Dr. Rabus, Markus

We validate the presence of a two-planet system orbiting the 0.15–1.4 Gyr K4 dwarf TOI 560 (HD 73583). The system consists of an inner moderately eccentric transiting mini-Neptune (TOI 560 b, P 6.3980661 0.00000970.0000095 = -+ days,e 0.294 0.0620.13= -+ , M M0.94 0.230.31 Nep= -+ ) initially discovered in the Sector 8 Transiting Exoplanet Survey Satellite (TESS) mission observations, and a transiting mini-Neptune (TOI 560 c, P 18.8805 0.00110.0024 = - + days, M M1.32 0.320.29 Nep= -+ ) discovered in the Sector 34 observations, in a rare near-1:3 orbital resonance. We utilize photometric data from TESS Spitzer, and ground-based follow-up observations to confirm the ephemerides and period of the transiting planets, vet false-positive scenarios, and detect the photoeccentric effect for TOI 560 b. We obtain follow-up spectroscopy and corresponding precise radial velocities (RVs) with the iSHELL spectrograph at the NASA Infrared Telescope Facility and the HIRES Spectrograph at Keck Observatory to validate the planetary nature of these signals, which we combine with published Planet Finder Spectrograph RVs from the Magellan Observatory. We detect the masses of both planets at >3σ significance. We apply a Gaussian process (GP) model to the TESS light curves to place priors on a chromatic RV GP model to constrain the stellar activity of the TOI 560 host star, and confirm a strong wavelength dependence for the stellar activity demonstrating the ability of near-IR RVs to mitigate stellar activity for young K dwarfs. TOI 560 is a nearby moderately young multiplanet system with two planets suitable for atmospheric characterization with the James Webb Space Telescope and other upcoming missions. In particular, it will undergo six transit pairs separated by <6 hr before 2027 June.

We present and confirm TOI-1751 b, a transiting sub-Neptune orbiting a slightly evolved, solar-type, metal-poor star (Teff = 5996 ± 110 K, log(g)=4.2 + 0.1, V = 9.3 mag, [Fe/H] = −0.40 ± 0.06 dex) every 37.47 days. We use TESS photometry to measure a planet radius of 2.77-0.07+0.15 R. We also use both Keck/HIRES and APF/Levy radial velocities (RV) to derive a planet mass of 14.5-3.14+3.15M, and thus a planet density of 3.6 ± 0.9 g cm−3. There is also a long-period (∼400 days) signal that is observed in only the Keck/HIRES data. We conclude that this long-period signal is not planetary in nature and is likely due to the window function of the Keck/HIRES observations. This highlights the role of complementary observations from multiple observatories to identify and exclude aliases in RV data. Finally, we investigate the potential compositions of this planet, including rocky and water-rich solutions, as well as theoretical irradiated ocean models. TOI-1751 b is a warm sub-Neptune with an equilibrium temperature of ∼820 K. As TOI-1751 is a metal-poor star, TOI-1751 b may have formed in a water-enriched formation environment. We thus favor a volatile-rich interior composition for this planet.

We report the confirmation of a TESS-discovered transiting super-Earth planet orbiting a mid-G star, HD 307842(TOI-784). The planet has a period of 2.8 days, and the radial velocity (RV) measurements constrain the mass to beM9.67 0.820.83-+ Å. We also report the discovery of an additional planet candidate on an outer orbit that is most likelynontransiting. The possible periods of the planet candidate are approximately 20–63 days, with the correspondingRV semiamplitudes expected to range from 3.2 to 5.4 m s−1 and minimum masses from 12.6 to 31.1 M⊕. Theradius of the transiting planet (planet b) is R1.93 0.090.11-+ Å, which results in a mean density of 7.4 g cm1.21.4 3-+ -suggesting that TOI-784 b is likely to be a rocky planet though it has a comparable radius to a sub-Neptune. Wefound TOI-784 b is located at the lower edge of the so-called “radius valley” in the radius versus insolation plane,which is consistent with the photoevaporation or core-powered mass-loss prediction. The TESS data did not revealany significant transit signal of the planet candidate, and our analysis shows that the orbital inclinations of planet band the planet candidate are 88.60 0.860.84-+ and 88°.3–89°.2, respectively. More RV observations are needed to determine the period and mass of the second object, and search for additional planets in this system