Resolving period aliases for TESS monotransits recovered during the extended mission

TL;DR

This study investigates methods to resolve period aliases in TESS monotransit exoplanet candidates by simulating observations and assessing the effectiveness of follow-up photometry and spectroscopy.

Contribution

It demonstrates that combined follow-up observations can significantly reduce period ambiguities for TESS monotransits, improving exoplanet characterization.

Findings

Approximately 400 exoplanets detected with one transit in each mission phase.

Average of 38 period aliases per system without follow-up.

Up to 207 systems' periods can be accurately determined with combined NGTS and CORALIE observations.

Abstract

We set out to explore how best to mitigate the number of period aliases for a transiting TESS system with two identified transits separated by a large time period on the order of years. We simulate a realistic population of doubly transiting planets based on the observing strategy of the TESS primary and extended missions. We next simulate additional observations using photometry (NGTS) and spectroscopy (HARPS and CORALIE) and assess its impact on the period aliases of systems with two TESS transits. We find that TESS will detect around 400 exoplanets that exhibit one transit in each of the primary and extended missions. Based on the temporal coverage, each of these systems will have an average of 38 period aliases. We find that, assuming a combination of NGTS and CORALIE over observing campaigns spanning 50 days, we can find the true alias, and thus solve the period, for up to 207 of these systems with even more being solved if the observing campaigns are extended or we upgrade to HARPS over CORALIE.