The SDSS-2MASS-WISE Ten Dimensional Stellar Color Locus
  We present the fiducial main sequence stellar locus traced by 10 photometric
colors observed by SDSS, 2MASS, and WISE. Median colors are determined using
1,052,793 stars with r-band extinction less than 0.125. We use this locus to
measure the dust extinction curve relative to the r-band, which is consistent
with previous measurements in the SDSS and 2MASS bands. The WISE band
extinction coefficients are larger than predicted by standard extinction
models. Using 13 lines of sight, we find variations in the extinction curve in
H, Ks, and WISE bandpasses. Relative extinction decreases towards Galactic
anti-center, in agreement with prior studies. Relative extinction increases
with Galactic latitude, in contrast to previous observations. This indicates a
universal mid-IR extinction law does not exist due to variations in dust grain
size and chemistry with Galactocentric position. A preliminary search for
outliers due to warm circumstellar dust is also presented, using stars with
high signal-to-noise in the W3-band. We find 199 such outliers, identified by
excess emission in Ks-W3. Inspection of SDSS images for these outliers reveals
a large number of contaminants due to nearby galaxies. Six sources appear to be
genuine dust candidates, yielding a fraction of systems with infrared excess of
0.12$\pm$0.05%.
