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We present multi-epoch, $R-$band imaging obtained from the Palomar TransientFactory of a small, fan-shaped reflection nebula in NGC 1333 that experiencesprominent brightness fluctuations. Photometry of HBC 340 (K7e) and HBC 341(M5e), a visual pair of late-type, young stellar objects lying near the apex ofthe nebula, demonstrates that while both are variable, the former hasbrightened by more than two magnitudes following a deep local minimum inSeptember 2014. Keck high dispersion (R$\sim$45,000-66,000), opticalspectroscopy of HBC 340 suggests that the protostar is a spectroscopic binary(HBC 340Aa + HBC 340Ab). Both HBC 340 and HBC 341 exhibit strong H$\alpha$ andforbidden line emission, consistent with accretion and outflow. We concludethat the brightness fluctuations in the reflection nebula represent light echosproduced by varying incident radiation emanating from HBC 340. The short-termvariability observed in the protostar is attributed to irregular accretionactivity, while correlated, dipping behavior on a several hundred day timescale may be due to eclipse-like events caused by orbiting circumstellarmaterial. Archival Hubble Space Telescope imaging of the region reveals asecond, faint (F814W$\sim$20.3 mag) companion to HBC 340 that lies 1.02"($\sim$235 AU) east of the protostar. If associated, this probable substellarmass object (20-50 Jupiter masses), HBC 340B, is likely unrelated to theobserved brightness variations. The sustained brightening of HBC 340 since late2014 can be explained by an EXor-like outburst, the recovery from a longduration eclipse event caused by obscuring circumstellar dust, or by thegradual removal of extincting material from along the line of sight. Ouranalysis here favors one of the extinction scenarios.

Interpretation of a Variable Reflection Nebula Associated with HBC 340 and HBC 341 in NGC 1333