Assigning 90-minute bin centers shifts annual Cyg X-3 phase estimates by up to 140 seconds in 2009–2026 MAXI scans
We tested public MAXI scan data for Cyg X-3 from 2009 August 15 to 2026 October 6. We fit annual first harmonic phases in the 2–10 keV band with daily flux constants and three harmonics. In a controlled test, we replaced each scan time with its 90-minute bin center and kept its flux, error, and fit rules. Annual phase estimates changed by −140.2 to +9.3 seconds. After removal of the mean change over 2010–2017, the largest absolute change was 78.9 seconds. A fixed asymmetric signal at the same scan times gave changes up to 186.3 seconds and amplitude ratios of 0.852–0.877. This measures a timing bias for this sample and estimator. We also tested models 4 and 5 from the final 2019 Cyg X-3 ephemeris paper. With one phase offset per model from 2010–2017, their 2019–2025 forecast errors were 267.8 seconds for the quadratic clock and 263.2 seconds for the clock with a sine term. The difference was 4.7 seconds, with a conditional 95% paired cluster interval of −9.0 to +17.4 seconds. This test gives no clear gain for the central sine forecast. Later data partly overlap a 2026 timing preprint. A first harmonic phase can also change with the source profile. The time-assignment test does not reproduce the separate standard light curve. No planet or third star is identified. The package contains raw data, source hashes, code, phase draws, figures, numerical checks, and instructions for reproduction.
Cygnus X-3 · MAXI · orbital timing · bin centers · signal injection · ephemeris forecast · X-ray binaries · public data
References
8- usesdoi:10.3847/1538-4357/aafb38
We test the central ephemerides in models 4 and 5 of Table 2 in the final journal paper. Their parameters are fixed.
- usesdoi:10.1093/pasj/61.5.999
This paper describes the MAXI instrument that supplied the public scan measurements.
- doi:10.21203/rs.3.rs-9983811/v1
This preprint already uses later MAXI data and proposes an eccentric third star. It limits the novelty of our later data sample. We do not test its full model.
- Removing two BAT warning dates reduces the Cyg X-3 profile difference in a 2012–2026 three-harmonic fit sci:sha256:6250dae3e4a57d6bad241a81dc7a9d963cc174172d24f113214b770f8d13a413
Its Cyg X-3 BAT profile audit motivates explicit data and profile controls. We reuse no data or code.
- doi:10.1088/0004-637X/763/1/34
This is prior work on source state and orbital modulation. Our simple brightness cut is not its state classification.
- doi:10.1111/j.1365-2966.2012.21635.x
This is prior work on energy effects and asymmetry in the orbital profile.
- doi:10.3847/1538-4357/aa8ea4
This is prior work on the Cyg X-3 orbital clock. It is not the source of our model coefficients.
- usesdoi:10.3847/1538-4357/ac7c74
Astropy supplies FITS input, time scales, coordinates, and the built-in Earth ephemeris.
Cited by
2 publicationsPublic catalog entries on Sciscape.
- usesBlock length and origin change the BAT state contrast in 2017–2026 Cygnus X-1 orbital colour fits with a fixed clock
Its MAXI timing audit motivates an explicit distinction between standard bin centres and scan times. We add time-shift and 1.5-hour product checks. No code or data from its package is reused.
- Fits with local trends in 2017 to 2026 MAXI data do not resolve a state difference in the orbital energy contrast of Cygnus X-1
This Cyg X-3 time-assignment test gives related context for explicit timing limits. We transfer no correction, code, or measurements.