A Well-aligned Orbit for the 45 Myr-old Transiting Neptune DS Tuc Ab

Abstract

DS Tuc Ab is a Neptune-sized planet that orbits around a G star in the 45 Myr old Tucana-Horologium moving group. Here, we report the measurement of the sky-projected angle between the stellar spin axis and the planet's orbital axis, based on the observation of the Rossiter-McLaughlin effect during three separate planetary transits. The orbit appears to be well aligned with the equator of the host star, with a projected obliquity of λ = 2.5 +1.0 −0.9• . In addition to the distortions in the stellar absorption lines due to the transiting planet, we observed variations that we attribute to large starspots, with angular sizes of tens of degrees. The technique we have developed for simultaneous modeling of starspots and the planet-induced distortions may be useful in other observations of planets around active stars.

TOI-2076 and TOI-1807: Two Young, Comoving Planetary Systems within 50 pc Identified by TESS that are Ideal Candidates for Further Follow Up

“…In this sense TOI-1807b is the most promising target for mass follow up, as its ultra-short orbital period suggests that the Keplerian signal will be separable from activity at the rotation period of the star. As demonstrated by recent Rossiter-McLaughlin (RM) effect measurements on very young and active stars, it is feasible to measure short-duration RV signals on timescales of hours even in the presence of high-amplitude stellar variability on longer timescales of days (Montet et al 2020;Zhou et al 2020). RV follow up of TOI-2076b/c/d will be more challenging because the planetary orbital periods are comparable to the stellar rotation, and the complexity of the multiplanet RV signal requires a larger number of observations.…”

Populating the brown dwarf and stellar boundary: Five stars with transiting companions near the hydrogen-burning mass limit

“…Each observation was composed of 3 × 20 min exposures. The spectral extraction was performed by the default CHIRON pipeline (Piskunov & Valenti 2002), and the RVs were derived from the CHIRON spectra by a least-squares deconvolution technique (Zhou et al 2020), and are listed in Table A.1.…”

Two Young Planetary Systems around Field Stars with Ages between 20 and 320 Myr from TESS

“…R. Newton et al 2020, in preparation;Mann et al 2020;Plavchan et al 2020;Rizzuto et al 2020). These are the first planets around bright young stars that are suitable for in-depth characterizations, enabling the first obliquity measurements of newly formed planets (Montet et al 2020;Zhou et al 2020), as well as atmospheric studies in the near future.…”