Single site observations of \textit{TESS} single transit detections

TL;DR

This study simulates TESS's 2-year mission to estimate the number of single transit detections, emphasizing their follow-up potential from a single ground-based site, especially for longer period exoplanets.

Contribution

It provides the first detailed simulation of TESS's single transit detections and assesses their feasibility for ground-based follow-up from a single site.

Findings

Approximately 4700 planets will be discovered by TESS, with around 460 being single transits.

A single ground-based site can observe about 1000 transit events from these detections annually.

Single transits for periods >45 days outnumber multitransits by a factor of 3, highlighting their importance.

Abstract

Context: TESS has been successfully launched and has begin data acquisition. To expedite the science that may be performed with the resulting data it is necessary to gain a good understanding of planetary yields. Given the observing strategy employed by TESS the probability of detecting single transits in long period systems is increased. These systems require careful consideration. Aims: To simulate the number of TESS transit detections during its 2 year mission with a particular emphasis on single transits. Additionally, to determine the feasibility of ground-based follow-up observations from a single site. Methods: A distribution of planets is simulated around the $\sim$ 4 million stars in the TESS Candidate Target List. These planets are tested for detectable transits and characterised. Based on simulated parameters the single transit detections are further analysed to determine which are amenable to ground-based follow-up. Results: TESS will discover an approximate lower bound of 4700 planets with around 460 being single transits. A large fraction of these will be observable from a single ground-based site. This paper finds that, in a single year, approximately 1000 transit events of around 320 unique TESS single transit detections are theoretically observable. Conclusions: As we consider longer period exoplanets the need for exploring single transit detections increases. For periods $\gtrsim45$ days the number of single transit detections outnumber multitransits by a factor of 3 (82$\pm$18 and 25$\pm$7 respectively) a factor which only grows as longer period detections are considered. Therefore, it is worth expending the extra effort required to follow-up these more challenging, but potentially very rewarding, discoveries. Additionally, we conclude that a large fraction of these targets can be theoretically observed from just a single ground-based site.