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Abstract We revisit the long-studied radial velocity (RV) target HD 26965 using recent observations from the NASA-NSF “NEID” precision Doppler facility. Leveraging a suite of classical activity indicators, combined with line-by-line RV analyses, we demonstrate that the claimed 45-day signal previously identified as a planet candidate is most likely an activity-induced signal. Correlating the bulk (spectrally averaged) RV with canonical line activity indicators confirms a multiday “lag” between the observed activity indicator time series and the measured RV. When accounting for this lag, we show that much of the observed RV signal can be removed by a linear detrending of the data. Investigating activity at the line-by-line level, we find a depth-dependent correlation between individual line RVs and the bulk RVs, further indicative of periodic suppression of convective blueshift causing the observed RV variability, rather than an orbiting planet. We conclude that the combined evidence of the activity correlations and depth dependence is consistent with an RV signature dominated by a rotationally modulated activity signal at a period of ∼42 days. We hypothesize that this activity signature is due to a combination of spots and convective blueshift suppression. The tools applied in our analysis are broadly applicable to other stars and could help paint a more comprehensive picture of the manifestations of stellar activity in future Doppler RV surveys.
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This content will become publicly available on February 18, 2026
Validation of Two Earth-mass Planets Orbiting GJ 1002
Abstract GJ 1002 is reported to host two Earth-mass planets in the habitable zone. We applied frequency-domain techniques for validating planet discoveries to the ESPRESSO and CARMENES radial velocity (RV) and cross-correlation full width at half maximum time series. Siegel’s test applied to Welch’s power spectrum estimates suggests that periodicity in the RV time series may not be statistically significant. The frequency response to a sinusoid with the frequency of planet b, or pseudowindow, shows excess power near the frequency of planet c. Finally, a Monte Carlo experiment where we create new RV time series realizations by adding white noise to original data reveals that the highest periodogram peak sometimes occurs at half the frequency of planet c. More extreme-precision observations are required to confirm RV oscillations and constrain the rotation period.
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- Award ID(s):
- 2307978
- PAR ID:
- 10625828
- Publisher / Repository:
- American Astronomical Society
- Date Published:
- Journal Name:
- Research Notes of the AAS
- Volume:
- 9
- Issue:
- 2
- ISSN:
- 2515-5172
- Page Range / eLocation ID:
- 42
- Subject(s) / Keyword(s):
- Period search Stellar activity Stellar rotation Radial velocity Time series analysis
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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