Planet Hunters TESS I: TOI 813, a subgiant hosting a transiting Saturn-sized planet on an 84-day orbit

Abstract

We report on the discovery and validation of TOI 813 b (TIC 55525572 b), a transiting exoplanet identified by citizen scientists in data from NASA's Transiting Exoplanet Survey Satellite (TESS ) and the first planet discovered by the Planet Hunters TESS project. The host star is a bright (V = 10.3 mag) subgiant (R = 1.94 R , M = 1.32 M ). It was observed almost continuously by TESS during its first year of operations, during which time four individual transit events were detected. The candidate passed all the standard light curve-based vetting checks, and ground-based follow-up spectroscopy and speckle imaging enabled us to statistically validate the planetary nature of the companion. Detailed modelling of the transits yields a period of 83.8911 +0.0027 −0.0031 days, a planet radius of 6.71 ± 0.38 R ⊕ and a semi major axis of 0.423 +0.031 −0.037 AU. The planet's orbital period combined with the evolved nature of the host star places this object in a relatively under-explored region of parameter space. We estimate that TOI 813 b induces a reflex motion in its host star with a semiamplitude of ∼ 6 m s −1 , making this system a promising target to measure the mass of a relatively long-period transiting planet. cated at low ecliptic latitudes (around 63 per cent of the sky) will be monitored for ≈27.4 continuous days, while a total of ∼2 per cent of the sky at the ecliptic poles will be observed continuously for ∼356 days. This observational strategy means that TESS will provide us with a plethora of short period planets ( 20 d) around bright (V 11 mag), nearby stars, which will allow for detailed characterization (e.g., Barclay et al. 2018;Gandolfi et al. 2018;Huang et al. 2018;Esposito et al. 2019).Longer-period planets will, however, be significantly

Multiple Explanations for the Single Transit of KIC 5951458 Based on Radial Velocity Measurements Extracted with a Novel Matched-template Technique∗

“…Finally, the evolving nature of the narrative describing the KIC5951458 system is one that will become more common owing to the ongoing transit hunting efforts of TESS (Ricker et al 2015). TESS is predicted to discover on the order of 1000 single-transit events in its primary mission alone (Villanueva et al 2019;Dalba et al 2020;Eisner et al 2020;Gill et al 2020). The need to conduct imaging, photometric, and spectroscopic follow-up for many of these discoveries will place an immense burden on the pool of observational resources available to the exoplanet community.…”

“…Additionally, the faintness of typical Kepler host stars severely limits the list of facilities capable of making precise RV measurements. In the case of TESS single-transit detections, time baselines are shorter and host stars are brighter (e.g., Dalba et al 2020;Eisner et al 2020;Gill et al 2020), and the number of detections is expected to be much higher than for Kepler (e.g., Villanueva et al 2019). As a result, follow-up resources must be used strategically to maximize the science return from single-transit detections.…”

The TESS Objects of Interest Catalog from the TESS Prime Mission

“…TOI 813-Members of the public can label transit-like features of TESS light curves on the Planet Hunters TESS platform. 86 The first TESS planet discovered by Planet Hunters was TOI 813 b (Eisner et al 2020). The Planet Hunters TESS team identified the candidate and released it as a CTOI.…”

The GALAH Survey: using galactic archaeology to refine our knowledge of TESS target stars

“…Huang et al 2018;Nielsen et al 2019b;Vanderspek et al 2019;Addison et al 2020;Gilbert et al 2020;Jordán et al 2020). In addition to the 66 confirmed TESS exoplanets, there are more than two thousand TESS Targets of Interest (TOI) and Community Targets of Interest (CTOI) 2 waiting for their exoplanetary status to be confirmed by ground-based teams (e.g Addison et al 2019;Davis et al 2019;Nielsen et al 2019b;Wang et al 2019a;Dalba et al 2020;Eisner et al 2020).…”