A Cold Stellar Stream in Pegasus
  We report the serendipitous discovery of a stellar stream in the
constellation Pegasus in the south Galactic hemisphere. The stellar stream was
detected using the SDSS Data Release 14 by means of a matched filter in the
color--magnitude diagram that is optimised for a stellar population that is 8
Gyr old with [Fe/H] = $-$0.46 dex, and located at heliocentric distance of 18
kpc. The candidate stream is faint (turnoff point at $r_0 \sim$ 19.6), sparse
and barely visible in SDSS photometry. It is also detected in the (shallower)
Pan-STARRs data. The residual stellar density in the $(u-g)_0$, $(g-r)_0$
color--color diagram gives the same estimate for the age and [Fe/H] of this
stellar population. The stream is located at a Galactic coordinates $(l,b) =
(79.4,-24.6)$ and extends over 9$^\circ$ (2.5 kpc), with a width of 112 pc. The
narrow width suggests a globular cluster progenitor.
