« lessĪs part of the Young Stellar Object VARiability (YSOVAR) program, we monitored NGC 1333 for ∼35 days at 3.6 and 4. If confirmed, our findings point to significant regional/environmental differences in the number of BDs and the minimum mass of the initial mass function. Our analysis here favors one of the extinction scenarios. The sustained brightening of HBC 340 since late 2014 can be explained by an EXor-like outburst, the recovery from a long duration eclipse event caused by obscuring circumstellar dust, or by the gradual removal of extincting material from along the line of sight. It was discovered by William Herschel in 1783 and is illuminated by variable star R Monocerotis (R Mon). If associated, more » this probable substellar mass object (20–50 Jupiter masses), HBC 340B, is likely unrelated to the observed brightness variations. NGC 2261 is a curious reflection nebula in Monoceros thats known as Hubbles Variable Nebula. Archival Hubble Space Telescope imaging of the region reveals a second, faint (F814W ∼ 20.3 mag) companion to HBC 340 that lies 1.″02 (∼235 au) east of the protostar. Reflection nebulae glow because they are made up of extremely tiny particles of solid matter, up to 10 or even 100 times smaller than dust particles on Earth. The short-term variability observed in the protostar is attributed to irregular accretion activity, while correlated, dipping behavior on a several hundred day timescale may be due to eclipse-like events caused by orbiting circumstellar material. We conclude that the brightness fluctuations in the reflection nebula represent light echos produced by varying incident radiation emanating from HBC 340. Both HBC 340 and HBC 341 exhibit strong H α and forbidden line emission, consistent with accretion and outflow. Keck high-dispersion ( R ∼ 45,000–66,000), optical spectroscopy of HBC 340 suggests that the protostar is a spectroscopic binary (HBC 340Aa + HBC 340Ab). Photometry of HBC 340 (K7e) and HBC 341 (M5e), a visual pair of late-type, young stellar objects lying near the apex of the nebula, demonstrates that while both are variable, the former has brightened by more than two magnitudes following a deep local minimum in 2014 September. Like a flashlight beam shining off the wall of a cave, the star is reflecting light off the surface of pitch black clouds of cold gas laced with dust. We present multi-epoch, R -band imaging obtained from the Palomar Transient Factory of a small, fan-shaped reflection nebula in NGC 1333 that experiences prominent brightness fluctuations. Caption NASA's Hubble Space Telescope has caught the eerie, wispy tendrils of a dark interstellar cloud being destroyed by the passage of one of the brightest stars in the Pleiades star cluster.
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