J/A+A/709/A35 Exotrojan TTV limits in hot Jupiter systems (Zhang+, 2026)
Constraining the presence of exotrojans in hot-Jupiter systems using transit
timing variation observations from TESS.
Zhang Z., Wang W., Ma X., Chen Z., Wang Y., Yu C., Liu S., Gao Y., Tang B.,
Chen D., Ma B.
<Astron. Astrophys. 709, A35 (2026)>
=2026A&A...709A..35Z 2026A&A...709A..35Z (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Ephemerides ; Optical
Keywords: methods: numerical - methods: observational - methods: statistical -
techniques: photometric - ephemerides -
planets and satellites: dynamical evolution and stability
Abstract:
Co-orbital objects, also known as Trojans, are celestial bodies that
share a 1:1 mean motion resonance orbit with a planet.
Many planets in our Solar System hold Trojans, yet none has been
confirmed in exoplanetary systems. While theoretical models suggest
that hot Jupiters are unlikely to retain co-orbitals, their high
transit cadence and deep transits make them accessible targets for
constraining the existence of massive companions using transit timing
variations (TTVs).
The Exoplanet Ephemerides Change Observations (ExoEcho) project aims
to study TTVs in exoplanetary systems using high- precision photometry
from space- and ground-based telescopes. As the third paper in the
ExoEcho project, we investigate the potential existence of exotrojans
in hot-Jupiter systems through a TTV analysis of TESS observations.
In this work, we analyzed TESS photometry for 260 confirmed hot
Jupiters with published radial-velocity-based (RV-based) mass
measurements to search for TTV signals compatible with Trojan
companions. We derived transit times and assessed the compatibility of
TTV residuals with co-orbital models through N-body simulation using
the REBOUND N-body code. Accounting for the physical degeneracy
between Trojan mass and libration amplitude, we placed upper mass
limits on possible companions for typical libration amplitudes.
For a typical libration amplitude of 15°, we rule out exotrojans
more massive than 1 Earth mass in 130 systems (∼50% of our sample).
A more conservative chi2 analysis incorporating observational
uncertainties places this limit at 3 Earth masses. Additionally, we
used the stability boundaries of the 1:1 resonance to exclude
dynamically unstable configurations, ensuring our derived mass limits
fall within the stable regime.
Our results provide stringent constraints on co-orbital formation in
short-period systems and establish a framework for future
high-precision missions such as the PLAnetary Transits and
Oscillations of stars (PLATO) or Earth 2.0 (ET) mission.
Description:
Table 1 gives the measured mid-transit times for the 260 hot Jupiter
systems analysed in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 41 326 List of studied sources
table1.dat 62 7069 Measured mid-transit times for the 260 hot
Jupiter systems analysed in the paper
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Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Planet Planet name
17- 18 I2 h RAh Simbad right ascension (J2000)
20- 21 I2 min RAm Simbad right ascension (J2000)
23- 27 F5.2 s RAs Simbad right ascension (J2000)
30 A1 --- DE- Simbad declination sign (J2000)
31- 32 I2 deg DEd Simbad declination (J2000)
34- 35 I2 arcmin DEm Simbad declination (J2000)
37- 41 F5.2 arcsec DEs Simbad declination (J2000)
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Planet Planet name
17- 20 I4 --- Epoch Transit epoch
22- 39 F18.10 d Tc Mid-transit time
41- 62 E22.20 d e_Tc Uncertainty on Tc
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Acknowledgements:
Zixin Zhang, zhangzx59(at)mail2.sysu.edu.cn
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Patricia Vannier [CDS] 15-Apr-2026