Families of Plausible Solutions to the Puzzle of Boyajian's Star
  Good explanations for the unusual light curve of Boyajian's Star have been
hard to find. Recent results by Montet & Simon lend strength and plausibility
to the conclusion of Schaefer that in addition to short-term dimmings, the star
also experiences large, secular decreases in brightness on decadal timescales.
This, combined with a lack of long-wavelength excess in the star's spectral
energy distribution, strongly constrains scenarios involving circumstellar
material, including hypotheses invoking a spherical cloud of artifacts. We show
that the timings of the deepest dimmings appear consistent with being randomly
distributed, and that the star's reddening and narrow sodium absorption is
consistent with the total, long-term dimming observed. Following Montet &
Simon's encouragement to generate alternative hypotheses, we attempt to
circumscribe the space of possible explanations with a range of plausibilities,
including: a cloud in the outer solar system, structure in the ISM, natural and
artificial material orbiting Boyajian's Star, an intervening object with a
large disk, and variations in Boyajian's Star itself. We find the ISM and
intervening disk models more plausible than the other natural models.
