  We have obtained extensive photometric observations of the polluted white
dwarf WD 1145+017 which has been reported to be transited by at least one, and
perhaps several, large asteroids (or, planetesimals) with dust emission. We
have carried out 53 observation sessions on 37 nights, totaling 192 hours, of
this 17th magnitude star with small to modest size telescopes covering the
interval 2015 November 1 to 2016 January 21. In all, we have detected some 237
significant dips in flux. Periodograms of the data reveal a significant
periodicity of 4.5004 hours that is consistent with the dominant ("A") period
detected with K2. The folded light curve at this period shows there is an
hour-long depression in flux with a mean depth of nearly 10%. This depression
is comprised of a series of shorter and sometimes deeper dips that do not
always occur at exactly the same orbital phase, and which would be unresolvable
with K2. In fact, we find numerous dips in flux at other orbital phases. Nearly
all of the dips associated with this activity appear to drift systematically in
phase with respect to the "A" period by about 2.5 minutes per day with a
dispersion of ~0.5 min/d, corresponding to a mean drift period of 4.4928 hours.
In all, we can track approximately 15 of these drifting features. There is no
detection of the "B"-"F" periods found with K2, but if they remain at the K2
levels we would not expect to have seen them. We explain the drifting motion as
that of smaller bodies (`fragments') that break off from the asteroid and go
into a slightly smaller orbit than that of the asteroid. If our interpretation
is correct, we can use the drift rate to determine the mass of the asteroid.
Under that scenario, we find that the mass of the asteroid is M_a ~ = 10^23
grams, or about 1/10th the mass of Ceres, with an uncertainty of about a factor
of 2.
