Exploring central star variability of planetary nebulae using gaia photometry

Abstract

This study presents an analysis of the variability of 81 central stars of planetary nebulae (CSPNe) are identified as variable in Gaia Data Release 3 (DR3). By combining Gaia time-series photometry with data from the Optical Gravitational Lensing Experiment (OGLE), the Transiting Exoplanet Survey Satellite (TESS), and the Kepler, we characterise their variability and identifed 17 new periodic systems. Among these, 13 are short-period variable: light-curve modelling reveals one eclipsing binary, two systems with combined eclipsing and ellipsoidal modulation, one with irradiation effect, two with irradiation/ellipsoidal effects and seven with uncommon variability. A further five systems exhibit long-period variability. Notably, the central star (CS) of PN Al 2-R displays dual periodicity–a short period of 0.99 days and a long period of 501.4 days–and is consequently included in both the short- and long-period categories. The host nebulae of the new short-period binaries are predominantly bipolar or elliptical, strengthening the link between binarity and asymmetric planetary nebula shaping. Furthermore, we provide the first systematic confirmation of binarity in 15 previously known variable CSPNe using Gaia data, with one further confirmation from TESS. For our variability-selected sample, we derive a short-period binary fraction of approximately 48%, exceeding values reported for non-selected samples and highlighting the impact of selection effects. Furthermore, the bipolar/elliptical fraction for wide-binary central stars (57–70%) remains lower than that for close binaries, reinforcing the stronger shaping influence of close binary interactions.