Dr. Oscar Barragan Villanueva

Abstract:

We report on the discovery and validation of a two-planet system around a bright (V = 8.85 mag) early G dwarf (1.43 $R_{\odot}$, 1.15 $M_{\odot}$, TOI 2319) using data from NASA's Transiting Exoplanet Survey Satellite (TESS). Three transit events from two planets were detected by citizen scientists in the month-long TESS light curve (sector 25), as part of the Planet Hunters TESS project. Modelling of the transits yields an orbital period of \Pb\ and radius of $3.41 _{ - 0.12 } ^ { + 0.14 }$ $R_{\oplus}$ for the inner planet, and a period in the range 19.26-35 days and a radius of $5.83 _{ - 0.14 } ^ { + 0.14 }$ $R_{\oplus}$ for the outer planet, which was only seen to transit once. Each signal was independently statistically validated, taking into consideration the TESS light curve as well as the ground-based spectroscopic follow-up observations. Radial velocities from HARPS-N and EXPRES yield a tentative detection of planet b, whose mass we estimate to be $11.56 _{ - 6.14 } ^ { + 6.58 }$ $M_{\oplus}$, and allow us to place an upper limit of $27.5$ $M_{\oplus}$ (99 per cent confidence) on the mass of planet c. Due to the brightness of the host star and the strong likelihood of an extended H/He atmosphere on both planets, this system offers excellent prospects for atmospheric characterisation and comparative planetology.

Abstract:

We present a new analysis of the light curve of the young planet-hosting star TOI 451 in the light of new observations from TESS Cycle 3. Our joint analysis of the transits of all three planets, using all available TESS data, results in an improved ephemeris for TOI 451 b and TOI 451 c, which will help to plan follow-up observations. The updated mid-transit times are BJD–2,457,000 = ${1410.9896}_{-0.0029}^{+0.0032}$ , ${1411.7982}_{-0.0020}^{+0.0022}$, and ${1416.63407}_{-0.00100}^{+0.00096}$ for TOI 451 b, c, and d, respectively, and the periods are ${1.8587028}_{-10e-06}^{+08e-06}$, ${9.192453}_{-3.3e-05}^{+4.1e-05}$ , and ${16.364932}_{-3.5e-05}^{+3.6e-05}$ days. We also model the out-of-transit light curve using a Gaussian Process with a quasi-periodic kernel, and infer a change in the properties of the active regions on the surface of TOI 451 between TESS Cycles 1 and 3.