Single site observations of TESS single transit detections

Abstract

Context. The Transiting Exoplanet Survey Satellite (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. We aim to simulate the number of TESS transit detections during its two-year mission with a particular emphasis on single transits. We also aim to determine the feasibility of ground-based follow-up observations from a single site. Methods. A distribution of planets was simulated around the approximately four million stars in the TESS candidate target list. These planets were tested for detectable transits and characterised. Based on simulated parameters the single transit detections were 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 ≳45 days the number of single transit detections outnumber multitransits by a factor of three (82 ± 18 and 25 ± 7, respectively) a factor which only grows as longer period detections are considered. Therefore, based on this paper, 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 a single ground-based site. However, further work is required to determine whether these follow-up efforts are feasible when accounting for target specific criteria.