# # Program information file # PROGRAM_ID 2023B050 PROGRAM_TITLE Expanding the Sample of NIR Changing-Look AGNs with SpeX PROGRAM_INV1 Jason Hinkle PROGRAM_INV2 Benjamin Shappee PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT extra-galactic PROGRAM_ABSTRACT_BEG The AGN unification model posits a separation between sources with broad lines [Type 1] and only narrow lines [Type 2] based on our viewing angle relative to the dusty torus. Its fundamental assumption is that all AGNs have broad lines that are only viewable if unobscured. However, the growing number of AGNs that have broad lines appear [turn-on] or disappear [turn-off] challenges this paradigm. These so-called changing-look AGNs [CL-AGNs] provide a unique test bed for the physics governing photoionization and the creation of a broad line region. Historically, studying CL-AGNs was difficult, owing to the lack of multi-wavelength data to contextualize the overall AGN evolution. Now in the golden era of time domain astronomy, we are well positioned to study CL-AGNs in detail. One notable gap in our observation coverage of CL-AGNs is NIR spectroscopy. Here we propose to obtain NIR spectra of ongoing and newly-discovered CL-AGNs to provide leverage on photoionization physics, search for high-ionization coronal lines, and probe the influence of dust on the changing-look phenomenon. We request 6 half-nights spaced throughout the semester and alternating first/second half to maximize our ability to conduct long-term NIR spectral monitoring of the rare CL-AGNs. PROGRAM_ABSTRACT_END