The BTSbot-nearby Discovery of SN 2024jlf: Rapid, Autonomous Follow-Up Probes Interaction in an 18.5 Mpc Type IIP Supernova

We present observations of the Type IIP supernova (SN) 2024jlf, including spectroscopy beginning just 0.7 days (∼17 hours) after first light. Rapid follow-up was enabled by the new program, which involves autonomously triggering target-of-opportunity requests for new transients in Zwicky Transient Facility data that are coincident with nearby (D<60 Mpc) galaxies and identified by the machine learning model. Early photometry and non-detections shortly prior to first light show that SN 2024jlf initially brightened by >4 mag/day, quicker than ∼90 Type II SNe. Early spectra reveal weak flash ionization features: narrow, short-lived (1.3 < τ [d] < 1.8) emission lines of Hα, He II, and C IV. Assuming a wind velocity of v_w=50 km s^-1, these properties indicate that the red supergiant progenitor exhibited enhanced mass-loss in the last year before explosion. We constrain the mass-loss rate to 10^-4 < Ṁ [M_⊙ yr^-1] < 10^-3 by matching observations to model grids from two independent radiative hydrodynamics codes. automation minimizes spectroscopic follow-up latency, enabling the observation of ephemeral early-time phenomena exhibited by transients.