Astronomy & Telescopes

The Impact of Observing Cadence and Undetected Companions on the Accuracy of Planet Mass Measurements From Radial Velocity Monitoring

By Keith Cowing

Status Report

astro-ph.EP

November 7, 2024

Filed under astro-ph.EP, Astrometry, astronomy, exoplanet, imaging, radial velocity

The Impact of Observing Cadence and Undetected Companions on the Accuracy of Planet Mass Measurements From Radial Velocity Monitoring — The results of our injection-recovery experiments on the synthetic data in the case of σRV, inst = 1.2 m s⁻¹ (i.e., the “HIRES” case for internal RV precision) and _{σRV, astro} = 0.4 m s⁻¹ (i.e., the “quiet” case for stellar jitter). Each panel represents a combination of P (columns) and M_p (rows) for the known planet, which is shown as the white star plotted at P = P_known and K = K_baseline, and whose the error bar (which is smaller than the size of the marker see in some cases) represents σ_{K_baseline} . Filled squares represent individual injected companions that failed to trigger a detection from RVSearch. The color of each square represents the difference between K_fit and K_baseline for the known planet from a one-planet fit to the synthetic RVs that now contains the signal of the undetected companion. The contours represent loci of 90%, 50%, and 10% detection efficiency. — astro-ph.EP

We conduct experiments on both real and synthetic radial velocity (RV) data to quantify the impact that observing cadence, the number of RV observations, and undetected companions all have on the accuracy of small planet mass measurements.

We run resampling experiments on four systems with small transiting planets and substantial public data from HIRES in order to explore how degrading observing cadence and the number of RVs affects the planets’ mass measurement relative to a baseline value.

From these experiments, we recommend that observers obtain 2–3 RVs per orbit of the inner-most planet and acquire at minimum 40 RVs. Following these guidelines, we then conduct simulations using synthetic RVs to explore the impact of undetected companions and untreated red noise on the masses of planets with known orbits.

While undetected companions generally do not bias the masses of known planets, in some cases, when coupled with an inadequate observing baseline, they can cause the mass of an inner transiting planet to be systematically overestimated on average.

Joseph M. Akana Murphy, Rafael Luque, Natalie M. Batalha

Comments: 17 pages, 13 figures, 4 tables. Accepted for publication in The Astronomical Journal. Code available online (see acknowledgments)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2411.02521 [astro-ph.EP] (or arXiv:2411.02521v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2411.02521
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Submission history
From: Joseph M. Akana Murphy
[v1] Mon, 4 Nov 2024 19:01:56 UTC (919 KB)
https://arxiv.org/abs/2411.02521
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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