Magellan-TESS Survey (MTS)

In 2018, myself and a wonderful group of collaborators started the Magellan-TESS Survey, a project to understand the origins of small planets by measuring their masses, host star compositions, and system architectures. Our sample is drawn from the planets detected by the Transiting Exoplanet Survey Satellite, a follow-up mission to Kepler/K2, searching the whole sky for transiting exoplanets around the closest stars, and our radial velocity observations come from Magellan/PFS. More specifically, we are interested in the following question:

I think the two most important/exciting aspects of this survey are: (1) We will very well characterize roughly 30 small transiting planets, but also use our results to place further constraints on the small end of the mass-radius relation, thus enabling better predictions and a better grasp on the diversity of small planet compositions, and (2) We are incorporating statistically-motivated choices for target selection and observation cadencing, to avoid biasing the mass-radius relation, which has happened in the past when transiting planet masses are measured only to a certain significance (see Montet 2018). I think this is the first ever RV survey designed to focus on the ensemble, versus just individual systems, and to be as unbiased as possible. 

We were lucky enough to be selected for a NASA Exoplanets Research Program grant for this project (I am the Science PI), which will help fund our travel and student and research associate salaries. Our first “year 1.5” results are described here — we find some preliminary but interesting differences with previous mass-radius relations! You can also learn more about our survey by checking out my slides from the January 2020 AAS meeting or my slides from the January 2019 AAS meeting (more survey motivation/background). The survey is on-going (and suffered pandemic-related delays), but I expect data collection to conclude in 2023.

You can also check out one of our first TESS papers, detailing the discovery of HD 21749b and possibly c. This system is interesting for its (relatively) long-period sub-Neptune planet -- the longest period planet yet discovered by TESS! -- and the suggestion of a second, shorter period but smaller planet, perhaps the size of Earth. We will have to collect more radial velocity data to better constrain planet c's mass, which we are doing. But this is another case (similar to our paper on GJ 9827) where we already had radial velocities of HD 21749 from our long-term survey, even before we knew TESS detected anything around this star! Hopefully we will see more serendipitous overlaps between our long-term survey with PFS and TESS in the future. 

There was lots of press for this paper, and it was featured during the TESS press release at the January 2019 AAS!