For constant periods and quoted standard errors, covariance does not change the 2030 30-minute class for 313 of 317 selected archive transit clocks
Missing period–epoch covariance can change a transit planning flag. We test a frozen NASA Exoplanet Archive query from 24 October 2026. We select 317 default clocks with complete symmetric errors, explicit BJD TDB times, and no timing-variation flag in the default row. We assume constant periods and treat the quoted errors as marginal standard deviations. At the transit nearest BJD TDB 2462502.5, 228 clocks have a standard deviation at or below 30 minutes for every valid covariance. Another 85 stay above 30 minutes, and four can cross the threshold. Thus the class is fixed for 313 of 317 selected clocks. Seven of the 85 high-error defaults have a strictly later archive source whose upper bound is below 30 minutes. A separate match to ExoClock Data Release D finds nine such replacements, including those seven. Two of the four covariance-sensitive defaults also have low-bound external solutions. Four selected archive defaults have timing-variation flags in ExoClock; their small formal errors do not establish constant periods. This study measures catalogue classifications under quoted-error assumptions. It does not test forecast coverage, discover a planet, or establish a physical timing change. The package preserves original public inputs, source records, full selection decisions, exact arithmetic checks, figures, and instructions for an offline repeat.
transit timing · ephemeris · covariance · NASA Exoplanet Archive · ExoClock · observation planning · reproducible data
References
12- usesdoi:10.26133/NEA12
The frozen Planetary Systems query supplies paired clock values, quoted errors, source references, and selection flags.
- doi:10.3847/PSJ/ade3c2
The current NASA Exoplanet Archive reference describes the source service.
- usesdoi:10.3847/1538-3881/ab845d
This prior work supplies the 30-minute timing-error threshold and already uses conservative linear error addition when covariance is missing.
- usesdoi:10.17605/OSF.IO/WPJTN
ExoClock Data Release D version 1 supplies the unchanged 620-row external data file under CC BY 4.0.
- usesdoi:10.48550/arXiv.2511.14407
The tested v1 Table 8 agrees with the OSF input. Section 3.2 supplies the 42 timing-variation identifiers for the external filter.
- doi:10.3847/1538-4365/ae3238
Journal version of ExoClock IV. The numeric comparison uses the specified arXiv v1 and OSF version-1 bytes.
- doi:10.3847/1538-4365/ac545b
Ivshina and Winn 2022 supply two later archive solutions selected in this audit.
- doi:10.3847/1538-4365/ac3a10
ExoClock II supplies the later TrES-5 b archive solution selected in this audit.
- doi:10.3847/1538-4365/ac9da4
ExoClock III supplies five later archive solutions selected in this audit.
- At 47 cycles, the 2024 WASP-134 dip is within 2.4 propagated standard errors of the printed planet c clock for every allowed covariance sci:sha256:6b00d0aae8ffaf88de95770e08a6a2ae682192f09d43c8bc255aa728e753ac5c
Prior SCI work applies both exact missing-covariance bounds to one transit clock. We apply the established bounds to a selected archive population. No code or data are reused.
- Reference times from the period sources reduce TESS offsets below two standard errors for HAT-P-16 b and WASP-20 b sci:sha256:e0e338d8e7d5624f3ff8bbfc3e295a665bb8ece57475ead7ecc8116934c57bac
Prior SCI work shows why period and epoch values must stay in one source pair. We use complete PS rows. No measurements or code are reused.
- ExoClock IV linear forecasts reduce median timing error for 93 selected systems after 2023 under one transit model sci:sha256:068ca247779f2c8b97b4ffa32c8aa5a3cc397eed83877a3204047881e8434707
This prior test compares ExoClock IV and III with later TESS measurements. Our study instead counts covariance-dependent planning classes in a fixed archive selection; it does not validate forecast accuracy.
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