FAST Polarization Catalog of FRB 20240114A

Abstract Polarization measurements of fast radio bursts (FRBs) probe the magnetized plasma surrounding their central engines. FRB 20240114A is an exceptionally active repeating source, with 17,356 bursts detected between 2024 January 28 and 2025 May 30 by FAST, enabling studies of the temporal evolution of its polarization properties. In this work, we present a polarimetric catalog of 6131 bright bursts (with a signal-to-noise ratio (S/N) ≥ 20, 35.3% of the total sample), including arrival time (MJD topo ), dispersion measure (DM), burst width ( W eff ), bandwidth, Faraday rotation measure (RM), linear and circular polarization degrees ( L / I , V / I ), and intrinsic polarization angle (PA 0 ). We confirm a clear temporal evolution of RM: after an initial stable phase, it decreases linearly by ∼200 rad m −2 over 200 days, forming a bimodal distribution, whereas DM remains stable at 529.3 ± 1.2 pc cm −3 . The linear polarization fraction is generally high, with the 3 σ lower bound around 76%, while circular polarization is low, with 1157 of 17,356 bursts (6.67%) having ∣ V ∣/ I ≥ 10%. We perform a power-law fit between ∣ V ∣/ I and ∣RM∣, which yields an index of −2.98 ± 0.80. It is found that the combined 2D distribution of L / I versus V / I remains stable, implying that the emission mechanism is largely invariant. Our PA 0 measurements show a broad, nonuniform distribution, implying a complex emission geometry. These results suggest that FRB 20240114A resides in a dynamically evolving magneto-ionic environment. This catalog provides a foundation for studies of repeating FRB progenitors and their environments.