Constraints on the circumstellar dust around KIC 8462852

TL;DR

This study uses millimetre and sub-millimetre observations to set strict limits on circumstellar dust around KIC 8462852, challenging planetary disruption hypotheses and supporting cometary breakup explanations for its brightness dips.

Contribution

First deep millimetre and sub-millimetre photometry of KIC 8462852, providing stringent dust mass upper limits and insights into the nature of its brightness dips.

Findings

No significant dust emission detected around KIC 8462852.

Dust mass upper limits between 10^{-6} and 10^{-3} Earth masses.

Supports cometary breakup hypothesis over planetary disruption.

Abstract

We present millimetre (SMA) and sub-millimetre (SCUBA-2) continuum observations of the peculiar star KIC 8462852 which displayed several deep and aperiodic dips in brightness during the Kepler mission. Our observations are approximately confusion-limited at 850 $\mu$m and are the deepest millimetre and sub-millimetre photometry of the star that has yet been carried out. No significant emission is detected towards KIC 8462852. We determine upper limits for dust between a few 10$^{-6}$ M$_{\oplus}$ and 10$^{-3}$ M$_{\oplus}$ for regions identified as the most likely to host occluding dust clumps and a total overall dust budget of $<$7.7 M$_{\oplus}$ within a radius of 200 AU. Such low limits for the inner system make the catastrophic planetary disruption hypothesis unlikely. Integrating over the Kepler lightcurve we determine that at least 10$^{-9}$ M$_{\oplus}$ of dust is required to cause the observed Q16 dip. This is consistent with the currently most favoured cometary breakup hypothesis, but nevertheless implies the complete breakup of $\sim$ 30 Comet 1/P Halley type objects. Finally, in the wide SCUBA-2 field-of-view we identify another candidate debris disc system that is potentially the largest yet discovered.