NGTS and WASP photometric recovery of a single-transit candidate from TESS

TL;DR

This study demonstrates how combining TESS, WASP, and NGTS photometry can effectively identify and characterize a long-period eclipsing binary system, revealing detailed properties of the M-dwarf companion.

Contribution

First detection of a single-transit event from TESS, followed by multi-instrument follow-up to determine the system's orbital and stellar parameters.

Findings

The orbital period is 38.20 days.

The M-dwarf companion has a mass of 0.148 solar masses.

The M-dwarf's radius is smaller than stellar models predict.

Abstract

The Transiting Exoplanet Survey Satellite (\tess) produces a large number of single-transit event candidates, since the mission monitors most stars for only $\sim$27\,days. Such candidates correspond to long-period planets or eclipsing binaries. Using the \tess\ Sector 1 full-frame images, we identified a 7750\,ppm single-transit event with a duration of 7\,hours around the moderately evolved F-dwarf star \tic\ (Tmag=10.23, \teff=6280$\pm{85}$\,K). Using archival WASP photometry we constrained the true orbital period to one of three possible values. We detected a subsequent transit-event with NGTS, which revealed the orbital period to be 38.20\,d. Radial velocity measurements from the CORALIE Spectrograph show the secondary object has a mass of $M_2$= $0.148\pm{0.003}$\,M$_{\odot}$, indicating this system is an F-M eclipsing binary. The radius of the M-dwarf companion is $R_2$ = $0.171\pm{0.003}$\,R$_{\odot}$, making this one of the most well characterised stars in this mass regime. We find that its radius is 2.3-$\sigma$ lower than expected from stellar evolution models.