Abstract
The GD-1 stream is one of the longest and coldest stellar streams discovered to date, and one of the best objects for constraining the dark matter properties of the Milky Way. Using data from Gaia DR2 we study the proper motions, distance, morphology and density of the streamto uncover small scale perturbations. The proper motion cleaned data shows a clear distance gradient across the stream, ranging from 7 to 12 kpc. However, unlike earlier studies thatfound a continuous gradient, we uncover a distance minimum atφ1≈-50 deg, after which the distance increases again. We can reliably trace the stream between -85< φ1<15 deg, show-ing an even further extent to GD-1 beyond the earlier extension of Price-Whelan & Bonaca(2018). We constrain the stream track and density using a Boolean matched filter approachand find three large under densities and find significant residuals in the stream track lining upwith these gaps. In particular, a gap is visible atφ1=-3 deg, surrounded by a clear sinusoidal wiggle. We argue that this wiggle is due to a perturbation since it has the wrong orientationto come from a progenitor. We compute a total initial stellar mass of the stream segment of 1.58±0.07×104M. With the extended view of the spur in this work, we argue that the spurmay be unrelated to the adjacent gap in the stream. Finally, we show that an interaction withthe Sagittarius dwarf can create features similar to the spur.