Title: A 3pi Search for Planet Nine at 3.4 microns with WISE and NEOWISE,
Abstract: The recent 'Planet Nine' hypothesis has led to many observational and
archival searches for this giant planet proposed to orbit the Sun at hundreds
of astronomical units. While trans-Neptunian object searches are typically
conducted in the optical, models suggest Planet Nine could be self-luminous and
potentially bright enough at ~3-5 microns to be detected by the Wide-field
Infrared Survey Explorer (WISE). We have previously demonstrated a Planet Nine
search methodology based on time-resolved WISE coadds, allowing us to detect
moving objects much fainter than would be possible using single-frame
extractions. In the present work, we extend our 3.4 micron (W1) search to cover
more than three quarters of the sky and incorporate four years of WISE
observations spanning a seven year time period. This represents the deepest and
widest-area WISE search for Planet Nine to date. We characterize the spatial
variation of our survey's sensitivity and rule out the presence of Planet Nine
in the parameter space searched at W1 < 16.7 in high Galactic latitude regions
(90% completeness).