# Studying the Evolution of Warm Dust Encircling BD +20 307 Using SOFIA

## TL;DR

This study monitors the warm dust around star BD +20 307 over nine years, revealing an unexpected increase in infrared emission that challenges steady-state models and suggests recent catastrophic events.

## Contribution

First observational evidence of short-term variability in warm debris disks around stars with extreme dustiness, highlighting the need for dynamic models.

## Key findings

- Infrared emission increased by 10% over nine years.
- Shorter wavelength flux increased more than longer wavelengths.
- Steady-state models cannot explain the observed variability.

## Abstract

The small class of known stars with unusually warm, dusty debris disks is a key sample to probe in order to understand cascade models and extreme collisions that likely lead to the final configurations of planetary systems. Because of its extreme dustiness and small radius, the disk of BD +20 307 has a short predicted collision time and is therefore an interesting target in which to look for changes in dust quantity and composition over time. To compare with previous ground and Spitzer Space Telescope data, SOFIA photometry and spectroscopy were obtained. The system's 8.8-12.5 $\mu$m infrared emission increased by $10 \pm 2 \%$ over nine years between the SOFIA and earlier Spitzer measurements. In addition to an overall increase in infrared excess, there is a suggestion of a greater increase in flux at shorter wavelengths (less than 10.6 $\mu$m) compared to longer wavelengths (greater than 10.6 $\mu$m). Steady-state collisional cascade models cannot explain the increase in BD +20 307's disk flux over such short timescales. A catastrophic collision between planetary-scale bodies is still the most likely origin for the system's extreme dust; however, the cause for its recent variation requires further investigation.