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The NEID Earth Twin Survey. IV. Confirming an 89 d, $m\sin i=10~\mathrm{M_\oplus}$ Planet Orbiting a Nearby Sun-like Star

Mark R. Giovinazzi, Evan Fitzmaurice, Arvind F. Gupta, Paul Robertson, Suvrath Mahadevan, Eric B. Ford, Jaime A. Alvarado-Montes, Chad F. Bender, Cullen H. Blake, Jiayin Dong, Rachel B. Fernandes, Samuel Halverson, Te Han, Shubham Kanodia, Daniel M. Krolikowski, Sarah E. Logsdon, Joe P. Ninan, Arpita Roy, Christian Schwab, Gudmundur Stefansson, Ryan C. Terrien, Jason T. Wright

Abstract

We present the confirmation of HD 190360 d, a warm ($P=88.690^{+0.051}_{-0.049}~\mathrm{d}$), low-mass ($m\sin i=10.23^{+0.81}_{-0.80}~\mathrm{M_\oplus}$) planet orbiting the nearby ($d=16.0$ pc), Sun-like (G7) star HD 190360. We detect HD 190360 d at high statistical significance even though its radial velocity (RV) semi-amplitude is only $K=1.48\pm0.11~\mathrm{m~s^{-1}}$. Such low-amplitude signals are often challenging to confirm due to potential confusion with low-amplitude stellar signals. The HD 190360 system previously had two known planets: the $1.7~\mathrm{M_J}$ (true mass) HD 190360 b on a $7.9$ yr orbit and the $21~\mathrm{M_\oplus}$ (minimum mass) HD 190360 c on a $17.1$ d orbit. Here, we present an in-depth analysis of the HD 190360 planetary system that comprises more than 30 years of RV measurements and absolute astrometry from the Hipparcos and Gaia spacecrafts. Our analysis uses more than 1400 RVs, including nearly 100 from NEID. The proper motion anomaly as measured by these two astrometric missions solves for the dynamical mass of HD 190360 b and contributes to our understanding of the overall system architecture, while the long baseline of RVs enables the robust characterization of HD 190360 c and confirms the discovery of HD 190360 d.

The NEID Earth Twin Survey. IV. Confirming an 89 d, $m\sin i=10~\mathrm{M_\oplus}$ Planet Orbiting a Nearby Sun-like Star

Abstract

We present the confirmation of HD 190360 d, a warm (), low-mass () planet orbiting the nearby ( pc), Sun-like (G7) star HD 190360. We detect HD 190360 d at high statistical significance even though its radial velocity (RV) semi-amplitude is only . Such low-amplitude signals are often challenging to confirm due to potential confusion with low-amplitude stellar signals. The HD 190360 system previously had two known planets: the (true mass) HD 190360 b on a yr orbit and the (minimum mass) HD 190360 c on a d orbit. Here, we present an in-depth analysis of the HD 190360 planetary system that comprises more than 30 years of RV measurements and absolute astrometry from the Hipparcos and Gaia spacecrafts. Our analysis uses more than 1400 RVs, including nearly 100 from NEID. The proper motion anomaly as measured by these two astrometric missions solves for the dynamical mass of HD 190360 b and contributes to our understanding of the overall system architecture, while the long baseline of RVs enables the robust characterization of HD 190360 c and confirms the discovery of HD 190360 d.

Paper Structure

This paper contains 14 sections, 1 equation, 7 figures, 1 table.

Table of Contents

  1. Introduction
  2. Data
  3. TESS
  4. NEID
  5. Archival RVs
  6. Stellar Parameters
  7. MCMC Analysis
  8. Results
  9. Discussion
  10. 89 d Period vs. Known Activity Cycles
  11. Long-term Stability
  12. HD 190360 d: Super-Earth or Sub-Neptune?
  13. Comparison to Other Multi-planet Systems
  14. Conclusion

Figures (7)

  • Figure 1: HD 190360 d period distribution for three unique MCMC fits with varying RV datasets. The blue histogram is the period determined from the joint astrometric and RV analysis outlined in Section \ref{['sec:analysis']} and adopted in this work. Both the red and gray histograms are constructed within the same framework; the red histogram includes only RVs from NEID, whereas the gray histogram includes all RVs except those from NEID. Each case jointly incorporates absolute astrometry from Hipparcos and Gaia. The "No NEID" fit yields two period peaks at 88.8 d and 90.2 d, but we find that the precision and phase coverage from NEID is sufficient for breaking the bimodality.
  • Figure 2: Top panel: RV timeseries for HD 190360. Bottom panel: phase-folded RV diagrams for HD 190360's three known planets. Here, only the NEID data are left opaque to showcase their constraint on each of the planets.
  • Figure 3: Corner plot of HD 190360 d. From left to right, parameters are stellar mass, minimum planet mass, semimajor axis, eccentricity, and argument of periastron.
  • Figure 4: Top: timeseries of NEID Ca II H and K values. Bottom: Lomb-Scargle periodogram for the same dataset. The horizontal dashed line marks the 0.1% false alarm probability (FAP) level, computed using astropy's Lomb-Scargle routine following the approach outlined in 2008MNRAS.385.1279B. We identify no strong periods at or near the signal reported for HD 190360 d.
  • Figure 5: Dynamical separation distributions for the three combinations of interacting planets. We observe that all three combinations have $\Delta>12$ by a relatively wide margin. A priori, interactions between HD 190360 c and HD 190360 d would be expected to be the largest, and so their $\Delta$ distribution being the highest is a promising indicator that this configuration of planets would have been long-term stable.
  • ...and 2 more figures