Scan-angle-controlled periodogram suppresses spurious ~54-day signal in Gaia DR4 prerelease data
Authors extended the phase-distance correlation periodogram to reduce scan-geometry dependence in Hipparcos and Gaia epoch astrometry, which matters for companion searches in Gaia DR4.
A preprint on arXiv (not yet peer reviewed) presents a non-parametric extension of the phase-distance correlation (PDC) periodogram. According to the authors, it quantifies and reduces dependence on scan geometry at the period-search stage. The method was tested on Hipparcos epoch data and on prerelease epoch astrometry for Gaia Data Release 4 (DR4). Source: arXiv · preprint arxiv.org
arXiv · препринтarxiv.orgOpen source ↗.
Why scanning produces false periods
Hipparcos and Gaia scan the sky following a complex scanning law. Each observation gives a one-dimensional measurement along the instantaneous scan direction, so the time series of a source consists of along-scan (abscissa) values and scan orientations arxiv.org
arXiv · препринтarxiv.orgOpen source ↗. This couples observation times, scan geometry and the measured signal. As a result, the periodogram reflects both the intrinsic variability of the source and the observing window set by the scanning law. The authors compare this to the spectral-window problem in unevenly sampled time series, with the added complication that the projection direction changes with time.
The paper cites earlier work showing that scan-angle signals can produce apparent orbital solutions and other false positives in Gaia. It also notes that spectroscopic follow-up of Gaia DR3 candidates found no evidence for the companion implied for HD 113283, whose period lies close to known scanning-law artifacts arxiv.org
arXiv · препринтarxiv.orgOpen source ↗.
Results on Hipparcos and Gaia DR4 prerelease data
In Hipparcos data, the authors identified recurrent periodicities associated with characteristic scanning-law timescales. They report that these are strongly suppressed by the scan-angle-controlled statistic arxiv.org
arXiv · препринтarxiv.orgOpen source ↗.
In Gaia DR4 prerelease epoch astrometry, a recurrent ~54-day feature is suppressed across multiple sources, while independently known orbital signals remain detectable, the authors report arxiv.org
arXiv · препринтarxiv.orgOpen source ↗. The method is built on the earlier model-independent PDC periodogram for scanning astrometry and serves as a diagnostic of scan-angle dependence and as a way to mitigate its effect on period searches.
Hipparcos epoch astrometry is public and shares the one-dimensional scanning nature of Gaia, which is why it was used as the main test set. The authors note that the result is particularly relevant for Gaia DR4, where public epoch astrometry will enable large-scale searches for companions ranging from exoplanets to dormant black holes arxiv.org
arXiv · препринтarxiv.orgOpen source ↗.
