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arXiv · 2611.08112

Photometric eclipse-center variations over the long cycles of Magellanic double-periodic variables

Ronald Mennickent
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Abstract

Double-periodic variables (DPVs) are interacting binaries with an orbital modulation and a longer cycle of uncertain origin. I searched for long-cycle-dependent eclipse-center variations in Magellanic DPVs and tested whether changing disk brightness can produce analogous shifts with fixed conjunctions. I analyzed Optical Gravitational Lensing Experiment (OGLE) photometry for 109 eclipsing-DPV candidates. In separate long-phase intervals, I measured centers of eclipses by profile fitting to local flux minima ($Q$) and by shifting a fixed eclipse template ($T$). A single synthetic semidetached DPV provided a separate numerical experiment. Of 49 curated systems with sufficient timing data, 27 show at least one $Q$ or $T$ modulation under the adopted procedure. Some selections depend on the fitting choice, but ten systems retain a selected $Q$ curve with all tested local functions and windows. Three have both estimators selected in both eclipses, without establishing whether conjunction times change. Using local color interpolation, 14 of 16 systems measured in both eclipses are redder at the deeper, phase-0 eclipse. In the artificial system, fixed conjunctions coexist with large photometric shifts and quadrature-brightness changes, although the large tilted-disk cases do not reproduce the selected observed crossing phases. Long-cycle-dependent photometric eclipse-center variations occur in a substantial fraction of the evaluable, curated sample, not necessarily of all DPVs. Circumstellar brightness changes can produce such shifts, but the single artificial system neither fits an observed DPV nor establishes disk tilt as the cause. Genuine conjunction-time changes remain possible in individual objects.

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Ronald Mennickent. 2026-11-05. Photometric eclipse-center variations over the long cycles of Magellanic double-periodic variables. https://arxiv.org/abs/2611.08112

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