Simultaneous emission from dust and gas in the planetary debris orbiting a white dwarf

There is increasing evidence for the presence and variability of circumstellar dust and gas around white dwarfs that are polluted with exoplanetary material, although the origin of this dust and gas remains debated. This paper presents the first near-simultaneous observations of both circumstellar dust (via broad-band emission) and gas (via emission lines) around a polluted white dwarf. From the optical spectra the gaseous emission lines, notably the calcium infrared triplet and magnesium lines, show significant increases and decreases in their strength over time-scales of weeks, while the oxygen and iron lines remain relatively stable. Near-infrared JHK$_{\rm s}$ photometry reveals dust emission changes of up to 0.2 magnitudes in the K$_{\rm s}$ band over similar time-scales, marking the shortest variability time-scales observed to date. The two epochs with the strongest emission were correlated between the dust (K$_{\rm s}$-band brightening) and gas (strengthened calcium and magnesium lines), showing for the first time that the dust and gas must be produced near-simultaneously with a common origin, likely in collisions.