Families of Plausible Solutions to the Puzzle of Boyajian's Star

TL;DR

This paper explores multiple plausible explanations for Boyajian's Star's unusual dimming patterns, favoring interstellar medium and intervening disk hypotheses over other natural models, based on recent observational constraints.

Contribution

It systematically evaluates a range of hypotheses for Boyajian's Star's dimming, narrowing down the most plausible scenarios based on observational data.

Findings

ISM and intervening disk models are more plausible.

Deep dimming timings are consistent with randomness.

Long-term dimming aligns with reddening and sodium absorption observations.

Abstract

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.