An all-sky catalogue of Be transition stars from WISE and Gaia

We present an all-sky catalogue of classical Be stars undergoing transitions between quiescent B-type and active Be-star phases, based on Gaia DR3 astrometry and multi-epoch mid-infrared photometry from WISE and NEOWISE-R. From a Gaia-selected parent sample of 4.2 million candidate OBA stars, we identify Be transition stars through correlated variability in W1 magnitude and W1 − W2 colour, which traces circumstellar disk formation and dissipation. The final catalogue contains 3,300 Be transition stars, including 2,743 newly identified objects, and provides a large, homogeneous sample for studying Be outburst activity across the sky. The median durations of the measured outburst and decay phases are 459 and 478 days, respectively, consistent with previous WISE-based measurements and compatible with the long disk-evolution timescales expected in the viscous decretion disk framework. As an initial application, we use TESS photometry for 3,017 targets to identify 63 eclipsing binary systems hosting Be transition stars, including 33 Algol-type, 17 Beta Lyrae-type, and 13 W Ursae Majoris-type systems. Among the multi-epoch LAMOST spectra, two sources show candidate radial-velocity shifts exceeding 20 km s −1; their line-profile behaviour suggests that RV variability in active Be transition stars may be influenced by outburst-related line-profile changes rather than being an unambiguous indicator of binary motion. This catalogue provides a basis for future statistical studies of Be outbursts, disk evolution, and their connection with binarity and spectroscopic variability.