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

A 39.76-day fit gives a 0.57 m/s amplitude for the difference between wing and core shifts in 2022 ESPRESSO data of GJ 825

We test whether the reported 39.76-day velocity signal of GJ 825 acts as a rigid shift of its combined spectral profile. We use 82 public ESPRESSO cross-correlation functions from 28 observing nights in 2022. The observations were used by an earlier SCI study that raised concerns about stellar activity. We measure apparent shifts in fixed core and wing windows. At the fixed HARPS period of 39.7602567152476 days, a mean, linear trend, and sine fit gives a semi-amplitude of 0.571 m/s for wing shift minus core shift. The HC3 standard error is 0.092 m/s if errors on different nights are independent. No null wild-bootstrap draw out of 19,999 reaches the measured statistic; the plus-one probability is 0.00005. Approximate sign tests with 20-day blocks give weaker probabilities of 0.031-0.063 from only six blocks. A translated fixed template gives differences below 0.00014 m/s over the observed velocity range. Fixed spectral-row continuum weights retain an amplitude of 0.575 m/s. Changes in those weights with fixed row shapes give 0.007 m/s. U1 data alone give 0.593 m/s. The result supports earlier concerns about profile changes near this period. It does not separate stellar and instrument effects or exclude a planet with additional profile changes. The 128-day span does not establish a unique period. The package preserves the original files, source hashes, code, results, figures, and reproduction instructions.

GJ 825 · AX Mic · HD 202560 · ESPRESSO · radial velocity · spectral profile · stellar activity · public astronomical data

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References

7
  1. usesIndependent RVs reject 13 of 25 testable HARPS-RVBank v2 candidates (3 if HARPS errors double) and agree with a 19.7-day HD 111232 signal, with linear-trend nuisance models sci:sha256:1b429149b29b478f8b85a22182153f1e36c4ea06d284bbeb276a362b6f2254b1

    We use its GJ825 ESPRESSO exposure list and fixed HARPS period. It already found activity concerns in these observations. We add a measured core and wing difference with translation and row-weight controls.

  2. A 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

    This survey reported the HARPS-RVBank v2 candidate that led to the target selection.

  3. usesdoi:10.18727/archive/21

    We use and preserve 82 original public ESPRESSO CCF files from this ESO archive collection.

  4. doi:10.1051/0004-6361/202348263

    HARPS-RVBank v2 supplied data for the earlier candidate search. We do not refit HARPS data.

  5. doi:10.1051/0004-6361/201220779

    This work provides prior methods and tests for spectral profile changes in radial-velocity searches.

  6. doi:10.1051/0004-6361/201833795

    This work provides prior measurements of velocities from separate spectral lines and their activity response.

  7. doi:10.1051/0004-6361/201935733

    This work includes AX Mic in an earlier study of companion limits from imaging and radial velocities.

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