Exoplanets, -moons, -comets

A Century of Radial Velocity and Astrometric Monitoring of 70 Oph AB: New PFS Data and Constraints on Planetary Companions

By Keith Cowing

Status Report

astro-ph.EP

March 24, 2026

Filed under 70 Oph A, 70 Oph AB, 70 Oph B, astro-ph.EP, binary star, exoplanet, Habitable Zone, Magellan II Clay Telescope, Stellar Cartography, Terrestrial Planet

A Century of Radial Velocity and Astrometric Monitoring of 70 Oph AB: New PFS Data and Constraints on Planetary Companions — The left panel shows the relative astrometric orbit of 70 Oph B around 70 Oph A. Red points denote archival visual and micrometric measurements from the WDS/ORB6 catalog, while the solid black curve shows the maximum-likelihood joint orbital solution. 50 orbits color-coded by companion mass are randomly drawn from the posterior and plotted, but they are indistinguishable from the black curve because of the tight constraint on the orbit. The dashed line marks the line of nodes, and the star indicates the primary’s position. The right panel shows the RV variation of 70 Oph A measured by eight instruments. Colors correspond to individual RV datasets as indicated in the legend. Residuals relative to the best-fit model are shown. — astro-ph.EP

At a distance of 5.1 pc, the 70 Oph AB binary star system is one of the most favorable targets for future direct imaging and astrometry missions surveying mature, terrestrial planets.

We present new radial velocities (RVs) obtained with the Planet Finder Spectrograph (PFS) on the 6.5,m Magellan II Clay Telescope in Chile. We collected 499 measurements of 70 Oph A and 334 measurements of 70 Oph B during 2023–2025. Combining these data with decades of archival RVs and astrometry, we derive an updated orbital solution for the binary and dynamical masses of 0.88±0.004M_⊙ and 0.73±0.003M_⊙ for the primary and secondary components, respectively.

We find that the long-term RV variability of both components is consistent with stellar activity modulated by rotation periods, and we detect no coherent planetary signals in either component.

We place upper limits on any planets orbiting in the plane of the binary. The 27 yr RV baseline for 70 Oph A excludes Jupiter-mass planets interior to 5 au and reaches a sensitivity of 0.3M_Jup at 1 au or 0.5M_Jup at 2 au. For 70 Oph B, with PFS data we rule out planets more massive than 0.25–0.3M_Jup inside 0.5 au.

We show that stable S-type orbits around 70 Oph A extend to ∼2.5 au, covering the habitable zone. Thus, Saturn-mass planets or smaller on stable orbits in the habitable zone of 70 Oph A are allowed. Overall, our results provide important guidance for future planet searches around this stellar system.

Yiting Li, Michael R. Meyer, Skylar D’Angiolillo, Stephen R. Kane, R. Paul Butler, Stephen A. Shectman, Eric E. Mamajek, Johanna Teske, Jack Lubin, Paul Robertson, Jessie L. Christiansen, Howard Isaacson, Caleb K. Harada, Bradford Holden, William D. Cochran, Michael Endl, Jennifer Burt, Juliette Becker, Alyssa Jankowski, Peter Tuthill, Catherine A. Clark, Rachael M. Roettenbacher, Eric Nielsen, Eduardo Bendek, Armen Tokadjian, William Roberson, Kaitlin M. Kratter, Edwin Bergin, Dave Osip, Jeffrey D. Crane, Alex Davis, Gautam Vasisht

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2603.20044 [astro-ph.EP] (or arXiv:2603.20044v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2603.20044
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Submission history
From: Yiting Li
[v1] Fri, 20 Mar 2026 15:29:32 UTC (2,749 KB)
https://arxiv.org/abs/2603.20044
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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