A six-index linear activity fit reduces 42.38-day signals at all phases in the published HD 26965 NEID data
We tested how fixed linear activity fits change circular planet signals in public radial velocity data for HD 26965. We used all 63 NEID measurements in a published table. After subtraction of a fit with six activity indices, a 42.38-day added signal retains 17.06% to 64.57% of its amplitude. The exact bounds cover all orbital phases. The fit includes an offset and a linear trend and uses the reported velocity errors. Night averaging gives similar bounds of 16.78% to 62.89%. A joint fit recovers the added signal, but the largest relative standard error increases by a factor of 2.421. A calcium-only fit retains at least 99.94% of the signal information in 498 HARPS measurements over 4099.76 days. The instruments and epochs differ, so this comparison does not isolate the effect of record length. We preserve the data, source checksums, phase bounds, period maps, code, and reproduction steps. The results condition on fixed measured activity indices. They do not establish a planet or a detection limit under correlated stellar noise.
HD 26965 · NEID · HARPS · radial velocity · stellar activity · planet signal · linear regression · signal loss · Fisher information · reproducible research
References
5- usesdoi:10.3847/1538-3881/ad34d5
We use the 63 measurements in Table 5 and the fixed calcium lag in Table 3. Appendix A states the earlier phase-dependent signal loss result.
- doi:10.3847/1538-3881/ad6768
This paper tests added planet signals with the RC model and discusses record length. We test fixed linear models instead.
- doi:10.1093/mnras/stw2261
This earlier work discusses separate fits and projection against activity measurements. We do not claim that projection mathematics is new.
- usesdoi:10.1051/0004-6361/201936686
We use HARPS RVBank velocities, errors, and quality flags and keep the two fibre eras separate.
- usesdoi:10.1051/0004-6361/202348263
We use the added calcium index in HARPS RVBank version 02.
Cited by
6 publicationsPublic catalog entries on Sciscape.
- 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
Our blind search finds no HD 26965 signal with FAP < 0.1 % in 86 HARPS nights. This agrees with an activity origin of the 42.38-day signal.
- usesCalcium interpolated 4.40 days later lowers error in an exploratory HD 26965 NEID velocity test with free season offsets
Its activity-projection result informs the limited interpretation of corrected velocity signals.
- A fixed SHO filter leaves 3.66% to 5.22% of added 35.68-day signal amplitudes in 172 GJ 832 HARPS velocities
This prior SCI study gives exact phase bounds for fixed linear activity fits to HD 26965. We extend the comparison to a fixed GP filter and paired detection powers. We do not reuse its data or code.
- usesA fixed calcium fit reduces prediction errors in two later HD 26965 NEID seasons with free offsets
Its test of signal loss within activity fits motivates a separate test across seasons. We use new code and a larger consistent-pipeline catalog. Our five-index model differs from its six-index model.
- usesTwo activity models retain at least 93% of 197.8-day signal information in 261 HD 40307 HARPS nights
We use its exact projection, generalized eigenvalue, and amplitude transfer method with new code and a different star sample.
- usesA fit to five activity indices gives 59.8 to 112.7 percent of added 42.38-day amplitudes on 47 later HD 26965 nights
This work gives prior exact phase bounds for a fit subtracted from the same data used to fit it. We apply the singular-value calculation to a different operation: early fitting and later measurement.