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Irradiated brown dwarfs (BDs) provide natural laboratories to test ourunderstanding of substellar and irradiated atmospheres. A handful ofshort-period BDs around white dwarfs (WDs) have been observed, but the uniquelyintense UV-dominated irradiation presents a modeling challenge. Here, wepresent the first fully self-consistent 1D atmosphere models that take intoaccount the UV irradiation's effect on the object's temperature structure. Weexplore two BD-WD systems, namely WD-0137-349 and EPIC-212235321. WD-0137-349Bhas an equilibrium temperature that would place it in the transition betweenhot and ultra-hot Jupiters, while EPIC-212235321B has an equilibriumtemperature higher than all ultra-hot Jupiters except KELT-9b. We explore somepeculiar aspects of irradiated BD atmospheres and show that existing photometrycan be well-fit with our models. Additionally, the detections of atomicemission lines from these BDs can be explained by a strong irradiation-inducedtemperature inversion, similar to inversions recently explored in ultra-hotJupiters. Our models of WD-0137-349B can reproduce the observed equivalentwidth of many but not all of these atomic lines. We use the observed photometryof these objects to retrieve the temperature structure using the PHOENIXExoplaneT Retrieval Algorithm (PETRA) and demonstrate that the structures areconsistent with our models, albeit somewhat cooler at low pressures. We thendiscuss the similarities and differences between this class of irradiated browndwarf and the lower-mass ultra-hot Jupiters. Lastly, we describe the behaviorof irradiated BDs in color-magnitude space to show the difficulty inclassifying irradiated BDs using otherwise well-tested methods for isolatedobjects.

Atmosphere Models of Brown Dwarfs Irradiated by White Dwarfs: Analogues for Hot and Ultra-Hot Jupiters