  In an earlier study we reported nearly 100 previously unknown dusty debris
disks around Hipparcos main sequence stars within 75 pc by selecting stars with
excesses in individual WISE colors. Here, we further scrutinize the Hipparcos
75 pc sample to (1) gain sensitivity to previously undetected, fainter mid-IR
excesses and (2) to remove spurious excesses contaminated by previously
unidentified blended sources. We improve upon our previous method by adopting a
more accurate measure of the confidence threshold for excess detection, and by
adding an optimally-weighted color average that incorporates all
shorter-wavelength WISE photometry, rather than using only individual WISE
colors. The latter is equivalent to spectral energy distribution fitting, but
only over WISE band passes. In addition, we leverage the higher resolution WISE
images available through the unWISE.me image service to identify contaminated
WISE excesses based on photocenter offsets among the W3- and W4-band images.
Altogether, we identify 19 previously unreported candidate debris disks.
Combined with the results from our earlier study, we have found a total of 107
new debris disks around 75 pc Hipparcos main sequence stars using precisely
calibrated WISE photometry. This expands the 75 pc debris disk sample by 22%
around Hipparcos main-sequence stars and by 20% overall (including non-main
sequence and non-Hipparcos stars).
