Time-Domain Classification of Bright Young Stellar Objects in the Carina Nebula

The evolution of Young Stellar Objects (YSOs) is governed by the accretion process and the magnetic activity. Time-domain photometric surveys are fundamental to understand these phenomena, and in massive star-forming regions such analysis can also unveil the feedback from the environment. We investigate the temporal variability and accretion-related activity of bright YSOs in the Carina Nebula to determine how circumstellar disks and the environment drive their photometric behavior and evolution. We analyzed 1148 YSO candidates using a 21-night high-cadence DECam z-band survey. We developed a new algorithm (PFˆ2) to rigorously extract periods from irregularly sampled light curves (LCs), and classified their morphology via symmetry and periodicity metrics. We combined optical data with MYStIX (near-IR), Spitzer (mid-IR), and Chandra (X-ray) catalogs to classify YSOs into six evolutionary stages. We determined periods for 52% of the sample and classified 740 YSOs. We find a bimodality in the periods: optically thick disk sources peak at 6.9 ± 0.6 d, indicating a disk-locking regime, while stars without clear signs of a disk undergo spin-up, peaking only at 0.98 ± 0.23 d. Disk-bearing sources present higher asymmetry, dominated by dippers (27%) over bursters (4.3%). The low burster fraction suggests the Carina environment inhibits the inner disk conditions leading to intense and episodic accretion. Optical LCs asymmetry is mainly driven by disk-related phenomena in early stages, switching to X-ray related magnetic activity later. The catalog of YSO candidates presented in this work (paper in submission) provides a robust benchmark for investigating the environmental impact on pre-main-sequence evolution.