TOI-1408: Discovery and Photodynamical Modeling of a Small Inner Companion to a Hot Jupiter Revealed by TTVs

Abstract

We report the discovery and characterization of a small planet, TOI-1408 c, on a 2.2-day orbit located interior to a previously known hot Jupiter, TOI-1408 b ($P=4.42$ d, $M=1.86\pm 0.02M_{\mathrm{Jup}}$, $R=2.4\pm 0.5R_{\mathrm{Jup}}$) that exhibits grazing transits. The two planets are near 2:1 period commensurability, resulting in significant transit timing variations (TTVs) for both planets and transit duration variations (TDVs) for the inner planet. The TTV amplitude for TOI-1408 c is 15% of the planet's orbital period, marking the largest TTV amplitude relative to the orbital period measured to date. Photodynamical modeling of ground-based radial velocity (RV) observations and transit light curves obtained with the Transiting Exoplanet Survey Satellite (TESS) and ground-based facilities leads to an inner planet radius of $2.22\pm 0.06R_{\oplus }$ and mass of $7.6\pm 0.2M_{\oplus }$ that locates the planet into the Sub-Neptune regime. The proximity to the 2:1 period commensurability leads to the libration of the resonant argument of the inner planet. The RV measurements support the existence of a third body with an orbital period of several thousand days. This discovery places the system among the rare systems featuring a hot Jupiter accompanied by an inner low-mass planet.

Accepted to ApJL, 17 pages, 6 figures, 4 tables

References in corpus (34)

• The NumPy array: a structure for efficient numerical computation
• The Gaia mission
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Data Release 3: Summary of the content and survey properties
• The Transiting Exoplanet Survey Satellite
• New Grids of ATLAS9 Model Atmospheres
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• Kepler constraints on planets near hot Jupiters
• PyTransit: Fast and Easy Exoplanet Transit Modelling in Python
• Gaia Data Release 3: Catalogue Validation
• Surface rotation and photometric activity for Kepler targets. II. G and F main-sequence stars, and cool subgiant stars
• Impact on asteroseismic analyses of regular gaps in Kepler data
• ARIADNE: Measuring accurate and precise stellar parameters through SED fitting
• On the Occurrence Rate of Hot Jupiters in Different Stellar Environments
• TESS spots a hot Jupiter with an inner transiting Neptune
• Evidence for Hidden Nearby Companions to Hot Jupiters
• Kepler-730: A hot Jupiter system with a close-in, transiting, Earth-sized planet
• The effect of type I migration on the formation of terrestrial planets in hot-Jupiter systems
• A study of the performance of the transit detection tool DST in space-based surveys. Application of the CoRoT pipeline to Kepler data
• The Discovery of a Planetary Companion Interior to Hot Jupiter WASP-132 b
• TOI-1130: A photodynamical analysis of a hot Jupiter in resonance with an inner low-mass planet
• Ondr}ejov echelle spectrograph, ground based support facility for exoplanet missions
• TESS spots a mini-neptune interior to a hot saturn in the TOI-2000 system
• A new dynamical modeling of the WASP-47 system with CHEOPS observations
• In situ formation of hot Jupiters with companion super-Earths
• Detection of solar-like oscillations in the bright red giant stars $\gamma$ Psc and ${\theta }^1$ Tau from a 190-day high-precision spectroscopic multisite campaign
• A hot super-Earth planet in the WASP-84 planetary system
• TOI-2046b, TOI-1181b and TOI-1516b, three new hot Jupiters from \textit{TESS}: planets orbiting a young star, a subgiant and a normal star
• TOI-1670 b and c: An Inner Sub-Neptune with an Outer Warm Jupiter Unlikely to have Originated from High-Eccentricity Migration
• The SOPHIE search for northern extrasolar planets-XIX. A system including a cold sub-Neptune potentially transiting a V = 6.5 star HD88986
• Going back to basics: accelerating exoplanet transit modelling using Taylor-series expansion of the orbital motion
• Constraining the Densities of the Three Kepler-289 Planets with Transit Timing Variations
• RoadRunner: a fast and flexible exoplanet transit model
• Doppler confirmation of TESS planet candidate TOI1408.01: grazing transit and likely eccentric orbit

Cited by in corpus (6)

• Architecture Classification for Extrasolar Planetary Systems
• TOI-4504: Exceptionally large Transit Timing Variations induced by two resonant warm gas giants in a three planet system
• A close outer companion to the ultra-hot Jupiter TOI-2109 b?
• Evidence for Primordial Alignment II: Insights from Stellar Obliquity Measurements for Hot Jupiters in Compact Multiplanet Systems
• A high mutual inclination system around KOI-134 revealed by transit timing variations
• Uncovering the Rapidly Evolving Orbits of the Dynamic TOI-201 System