When Fast Turns Slow: Unraveling the Rotation Puzzle in the Young Open Cluster Trumpler 14

Khushboo Kunwar Rao^1*, Wen-Ping Chen¹, Hsiang-Yu Chen¹

¹Institute of Astronomy, National Central University, Zhongli, Taoyuan, Taiwan

* Presenter:Khushboo Kunwar Rao, email:khushboo@astro.ncu.edu.tw

The main-sequence turnoffs of young and intermediate-age clusters often appear unusually broad, commonly attributed to a range of stellar rotation rates: fast rotators occupy the redder regions of color magnitude diagrams, while slow rotators lie on the bluer side. For intermediate-mass stars, fast rotation is expected due to their radiative envelopes, but the presence of slow rotators is puzzling. Proposed explanations include tidal synchronization, stellar mergers, or star–disk interaction during the pre-main sequence (PMS) phase. We investigate the role of PMS star–disk interaction in Trumpler 14, a young cluster in the Carina Nebula. Using infrared spectral indices derived from spectral energy distributions, we identified four Class II and ten Class III young stellar objects among stars with masses >1.3 M⊙. Most (13) of these are located in outer regions of the cluster, consistent with slower disk dispersal. Surprisingly, the cluster center hosts more slow rotators despite the intense radiation field. We discuss these findings in the context of disk dispersal timescales and their impact on the rotational evolution of intermediate-mass stars.

Keywords: open clusters and associations: individual (Trumpler 14), stars: early-type, stars: pre-main sequence, stars: variables: Herbig Ae/Be, stars: rotation