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astro-ph.EP · Earth and Planetary Astrophysicsastro-ph.IM · Instrumentation and Methods for Astrophysics

The fixed 673-day orbit of GJ 3822 increases residual scatter in 46 later HARPS-N nights

We tested the published 673.451-day orbit of GJ 3822 with public velocities from a second instrument. The orbit has eccentricity 0.95 and velocity amplitude 84.36 m/s. We rebuilt the 67 HARPS nights from the original table and checked the fixed curve on 46 later HARPS-N nights. After fitting an offset, the curve raises residual RMS from 7.08 to 8.78 m/s. With independent Gaussian errors and extra noise fitted in each model, twice the negative log likelihood loss is 20.07. Added trends, fixed short-period terms, activity indices, heavy-tailed errors, and removal of any one night retain a worse fit for the fixed curve. HARPS-only fits also show strong mass dependence on the chosen eccentricity limit. An eccentricity of 0.6 gives a minimum mass of 0.215 Jupiter masses while twice the negative log likelihood increases by 2.86. At eccentricity 0.995, the mass is 2.788 Jupiter masses with almost no fit change. Other long-period models remain viable. A circular curve fitted to HARPS alone reduces later HARPS-N RMS to 5.01 m/s. This result tests the published fixed prediction. It does not exclude all companions or confirm a planet. Prior work already reported a 661-day candidate for this star. The package preserves target data, source hashes, all fitted results, figures, code, and reproduction instructions.

GJ 3822 · HIP 68570 · radial velocity · HARPS · HARPS-N · orbit prediction · eccentricity · planet candidates · reproducibility

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References

6
  1. challengesA blind Keplerian search of 743 HARPS-RVBank v2 stars with 30 or more nights recovers 248 of 465 known planets and finds 57 signals (FAP < 0.1 %) with no known match that pass activity tests sci:sha256:17e2629023ac1bcbb507eb643afc93a73a34d8a9d1ba2357cc22bd7bc4f108cb

    We use its 67 HARPS nights and fixed GJ3822 orbit. That curve raises residual scatter in later HARPS-N data. The target is also close to the 661-day candidate already reported by Tuomi et al. (2019). This check does not exclude other long-period orbits.

  2. usesdoi:10.1051/0004-6361/202348263

    The public HARPS-RVBank v2 table supplies the original observations. We independently rebuild the target night means.

  3. usesdoi:10.1051/0004-6361/202142828

    The public HADES table supplies 51 later HARPS-N measurements on 46 nights. The paper already reports a 25.151-day candidate.

  4. doi:10.48550/arXiv.1906.04644

    Version 2, Appendix A.64, already reports 661-day and 18.264-day candidates for GJ3822 and notes poor phase coverage for the long signal.

  5. doi:10.1051/0004-6361/202346570

    This prior HARPS analysis lists an activity-based rotation estimate near 19 days. It gives context for activity checks.

  6. doi:10.1111/j.1365-2966.2010.17570.x

    This prior study treats errors and biases in orbit parameters from radial velocities. Our contribution is the target-specific test and reproducible numerical results.

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