−1 from MJD 54980 to 58450. The white dashed line separates the region in the WWZ plot, where edge effects become dominant, with our QPO of ∼ 433 days in the safe region. On right: Time-averaged WWZ plot. Credit: arXiv (2026). DOI: 10.48550/arxiv.2604.27503"> On left: Result of the WWZ analysis with a dominant signal at 0.00231 day −1 from MJD 54980 to 58450. The white dashed line separates the region in the WWZ plot, where edge effects become dominant, with our QPO of ∼ 433 days in the safe region. On right: Time-averaged WWZ plot. Credit: arXiv (2026). DOI: 10.48550/arxiv.2604.27503

By analyzing the data from the Whole Earth Blazar Telescope (WEBT), an international team of astronomers has discovered optical quasi-periodic oscillation (QPO) in a bright quasar known as 3C 454.3. It is so far one of the most persistent QPOs detected in the optical band.…