Simultaneous infrared and optical observations of the transiting debris cloud around WD 1145+017

TL;DR

This study provides multi-wavelength photometric observations of WD 1145+017, revealing consistent transit depths across optical and near-infrared bands, and constrains the grain size of the orbiting debris cloud.

Contribution

First simultaneous optical and near-infrared observations of WD 1145+017's transiting debris, constraining grain sizes and debris cloud properties.

Findings

No measurable difference in transit depths across wavelengths

Lower limit of 0.8 microns on grain size

Debris disc modeled with minimum particle size of ~10 microns

Abstract

We present multi-wavelength photometric monitoring of WD 1145+017, a white dwarf exhibiting periodic dimming events interpreted to be the transits of orbiting, disintegrating planetesimals. Our observations include the first set of near-infrared light curves for the object, obtained on multiple nights over the span of one month, and recorded multiple transit events with depths varying between ~20 to 50 per cent. Simultaneous near-infrared and optical observations of the deepest and longest duration transit event were obtained on two epochs with the Anglo-Australian Telescope and three optical facilities, over the wavelength range of 0.5 to 1.2 microns. These observations revealed no measurable difference in transit depths for multiple photometric pass bands, allowing us to place a 2 sigma lower limit of 0.8 microns on the grain size in the putative transiting debris cloud. This conclusion is consistent with the spectral energy distribution of the system, which can be fit with an optically thin debris disc with minimum particle sizes of 10 +5/-3 microns.