Exoplanets & Exomoons

Octofitter: Fast, Flexible, and Accurate Orbit Modelling to Detect Exoplanets

By Keith Cowing
Status Report
February 6, 2024
Filed under , , , , , , , , ,
Octofitter: Fast, Flexible, and Accurate Orbit Modelling to Detect Exoplanets
Conceptual schematic of three different ways to use Octofitter. Other possibilities, like combining images with Doppler or astrometric velocimetry or using a mix of relative astrometry and images without detections to constrain orbits, are also possible. — astro-ph.EP

As next-generation imaging instruments and interferometers search for planets closer to their stars, they must contend with increasing orbital motion and longer integration times. These compounding effects make it difficult to detect faint planets but also present an opportunity.

Increased orbital motion makes it possible to move the search for planets into the orbital domain, where direct images can be freely combined with the radial velocity and proper motion anomaly, even without a confirmed detection in any single epoch.

In this paper, we present a fast and differentiable multimethod orbit-modeling and planet detection code called Octofitter. This code is designed to be highly modular and allows users to easily adjust priors, change parameterizations, and specify arbitrary function relations between the parameters of one or more planets. Octofitter further supplies tools for examining model outputs including prior and posterior predictive checks and simulation-based calibration.

We demonstrate the capabilities of Octofitter on real and simulated data from different instruments and methods, including HD 91312, simulated JWST/NIRISS aperture masking interferometry observations, radial velocity curves, and grids of images from the Gemini Planet Imager.

We show that Octofitter can reliably recover faint planets in long sequences of images with arbitrary orbital motion. This publicly available tool will enable the broad application of multiepoch and multimethod exoplanet detection, which could improve how future targeted ground- and space-based surveys are performed.

Finally, its rapid convergence makes it a useful addition to the existing ecosystem of tools for modeling the orbits of directly imaged planets.

William Thompson, Jensen Lawrence, Dori Blakely, Christian Marois, Jason Wang, Mosé Giordano, Timothy Brandt, Doug Johnstone, Jean-Baptiste Ruffio, S. Mark Ammons, Katie A. Crotts, Clarissa R. Do Ó, Eileen C. Gonzales, Malena Rice

Comments: Published in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2402.01971 [astro-ph.EP] (or arXiv:2402.01971v1 [astro-ph.EP] for this version)
Journal reference: The Astronomical Journal, Volume 166, Issue 4, id.164, 20 pp. 2024
Related DOI:
Focus to learn more
Submission history
From: William Thompson
[v1] Sat, 3 Feb 2024 00:41:16 UTC (12,672 KB)

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) 🖖🏻