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

An unprecedented number of exoplanets are being discovered by the Transiting Exoplanet Survey Satellite (TESS). Determining the orbital parameters of these exoplanets, and especially their mass and radius, will depend heavily upon the measured physical characteristics of their host stars. We have cross-matched spectroscopic, photometric, and astrometric data from GALAH Data Release 2, the TESS Input Catalog and Gaia Data Release 2, to create a curated, self-consistent catalogue of physical and chemical properties for 47 285 stars. Using these data, we have derived isochrone masses and radii that are precise to within 5 per cent. We have revised the parameters of three confirmed, and twelve candidate, TESS planetary systems. These results cast doubt on whether CTOI-20125677 is indeed a planetary system, since the revised planetary radii are now comparable to stellar sizes. Our GALAH-TESS catalogue contains abundances for up to 23 elements. We have specifically analysed the molar ratios for C/O, Mg/Si, Fe/Si, and Fe/Mg, to assist in determining the composition and structure of planets with Rp < 4R⊕. From these ratios, 36 per cent fall within 2$\sigma$ sigma of the Sun/Earth values, suggesting that these stars may host rocky exoplanets with geological compositions similar to planets found within our own Solar system.JTC would like to thank SW, BC, and DN, and is supported by the Australian Government Research Training Program (RTP) Scholarship. JTC would also like to thank Vardan Adibekyan for their valuable comments which have significantly improved the science of this manuscript. JDS and SM acknowledges the support of the Australian Research Council through Discovery Project grant DP180101791. SB acknowledges funds from the Australian Research Council (grants DP150100250 and DP160103747). Parts of this research were supported by the Australian Research Council (ARC) Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. YST is grateful to be supported by the NASA Hubble Fellowship grant HSTHF2-51425.001 awarded by the Space Telescope Science Institute

Spinning up a Daze: TESS Uncovers a Hot Jupiter orbiting the Rapid-Rotator TOI-778

NASA's Transiting Exoplanet Survey Satellite (TESS) mission, has been uncovering a growing number of exoplanets orbiting nearby, bright stars. Most exoplanets that have been discovered by TESS orbit narrow-line, slow-rotating stars, facilitating the confirmation and mass determination of these worlds. We present the discovery of a hot Jupiter orbiting a rapidly rotating (vsin(i)=35.1±1.0km/s) early F3V-dwarf, HD115447 (TOI-778). The transit signal taken from Sectors 10 and 37 of TESS's initial detection of the exoplanet is combined with follow-up ground-based photometry and velocity measurements taken from Minerva-Australis, TRES, CORALIE and CHIRON to confirm and characterise TOI-778b. A joint analysis of the light curves and the radial velocity measurements yield a mass, radius, and orbital period for TOI-778b of 2.76+0.24−0.23Mjup, 1.370±0.043Rjup and ∼4.63 days, respectively. The planet orbits a bright (V=9.1mag) F3-dwarf with M=1.40±0.05Msun, R=1.70±0.05Rsun, and logg=4.05±0.17. We observed a spectroscopic transit of TOI-778b, which allowed us to derive a sky-projected spin-orbit angle of 18∘±11∘, consistent with an aligned planetary system. This discovery demonstrates the capability of smaller aperture telescopes such as Minerva-Australis to detect the radial velocity signals produced by planets orbiting broad-line, rapidly rotating stars