Activity terms reduce the instrument amplitude gap in Gaussian orbit fits near 71 days for HD 140538 A
We tested a reported 71.45-day signal in HD 140538 A, also called GJ 9527. We asked how activity and noise terms change the instrument amplitude comparison. We used 40 saved HARPS nightly velocities and 112 nightly velocities from the public 2025 HIRES catalog. The target had the largest fixed-curve gap in an earlier SCI test. We fitted a common orbit shape with either one or two instrument amplitudes. The main period interval was 71.340 to 71.553 days. Eccentricity was at most 0.8. The Gaussian likelihood gain from separate amplitudes, D, fell from 27.375 to 2.187 with a 1417-day activity cycle. Each instrument had separate sine and cosine cycle terms. The cycle common fit gave K=4.834 m/s and e=0.760. This shape differs from the source orbit. With fixed weights, the cycle terms removed 79.61% of the source template information in HARPS. The corresponding loss in HIRES was 2.33%. We also tested measured activity, correlated noise, and a wider period interval. All seven main common fits reach a period or eccentricity bound. The gaps are descriptive and have no calibrated detection probability. The result shows model dependence. It does not confirm a planet or give a general planet limit. The package preserves data, source records, code, results, figures, and instructions.
HD 140538 A · GJ 9527 · radial velocity · HARPS · HIRES · stellar activity · orbit fitting · model dependence · reproducible research
References
8- usesA 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 saved HARPS nightly arrays, target record, and source orbit. We extend its candidate analysis with joint HARPS and HIRES fits.
- usesThree of 12 fixed HARPS candidate curves have lower HIRES amplitudes in a block residual test sci:sha256:c6868b65a79bdeaf7f316721fd4d1fbffdd86a513ad091f02f687f4af45ad97f
Its fixed-curve test selected this target for follow-up. It supplies the unit-control specification and alias evidence. We extend its limited comparison with free orbit and activity fits.
- usesdoi:10.1051/0004-6361/202348263
HARPS-RVBank v2 is the catalog underlying the saved source nightly product.
- usesdoi:10.1051/0004-6361/202555034
We use its corrected HIRES velocities, errors, and activity indices and check its printed unit-control row.
- doi:10.1093/mnrasl/sly227
This paper describes the earlier HIRES zero-point correction method.
- usesdoi:10.1051/0004-6361/201935654
Its measured cycle and rotation period guide the activity and sampling checks.
- usesdoi:10.3847/1538-4365/abe23c
Its 1417-day activity signal sets the main fixed cycle period.
- usesdoi:10.3847/1538-3881/ae0b62
Its HD 140538 A activity result gives the 1449-day cycle sensitivity test and prior multi-instrument context.
Cited by
4 publicationsPublic catalog entries on Sciscape.
- Independent 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
Activity terms reduce the instrument amplitude gap near 71 d for HD 140538 A (GJ 9527). We reject GJ 9527 71.45 d robustly with 122 CLS nights.
- usesThe GJ 176 fit gap near 109 days is exceeded in 0 to 70 of 512 draws on one bank under four Gaussian noise models
This earlier free common-orbit fit for HD 140538 A gives activity context. We add separate full orbit shapes and finite bank simulations under stated fixed covariances.
- usesA 1417-day term reverses the prediction gain at a fixed 71.45-day period in the GJ 9527 HARPS velocity difference
This prior GJ9527 study motivates the 1417-day cycle control. It tests HARPS and HIRES amplitude model dependence. We test the paired HARPS difference on omitted groups.
- uses167 APF nights give a lower amplitude for the fixed 21.35-day HARPS curve of HD 14412 in Gaussian fits
We adapt its MIT Gaussian orbit code and use its model checks as a method precedent for another star.