TIC65910228b: A single-transit discovery of a massive long-period warm Jupiter with TESS

TL;DR

This work addresses the scarcity of well-characterized long-period warm Jupiters, starting from a single TESS transit and confirming TIC65910228b as a transiting giant. A joint analysis of TESS photometry, ground-based light curves (HATPI, OM-ES1), and precise RVs from FEROS and PLATOSpec yields $P=180.524140$ days, $M_p=4.554_{-0.247}^{+0.255} m{M_J}$, $R_p=1.088_{-0.057}^{+0.061} m{R_J}$, and $e=0.25_{-0.04}^{+0.03}$ around an evolved F-type host with $T_{ m eff} eq$6235 K and [Fe/H] ≈ $+0.14$. Interior modeling suggests a low-heavy-element composition, compatible with a solar-envelope envelope and a possible core up to ~160 M⊕, implying $Z_p/Z_* oughly0.7^{+3.0}_{-0.7}$. The planet expands the cohort of long-period ($P>100$ d), massive ($M_p>4$ M_J) transiting giants and highlights the utility of single-transit follow-up for mapping this region of parameter space, with RM or high-precision follow-up offering avenues to constrain obliquity and formation history. The study also notes that, despite modest atmospheric prospects (TSM ≈ 3.44, ESM ≈ 4.8), the system serves as a benchmark for combining transit and RV data to characterize distant giant planets around evolved stars.

Abstract

Context. Warm Jupiters are excellent case studies for the investigation of giant planet internal structures and formation theories. However, the sample of long-period transiting giants is still small today for a better understanding of this population. Aims. Starting from a single transit found in the Transiting Exoplanet Survey Satellite (TESS) data, we confirm the planetary nature of the signal and measure its orbital parameters, mass, and radius. We put this system in the context of long-period giant transiting planets and analyzed the viability to sustain atmospheric or dynamical follow-up. Methods. We carried out a spectroscopic follow-up using FEROS and PLATOSpec to obtain precise radial velocities. We added a photometric follow-up with HATPI and Observatoire Moana to obtain a more precise estimate of the orbital period. We derived the orbital and physical parameters through a joint analysis of this data. Results. We report the discovery and characterization of TIC65910228b, a transiting warm Jupiter with a mass of $4.554 \pm 0.255$ $M_J$ and a radius of $1.088 \pm 0.061$ $R_J$, orbiting an evolved F-type star every $\sim 180.52$ days in an eccentric orbit ($e = 0.25 \pm 0.04$). Conclusions. This planet joins a still under-explored population of long-period ($P > 100$) massive ($M_p > 4$ $M_J$) transiting giant planets, being one of the few with a mild eccentricity. This target is a nice example of the potential of single-transit events to populate this region of the parameter space.

Figures (11)

• Figure 1: TESS Target Pixel File preview of TIC65910228 . Aperture used in TESS-SPOC light curve corresponds to the overplotted red dashed area. Gaia DR3 sources up to 7 magnitudes of difference are overplotted in red dots. Dot size is proportional to brightness.
• Figure 2: Periodograms displaying periodic signals in the radial velocities, HATPI photometry, radial-velocity bisector span and radial-velocity FWHM. The green vertical line indicates the optimal period derived from radial-velocity data. Horizontal dashed line corresponds to the 1% false alarm probability.
• Figure 3: Bisector vs radial velocity scatter plot. Spearman's rank correlation coefficient $\rho$ shows no significant correlation between the two variables, ruling out the possibility that the RV signal has an activity origin traced by the Bisector.
• Figure 4: Light curve of TESS Sector 33. The best-fit model is overplotted in black.
• Figure 5: Top panel: Observed transits with TESS, HATPI and OM-ES1, respectively. Model from joint-fit is overplotted. White circles correspond to 1-hour bins in HATPI and OMES1 light curves. Bottom panel: Residuals after removing the transit model.