A Tale of Two Peas in a Pod: The Kepler-323 and Kepler-104 Systems
Abstract
In order to understand the relationship between planet multiplicity, mass, and composition, we present newly measured masses of five planets in two planetary systems: Kepler-323 and Kepler-104. We used the HIRES instrument at the W.M. Keck Observatory to collect 79 new radial velocity (RV) measurements for Kepler-323, which we combined with 48 literature RVs from TNG/HARPS-N. We also conducted a reanalysis of the Kepler-104 system, using 44 previously published RV measurements. Kepler-323 b and c have masses of ${2.0}_{-1.1}^{+1.2}$ M ⊕ and 6.5±1.6 M ⊕, respectively, whereas the three Kepler-104 planets are more massive (10.0±2.8 M ⊕, ${7.1}_{-3.5}^{+3.8}$ M ⊕, and ${5.5}_{-3.5}^{+4.6}$ M ⊕ for planets b, c, and d, respectively). The Kepler-104 planets have densities consistent with rocky cores overlaid with gaseous envelopes ( ${4.1}_{-1.1}^{+1.2}$ g cc‑1, ${2.9}_{-1.5}^{+1.7}$ g cc‑1, and ${1.6}_{-1.1}^{+1.5}$ g cc‑1 respectively), whereas the Kepler-323 planets are consistent with having rocky compositions ( ${4.5}_{-2.4}^{+2.8}$ g cc‑1 and ${9.9}_{-2.5}^{+2.7}$ g cc‑1). The Kepler-104 system has among the lowest values for gap complexity ( ${ \mathcal C }$ = 0.004) and mass partitioning ( ${ \mathcal Q }$ = 0.03); whereas, the Kepler-323 planets have a mass partitioning similar to that of the Inner Solar System ( ${ \mathcal Q }$ = 0.28 and ${ \mathcal Q }$ = 0.24, respectively). For both exoplanet systems, the uncertainty in the mass partitioning is affected equally by (1) individual mass errors of the planets and (2) the possible existence of undetected low-mass planets, meaning that both improved mass characterization and improved sensitivity to low-mass planets in these systems would better elucidate the mass distribution among the planets.
- Publication:
-
The Astronomical Journal
- Pub Date:
- April 2024
- DOI:
- 10.3847/1538-3881/ad2840
- arXiv:
- arXiv:2402.13386
- Bibcode:
- 2024AJ....167..160T
- Keywords:
-
- Exoplanets;
- Super Earths;
- Mini Neptunes;
- Extrasolar rocky planets;
- Exoplanet astronomy;
- Exoplanet systems;
- 498;
- 1655;
- 1063;
- 511;
- 486;
- 484;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted for publication in Astronomical Journal