WD 1145+017: A White Dwarf Orbited by Multiple Transiting Asteroids

Saul Rappaport ( M.I.T. )

A substantial fraction of all isolated white dwarfs have atmospheres that are polluted with heavy elements such as are found in the Earth, including O, Si, Al and Fe, and these are inferred to be replenished regularly. One of these heavily polluted white dwarfs, WD 1145+017, was discovered with the K2 mission to exhibit periodic transits with several distinct periods in the range of 4.5-4.8 hours. Through a variety of arguments, it is inferred that the transits are due to dust emitted by a collection of planetesimals or asteroids. Subsequent ground-based observations have tracked at least a dozen independent bodies via their dusty transits. Their orbital periods appear to be quite stable, and their disintegration lifetimes may be as short as weeks to as long as years. While there is now a large collection of phase-tracking information about these bodies, the origin of asteroids in such short period orbits it is still unclear. I report on the observations to date, including the K2 discovery, six months of ground-based monitoring, and GTC searches for a wavelength dependence of the transit depths.