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Register a new userNGTS and WASP photometric recovery of a single-transit candidate from TESS
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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 $M_2$= $0.148pm{0.003}$,M$_{odot}$, indicating this system is an F-M eclipsing binary. The radius of the M-dwarf companion is $R_2$ = $0.171pm{0.003}$,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.
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We observed a transit of WASP-166 b using nine NGTS telescopes simultaneously with TESS observations of the same transit. We achieved a photometric precision of 152 ppm per 30 minutes with the nine NGTS telescopes combined, matching the precision reached by TESS for the transit event around this bright (T=8.87) star. The individual NGTS light curve noise is found to be dominated by scintillation noise and appears free from any time-correlated noise or any correlation between telescope systems. We fit the NGTS data for $T_C$ and $R_p/R_*$. We find $T_C$ to be consistent to within 0.25$sigma$ of the result from the TESS data, and the difference between the TESS and NGTS measured $R_p/R_*$ values is 0.9$sigma$. This experiment shows that multi-telescope NGTS photometry can match the precision of TESS for bright stars, and will be a valuable tool in refining the radii and ephemerides for bright TESS candidates and planets. The transit timing achieved will also enable NGTS to measure significant transit timing variations in multi-planet systems.
We report the period, eccentricity, and mass determination for the TESS single-transit event candidate TOI-222, which displayed a single 3000 ppm transit in the TESS two-minute cadence data from Sector 2. We determine the orbital period via radial velocity measurements (P=33.9,days), which allowed for ground-based photometric detection of two subsequent transits. Our data show that the companion to TOI-222 is a low mass star, with a radius of $0.18_{-0.10}^{+0.39}$ Rsun and a mass of $0.23pm0.01$ Msun. This discovery showcases the ability to efficiently discover long-period systems from TESS single transit events using a combination of radial velocity monitoring coupled with high precision ground-based photometry.
We report the discovery of NGTS-11 b (=TOI-1847 b), a transiting Saturn in a 35.46-day orbit around a mid K-type star (Teff=5050 K). We initially identified the system from a single-transit event in a TESS full-frame image light-curve. Following seventy-nine nights of photometric monitoring with an NGTS telescope, we observed a second full transit of NGTS-11 b approximately one year after the TESS single-transit event. The NGTS transit confirmed the parameters of the transit signal and restricted the orbital period to a set of 13 discrete periods. We combined our transit detections with precise radial velocity measurements to determine the true orbital period and measure the mass of the planet. We find NGTS-11 b has a radius of 0.817+0.028-0.032 $R_J$, a mass of 0.344+0.092-0.073 $M_J$, and an equilibrium temperature of just 435+34-32 K, making it one of the coolest known transiting gas giants. NGTS-11 b is the first exoplanet to be discovered after being initially identified as a TESS single-transit event, and its discovery highlights the power of intense photometric monitoring in recovering longer-period transiting exoplanets from single-transit events.
The Transiting Exoplanet Survey Satellite (TESS) has produced a large number of single transit event candidates which are being monitored by the Next Generation Transit Survey (NGTS). We observed a second epoch for the TIC-231005575 system (Tmag = 12.06, Teff = 5500 +- 85 K) with NGTS and a third epoch with Las Cumbres Observatorys (LCO) telescope in South Africa to constrain the orbital period (P = 61.777 d). Subsequent radial velocity measurements with CORALIE revealed the transiting object has a mass of M2 = 0.128 +- 0.003 M$_odot$, indicating the system is a G-M binary. The radius of the secondary is R2 = 0.154 +- 0.008 R$_odot$ and is consistent with models of stellar evolution to better than 1-$sigma$.
We describe the catalogs assembled and the algorithms used to populate the revised TESS Input Catalog (TIC), based on the incorporation of the Gaia second data release. We also describe a revised ranking system for prioritizing stars for 2-minute cadence observations, and assemble a revised Candidate Target List (CTL) using that ranking. The TIC is available on the Mikulski Archive for Space Telescopes (MAST) server, and an enhanced CTL is available through the Filtergraph data visualization portal system at the URL http://filtergraph.vanderbilt.edu/tess_ctl.
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