Serendipitous discovery of a dusty disc around WDJ181417.84-735459.83
Cooper, W. J.; Marocco, F.; Koester, D.; Raddi, R.; Pinfield, D. J.; Rogers, L. K.; Burningham, B.; Forbrich, J.; González Egea, E.; Beamin, J. C.; Day-Jones, A.
United Kingdom, Spain, Germany, United States, Italy, Chile
Abstract
Spectroscopic observations of white dwarfs reveal that many of them are polluted by exoplanetary material, whose bulk composition can be uniquely probed this way. We present a spectroscopic and photometric analysis of the DA white dwarf WDJ181417.84-735459.83, an object originally identified to have a strong infrared (IR) excess in the 2MASS and WISE catalogues that we confirmed to be intrinsic to the white dwarf, and likely corresponding to the emission of a dusty disc around the star. The finding of Ca, Fe, and Mg absorption lines in two X-SHOOTER spectra of the white dwarf, taken 8 years apart, is further evidence of accretion from a dusty disc. We do not report variability in the absorption lines between these two spectra. Fitting a blackbody model to the IR excess gives a temperature of 910 ± 50 K. We have estimated a total accretion flux from the spectroscopic metal lines of $|\dot{\rm M}| = 1.784 \times 10^{9}\,$g s-1.