J/AJ/162/55 65 Transit-timing variation planets properties (Yee+, 2021)
How close are compact multiplanet systems to the stability limit?
Yee S.W., Tamayo D., Hadden S., Winn J.N.
<Astron. J., 162, 55-55 (2021)>
=2021AJ....162...55Y 2021AJ....162...55Y (SIMBAD/NED BibCode)
ADC_Keywords: Exoplanets; Stars, variable; Stars, masses
Keywords: Exoplanet dynamics; Exoplanet formation; Exoplanet astronomy
Celestial mechanics
Abstract:
Transit surveys have revealed a significant population of compact
multiplanet systems, containing several sub-Neptune-mass planets on
close-in, tightly-packed orbits. These systems are thought to have
formed through a final phase of giant impacts, which would tend to
leave systems close to the edge of stability. Here, we assess this
hypothesis, comparing observed eccentricities in systems exhibiting
transit-timing variations versus the maximum eccentricities compatible
with long-term stability. We use the machine-learning classifier SPOCK
(Tamayo et al.) to rapidly classify the stability of numerous initial
configurations and hence determine these stability limits. While
previous studies have argued that multiplanet systems are often
maximally packed, in the sense that they could not host any additional
planets, we find that the existing planets in these systems have
measured eccentricities below the limits allowed by stability by a
factor of 2-10. We compare these results against predictions from the
giant-impact theory of planet formation, derived from both N-body
integrations and theoretical expectations that, in the absence of
dissipation, the orbits of such planets should be distributed
uniformly throughout the phase space volume allowed by stability. We
find that the observed systems have systematically lower
eccentricities than this scenario predicts, with a median eccentricity
about four times lower than predicted. This suggests that, if these
systems formed through giant impacts, then some dissipation must occur
to damp their eccentricities. This may occur through interactions with
the natal gas disk or a leftover population of planetesimals, or over
longer timescales through the coupling of tidal and secular processes.
Description:
In this paper, we focus our investigation on Transit-timing variation
(TTV) systems containing three or more planets with good mass and
eccentricity constraints. We draw the systems for our study from the
analysis of Hadden & Lithwick, 2017,J/AJ/154/5, who derived masses and
eccentricities for 55 planetary systems based on the Kepler TTV
catalog of Rowe+, 2015, J/ApJS/217/16.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 103 65 *Transit-timing variation (TTV) planet properties
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Note on table1.dat : The values and uncertainties reflect the mode of
the posterior probabilities and 68.3% highest posterior density
intervals around the mode, or 68.3% upper limits if this interval is
consistent with zero.
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See also:
J/ApJS/217/16 : Kepler planetary candidates. V. 3yr Q1-Q12 (Rowe+, 2015)
J/MNRAS/448/1044 : Simul. data for 50 planetary model systems (Hansen+, 2015)
J/ApJ/821/47 : KOI transit proba. of multi-planet syst. (Brakensiek+, 2016)
J/A+A/605/A72 : Planetary systems AMD-stability (Laskar+, 2017)
J/AJ/154/5 : Transit timing variations of 145 Kepler planets (Hadden+, 2017)
J/AJ/156/18 : APOGEE DR14:Binary comp. of evolved stars (Price-Whelan+, 2018)
J/AJ/159/281 : Characteristics of 335 KOI stars (Gilbert+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- ID Planet identifier
14- 20 F7.3 d Per [3.6/131] Orbital period
22- 24 F3.1 Msun Mass* [0.5/1.2] Stellar mass
26- 29 F4.2 Msun E_Mass* [0.03/0.1] Upper uncertainty in M*
31- 34 F4.2 Msun e_Mass* [0.03/0.1] Lower uncertainty in M*
36 I1 --- f_Massp [0/1]Limit flag on Mp (1)
38- 42 F5.2 Mgeo Massp [0.01/35.2] Planetary mass
44- 47 F4.2 Mgeo E_Massp [0.01/6.7]? Upper uncertainty in Mp
49- 52 F4.2 Mgeo e_Massp [0.01/3.8]? Lower uncertainty in Mp
54- 58 F5.3 --- Z [0.001/0.16]? Free eccentricity (2)
60- 64 F5.3 --- E_Z [0/0.1]? Upper uncertainty in Z
66- 70 F5.3 --- e_Z [0/0.1]? Lower uncertainty in Z
72- 76 F5.3 --- Zcom [0.002/0.13]? Center-of-mass eccentricity (3)
78- 82 F5.3 --- E_Zcom [0.004/0.08]? Upper uncertainty in Zcom
84- 88 F5.3 --- e_Zcom [0.002/0.05]? Lower uncertainty in Zcom
90- 93 F4.2 --- Z/Zuns [0.09/09]? Fractional distance to instability of
system
95- 98 F4.2 --- E_Z/Zuns [0.06/0.3]? Upper uncertainty in Z/Zuns
100-103 F4.2 --- e_Z/Zuns [0/0.2]? Lower uncertainty in Z/Zuns
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Note (1): Flags as follows:
0 = not a limit;
1 = lower limit.
Note (2): Derived by Hadden & Lithwick+, 2017, J/AJ/154/5. Because
the free eccentricity Z is a property of adjacent pairs of planets,
we have recorded Z in the row of the inner planet of the pair.
Note (3): Computed according to Eq. 3, and recorded in the row of
the innermost planet.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 16-Nov-2021