Free sky positions retain less than 0.05% of 365.25-day signal information in seven fixed-noise NANOGrav models

Can an independent sky position restore an annual circular timing signal? We use 82,598 times of arrival and the delivered models for seven isolated pulsars in NANOGrav release 2.1.0. We hold noise values fixed and retain all free timing terms. At 365.25 days, free sky positions retain 6.00e-9 to 4.20e-4 of the information available with both position coordinates fixed, across targets and phases. Independent isotropic position errors of 10.3 to 98.9 microarcseconds per coordinate, at the delivered position epoch, retain at least half of the reference information at every phase. Each target has its own error threshold. An exploratory control reduces the ratio of the largest to smallest retained fraction from 44.8–10,946 to 1.04–1.80 when parallax is fixed. The general annual loss and the benefit of independent astrometry are known. We add target-specific phase bounds, prior thresholds, period curves, and compact data for an offline calculation. We preserve original data, source hashes, code, figures, and numerical checks. This is a linear Gaussian model study. It does not search pulse residuals, detect a planet, or set mass limits. The position prior assumes independent errors and correct frame and epoch alignment.

pulsar timing · planet sensitivity · annual signals · astrometry · Fisher information · NANOGrav · independent position priors · reproducible benchmark