TASSIE: a TASmanian Search for Inclined Exoplanets

TL;DR

The TASSIE program conducted initial observations of five TESS exoplanet candidates, validating one as a Jovian-sized planet and ruling out planetary signals for three others, focusing on southern giant planet candidates.

Contribution

First pilot study using TESS and ground-based follow-up to validate and characterize short-period exoplanets in the southern hemisphere, especially in the sub-Jovian desert.

Findings

Confirmed one hot sub-Jovian to Jovian planet (TOI3097Ab).

Ruled out planetary nature for three candidates (TOI3070, TOI3124, TOI4266).

Detected a Jovian-sized planet around a late F dwarf star (TOI3163).

Abstract

We present the first results of a pilot 'TASmanian Search for Inclined Exoplanets' (TASSIE) program. This includes observations and analysis of five short-period exoplanet candidates using data from TESS and the Harlingten 50 cm telescope at the Greenhill Observatory. We describe the instrumentation, data reduction process and target selection strategy for the program. We utilise archival multi-band photometry and new mid-resolution spectra to determine stellar parameters for five TESS Objects of Interest (TOIs). We then perform a statistical validation to rule out false positives, before moving on to a joint transit analysis of the remaining systems. We find that TOI3070, TOI3124 and TOI4266 are likely non-planetary signals, which we attribute to either short-period binary stars on grazing orbits or stellar spots. For TOI3097, we find a hot sub-Jovian to Jovian size planet ($R_{3097Ab}$ = 0.89 $\pm$ 0.04 $R_{J}$, $P_{3097Ab}$ = 1.368386 $\pm$ 0.000006 days) orbiting the primary K dwarf star in a wide binary system. This system shows indications of low metallicity ([Fe/H] $\approx$ -1), making it an unlikely host for a giant planet. For TOI3163, we find a Jovian-size companion on a circular orbit around a late F dwarf star, with $R_{3163b}$ = 1.42 $\pm$ 0.05 $R_{J}$ and $P_{3163b}$ = 3.074966 $\pm$ 0.000022 days. In future, we aim to validate further southern giant planet candidates with a particular focus on those residing in the sub-Jovian desert/savanna.