A Cold Stellar Stream in Pegasus

We report the serendipitous discovery of a stellarstream in the constellation Pegasus in the south Galactic hemisphere. The stellarstream was detected using the SDSS Data Release 14 by means of a matched filterin the color--magnitude diagram that is optimised for a stellar populationthat is 8 Gyr old with [Fe/H] = $-$0.46 dex, and located at heliocentricdistance of 18 kpc. The candidate stream is faint ( turnoff pointat $r_0 \sim$ 19.6), sparse and barely visible in SDSS photometry. It is also detected in the (shallower) Pan-STARRs data. The residual stellar densityin the $(u-g)_0$, $(g-r)_0$ color-- color diagramgives 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 clusterprogenitor.