2025MNRAS.541.2246B

We study the protoplanetary disc lifetimes using a large sample of young stellar objects in nearby clusters. To investigate the final phase of disc dissipation, we selected 32 clusters, located within 500 pc and aged between 1 and 100 Myr, with membership determined using Gaia data. The age and mass information of the sources are obtained through spectral energy distribution analysis and using evolutionary models of various ages. Using the infrared data from 2MASS and WISE catalogues, we employ three methods to identify discs across the different wavelength regimes (1.1-22 $\mu$m). We find that disc fraction consistently decreases as stellar systems age, a trend observed across all wavelengths included in this study. However, there is an increase in the time-scale of disc decay as wavelength increases, with characteristic time-scales of $\tau _{\text{short}}$ = 1.6 $\pm$ 0.1 Myr for shorter wavelengths (1.6-4.6 $\mu$m) versus $\tau _{\text{W3}}$ = 4.4 $\pm$ 0.3 Myr for 12 $\mu$m. This supports the idea that outer disc regions evolve more slowly. Notably, we detect infrared excesses at 12 and 22 $\mu$m in relatively older systems ($>$10 Myr), with some discs with estimated ages up to $\sim$100 Myr. Among these, we identify a population of full discs that persist beyond the typical dissipation time-scale. We also observe that the median mass of disc-hosting stars decreases from 0.62 to 0.27 $M_\odot$ in clusters younger and older than 40 Myr, respectively, indicating slower disc dissipation around lower mass stars. We identify 33 transitional disc candidates using various colour-colour diagrams. Using LAMOST DR8 optical spectra and H-alpha equivalent widths, we identify possible accretors and estimate their mass accretion rates, finding most are younger than 10 Myr.