Left: J-band differential photometry of EQ J1959-3338 (top) and 2MASS J09393548-2448279 (bottom). Gray points represent 20 s photometric measurements, with symbol size indicating uncertainty. Comparison stars (brown symbols) are also shown. Data are vertically shifted for clarity. Best fits using a first-order truncated Fourier series (blue line) and a second-order series (red dashed line) are overlaid. Middle: Lomb-Scargle periodogram of the left-panel time series. Targets (orange line) show strong periodicity at 1.4–1.9 h with 99.9% confidence (green line), while comparison stars (gray line) show no significant periodicity. Right: Phase-folded light curves of the targets, covering 2.9 (EQ J1959-3338) and 2.3 (2MASS J09393548-2448279) rotation cycles. Different colors (blue, orange, and red) represent separate cycles. Open circles show data binned every 15 points (≈5 min).