Top: SED of ZTF J2008+4449 plotting the AB magnitude against wavelength. The light blue, orange, and deep blue data points respectively show the IR (WIRC), optical (PanSTARRS) and NUV (Swift) photometry. The cyan line shows HST STIS and COS concatenated spectra spanning the NUV and FUV, with the COS spectrum truncated at the lowest wavelengths. The solid black and dashed gray lines show the best fitting pure Hydrogen magnetic and non-magnetic atmosphere models respectively. Lastly, a 1700 K (800 K) brown dwarf model is shown in purple (pink), by itself (faded line) and added to the best fitting magnetic white dwarf model (solid line). Bottom: Irradiated face temperatures for a series of Roche-lobe-filling brown dwarf and planetary companions of varying ages against their orbital separation from the white dwarf primary. The upper y-axis shows the orbital period given by each respective orbital separation. The four different tracks correspond to four different brown dwarf or planet ages (0.01, 0.1, 1 and 10 Gyr), marked next to each track. Brown dwarf models (≥13 M_Jup) are plotted in colors corresponding to their respective masses; all planetary models (≤13 M_Jup) are plotted in black. The size of each data point is representative of (but not linearly proportional to) the model radius. The golden (black) horizontal dashed line marks the minimal irradiation temperature for a brown dwarf (planet) among the evolutionary models utilized, i.e., ≈1700 K (≈900 K). The irradiated temperatures and corresponding orbital separations were calculated using the Sonora Bobcat brown dwarf evolutionary models grid (Marley et al. 2021).