# Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X

**Authors:** James Sikora, Jason Rowe, Saugata Barat, Jacob L. Bean, Madison Brady, Jean-Michel Désert, Adina D. Feinstein, Emily A. Gilbert, Gregory Henry, David Kasper, Déreck-Alexandre Lizotte, Michael R. B. Matesic, Vatsal Panwar, Andreas Seifahrt, Hinna Shivkumar, Gudmundur Stefánsson, Julian Stürmer  
**arXiv:** [2304.00797](https://arxiv.org/abs/2304.00797)  
**Date:** 2023-04-03  
**Summary page:** https://www.summarizepaper.com/en/paper/2304.00797v1/

## Key points

- The V1298 Tau system is a young K-type T-Tauri star with an age of approximately 20-30 million years and a magnitude of $V=10$, hosting four transiting planets.
- The radii of the four planets range from $4.9$ to $9.6$ Earth radii, and their orbital periods range from approximately 8 to 24 days for the three inner planets.
- Planets b, c, and d are proto-sub-Neptunes that may be undergoing significant mass loss, but are expected to evolve into super-Earths/sub-Neptunes that bound the radius valley.
- A joint transit and radial velocity (RV) modelling analysis using recently obtained \emph{TESS} photometry and MAROON-X RV measurements was conducted.
- Planet c has a mass of $19.8_{-8.9}^{+9.3}\,M_\oplus$ with a conservative $2\sigma$ upper limit of $<39\,M_\oplus$. For planets b and d, they derive $2\sigma$ upper limits of $M_{\rm b}<159\,M_\oplus$ and $M_{\rm d}<41\,M_\oplus$.
- Plausible discrete periods longer than 55.4 days are ruled out for planet e at a $3\sigma$ level while seven solutions with periods ranging between 43.3 and 55.4 days are consistent with the most probable solution within $3\sigma$. Adopting the most probable solution yields a mass of $0.66 \pm 0.26 M_{Jup}$.
- Comparing the updated mass and radius constraints with planetary evolution and interior structure models shows that planets b, d, and e are consistent with predictions for young gas-rich planets while planet c is consistent with having a water-rich core with a substantial ($5 \%$ by mass) H$_2$ envelope.
- The authors also present the best fit to the K2 light curve using the ne = 51 (Pe ≈ 46.8 d) solution as well as selected individual transits observed in the K2 LC data set.
- Potential effects of stellar activity on the system's evolution are discussed, as well as future observations that could provide further insights into its properties such as high resolution spectroscopy at longer wavelength ranges.

## Summary

The V1298 Tau system is a young K-type T-Tauri star with an age of approximately 20-30 million years and a magnitude of $V=10$, hosting four transiting planets. The radii of these planets range from $4.9$ to $9.6$ Earth radii, and their orbital periods range from approximately 8 to 24 days for the three inner planets. The period of the outer planet is poorly constrained due to single transits observed with \emph{K2} and \emph{TESS}. Planets b, c, and d are proto-sub-Neptunes that may be undergoing significant mass loss, but depending on the stellar activity and planet masses, they are expected to evolve into super-Earths/sub-Neptunes that bound the radius valley. In this study, the authors present results from a joint transit and radial velocity (RV) modelling analysis using recently obtained \emph{TESS} photometry and MAROON-X RV measurements. Assuming circular orbits, they obtain a low-significance ($\approx2\sigma$) RV detection of planet c implying a mass of $19.8_{-8.9}^{+9.3}\,M_\oplus$ with a conservative $2\sigma$ upper limit of $<39\,M_\oplus$. For planets b and d, they derive $2\sigma$ upper limits of $M_{\rm b}<159\,M_\oplus$ and $M_{\rm d}<41\,M_\oplus$. For planet e, plausible discrete periods longer than 55.4 days are ruled out at a $3\sigma$ level while seven solutions with periods ranging between 43.3 and 55.4 days are consistent with the most probable solution within $3\sigma$. Adopting the most probable solution yields a $2.6\sigma$ RV detection with a mass of $0.66 \pm 0.26 M_{Jup}$. Comparing the updated mass and radius constraints with planetary evolution and interior structure models shows that planets b, d, and e are consistent with predictions for young gas-rich planets while planet c is consistent with having a water-rich core with a substantial ($5 \%$ by mass) H$_2$ envelope. The authors also present the best fit to the K2 light curve using the ne = 51 (Pe ≈ 46.8 d) solution as well as selected individual transits observed in the K2 LC data set . Additionally , they discuss potential effects of stellar activity on the system's evolution , as well as highlight future observations that could provide further insights into its properties such as high resolution spectroscopy at longer wavelength ranges .