Derived linear trend of the transit
duration (Tdot)
62- 67 F6.3 min/yr e_dT/dt Mean error on dTd/dt (Tdot_err)
69- 76 E8.3 --- p-value Probability that the fitted slope was
consistent with zero (p-value)
78- 81 F4.2 --- Abbe Abbe statistic value of the duration
measurements before subtracting the
best-fitting linear trend (Abbe)
83- 86 F4.2 --- Abbe-res Abbe statistic value of the duration
measurements after subtracting the
best-fitting linear trend (Abbe-residual)
88- 91 I4 --- N Number of transits with a duration
measurement (N)
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Note (1): KOI number, period, impact parameter b, and planetary radius, RP,
are taken from the NASA exoplanet catalogue
exoplanetarchive.ipac.caltech.edu.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 21-May-2024