Multi-wavelength Photometric Study of the Transits of an Extrasolar Asteroid

White dwarf WD 1145+017 is recently discovered by K2 to be orbited by at least one actively disintegrating asteroid. There are deep, broad, and evolving transits in the star's light curve. Here, we present multi-wavelength photometric observations from ultraviolet (Hubble), optical (multiple telescopes), K band (VLT) and 4.5 micron (Spitzer). Nominally, the transit depths are different in all the observed wavelengths. After correcting for contaminations from circumstellar lines in the ultraviolet and dust emission in the infrared, we find no difference in the transit depth. This can be explained by a deficit of small dust particles in the transiting material. We propose a model wherein only large partices can survive the high equilibrium temperature environment around WD 1145+017, while small particles sublimate rapidly. WD 1145+017 is a unique system that allows us to perform a detailed characterization of an extrasolar asteroid.