Pre-MAP Search for Transiting Objects Orbiting White Dwarfs

Abstract

Metal pollution in white dwarf atmospheres may be the accreted remnants of planetary objects. After the discovery of disintegrating planetary objects transiting WD 1145+017 (Vanderburg et al. 2015), undergraduates in the University of Washington's Pre- Major in Astronomy Program (Pre-MAP) were inspired to collect photometry of the brightest white dwarfs to hunt for similar transiting objects around other metal-polluted white dwarfs. Prior surveys have yet to make a detection of a transiting planet orbiting a white dwarf, yet white dwarfs are still an attractive target for searches of small, rocky planetary material. Since a typical white dwarf is Earth-sized, transits of Earth-sized planets could have depths >50%, so even low S/N photometry has a chance at discovering transiting material. We identified bright, northern, metal-polluted white dwarfs in the SDSS DR10 white dwarf catalog, and observed five targets with the Astrophysical Research Consortium Small Aperture Telescope (ARCSAT) 0.5-meter telescope at Apache Point Observatory. The ARCSAT photometry had sufficient precision to detect Moon-sized objects or larger at short orbital periods, though no such planets were detected for these targets. We look forward to surveys which may find planets orbiting white dwarfs, such as NASA's TESS, ESA's PLATO, and the Evryscope.